What are the key points of tunnel construction?

Tunnel construction is a difficult point in road and bridge construction. It has a complicated construction process and is different from other projects. It has the characteristics of concealment. If the survey and design estimates are insufficient or some precautions are not done during the construction, the safety of the tunnel may be affected and the project cannot be carried out normally. Therefore, when carrying out tunnel construction, it is necessary to understand the key points of the construction, strictly control the quality of each key point, strengthen management, and ensure safety.

Jet machine

1. The spraying equipment should have good sealing performance, and the conveying material should be continuous and uniform to meet the requirements of spraying operations.

2. Determine the reasonable water-binder ratio, water consumption, cementing material consumption and sand rate to ensure workability and early strength.

3. Sequential spraying from bottom to top in segments, the length of the segment is not more than 6m; the thickness of the arch should not exceed 6cm at a time, and the side wall should not exceed 10 cm. When spraying in layers, the next layer should be sprayed on the previous layer. The concrete should be set after the final setting. If spraying is carried out after 1h of final setting, the surface of the spray layer should be cleaned with high-pressure air and water first. The nozzle should be perpendicular to the rock surface and the distance from the sprayed surface should be 0.8~1.2m.

4. The spray pressure should be controlled at 0.15~0.2Mpa, and the concrete should be wet cured after spraying for 2h after final setting, and the curing time should not be less than 14d.

5. The spraying workers should wear protective equipment such as dust masks, protective caps, protective glasses, dust masks, etc. The workers should avoid direct contact with alkaline liquid quick-setting agents. After accidental contact, they should immediately rinse with water and spray concrete. After completion, the equipment should be cleaned in time.

6. The surface of the shotcrete should be flat, without hollows, cracks, or looseness. The base surface should be leveled with shotcrete. The flatness should be checked with a 2 m ruler. The allowable deviation of the surface flatness is 5 cm for side walls and 7 cm for arches.

Common problems on site

1. There are cavities and not dense behind the vault and side walls of the tunnel.

2. The thickness of the sprayed concrete is insufficient, uneven, and the steel frame is not completely covered.

3. Use dry spray. All tunnels that do not use wet spraying are required to stop construction.

4. The spraying distance is too far, and the sprayed surface is above 1.2 meters, which cannot guarantee the compactness of the concrete.

5. The spraying sequence is wrong, not bottom-up, but rather random.

6. The thickness of one shot is too thick, causing the concrete to hollow, not compact and collapse.

Tunnel formwork channel

Anchor rod

Anchor rod is a rod body made of solid or hollow steel in the rock mass in order to avoid the loose collapse of the rock mass during the excavation of the surrounding rock, which plays the role of reinforcing the soil and connecting it into a whole. The rock space is consolidated with mortar or other materials and fixed with steel pads.

Construction points

1. The anchor rod construction should be carried out after the initial spraying of concrete. The anchor rod shall be drilled in by special machinery. When using a general pneumatic rock drill, a special impactor shall be equipped. The main structural plane is vertical.

2. Arrange the position according to the design requirements, the allowable deviation of the hole position is not more than 10cm, and the insertion length of the rod shall not be shorter than 95% of the design length.

3. When the rod body is inserted into the anchor rod hole, the position should be kept centered and the insertion depth should meet the design requirements.

4. The mortar pouring into the mortar bolt hole should be full and dense, and an appropriate amount of micro-expansion agent and accelerator can be added into the mortar or cement slurry.

5. After the anchor rod is installed and the filled mortar is finally set, the supporting plate should be installed immediately and the nut should be tightened.

Common problems on site

1. The number and length of bolts are lower than the design value, and the distance between bolts is large. The lock foot anchor rod and the steel frame are not U-shaped welding. The on-site inspection should separate the leading small pipe, leading anchor rod, hollow anchor rod, and locking foot anchor tube (rod) in detail.

2. The raw material of the anchor rod is not up to the standard, and the wall thickness of the anchor rod and weighing inspection shall be checked on site.

3. The hollow bolt designed for grouting is not grouted or replaced by mortar bolts.

4. The penetration angle of the anchor rod does not meet the design requirements.

Tunnel waterproof board laying formwork

Steel frame

The steel frame is a support skeleton structure made of steel gratings, section steel, steel rails, etc., which are laid out according to the tunnel excavation contour line in order to keep the surrounding rock stable during the initial support period of the tunnel excavation in the tunnel escape pipeline project. After installation, it can achieve the purpose of supporting the stability of the surrounding rock and limiting the deformation of the surrounding rock. It is usually combined with steel mesh and shotcrete to bear the force.

Construction points

1. The steel frame shall be erected in time after the initial spraying of concrete.

2. The steel frame should not be sectioned on the vault with greater force and other places with greater force. The diameter of the main reinforcement of the grid steel frame should not be less than 18mm, and the welding between the steel bars should be firm.

3. Each section of the steel frame should be connected by bolts, and the connecting plates should be closely attached, and the gap should not exceed 2mm.

4. The outer edge of the steel frame should be tightly wedged with steel wedges or precast concrete blocks. The steel frame should be covered by sprayed concrete. The thickness of the protective layer should not be less than 40mm. The gap between the steel frame and the surrounding rock must be filled with sprayed concrete.

5. After the steel frame is processed, a trial assembly check must be carried out. The allowable error of the peripheral assembly is plus or minus 3 cm, and the plane warpage should be less than 2 cm; the erection position is accurate, and the deviation of the steel frame spacing, lateral position and elevation from the design position does not exceed Plus or minus 5 cm, the verticality error is plus or minus 2°; in the case of the partial excavation method, the steel arch frame is positioned by locking foot anchor pipes (rods) after installation, and the number is two. After the lower half of the excavation, the steel frame should be extended in time to form a closed loop; the two rows of steel frames shall be firmly connected longitudinally with a 22-diameter steel rod with a circumferential spacing of 1m to form an overall stressed structure.

6. When the steel frame is installed, the inner contour size should be strictly controlled, and the amount of settlement and deformation should be reserved to prevent intrusion into the lining clearance.

The rescue process of tunnel collapse is very complicated, and the rescue time is relatively long. The rescue situation usually takes 3 to 6 days. Therefore, it is very necessary to quickly open the “life channel” to transport air and food to the trapped persons, and to carry out information transmission and psychological intervention. ; The tunnel escape pipeline can reconfirm the length of the collapsed body and guide the construction of the escape channel.

What are the key points of highway tunnel construction technology?

As we all know, the construction of tunnels is relatively complicated and involves many difficult technologies, which brings great difficulties to highway construction. For this reason, it is necessary to strengthen technical research, improve the control level of tunnel quality management, and improve the overall quality of highways.

Construction characteristics of highway tunnels

Double-track railway lining trolley

During highway tunnel construction, it is easily affected by natural factors and the surrounding environment. The tunnel project itself is very complicated, and some unpredictable situations may occur during construction, which makes the entire tunnel project more difficult, and the tunnel project is also very susceptible to the influence of different engineering operations. Because the space inside the tunnel project has great limitations, the entire project construction process will have a crossover phenomenon. Construction within such a narrow internal space increases the difficulty of construction. Tunnel engineering is also susceptible to geological influences. The geology of the tunnel site is generally very complicated, and conditions such as collapse are prone to occur, which also poses a great threat to engineering construction.

Key points of highway tunnel construction technology

Tunnel waterproof board laying formwork

(1) Geological exploration technology

In the detection stage, infrared or electromagnetic techniques can be used to provide early warning of areas that have not been surveyed with the help of advanced geological forecasting technology, so that construction personnel have sufficient time to respond to possible threats and can also adjust the plan in time And technology to ensure the orderly development of construction. The above-mentioned technology can effectively predict the geological conditions and water-bearing conditions of the mountains, thereby effectively ensuring engineering safety. In addition, monitoring and measurement must be carried out. Monitoring and measurement are divided into two types: mandatory measurement and selective measurement. The purpose of the mandatory test is to ensure the stability and safety of the rock during construction, the operation is relatively simple and convenient, there are more sections, and the measurement results are more reliable. The required measurement link is mainly to observe the support status and geology directly, and to measure the surface subsidence and surrounding displacement. The selective test link is a supplement to the required test link, mainly by measuring relatively special sections, and after in-depth understanding and grasping of the surrounding rock and support conditions, effective control of the support, and then providing areas without excavation reference.

(2) Anchor rod construction technology

The construction environment of the anchor rod should be kept clean, and all the rock debris and impurities in the hole near the drill hole should be removed to prevent pollution of the construction. In the construction of the anchor rod, the different functions are adapted to the different technical points. If it is the coil anchor rod, then in the actual construction, there is a sequence of insertion of the anchor rod and the medicine pack in the hole. Note The pulping link also followed closely. Since the anchor rod may still move in the hole after grouting, in order to ensure the firmness and stability of the anchor rod, steel arches or steel mesh can be used to make the anchor rod and the hole more closely connected.

(3) Concrete spraying technology

First, before spraying the concrete, it is necessary to ensure that the sprayed object is free of impurities and kept clean. If concrete and impurities are mixed with each other, the adhesion between the concrete and the sprayed object will be reduced. The target of spraying is usually the excavation section to keep clean, which can also improve the quality of the section.

Second, in the mix ratio of concrete, when designing the mix ratio, it needs to be based on actual tests. When selecting additives, it needs to match the actual configuration requirements of the concrete. The concrete link is very important. Only by using concrete that meets the design requirements can concrete really play its role. When selecting the specific method of spraying, in addition to determining according to the entire project situation, it is also necessary to pay attention to changes during the actual construction. It cannot be fixed and needs to be adjusted according to the actual construction situation.

Third, pay attention to spraying continuously, not intermittent spraying. After choosing the right method, you also need to choose a high-quality sprayer, and do a good job of mixing the concrete to ensure that it is evenly distributed in the section.

(4) Waterproof and drainage construction technology

In this link, deep-buried water ditches can be used to drain the water that may seep out of the tunnel. When designing drainage, consider whether the water body may be frozen. Waterproof technology can be used in the open tunnel section, generally using water barrier and waterproof layer to prevent water leakage. In deformation joints or construction joints where leakage may occur, it should be prevented in advance, and rubber waterstops can be installed to avoid leakage. Also set up drainage pipes at appropriate locations so that water can flow out of the tunnel and into the surrounding rivers or lakes.

(5) Tunnel body excavation technology

The excavation of the hole is mainly the excavation of the middle pilot hole and the left and right holes. For the pilot tunnel, trenching must be strictly carried out in accordance with the set contour line. After the initial spraying of concrete, a steel grille arch shall be installed, and then it shall be connected with the steel grille outside the hole to make it a whole. The cyclic footage generally ranges from 0.5 to 1.2m. After the excavation is formed, the centerline and level must be strictly inspected. If both meet the relevant requirements, it is necessary to spray 0.05m thick C25 strength grade concrete. The soil excavated on the upper steps can be manually turned to the lower steps, and then transported out using machines and cars. To excavate the annular pilot pit and then to dig the middle core, it is generally necessary to make the middle core within the interval of 1.6 to 2m from the vault.

Tunnel construction quality control measures

Tunnel waterproof board laying formwork

(1) Ensure the quality of drawings

Drawing design is the foundation of tunnel engineering, and good drawings are essential to the entire project. When controlling the quality of the project, we must first start from the drawings, try to minimize the phenomenon of changing drawings, and then reduce the changes in the construction process. Changes in drawings or construction will bring great hidden dangers. For this reason, it is necessary to conduct detailed studies on drawings before construction to ensure design quality. When designing the drawings, it is necessary to make preparations to conduct detailed surveys of the geological environment, hydrology, weather and other conditions around the construction site to ensure the accuracy of the data, and then design scientific and reasonable drawings to lay the foundation for construction. When reviewing drawings, a layered review mode should be used. The person in charge of the project should communicate well with the designer to ensure that the design meets the project requirements and promote the smooth development of the project.

(2) Improve construction technology

The construction unit needs to truly understand that in order to effectively improve the quality of the tunnel project, it needs to develop and improve the construction technology, strengthen the learning of new technologies, and apply them in the actual process. Of course, this application also needs to be in line with the actual engineering. Combine each other, learn from each other’s strengths, and ensure that the technology is reasonable. For example, the method of arching first and then wall is common in tunnel engineering, especially in some fault-fractured areas or places with very complicated geological conditions. However, advances in science and technology have increasingly highlighted the backwardness of this method, which has been unable to meet the requirements of tunnel construction. , Gradually replaced by the step method. The step method has many advantages in construction, which can effectively improve the stability of the tunnel, ensure the safety of the tunnel, and to a certain extent can shorten the entire project practice, thereby effectively reducing the project cost. For this reason, it is necessary to continuously research and develop various new technologies in accordance with the development requirements of the times to improve construction efficiency and promote the development of the industry.

(3) Reasonably allocate engineering resources to ensure safety

In order to effectively apply various technologies and ensure the use effect, we must also pay attention to other factors in the project, such as the quality of materials required for construction, or the performance and usage of construction equipment, etc. These essential resources in construction are essential Construction technology has an important impact. In construction, the reasonable allocation of various resources and the quality of the resources themselves are very important, which is an important part of ensuring the quality of the project. The various materials required in the construction should be started from the source, the quality of the materials should be strictly checked, and the inspection should be done. If the quality is unqualified, it should be replaced in time. Also pay attention to the storage of materials, such as explosives that may be used in tunnel construction, need to be strictly managed, and stored in a clean area, kept dry to prevent it from being unusable due to dampness, and also pay attention to fire prevention and avoid mismanagement And cause an explosion and so on. In daily life, we must do a good job in the maintenance and repair of equipment, and we must not wait for the equipment to be broken before thinking of repairs. We must ensure that the equipment can provide support for the implementation of the technology and make the project proceed in an orderly manner.

(4) Strengthen later detection

It is necessary to adopt advanced detection technology to detect tunnel entities, guide the on-site defect remediation, and enhance the safety and usability of tunnel engineering. For example, advanced tunnel compactness testing equipment and geological radar testing equipment, etc., the use of various advanced technologies needs to make it effective, optimize the inspection quality, and determine the width of the roadway in the tunnel, the total width of the tunnel, For inspection of clear height, etc., it is also necessary to inspect the hollow and thickness of the tunnel lining, the actual strength of the concrete, and the grouting situation to ensure that all contents meet the relevant requirements. It is necessary to ensure that the inspection quality is qualified, strengthen the construction of quality levels, make the inspection results more real and effective, ensure that the project is qualified for acceptance, and ensure the quality of the project.

In short, the construction of highway tunnels is complicated, cumbersome and difficult. It needs to be paid attention to by relevant personnel, combined with the actual characteristics of the project, design drawings that meet the requirements, select appropriate processes, strictly manage the materials required for the project, and strengthen personnel supervision. Continuously develop various new processes. Particular attention should be paid to the construction details. Since the tunnel involves many complicated processes, any small detail error may bring a major threat to the entire project. Therefore, we must pay more attention to improve the construction quality of the project to ensure the safety and stability of the tunnel.

What are the factors affecting tunnel construction?

In recent years, due to the acceleration of the internationalization process, the transportation industry has developed rapidly. Road construction is not only related to people’s livelihood, but also an important pillar to promote national economic growth. In order to promote regional economic development, many regions have overcome geographical restrictions to build highways, and tunnel engineering is an important construction link. Tunnel projects are often located in areas with very complex geographic environments, including geological conditions and topography, etc., which require tunnel engineering construction technology. As a large-scale project, tunnel engineering not only has many and complex construction techniques, but also has high requirements for professional technology. In particular, there are many influencing factors in the tunnel engineering environment, which will inevitably cause various quality problems in tunnel construction. In order to ensure the construction quality, it is very necessary to formulate supervision measures according to the actual needs of the tunnel project.

Features of tunnel construction

The tunnel concrete maintenance formwork

Concealment

Tunnel engineering is a concealed project, and the construction of tunnel engineering must also have the characteristics of concealment. During construction, there is often only one visible side, and other constructions are concealed, which will inevitably have many unforeseen conditions. Even if there are hidden dangers left during construction, it is difficult to find out in time and make judgments.

Dynamic

The environment where the tunnel project is located is often complex and changeable. During the construction, this change will inevitably produce various accidental factors, which will cause the construction design to be inconsistent with the construction site. This means that to design a tunnel project, it is necessary not only to conduct site surveys, but also to fully understand the local surrounding rock conditions, so that the tunnel lining trolley is dynamic, so that the initial design is convenient when the construction site conditions change. to modify.

Risk

The area where tunnel construction is located is often in harsh environmental conditions, and most of the construction is carried out in caves or underground. Even if the operation is carried out in the same environmental space, the technical requirements of each operation link will be different, including tunnel lining technology, support technology and ventilation technology, etc., which must be selected according to the actual needs of the construction to ensure that each construction The links are closely connected, which will inevitably make the construction environment cramped, and different construction technologies will interfere with each other, which will inevitably have risk factors. In particular, the geological conditions of the tunnel construction area are changeable, and the lack of stability will inevitably have risks, making the tunnel construction dangerous accidents at any time.

Influencing factors existing in tunnel construction

Tunnel waterproof board laying formwork

Human Factors

In tunnel construction, people are the most active factor and also the factor lacking stability. To effectively control the tunnel construction, it is necessary to analyze in detail the potential safety hazards in each link of the construction, and formulate targeted control measures to play a management role in the construction. The staff involved in the construction activities should control the basic work in the construction, and analyze various intervention forms based on this. As the constructors in the construction proceed from their personal interests and ignore the responsibilities they should perform in the work, there will be problems in the adjustment of construction management procedures, which will inevitably affect the quality of tunnel construction.

Hard factor

The rigid factors that affect tunnel construction include material factors and equipment factors throughout the entire tunnel construction process. An important measure of the quality of tunnel construction is the material. To ensure that construction materials comply with relevant regulations, it is necessary to consider various factors that affect material quality. These factors are often important influencing factors leading to material problems, as well as basic factors affecting the quality of tunnel engineering. In tunnel construction, construction equipment is indispensable and the main object of construction safety management. To control and manage construction equipment, it is necessary for construction personnel to pay attention to equipment inspection. However, because the construction personnel neglect the daily maintenance of the equipment, it will inevitably have a negative impact on the construction of the tunnel project.

Technical control measures

During tunnel construction, scientific and reasonable technical control measures are the key to ensuring construction quality. However, when entering specific operations, it will be affected by a variety of factors, making it difficult for technical control measures to function. This is usually reflected in changes in construction procedures or adjustments to construction procedures, which will inevitably cause adverse effects on subsequent construction . To do a good job of technical control in tunnel construction, it is necessary to analyze various influencing factors and propose scientific and effective intervention measures to make technical control time-effective.

Key points of supervision and control of tunnel construction

Two-lane highway lining trolley

Supervision and control of excavation site

Tunnel construction will have problems with over-excavation and under-excavation at the excavation site. Supervisors should conduct excavation quality inspections in accordance with the content specified in the relevant technical specifications. For under-excavation, if the rock formation is complete, the strength and structure of the lining will not be disturbed. When the compressive strength of the rock exceeds 30 MPa, the under-excavation amplitude in individual places should be defined within 0.1 square meters, and the uplift should not exceed 5 meters. . Including the position of the vault of the tunnel less than 1 meter and the corners of the walls must not be under-excavated to avoid dangerous accidents. The over-excavation phenomenon has been clearly stipulated in the tunnel engineering construction technical specifications. Due to the different geological rings of the surrounding rock, there will be different requirements for over-excavation.

Supervision and Control of Anchor Shotcrete Support

In tunnel construction, the bolting and shotcrete support cannot be ignored. In the process of acceptance of the tunnel project, the supervisor shall formulate the acceptance method according to the actual situation of the tunnel construction and notify the construction party in advance. Acceptance is required for every construction link in tunnel construction, and follow-up work can only be carried out after the acceptance is qualified. In the acceptance of the construction quality of anchor rods, attention should be paid to checking the angled anchor rods. In the acceptance of grouting construction, the supervisor must attach great importance to this process, because this process is not only technically difficult, but also has strict requirements on the grouting procedure.

Supervision and control of shotcrete

If there are omissions in the process of spraying concrete during tunnel construction, not only cracks will occur, but even water seepage will occur, which will cause adverse effects on the construction. The supervisor shall strictly control the sprayed concrete construction and require the construction personnel to adopt advanced technical measures to ensure the quality of the tunnel project.

Supervision and control of invert

In tunnel construction, the invert is an important construction part, which is related to the stability of the entire tunnel. If there are quality problems in the invert construction, it will affect the stability of the superstructure, especially the junction between the wall corner and the invert. It needs to be cleaned up before entering the construction process to avoid impurity in this part. The arch is not strong and produces uneven settlement.

In summary, there are high requirements for construction technology in tunnel construction, mainly because tunnel construction is a hidden project, and it is difficult to find hidden quality problems. This requires the analysis of the possible influencing factors in the tunnel construction, the exploration of technical methods, and the adoption of supervision and control measures that conform to the actual construction to avoid quality problems during the construction and ensure the smooth construction of the tunnel construction.

What are the performance advantages of the automatic invert trestle?

Tunnel invert construction has always been an important factor affecting construction progress and quality control. In order to reduce the interference of invert construction on ballast vehicles and achieve the goal of accelerating construction progress, our company has developed a new automatic control hydraulic invert trestle.

The automatic invert trestle has the following advantages:

1. Modular assembly structure: The automatic inverted arch trestle adopts a plate-beam structure, which can be quickly modularized and assembled to realize variable span and convenient transportation.

Crawler Hydraulic inverting bridge formwork

2. Cantilever mobile structure: The automatic inverted arch trestle realizes the front cantilever, and the whole machine can be cantilevered. It has the function of retreating across the pit, avoiding the impact of the tunnel face and the inverted blasting flying rocks. The inverted arch trestle bridge can be crossed or withdrawn from the invert construction area at any time according to the technological requirements of the tunnel construction operation.

3. Hydraulic drive mode: The whole machine part of the automatic invert trestle adopts hydraulic drive, which has flexible control, simple structure, low noise, stable and reliable performance, and convenient maintenance and repair.

4. Sliding shoe walking mode: The trestle adopts a sliding shoe walking mode, which has the advantages of compact structure, small space occupation, no noise, stable and reliable walking, etc. The selected high-performance wear-resistant materials have long service life , simple maintenance and repair etc.

Wheeled Hydraulic inverting bridge formwork

5. Automatic control system: The trestle introduces an automatic PLC control system, which uses microcomputer operation to realize automatic walking, which greatly facilitates driving operations.

6. High construction safety: The overall structure is novel and reasonable in design, with large carrying capacity, stable structure and reliable safety, which provides safety guarantee for construction vehicles and operators.

The invert is one of the main components of the tunnel structure, and it is the foundation of the tunnel structure. In terms of it, the ground pressure on the upper part of the tunnel is transmitted to the underground through the side wall structure of the tunnel or the load on the road surface, and some resist the reaction force from the ground under the tunnel. In fact, it is a kind of foundation beam (slab) that can withstand the permanent load of the ground and the temporary load of the road surface (dynamic load). For this reason, the stress state of the invert is more complicated.

Judging from the examples of internal and external traffic tunnel engineering diseases, due to the design and construction of the tunnel invert structure, there are many examples of tunnel structural instability, road surface settlement and cracking, and mud and mud. For this reason, the invert structure must be refined, and its structure must meet the specifications and design requirements.

Construction technology and technical points of tunnel invert

The invert is a reverse arch structure set at the bottom of the tunnel to improve the stress conditions of the upper supporting structure. It is one of the important components of the tunnel structure, and it is the foundation of the tunnel structure. On the one hand, it needs to effectively transmit the ground pressure on the upper part of the tunnel to the underground through the side wall structure of the tunnel or the load on the road surface, and it also effectively resists the reaction force from the ground under the tunnel. In fact, it is a kind of foundation beam that can bear the permanent load of the ground and the temporary load of the road surface (dynamic load). The invert and the secondary lining form the entire tunnel, increasing structural stability.

The role of invert

1. Solve the problem of insufficient foundation bearing capacity, reduce ground subsidence, prevent the uplift and deformation of the bottom drum, and adjust the lining stress;

2. Seal the surrounding rock to prevent excessive deformation of the surrounding rock and improve the overall bearing capacity of the mechanism;

3. Increase the support resistance of the bottom and the wall to prevent shear damage caused by internal squeezing.

Construction requirements for invert

Tunnel waterproof board laying formwork

The invert arch should be constructed in a timely manner according to the surrounding rock stress condition and the initial support detection situation, and the traffic in the tunnel should be guaranteed to be unimpeded, without affecting the advancement construction in front, and the construction should be carried out in strict accordance with the excavation plan, and the construction of the arch wall should be carried out. Early arch support and invert arch molding concrete construction to realize early closure of the support structure; formwork must be used during invert arch construction to ensure the quality of concrete pouring; invert arch cushion, initial support, molded concrete, inverted arch Arch backfilling should be constructed separately to ensure the construction quality of each unit; the invert arch should be formed at one time, and should not be poured in stages, the joints should be smooth and waterproof, and the over-excavated parts should be backfilled with concrete with the same strength as the lining; The invert, filling layer and floor concrete should be constructed as soon as possible to ensure the construction of the arch wall concrete and the second lining and the normal working length of the lining trolley. The floor concrete should be strictly controlled to ensure the thickness and elevation of the concrete pavement.

During the construction of invert and slab, drainage facilities such as central drainage ditch, horizontal drainage pipe, and longitudinal drainage pipe should be implemented as required to ensure smooth drainage in the tunnel, and attention should be paid to the provision of deformation joints through the second lining; the invert of the opening section should be in Excavated into the hole within 150m and closed into a ring. Set up guardrails around the excavation of the inverted arch, and install a dense mesh safety net; set up warning signs at the exit. During invert construction, trestle bridge construction is adopted to ensure continuous invert construction and ensure that the excavation of the tunnel and the transportation of materials in the tunnel are not affected by the invert excavation, and the strength of the poured invert concrete will be satisfied. After the traffic intensity is required, the trestle bridge will be removed for the next stage of invert construction.

Invert construction process

Tunnel formwork channel

1. Trestle construction

In the construction of the trestle bridge, attention should be paid to the flatness and width of the installation to ensure the safety of vehicles and the smooth passage of different construction vehicles. One side of the trestle bridge is erected on the completed invert backfill and base plate construction site, and the other side is erected on the original ground. The trestle bridge should be erected in consideration of the bearing capacity of the trestle bridge, and the foundation of the trestle bridge should be reinforced according to different geological conditions.

The excavation of the inverted arch soil layer should be assisted by mechanical cooperation and manual excavation; for soil and rock excavation, the excavation length must be controlled, and the excavation vibration must be avoided during blasting operations to affect the formed lining and other structures. The over-excavation and under-excavation should be controlled as much as possible. The invert section should be checked immediately after excavation, and the insufficient part should be re-excavated to ensure the thickness of the invert; the tunnel invert excavation should be smooth to avoid stress concentration in. The debris at the bottom of the side wall steel frame is clear and clean to ensure a good connection with the inverted steel frame, creating a reasonable working surface for the construction of the low side wall.

2. Initial support and second lining steel pre-embedded

(1) The excavation of the invert and the initial support of the invert should be closely connected. Before installing the steel arch frame, a 5-250px low-grade concrete cushion should be laid on the base, and then the invert arch steel frame should be installed, and then sprayed concrete or The use of moulded concrete facilitates the installation of inverted arch reinforcement and installation of templates;

(2) The inverted arch steel support installation must meet the design and specification requirements, and be welded smoothly and firmly with the side wall arch frame;

(3) The extension length of the pre-embedded steel bars at the side walls of the two side linings on both sides of the invert should meet the requirements for welding with the second lining steel bars in the circumferential direction, and the joints should be staggered so that the number of steel joints of the same section is not more than one percent of the total. Fifty. The spacing between the second and second lining steel bars of the inverted arch must be ensured, and the layer spacing must be ensured by welding the positioning steel bars.The tunnel concrete maintenance formwork

3. Invert pouring and invert filling

(1) Before pouring the invert arch, the mixing ratio of concrete should be strictly demonstrated, and the top form with reserved vibrating holes should be used to ensure the compactness of the concrete. The invert concrete can be built with pumped concrete; the invert should be constructed before The position of the settling joint should be designed in advance. The settling joint should ensure that the second lining concrete, arch wall, and invert are disconnected on the same vertical plane, and the settlement joint should be treated as required to ensure the quality of construction, and the surrounding rock will not change.
In large lots, there should be as few or no expansion joints as possible to ensure that the lining does not have water-proof and drainage problems.

(2) Invert backfilling should start construction after the invert concrete reaches 70% of the design value. When invert backfilling, a layer of concrete should be poured to ensure that the rubble does not directly contact the invert, and the rubble is manually put in, and then the concrete is poured. The order of placing the rubble shall be carried out. The amount of stone backfill shall not exceed 25%, the distance between the stone shall be more than 250px from the edge of the formwork, and the distance between the auxiliary stones shall not be greater than the maximum diameter of the coarse aggregate.

(3) Treatment of construction joints and deformation joints. The surface of the joints should be cleaned of floating slurry and sundries, brushed with no less than the strength grade of the structural concrete or coated with concrete cross-section treatment agent, poured concrete in time, and applied formwork to the construction joint Or other measures to form a predetermined shape to ensure that subsequent projects are closely connected; the maximum allowable settlement difference of the settlement deformation joint should not be greater than 30mm, the width of the settlement deformation joint should be 20~30mm, and the thickness of the concrete structure at the joint It should not be less than 300mm, and the color seam should be set with a backing material that does not adhere to the caulking material or a water-swellable water-stop strip to meet the requirements of sealing and waterproofing, adapting to deformation, convenient construction, and easy maintenance.

The construction quality of the tunnel invert is an important indicator to ensure that the tunnel bears the permanent load of the ground and the temporary load of the road surface. The construction of the invert must be meticulous and constructed in accordance with the construction requirements to ensure the integrity of the tunnel structure, make the tunnel structure instability, pavement settlement, cracking, and tumbling Phenomena such as mud will not appear after the tunnel is delivered to use, so as to ensure the safety and normal operation of the tunnel.

How to improve the construction efficiency of tunnel waterproof board laying formwork

It is understood that the water ditch cable trough is the final project of the tunnel’s preliminary construction, which is responsible for the drainage, the shielding interference of the control cable, and the protection function of the cable in the heavy corrosive environment. The construction process is relatively cumbersome, and the construction pays more attention to details. For this reason, the project engineering department has made sufficient arrangements and arrangements.

Construction preparation

Technical personnel are required to supervise and manage on-site, and strictly control the quality of the project. First, make reasonable deployment of equipment and material personnel, and secondly make technical clarifications to the work team. Operators are required to strictly follow the design drawings and construction technical specifications.

Process control

Strengthen the quality control of each process, first measure the line, and accurately locate the size of the cable trough according to the construction drawings; then clean the base, before the construction of the tunnel cable trough, clean the silt and debris in the tunnel. Chiseling is carried out in the height range of the cable trough of the side wall, followed by the installation of the steel bar of the groove wall, the installation of the waterproof and drainage system, the installation of the formwork and the washing of the base surface, the concrete pouring, demoulding, curing, cover paving, etc. Process.

Advantages of automatic tunnel waterproof board laying formwork

Tunnel waterproof board laying formwork

1. Fast construction speed

Adopting traditional manual backward transportation and moulding construction, the construction progress of single-sided trenches is 4-6 meters per day, and both sides are 60 to 90 meters per month; automatic tunnel waterproof board laying formwork is adopted, and simultaneous construction on both sides can reach 360 to 720 meters per month. , Which is more than 5 times that of traditional construction methods, greatly speeding up the progress of tunnel construction.

2. Good integrity

After lining, the groove section is standardized and standardized, with beautiful appearance, precise alignment, beautiful seams and smooth line.

3. High degree of mechanization

It saves manpower and reduces the labor intensity of the operators. The original operator was about 5 to 6, but now only 2 people can operate.

Double-track railway lining trolley

4. Good on-site civilized construction

The construction site of the traditional water trench cable trough was manually assembled, erected, positioned, and transported. The site was messy. The automatic tunnel waterproof board laying formwork was used to complete the work and quickly deploy to ensure the site is clean and tidy.

5. Easy to disassemble and transfer

It can be recycled and used for many times, the car can be freely disassembled and combined, and the structural parts are designed reasonably, which is convenient for transportation and transfer.

The gutter cable trough adopts a single-sided cable trough trolley manufactured by the mechanical work area of ​​the project. The trolley has the advantages of small space occupation, convenient movement and reasonable structure design. The demolding system is hydraulically designed, which shortens the demolding time. , It also protects the forming of the water trench cable trough, and ensures the straight edges of the water trench cable trough.

What are the safety guarantee measures for tunnel construction?

Tunnel construction can be divided into mountain tunnels, underwater tunnels and urban tunnels according to the location of the tunnel. Therefore, relevant departments must ensure the safety of their construction personnel. At present, with the extensive application of aerial survey, remote sensing technology, geophysical technology, measurement technology, electronic computer technology, etc., the technical level of tunnel survey and design has also been greatly improved. Accurate blasting technology, horizontal drilling technology and pre-grouting technology continue to improve, it is possible to improve the safety of the tunnel excavation process, and can ensure the quality of tunnel engineering, while also ensuring the safety of construction to a certain extent.

Organizational assurance measures

Establish a production safety leadership group led by the project manager to be fully responsible for the safety production work of this project. The deputy manager in charge of safety production is the direct person in charge of safety production, and the chief engineer is the technical person in charge of safety production. Management personnel and production personnel who have not passed the safety education and training and passed the examination are not allowed to work.

System guarantee measures

① The safety production responsibility system must be strictly implemented. All levels and departments must have clear safety responsibilities, and there must be safety production indicators in economic contracts.

② Implement the three-level safety education system and register. Before changing the type of work or process, you should receive safety education about the process you are engaged in.

③All special operations personnel (blasters, electric welders, etc.) must be certified to work, and non-special workers are strictly prohibited from engaging in special operations.

③Regular safety inspection system must be implemented, and each inspection must be recorded to identify hidden accidents; rectification must be ordered, time, and measures, and the rectification notice for major hidden dangers must be completed as required.

④ Personnel entering the construction site must wear safety helmets. Personnel working in dangerous and high-altitude operations must wear labor protection equipment and safety equipment as required.

The tunnel concrete maintenance formwork

Technical guarantee measures

①Construction site

1. The construction site must be designed according to the construction organization to do a good job of “three connections and one leveling” large-scale components, reasonable and orderly stacking of materials, eye-catching slogans, publicity boards, safety measures, and safety signs on site.

2. Participants in construction must go through safety education, be familiar with the safety operating procedures of this type of work, and hold certificates for special operations. Abide by the operating procedures at work and stick to the job position. It is strictly prohibited to work after drinking.

3. Use safety protection products and safety protection measures correctly. Personnel entering the construction site must wear safety helmets. High heels, slippers, hard-soled slippery shoes are not allowed. Safety belts must be worn when working at high places without protective facilities. Protective railings, baffles or safety nets are required for operations in spaces above 2 meters from the ground.

4. Dangerous places such as pits, ditches, holes, and wells on the construction site should be protected, and there should be red warning lights.

5. The material of scaffolding, pole foundation, pole cabinet, sweeping pole, pole connection, outer protection, scaffolding board laying, etc. must meet the requirements of regulations. Set up by professional shelf workers. Remove the scaffold gradually from top to bottom, and it is strictly forbidden to remove it by overturning or pulling down. Do not work up and down at the same time. It is strictly forbidden to put the removed materials.

② Process construction safety measures

1. For tunnel construction, the pre-construction preparations should be done, the construction method should be correctly selected, and the construction technical plan should be compiled in combination with the actual conditions such as topography and geology, and the construction personnel should be technically informed to rationally arrange the construction.

2. A complete shift system should be established between each team in tunnel construction. When handing over the shift, the shift person should give the successor a detailed account of the construction situation and related safety issues and measures of the shift and group, and record it in the handover record book. The person in charge of the work site (leader) should carefully check the handover situation . Construction is not allowed if the safety status of the working face is not carefully checked before the start of each shift.

3. Strengthen inspection and measurement of surrounding rock during construction. For tunnel construction in poor geological sections, a small cycle construction method such as weak blasting, short excavation, strong support, early lining, and top protection should be adopted. Tunnel construction must make full use of monitoring methods to predict and forecast the surrounding rock displacement and the force status of the supporting structure, and the measurement must serve production safety.

4. If there is a dangerous situation in the tunnel, it is necessary to set up obvious signs or send a special person to guard the dangerous area, and promptly report to the person in charge of the construction site, and take timely measures to deal with it. When the situation is dangerous, all the staff should be evacuated from the dangerous area and immediately Reported.

5. All personnel entering the tunnel construction site must be equipped with safety protection equipment according to the regulations, and obey the command.

6. Do not dig into the hole if the opening of the hole has not been painted on the slope or the roof of the hole has not been protected and drainage facilities have been installed.

7. Drilling on the tunnel face

(1) When drilling personnel arrive at the work site, they should first check whether the working surface is in a safe state, such as whether the support, roof and two sides are firm. If there are loose rocks, they should be supported or treated immediately.

(2) Wet rock drilling must be used when drilling a hole with a trolley and a rock drill.

(3) It is strictly forbidden to continue drilling in the residual eye.

(4) Do not disassemble and repair rock drilling equipment at the working face.

8. Blasting operations

(1) The blasting operation in the cave must be certificated and commanded uniformly.

(2) When blasting, all personnel must be evacuated outside the warning zone protected from harmful gas, vibration and flying rocks, and safety guards should be set up. The safety guard distance should comply with relevant regulations.

Two-lane highway lining trolley

a. No less than 100m in the Dutou tunnel;

b. The adjacent upper and lower pilot pits are not less than 200m;

c. Do not use TNT (trinitrotoluene), picric acid, black gunpowder and other explosives that generate a large amount of harmful gas for blasting in the cave. After blasting, ventilation and smoke must be exhausted for 15 minutes before other workers are allowed to enter the working surface.

d. If a blind cannon is found, it must be handled by the original blasting personnel according to regulations.

e. It is strictly forbidden to carry out explosive processing work outside the explosive processing room, and processing personnel are strictly forbidden to wear chemical fiber clothing. The daily firing time and frequency should be clearly stipulated according to the construction conditions, and the time to fire after charging should not be too long.

9. Support

(1) All parts of the tunnel shall be supported immediately after excavation.

(2) During the construction period, the person in charge of on-site construction I should conduct regular inspections on the support of each department in conjunction with relevant personnel. In bad geological areas, each shift should be instructed to inspect by special personnel. When the support is found to be altered or damaged, it should be repaired and reinforced immediately.

(3) When the sprayed concrete has not reached a certain strength, the surrounding rock that tends to become unstable, or the surrounding rock whose deformation exceeds the design allowable value and sudden changes after spray anchoring, should be supported by steel support.

(4) When installing the steel frame support, the relevant safety rules such as lifting and high-altitude operations should be observed, and small equipment should be used for hoisting.

(5) For surrounding rock with poor self-stability after excavation, the method of using advanced bolts and hanging nets to spray concrete should be used for temporary support.

(6) The abnormal cracks in the sprayed layer should be regarded as one of the main safety inspection contents, and frequent observation and inspection should be performed as a danger signal for construction to cause vigilance.

(7) For concrete spraying and grouting operations, you must bring protective equipment as required.

10. Ballast loading and transportation

(1) Before and during ballast loading, check the stability of the surrounding rock of the excavation surface. When loose rock or signs of collapse are found, the ballast must be treated first and then loaded.

(2) It is proposed to use a loader to load the ballast. During the construction process, no one can pass within the mechanical swing range. Prevent crowding with people.

11. Secondary lining

(1) Railings of no less than 1m should be erected on the lining workbench, anti-skid strips should be set up on the springboard, and the ladder should be installed firmly without nails outcropping and protruding sharp corners.

(2) The load-bearing capacity of workbenches, springboards, and scaffolding should not be overloaded, and should be marked on the spot. The scaffolding and the bottom plate of the workbench should be laid tightly, and the ends of the wooden boards must be placed on the fulcrum.

(3) When hoisting arches and model plates, the working area should be supervised by a dedicated person.

(4) When dumping the lining material in the operation section of the tunnel, personnel and vehicles are not allowed to pass through.

(5) When working at heights above 2m, the relevant regulations for working at heights shall be met.

(6) To check and repair the squeezing machine and pipeline, shut down and cut off the air source and power source.

(7) When removing the concrete conveying hose or pipeline, the operation of the concrete pump must be stopped.

Two-lane highway lining trolley

12. Dustproof

(1) Comprehensive dust prevention measures must be adopted for tunnel construction, and dust concentration must be checked regularly.

(2) The following dust prevention work must be done in tunnel construction on the rock drilling and ballast loading face:

a. Spraying and watering must be carried out before and after the shot;

b. Use water to soak the ballast pile and spray wet the rock wall before the ballast is discharged.

13. Power supply and electrical equipment

(1) Construction machinery, machinery and electrical equipment should be tested in accordance with safety technical standards before installation, and can be installed only after passing the test, and can only be operated after confirming that the condition is good.

(2) The voltage of the tunnel construction lighting circuit is not greater than 36V in the construction area. All power equipment shall be inspected and maintained by special personnel, and warning signs shall be set.

(3) When operating electrical equipment in the cave, the following requirements must be met:

a. Non-full-time electrical operators shall not operate electrical equipment.

b. When operating the main circuit of high-voltage electrical equipment, you must wear insulating gloves, electrician insulating rubber shoes and stand on the insulating board.

c. The operating handle of hand-held electrical equipment and the parts that must be contacted during work must have good insulation, and insulation inspection should be carried out before use.

d. Low-voltage electrical equipment should be equipped with electric shock inspection.

(4) Electrical equipment must have good grounding protection, and each shift shall be inspected by a full-time electrician.

(5) The inspection, maintenance and adjustment of electrical equipment must be carried out by a full-time electrical maintenance worker.

(6) The lighting in the cave should ensure sufficient brightness, uniformity and no flicker. For warehouses or caverns with flammable, explosive and other dangerous goods, explosion-proof lamps or indirect lighting must be used.

14. Emergency plan

It is inevitable that emergencies will occur during the construction process, so it is necessary to formulate practical emergency plans to prevent emergencies. For every possible accident or emergency, the person in charge of the scene can report to the higher level and immediately direct the handling of the emergency on the spot.

Introduction to Construction Technology of Highway Tunnel Lining

Due to the large cross-section of the highway tunnel, the quality requirements of the molded concrete lining are high, especially if the highway tunnel cancels the secondary treatment of the fireproof coating and cement paint on the second lining surface, the molded concrete lining will have appearance quality problems. Such as: ring-shaped joints are staggered and leaking; working windows are staggered; there are many cold joints; there are spots and colors on the concrete surface; water leakage; low side walls are not straight, etc. The performance is particularly prominent, and it is directly affected by poor handling .The appearance quality of the second tunnel lining. There are many reasons for the above problems, but they are mainly caused by insufficient rigidity of the lining trolley and improper construction methods and techniques.

Steel formwork trolley structure

The steel formwork trolley structure is generally divided into the car body, formwork, hydraulic or screw support and disassembly system, which is manufactured in the factory and shipped to the site for assembly.

1. Trolley body

The trolley body adopts a truss structure, the longitudinal beams are made of 40C channel steel, 2 upper and lower sides respectively; the columns are made of HK450 steel, with a spacing of 1 per 3m, and a “meter” brace is set between the columns; the beam is 56C For the I-beam, the spacing is 1 per 1.5m; the other auxiliary components adopt HKl60c steel, and the above structure can better meet the requirements of rigidity and stability.

2. Template and assembly

Due to the large cross-section of the highway tunnel, practice has proved that the rigidity of the steel plate is less than 6mm, and it is prone to deformation after a period of use. In view of this, the template should be made of cold-rolled steel plate with a thickness of 8mm or a width of 10mm and a width of 150cm. When the formwork is processed, the rolling radius should be 5cm larger than the design clearance section radius of the tunnel to offset the construction error; the bottom end of the formwork should be 5-10cm lower than the top surface of the side trench of the tunnel to ensure that the joint between the second lining and the low side wall is not exposed. After the on-site assembly is completed and checked and corrected, the joints of the template plates are welded and the welds are smoothed. After the template is assembled, three blocks (one arch and one left and right wall) are formed. The large template can effectively suppress warping deformation.

3. Screw support and removal system

Screw support and disassembly system, the diameter of the rod body is 90mm, the longitudinal spacing is 150cm (the same as the width of the plate), and the two ends of the trolley are laterally adjusted on each side of the screw.

4. Work window setting

The size of the working window is 50×50cm, and there are 19 rows in 5 rows, that is, there are 3 in a row at the top of the dome, which are arranged alternately with 3 capping holes. There is a row on both sides above the arch line, each row has 4, the height should be about 20cm higher than the position of the embedded lighting cable pipe and junction box, so as to check and correct the position of the embedded parts during the concrete pouring process. There are 1 row of windows on the side walls on both sides, 4 in each row, and the appropriate height is 3.0m from the bottom of the formwork.

5. Determine the length of the trolley

The actual length of the trolley is preferably 1210cm, the effective length is 1200cm, and the overlap length between each ring is 10cm. Practice has proved that it is applicable when the line radius is greater than or equal to 500m, and the chord-vector difference can be offset by the screw adjustment. Too short trolley length will cause too many ring joints in the lining, which will affect the appearance of concrete and the progress. The lap length between the trolley formwork and the concrete surface of the upper ring is preferably 10-15cm. If the lap length is too small, the concrete at the lap joint of the upper ring will be easily cracked; if it is too large, the lap joint will not be easy to stick closely. Causes slurry leakage at the annular joint.

Commissioning after assembly of trolley

The trolley car body truss, local deformation of the formwork, and processing size deviation are the main reasons for the appearance quality problems of the lining such as staggered lining. After the trolley is assembled, the debugging is very important to the appearance quality of the secondary lining concrete. The following aspects should be paid attention to during the debugging:

a. After the on-site assembly of the lining trolley is completed, it must travel 3-5 times on the track, then tighten the bolts again, and strengthen welding on some of the connecting parts to improve its integrity.

b. Check whether the size of the trolley template is accurate, and the relative deviation of the structural size at both ends should not be greater than 3mm, otherwise it needs to be refurbished.

c. Use a polishing machine to thoroughly polish the surface of the steel template before lining, remove rust spots, and apply oil to prevent rust.

d. Every time 500-800m of lining is constructed, the trolley should be fully checked once, and the check is generally carried out in the tunnel with broadband.

Trolley in place

The tunnel concrete maintenance formwork

1. Track layout

The track should be steel rails above P38, wooden sleepers should be used for short sleepers, and rail pads should be used between the steel rails and short sleepers, and the track should be placed on the paved concrete floor to ensure the stability of the trolley. The track centerline coincides with the tunnel centerline as much as possible, and the deviation should be controlled within ±1cm.

2. Accurate positioning of the trolley

Trolley positioning adopts five-point positioning method, that is, a plane coordinate system is established with the center of the lining circle as the origin, and the center point of the arch template, the two hinge points of the arch template and the wall template, and the foot points of the two wall templates are controlled. The precise console car is in place. After the trolley travels to the position of the standing mold, first use the vertical screw to adjust its elevation, and then use the horizontal and lateral screws to adjust its plane position, so that the centerline of the template coincides with the centerline of the tunnel, and use the five-point positioning method to retest the platform For the cross section at both ends of the car template, pull the wire to check whether the middle template is warped or twisted until it is accurate.

In the construction of the curve section, the change in the overlap length between the left and right sides caused by the difference between the inner and outer arc lengths should also be considered, and the arc should be as smooth as possible during the adjustment process.

In order to prevent the trolley from floating during the concrete pouring process (usually up to 15mm), three 30t jacks are used to add support to the arch at the front end of the trolley to prevent the trolley from floating and causing the arch to be staggered.

Key Process Control of Molded Concrete

Pipeline municipal lining trolley

1. Raw material and concrete quality control

(1) Raw materials

The raw materials are used after passing the inspection, especially the floor materials and special materials. The crushed stone should be counter-attack crushed stone. The size of the screen hole should be strictly controlled during the production of crushed stone to ensure the shape and gradation of the crushed stone.

(2) Concrete slump control

The concrete slump is generally 14-17cm. According to the different pouring parts, the concrete slump of the wall should be small, and the arch should be larger. In the case of ensuring the pumpability of concrete, it is advisable to reduce the slump of concrete as much as possible, and improve the workability and water retention of concrete to avoid bleeding of concrete.

(3) Selection of admixture (material)

Adding an appropriate amount of high-efficiency retarding type water-reducing agent can improve the workability of concrete and increase its fluidity; adding fly ash to lining concrete is beneficial to improve the workability, water retention and compactness of concrete.

2. Concrete pouring

(1) Perfusion sequence

The concrete is poured in layers and alternately and symmetrically on the left and right sides, and the thickness of each layer is not more than lm. The height difference on both sides is controlled within 50cm . The pouring process should be continuous to avoid “cold joints” caused by stoppages. If the intermittent time exceeds 1.5h, it will be treated as construction joints.

(2) Bilateral symmetrical perfusion replacement time control
Two indicators of concrete pouring time and pouring height are used for dual control. That is, when the height of single-sided concrete pouring reaches 1m, the pipe must be replaced; the intermittent time of single-sided concrete pouring does not exceed the initial setting time of concrete. The construction of Meijianlin Tunnel stipulates that every When the side continuous perfusion time reaches 70min, the tube must be replaced.

(3) Measures to ensure the continuity of concrete pouring

a. Reasonably configure mechanical equipment and reserve sufficient wearing parts to ensure that the equipment is useful and well prepared; strengthen on-site training of mechanical equipment operators and equipment maintenance.

b. Establish an equipment inspection system before the lining operation, and the equipment fails or does not match the capacity and does not open.

c. For lining sections with a large amount of work, two sets of equipment can be used to work on the left and right sides at the same time, but the concrete pouring speed should be appropriately slowed to avoid the trolley from floating.

3. Concrete tamping

The full-time tamping hand is fixed and positioned with a plug-in vibrator to ensure the compactness of the concrete; below the arching line, it is supplemented with wooden hammer mould external percussion and tamping shovel to insert and tamping to suppress air bubbles on the concrete surface. It is strictly prohibited to drag the concrete with a vibrating rod during the pouring process.

4. Lining concrete capping

The roofing adopts the top mold center to seal the aluminum connecting pipe, and gradually pressure injects the concrete to seal the roof. When there is slurry overflow from the observation hole on the stop plate, it means that the capping is completed.

5. Demolition

According to the construction specifications, the strength achieved by the final test piece of the capped concrete on site is used to control, and the mold is removed when the strength of the molded lining concrete is not less than 2.5MPa.

6. Repair of concrete surface defects

After demoulding, if defects are found, they shall be dealt with in time after approval by the supervision engineer.

a. Air bubbles: After mixing white cement and ordinary cement according to the ratio determined by the lining surface color comparison test, they are partially filled and smoothed.

b. Circular seam treatment: draw lines with a radian ruler, cut the seams with a cutting machine, the seam depth is about 2cm, and the irregularities are locally repaired or polished by a grinder, then modified with high-grade cement mortar, and smoothed with a steel trowel. The seams are round and neat.

c. Inconsistent surface color: Use sandpaper to wipe several times.

d. Treatment of the periphery of the reserved cavern: The periphery of the reserved cavern should also be cleaned first, and then sprayed with water to moisten it. Use high-grade mortar with the same color as the molded lining to smooth and calender.

7. Several process details in lining concrete pouring operation

Tunnel waterproof board laying formwork

(1) Concrete delivery pipeline layout

The joint pipe clamp should be connected firmly to avoid bursting off, and the pipeline shall be raised above the ground with square wood, and the pipe clamp shall not directly contact the trolley components when passing through the trolley. A hose is set at the end of the concrete delivery pipeline, and the vertical distance from the hose nozzle to the pouring surface is controlled within 1.5m to avoid segregation of the concrete.

(2) Measures to ensure the thickness of the reinforced protective layer

Due to the use of pumped concrete, the pouring speed is faster, and the deformation of the steel bar is more significant, which is likely to cause the steel protection layer of the arch to be reduced, and even the bars are exposed. Therefore, it is necessary to ensure that the arch concrete pad has sufficient strength and pay attention to the concrete pouring speed during the pouring process.

(3) Control of air bubbles on the concrete surface of the reverse arc section of the side wall

In order to control the air bubbles on the concrete surface during the construction of the reverse arc, the following three measures are mainly adopted:

a. Add high-efficiency retarding water reducer (generally 1% of cement weight) and fly ash (generally about 20% of cement weight) to improve concrete performance;

b. Control the slump of concrete (usually 14cm);

c. The proper tamping method and comprehensive application can reduce the bubbles in the anti-arc section and effectively improve the surface quality of the lining concrete.

(4) Measures to overcome the dislocation of concrete joints

Staggered concrete joints is one of the common problems in the appearance quality of molded linings, but it can be overcome by taking some specific measures. The deviation of wall flatness can be controlled within 3mm, far less than the allowable value of 20mm.

a. Measures to overcome misalignment at annular joints

The following measures should be taken to overcome the misalignment of the circular joints: First, before the trolley is in place, thoroughly clean up the concrete overlapping part and the surface of the trolley overlapping part, so that the trolley and the concrete surface are as close as possible; The second is to strengthen the support of the trolley. All supports should be supported in place to ensure the overall force of the trolley. Screw supports should be added to the side walls at both ends of the trolley. The third is to add vertical supports at the top of the front end of the trolley. (Using three 30t jacks) to prevent the floating of the trolley from causing misalignment of the arch; the fourth is to slow down the concrete pouring speed of the 0-3m high part of the side wall (usually about 4 hours) and strictly control the concrete slump ( Generally 14cm); Fifth, check and eliminate the cross-section error at both ends of the trolley in time; Sixth, the center line and elevation must be controlled accurately; Seventh, ensure that the overlap length between the trolley template and the concrete of the upper ring is 10-15cm.

b. Measures to overcome the misalignment of the joints of the trolley template plates

Weld the joints of the template plates and smooth the welds to form three large templates (one arch and one on the left and right side walls) to suppress local warpage and deformation of the template during use, and avoid wrong joints of the plates station.

c. Wrong platform at the operating window of the console car

Before closing the operation window, the residual concrete slurry on the window frame must be cleaned up, wiped with a damp cloth, and then tighten the compression card, and the closing fulcrum should be plugged tightly with a wedge-shaped wood to prevent the window frame from being closed tightly and the concrete surface of the window Uneven.

(5) Measures to overcome slurry leakage

a. Treatment measures for slurry leakage at annular joints: First, the baffle should be thick, and can be made of 5cm thick wood. The wooden mold is installed radially to adapt to the irregularity of the end size. Drill holes at the ribs of the template plate at the end of the trolley Fix with channel steel and bolts; second, the lap length between the trolley steel formwork and the concrete surface of the upper ring should be 10-15cm, and should not be too large, otherwise the lap joints will not be easy to stick closely and cause slurry leakage; the third is lap joint Paste sponge strips to stop the grout on the concrete surface.

b. Treatment measures for the concrete joint mortar on the top surface of the low side wall: one is to seal the gap between the top surface of the low side wall and the bottom edge of the trolley formwork with   trapezoidal wood; the other is to pump the same grade mortar and mortar before opening The appropriate amount is 2cm flat on the low side wall, which can not only ensure the connection between the low side wall and the arch wall concrete, but also prevent the leakage of the formwork from causing the concrete to flood or expose the aggregate.

(6) Measures to overcome the inconsistency of concrete surface patterns and colors

a. Eliminate cold joints and reduce unnecessary construction joints. As mentioned above, the concrete should be layered and poured alternately and symmetrically on the left and right sides, and the pouring process should be continuous to avoid “cold joints” caused by pauses, and control the replacement time of symmetrical pouring on both sides to avoid unnecessary construction joints.

b. Use a suitable release agent. After repeated comparison experiments, the mixture of engine oil and diesel oil is mixed in a ratio of 4:6 and used as a release agent, and the effect is better. The brush should be thin and even. After the first brush, the brush should not be dipped in oil and then brush it evenly. Cut the flow range of the concrete.

Construction method and technology of low side wall

Before lining the large formwork trolley, a shaped steel formwork must be used to construct the low side wall first. There are generally two options for the construction height of low side walls: that is, slightly higher or lower than the bottom of the lining trolley formwork. The first solution requires high elevation and straightness of the low side wall, otherwise it is difficult for the console car template to be accurately positioned or the stubble joint is prone to leakage, but it is easy to demold. The second solution is easy to realize the accurate positioning of the trolley. The disadvantage is that the height difference is kept small, which makes it difficult to demold. The edges and corners of the low side wall are often broken, the height difference is too large, the gap is not easy to seal, and the slurry is easy to leak when pouring concrete.

After comparative analysis and combined with the construction experience of multiple highway tunnels, we choose the second option. The top surface of the low side wall is about 8cm lower than the bottom of the lining trolley formwork. This part is sealed with trapezoidal wood before the concrete is poured. Paste to prevent leakage.

Design, installation and operation of lining trolley

Today’s tunnel construction requires not only high quality but also fast speed. In order to ensure the quality and construction speed of the tunnel’s lining, a full-section and integral translational trolley is used in the lining construction to ensure the “inside real and outside beauty” of the lining The construction progress of the tunnel.

First, design of lining trolley

The formwork trolley used in tunnel construction is a translational lining trolley. The trolley and formwork are a complete system. The formwork is formed by laying steel plates on the profile steel as the framework to form a shell, and is equipped with a retractable mechanism.

The overall rigidity, strength and stability of the trolley under the construction load of one-time concrete pouring were considered during the design of the trolley. At the same time, it should be considered that the template can be easily and quickly replaced when lining different end faces. There must be enough passing section under the trolley to facilitate the smooth passage of construction machinery.

1, trolley template part

The formwork trolley used in the tunnel has a total length of 12m and consists of 8 splicing sections with a length of 1.5m. Among them, it is mainly composed of vault widening block, arch waist template, arch foot and side wall template, and curved wall lining side wall template. The arch foot and the side wall template are designed as a whole, which is hinged with the arch waist template, and the other modules are connected by bolts. The dome widening block can be replaced according to different widening requirements of the curve. The arch waist template is hinged with the arch foot side wall template, and the side wall template is opened and closed by 6 lateral hydraulic cylinders on the trolley. The whole set of templates are vertically raised and lowered by four hydraulic cylinders on the top of the trolley. There are 32 windows on the arch waist and side wall formwork for concrete pouring and vibrating. An attached vibrator is installed on the arch waist mold board. The end of the trolley is equipped with a plug steel plate to facilitate the concrete plugging of the lining end.

2, the overall part of the lining trolley:

The trolley is a truss structure as a whole, the beams are all made of box-shaped cross-section structure, and the other parts are of steel composite structure. The trolley is divided into upper and lower platforms, and 1500mm air ducts can pass between the platforms. The lower part of the trolley is equipped with a wheel-rail walking mechanism, which is driven by two 7.5kw three-phase asynchronous motors for short-distance movement.

3, electric hydraulic system:

a. Hydraulic system: It consists of 4 vertical oil cylinders for lifting the template, 6 lateral oil cylinders for opening and closing the side template, and high-pressure oil pump, one-way valve, overflow valve, oil pipe, etc.

b. The electricity used on the trolley is divided into lighting and power electricity. The lighting must meet the requirements of safe electricity use, and be used for lighting after being reduced to 36V by a low-voltage transformer. The power consumption is 380V, which is mainly used for trolley walking, hydraulic oil pump and vibrating rod. The power line must be equipped with electric leakage protector and knife box and other safe power equipment.

Second, main performance of trolley

Serial number Project Unit Content Remarks
1 Template size m 12*5.04 Length * width
2 Clearance under the trolley m 2.9*2.9 Length * width
3 Trolley track center distance m 3.2  
4 Vertical cylinder adjustment cm 25  
5 Horizontal adjustment cm 5  
6 Number of vertical cylinders Piece 4  
7 Number of lateral cylinders Piece 6 Wall waist
8 Number of screw jacks Piece 42 12 up and down, 30 left and right
9 Perfusion window Piece 32  

Third, the use of template trolley

1. Move the trolley into place:

a. Laying the track before the trolley moves, the requirements are as follows:

Trolley track laying requirements

Serial number Project Parameter
1 Track type 38kg/m
2 Gauge 320cm
3 Allowable error of gauge ±3cm
4 Allowable offset between track center and tunnel center ≤3cm
5 Height from the top surface of the track to the bottom surface ≤30cm
6 Rail surface difference on the left and right sides of the same cross section <1cm
7 Track longitudinal slope Consistent with the tunnel longitudinal slope
8 Sleeper specifications (length * width * height) 60*22*16cm
9 Sleeper spacing ≤50cm

b. Use the traveling mechanism of the trolley to move the trolley to the section to be lined, and fix the traveling part of the trolley;

c. Descaling, derusting, and brushing release agent on the template.

2. Trolley positioning and moulding:

Tunnel waterproof board laying formwork

a. When positioning the standing formwork, the back end of the formwork should be based on the concrete surface of the lined section, and the back end of the formwork should be raised against the top surface of the concrete vault of the lined section, and the slab seams should be aligned;

b. Raise the front end of the template to the design elevation (plus reserve);

c. Use a horizontal jack to align the vertical line of the front end of the template with the center of the ground. The curve segment should make the center line of the template coincide with the black line of the curve of the group of lining segments;

d. Spread the side board and stick to the low side wall. It is required that the distance from the bottom of the formwork to the centerline of the tunnel and the distance from the formwork to the centerline at the arch line must meet the design net width requirements.

e. Matters needing attention:

①The overlapping length between the trolley formwork and the lining ≤5cm can effectively control the staggered concrete platform;

②The sleepers under the trolley should not be too high, and it is necessary to ensure that there is enough room for contraction after the template is raised to the design elevation to ensure that the trolley can pass through the lining section smoothly after being folded;

③In the pouring lining concrete, when there is a large or small avoidance hole, all the templates of the avoidance hole should be installed first, and then the formwork of the formwork trolley shall be carried out;

④For the specific operation method of the trolley, please refer to the manual of the template trolley.

3. Reinforcement of template:

a. After the above process is completed, a sponge strip is inserted at the overlapping part of the formwork and concrete to prevent leakage;

b. Fasten the support jacks on the upper and lower parts, and the plug plates can be installed at the same time;

c. Tighten the horizontal jacks on both sides of the trolley, requiring the jacks to be perpendicular to the template and the support;

d. Matters needing attention:

①The wall waist part of the overlapping end with the lining must be reinforced with a jack to make it close to the concrete surface;

② At least 6 supports shall be used to reinforce the side of the overlap between the lower part of the trolley and the side wall foundation;

③The position of the screw must be horizontally supported and perpendicular to the template. It must not be added to the screw base, but must be added to the column;

④The screw at the wall waist of the front end of the formwork trolley (near the face of the hand) cannot be reinforced too tightly, and no support can be added to ensure that the formwork can be closely attached to the concrete when the next set of linings are laid;

⑤The car shelter model can be made of wood, steel or steel-wood according to the actual situation. The model is required to have sufficient rigidity, and the surface is flat and free of errors. It is best to use an integrally formed steel mold. The connecting seam between the avoiding hole and the formwork trolley should be tightly sealed.

Two-lane highway lining trolley

4. Concrete pouring

a. The automatic metering concrete mixing station can ensure the accuracy of various concrete parameters and the uniform mixing. Transported by a concrete tanker and poured by a pump to ensure the quality of concrete construction;
b. Pumping concrete must be mixed with pumping agent, the slump of concrete is 8cm~15cm, and the water-cement ratio is not more than 0.7. Check the slump after opening and adjust according to the situation;

c. Before pumping the concrete, pump the mortar with the same mark as the concrete to lubricate the pipe wall. The pumping of concrete should be carried out continuously, and the interruption time should generally not exceed 20 minutes;

d. The concrete of the side wall and the arch foot part can be poured by the window on the mold board, and vibrated with the plug-in vibrating rod;

e. The concrete of the arch is injected into the mould by the sprinkler port on the top mould board. When the first section of concrete lining is poured by the trolley, the concrete pumping pipe presses the concrete into the model from the spray nozzle in the middle, so that the concrete is squeezed from the middle forward and the rear ends to achieve the purpose of capping.

When overlapping with the lining concrete, the concrete is pressed in from the sprinkler nozzle at the overlapping end, so that the concrete gradually moves outward to achieve the purpose of capping. If hopped and segmented pouring is used, vent holes should be punched at both ends of the lining vault of the trolley during the concrete construction of the sealing section to prevent the air from being removed during pouring. The concrete of the arch can be vibrated with the attached vibrator on the trolley, or the plug-in vibrator can be used to vibrate the inner surface of the die plate;

f. Matters needing attention:

①The height difference between the left and right sides of the concrete pouring is not more than 50cm, and the pipes fall frequently to prevent bias;

②When the side wall concrete is poured, the front end of the pump pipe should be a rubber conveying pipe and extend into the window, and the pipe mouth should not exceed 2 meters from the concrete surface;

③For the part with over-excavation greater than 30cm, it can be backfilled with rubble concrete or grout rubble;

④Concrete construction is carried out strictly in accordance with the “Concrete Construction Code”.

5. Demoulding and maintenance:

a. The demoulding time of concrete meets the following requirements:

①The concrete strength of the arch wall that is not subject to external load reaches 5Mpa, or the concrete surface and edges and corners will not be damaged when the form is removed, and it can bear its own weight;

②The arch wall concrete with less surrounding rock pressure reaches 70% of the design strength.

b. Trolley demoulding:

① Loosen the upper and lower side mold screw jacks;

②Loosen the upper and lower middle supporting screw jacks;

③ Use the side form hydraulic jack to pull the side wall form towards the center of the tunnel and shrink it by 15-20cm to separate the side form from the concrete surface;

④ Use the side mold hydraulic jack to lower the arch formwork 10~15cm to separate the arch formwork from the concrete surface.

C. Concrete curing:

①Cure the concrete immediately after 10-20 hours of pouring, and the curing time shall not be less than 7 days;

②For the lining and open tunnel near the tunnel portal, the maintenance should be strengthened due to the greater impact from outside the tunnel, and the maintenance time should not be less than 14 days.

Single-track railway lining trolley

Fourth, the restructuring of the die pull trolley

The tunnel lining section includes: 30cm widened and 50cm widened curved wall integral lining, 30cm, 50cm and unwidened straight wall integral lining, so the formwork should be replaced in different lining sections.

1. Replacement of side panels: The replacement of side wall templates needs to be done outside the hole. After moving the formwork trolley to the outside of the hole, first remove the connecting bolts between the formwork and between the formwork and the longitudinal beam, and then hang the side plate with a crane, remove the latch between the side plate and the arched waist formwork, and set the formwork Lift off the trolley. Replace the curved or straight wall template, hoist the template with a crane, the process: the opposite of the disassembly. After replacement, push the template trolley to the designated position for construction.

2. Replacement of widening module: Considering the need for widening when designing the trolley, a replaceable die plate is designed in the center of the vault. When the dome is not widened, the center of the dome is 35cm wide, when it is 30cm widened, it is 65cm wide, and when 50cm widened, it is 85cm wide. The widening template and the arch-waist template are connected by bolts. When replacing, it can be replaced manually in the hole. Remove the longitudinal connecting bolts between the mold plates, and then remove the connecting bolts between the center template and the arch-waist template, and replace them with widened ones. Tighten the bolts after the template.

During the construction, it was found that the wall waist of the overlapping part of the trolley and the lining cannot be closely attached to the concrete surface after the screw is tightened, and the expansion mode will appear during the pouring process, until the wall waist at the lining connection is staggered by 5 ~8mm or so. In order to ensure the apparent quality of the concrete and reduce the misalignment, a 2m-long vertical channel steel is added to the back of the formwork and a screw is installed between the vertical channel and the column at the wall waist part of the lap end of the formwork and the concrete. Tighten the lead screw before construction, so that the formwork can be closely attached to the concrete surface. After treatment, the misalignment can be reduced to about 2mm.

Five, formwork trolley entry and exit organization

1. Lay the track before the trolley moves, and the laying of the track must meet the requirements.

2. Mobile trolley:

a. For trackless transportation, a forklift can be used to drag the trolley, move about 25 meters to remove the rear track of the trolley and move it to the front of the trolley for connection, and then drag the trolley to the designated position;

b. The trolley can be driven by a battery car when transporting on rails. When the transport track is in the center of the line, the trolley track will not affect each other. If the line track is on the bottom side, the trolley rail on the same side as the line track can be directly laid on the sleepers of the transportation line, and the battery car can be towed in front;

c. When moving in a short distance, the traveling mechanism of the trolley can be used to move, but the power supply plug must be connected for the traveling motor of the trolley;

3. The method of trolley entering and exiting the hole is the same. It should be noted that when the track is laid, it overlaps with the center of the line as much as possible to prevent the trolley from shifting and scratching the concrete surface. The moving speed cannot be too fast, and it can be stopped at any time when an accident occurs. When stopping moving, a stop wedge should be added to the wheels to prevent accidental sliding of the trolley.

Construction standards for tunnel construction facilities

During the construction of the tunnel, construction facilities that meet the construction needs should be set up at each driving end, and the construction facilities should be managed in a closed manner. Tunnel construction facilities generally mainly refer to tunnel office and living facilities, jet concrete mixing station, steel bar processing plant (or assembly plant), construction air supply facilities, oil depot, explosive depot, etc.

The construction of tunnel construction facilities shall comply with the provisions of laws and regulations and comply with the requirements of relevant competent authorities, and follow the principle of “adapting measures to local conditions, saving land, protecting the environment, being safe and reliable, orderly, fully functional, reasonable layout, convenient for life, and satisfying production.” in principle.

The layout of the tunnel construction site should be carried out in accordance with the conditions of the project scale, construction period, topographic characteristics, spoil yard and water source, and in accordance with local conditions, making full use of the topography, rational layout, and overall arrangement.

The construction of office and living facilities shall be constructed in accordance with the relevant requirements of “Construction Site Construction”; the oil depot and explosive depot shall be implemented in accordance with the relevant requirements of “Other Material Warehouse and Storage”; the construction of inclined shafts and vertical shafts shall be implemented by reference.

1. Basic requirements for site selection

The tunnel construction facilities should be arranged near the tunnel entrance as far as possible. It is strictly forbidden to damage the mountain near the entrance and affect the safety of tunnel construction. Sites such as Yanyan; office and living facilities should be 50m away from the entrance of the cave; communication is smooth to meet the requirements of information management.

2. Hardware facilities requirements

total requirements

(1) The scale and function of the tunnel construction facilities should meet the relevant requirements as promised in the bidding documents and meet the construction needs, and reasonably divide the tunnel office and living facilities, spray concrete mixing station, steel processing plant, construction air supply facilities, oil depot, explosive depot, etc.

(2) Equipped with at least one set of backup power source for tunnel construction, and the generator should be as far away from the living area as possible.

(3) Fire-fighting facilities and temporary electricity use in tunnel construction facilities shall be handled in accordance with relevant documents issued by relevant industry authorities.

(4) Production and living areas should be prepared for temporary rainwater, sewage discharge and garbage disposal to prevent environmental pollution.

Specific requirements

1) Jet concrete mixing station

The sprayed concrete for the initial support can be supplied centrally by the mixing station, or a small mixing station specially used for sprayed concrete construction can be built near the tunnel entrance, but the following requirements must be met:

(1) The mixer model (mixing capacity) should be calculated based on the tunnel construction period and the total amount of shotcrete. A forced mixer must be used, with dual operation, and a single machine with a rated mixing capacity of not less than 30m3/h.

(2) Mixing equipment with two warehouses for automatic metering should be used. It should be equipped with no less than two bulk cement tanks. Each mixing station shall be equipped with 2×2 storage bins.

(3) The floor area is not less than 1000 m2.

(4) For silo construction, site hardening, drainage and fire-fighting facilities, refer to the relevant requirements of “Mixing Station Construction”.

2) Steel bar processing plant

In principle, the steel bar processing of the tunnel adopts the centralized processing of the steel bar processing plant. For long and extra-long tunnels, a tunnel steel bar processing plant can be built near the entrance, but the following requirements must be met:

(1) The processing shed area is not less than 800m2.

(2) The functional areas are reasonably divided into raw material storage area, steel mesh processing area, grid arch processing area, section steel arch processing area, and finished semi-finished product storage area.

(3) A positioning frame should be installed in the processing area to meet the requirements of processing accuracy.

(4) At least one gantry crane no less than 5t and one set of cold bending equipment for section steel shall be equipped in the long and extra-long tunnel yard. Other equipment should meet the requirements of steel bar processing.

(5) The construction of processing shed, site hardening, drainage and fire-fighting facilities shall refer to the relevant requirements of “Rebar Processing Plant Construction”.

3) Construction of air supply facilities

(1) The equipment capacity of the air compressor station should be able to meet the requirements of maximum air consumption and air pressure of various air machines working at the same time.

(2) When there are multiple openings that require centralized air supply, they can be placed in a moderate location, but they should be close to the opening with a large air volume. Long and large tunnels should be equipped with independent air compressor stations, which should be arranged on both sides of the opening. The foundation is firm, there is no damage from collapse and falling rocks around, and it is not threatened by floods. The air compressor station shall have waterproof, cooling and lightning protection measures.

(3) A circulating pool (2m×2m×1m) should be set up beside the air compressor station.

(4) The pipeline should be laid firmly and smoothly, with tight joints and no air leakage.

(5) Drainage ditch (depth 0.4m×width 0.3m) shall be set all around, and another fence shall be set when conditions are available.

3) Cavern site and facilities

(1) The site of the entrance of the cave must be hardened concrete, and the range is that the longitudinal distance from the entrance of the cave should not be less than 30m. It is required to use a 20cm gravel cushion, and the surface layer should be 20cm thick C20 concrete. It can be considered to set the base of the tunnel entrance section as a concrete base, and implement it in advance.

(2) Duty rooms and railings are set up at each entrance of the cave, and a dedicated person is responsible for registration and management of entrance and exit.

①The specification of the duty room is not less than 2mx3m, and the material should be a prefab house with colored steel tiles.

② Railings should be installed at the entrance of the cave, and it is advisable to adopt an integrated intelligent barrier machine (automatic railing).

Long tunnels over 1km must be equipped with an electronic management system for tunnel safety personnel. The personnel electronic management system is mainly composed of electronic IC card sensors, LED electronic displays, card reader chips, computer systems, etc., which will reflect the number of personnel entering and exiting the cave, the type of work, time, the distribution position in the cave, and the construction status of each process in the cave. On the electronic display screen, the computer system can store personnel information for future reference. The size of the electronic screen is not less than 2.5mx2m, and it is erected with a stainless steel bracket. For joint-arch tunnels above 500m, an electronic management system for tunnel safety personnel must also be installed in accordance with the above requirements.

(4) Long and large tunnels over 2km must be equipped with a tunnel video monitoring system. The surveillance system cameras are installed in the entrance area, and the number of settings meets the requirements of the surveillance range.

(5) A safety mirror and a safety commentary stand are set up at a conspicuous place at the entrance of the cave.

4) Tunnel ventilation facilities

For tunnels over 150m, duct ventilation must be implemented for tunnel construction. Long and large tunnels and gas tunnels must prepare ventilation plans.

The foundation of the ventilating frame is fixed by concrete, channel steel or I-steel is welded at 2 to 4 times the total weight of the load-bearing ventilator, and set at a reasonable position outside the hole.

5) Drainage facilities at the entrance of the cave

The intercepting ditch on the top of the cave is constructed before the construction of the earth and stone works at the entrance of the cave, and the drainage system of the cave entrance is improved according to the topography. A 16mx8mx5m (length x width x depth) sedimentation tank is set 20 ~ 30m away from the tunnel, and safety guardrails are set around the drainage sedimentation tank and a dense mesh safety net is hung.

6) Construction of water supply facilities

(1) When there is a high mountain natural water source, high-level pools should be built to store water. The location of the pool should not be set on the roof of the tunnel, and the height of the pool should be able to meet the water supply pressure required by the construction (water pressure not less than 0.3MPa).
(2) For tunnels where it is difficult to build a high-level pool, a frequency conversion high-pressure water supply device should be used to meet the construction needs.

(3) The laying of water supply pipelines should avoid areas with heavy traffic and areas with poor geology, and the laying of pipelines should not be in the form of elevated. The pipeline should be laid smoothly, without water leakage, and tightly connected.

7) Construction of power supply facilities

(1) For short tunnels, high pressure should be used to reach the entrance, and then low pressure should be used to enter the tunnel. For long and extra-long tunnels, high and medium pressure entry should be considered to meet the construction needs.

(2) The capacity of the transformer should be determined according to the total consumption of electrical equipment. When the capacity of a single electric equipment exceeds 1/3 of the capacity of the transformer, additional starting capacity should be increased.

(3) The substation should be located near the load concentration location and on the side of the power supply line. Long and extra-long tunnels should be located on both sides of the entrance. The site has a solid foundation, surrounded by 2.5m high wire mesh or fence.

(4) When the power line of the substation needs to cross the construction area, the minimum height from its lowest point to the sidewalk and transportation line is 7.5m.

3. Civilized construction and management

1)  Signage of the entrance site

A fixed banner should be set up outside the interception ditch at the top of the two tunnels, including the name of the tunnel, construction unit, etc., with red letters on a white background, and a single font not less than 1.2mx1.5m. Appropriate locations at the entrance of the two holes should set up a project overview card, a list of management personnel, and a supervisory telephone card, a quality assurance card, a safety production card, a civilized construction card, a fire protection card, a risk notification card, a safety warning card, and a construction site layout plan, with conditions Should be set between the two entrances, the main contents are as follows:

Project overview card: a brief introduction to the tunnel’s engineering volume, main structure, geological conditions, construction plan, construction schedule, etc.;.

List of management personnel and supervision telephone cards: publicize the project organization and key management personnel of tunnel construction;

Quality assurance card: quality management measures taken in conjunction with tunnel construction content, scale and characteristics;
Safety production license: safety management system or measures, etc.;

Fire protection card: fire protection, security management system or measures, etc.;

Civilized construction card: civilized construction system or measures taken in combination with the content, scale and characteristics of tunnel construction;

Risk notice board: Informs about possible hazards and pre-control measures during tunnel construction;

Safety warning signs: Inform the pictures and definitions of safety warnings, prohibitions and instruction signs set during tunnel construction;

The layout of the construction site: computer color inkjet is used, and the layout of the construction site is expressed in a graphic manner, indicating the location, area, and function.

The size of each sign is 2.5mx 2m, the bottom of the sign is 0.8m from the ground, and the upper part is equipped with a rain shed, made of stainless steel or iron material.

The roof of the cave is welded with a steel reinforcement bracket, and warning signs such as “safety helmet must be worn when entering the cave, beware of electric shock, and safety” are hung. The size of the warning sign is 8.0mx 1.0m.

Set up other signs in eye-catching locations according to the entrance of the cave, including the leader’s shift system card, the safety production operation procedure card, the clean government supervision card, the registration card for entry and exit personnel, the construction progress card, the tunnel construction process drawing, and the safety publicity column. The main contents are as follows:

Leadership system card: Inform the leader of the class of the time arrangement, contact number, reporting process when encountering an emergency, etc., and clarify the scope of responsibility or work content of the leader. The size is 0.8mx 1.2m.

Safety operation regulations card: The safety operation regulations of the main construction procedures, equipment and work types of the tunnel are collectively set; the height is 1.2m, and the length is determined according to the content.

Integrity supervision card: mainly clarify the integrity system, the integrity leadership team, the integrity supervision team and the integrity supervision telephone, etc.; the size is 2mx 1.2m.

Registration card for entry and exit personnel (tunnels with electronic display screens do not need to be set up): The operator must have a card in hand, put the card in the hole, and flop the card out of the hole. The size is 3mx 1.2m.

Construction progress sign (tunnels with electronic display screens do not need to be set): Mainly reflect the construction progress of tunnel excavation, initial support, paving, and second lining. The size is 2mx 1.2m.

Tunnel construction process map (tunnels with electronic display screens do not need to be set up): reflect the process conditions under construction in the tunnel. Round clock type with a diameter of 2m.

Safety Bulletin: It mainly promotes the importance of safe production in the form of pictures, and explains safety knowledge and the use of safety protection products. The height is 1.2m, and the length depends on the content. Guide signs are set in the entrance of the cave.

2) Other facilities identification signs

(1) The duty room is clearly marked with “Please register for entering and exiting the cave” and “Duty room”. The “Tunnel Duty System” sign is hung inside, the size is 600mmx 800mm.

(2) At the entrance of the substation, a post safety operation procedure card and a warning sign of “power distribution, no idlers should be allowed to enter” are set up at the entrance of the substation; a “high risk” warning sign (0.6mx0.6m) is hung beside the transformer. The size of the operating instructions board is 600mmx 800mm, and the size of the warning board is 800mmx 600mm.

(3) At the entrance of the air compressor station, there is a post safety operation procedure card and a driver’s job responsibility card. The “Beware of electric shock, pay attention to safety” notice board is hung on the wall of the station building. The size of the operation procedure card is 600mmx 800mm and the size of the notice board is 800mmx 600mm.

(4) A safety operation instruction card (600mmx 800mm) and a warning sign (400mmx 300mm) should be set up at the backup power supply.

(5) Indication signs (400mmx 300mm) and operating instructions (600mmx 800mm) shall be set at the fire extinguisher.