Principles of Tunnel Construction Equipment Configuration

The mechanized construction of the tunnel has experienced three stages: small equipment drilling and blasting construction, large trackless transportation equipment drilling and blasting construction, and non-drilling and blasting construction. Part of the mechanized operation is gradually embarked on a process of comprehensive mechanized operation. From manual excavation to the use of TBM (tunnel boring machine), the current comprehensive level of tunnel mechanization construction has made a qualitative leap compared with the last century.

Principles of Tunnel Construction Machinery Configuration

Productivity: refers to the comprehensive performance and production capacity of the production work surface formed by the combination of single machines. The selection and configuration of tunnel construction machinery should start with the overall capacity after the configuration of the machinery, so that the mechanical performance of each single machine can be matched with the overall production capacity to achieve the best combination that is both economical and reasonable.

Reliability: refers to the requirement that each single machine can maintain its good technical performance stably during operation, and reliably complete the rated power required for the construction period under the specified time and construction conditions.

Safety: One refers to the safe operation function of the machine itself; the other refers to the safety guarantee for equipment operators and surrounding construction personnel when the machine is running, and the machine should be equipped with corresponding safety protection devices.
Durability: It means that each single unit in the configuration unit should be durable and match the technical life.

Maintainability: Refers to the configuration of the equipment is easy to check, repair and maintain, which is conducive to the purchase and storage of equipment spare parts.

Economical: It means that economical and reasonable energy-saving equipment should be considered first when configuring mechanical equipment, and it should be based on national conditions and try to face the domestic market. The equipment configured should be adapted to the status and investment capacity of the tunnel itself.

Adaptability: It means that the equipment can adapt to different construction schemes under various geological conditions and can meet the construction needs of auxiliary construction methods.

Pipeline municipal lining trolley

Several key issues that must be solved when configuring equipment

The construction progress depends not only on the level of mechanization and the production capacity of the configuration equipment, but also on the management and scheduling of the mechanical equipment on site, so that different equipment can be used reasonably. Maximize equipment operators. The comprehensive quality of equipment maintenance personnel and equipment management personnel can effectively reduce the failure rate and shutdown rate of equipment to the lowest point and ensure the smooth progress of construction and production.

To solve the problem of matching the parts and the life of the whole machine, it is necessary to have a certain degree of foresight and sufficient spare parts reserves. Solve the configuration and connection of construction machinery and civil technology. For large-scale machinery and equipment to be transported in the tunnel, the corresponding transportation track must be laid. The shunting track in the tunnel is reasonably arranged, which is conducive to avoiding vehicles and saves shunting. time.

The ventilation and dust removal equipment and the water-proof and drainage equipment in the tunnel should be included in the equipment configuration. The main sources of dust and harmful gases in the tunnel are harmful gases generated during construction blasting and dust generated by sprayed concrete operations. Face construction excavation, supporting sprayed concrete, secondary lining protection working face and parallel operation of inverted arch bottom inspection. According to the specific construction situation and project construction needs, accurately adjust the three operation line procedures and reasonable spacing to minimize the mutual interference of various construction links.

Tunnel waterproof board laying formwork

Principles of mechanical equipment configuration

The configuration of tunnel construction equipment must first meet the construction period, quality, safety, environmental protection, etc. required by the construction contract, as well as technical and economic conditions. Technical conditions include workload, work efficiency, various consumption, operability, versatility, durability, and ease of maintenance; economic conditions include purchase costs (lease costs), utilization rate, construction period requirements, reasonable construction schedules, etc.

The specific configuration principles are:

It should be matched with the construction plan and compatible with the design requirements of the construction organization. It should have the ability to adapt to different surrounding rock conditions and be compatible with the overall quality and management level of operators, maintenance personnel, and management personnel.

Due to the long construction time of Qiling Tunnel, the remote location, and the difficulty in purchasing equipment accessories, we conduct professional training for equipment operators and maintenance personnel, and we must understand the condition of each equipment clearly to achieve predictability of equipment maintenance , Procurement of spare parts for maintenance in time.

Mechanical equipment commonly used in tunnel construction

The tunnel concrete maintenance formwork

TBM (Tunnel Boring Machine)

TBM can be divided into three types according to the tunneling type: open TBM, single-shield TBM, and double-shield TBM.

(1) Open TBM. Typical models include the double-row support shoe structure of German With and the single-row support shoe structure of Robbins of the United States, which are suitable for tunnel construction with relatively stable rock formations. In the construction of relatively broken rock formations, it is necessary to carry out spray-anchor support in time behind the shield, and the final protection method is the secondary lining of reinforced concrete.

(2) Single shield TBM. Unlike the open TBM, the single-shield TBM is equipped with a complete circular shield. The propulsion depends on the propulsion cylinder to support the installed tube or the overall lining to obtain a reaction force. The single-shield TBM cannot be carried out at the same time as the tunneling and installation of the segments, and the progress is slow, so the application is relatively small.

(3) Double shield type TBM. The propulsion principle is the same as the single-shield TBM, but it is equipped with front and rear shields, with a telescopic shield between the front and rear shields, and a set of support boots on the rear shield. When the geological conditions are good, the double-shield TBM and segment installation can be carried out at the same time, and the tunneling speed is faster; when the geological conditions are poor, the double-shield TBM adopts the single-shield TBM mode.

Excavation equipment

Hydraulic rock drilling rig. According to the structure, it can be divided into gantry type and solid web type. According to the walking mode, it can be divided into tire type, track type and crawler type. The abdomen of the gantry-type rock drilling rig can pass slag transportation vehicles, which effectively utilizes the limited cross-sectional space in the tunnel, so that the construction equipment on each work surface does not interfere with each other, and effectively improves the efficiency of the equipment. It is often used in single-track railway tunnels. construction. The hydraulic rock drilling rig has high efficiency in excavation and drilling operations, low labor intensity, and good working environment conditions, but the one-time investment is relatively large.

Multifunctional excavation trolley. In order to reduce investment, in the early 1990s, domestic tunnel construction units developed a pneumatic drill multi-function rig supporting method. Its advantages are: easy production, low cost, easy promotion; strong flexibility and wide application; it is conducive to full-face blasting technology The implementation of the blasting effect is good, and the advancement speed is relatively fast, which is suitable for the basic national conditions of sufficient and cheap domestic labor. This kind of excavation method is generally accepted for a certain period of time due to various advantages, but there are also serious shortcomings, that is, low technology content, high labor intensity of workers, poor working environment conditions, and cannot meet the needs of the development of the situation.

Transportation Equipment

There are three main methods of tunnel waste slag transportation: trackless transportation, track transportation and belt transportation. The first two transportation methods are commonly used. Belt transportation is only used in a small number of tunnel constructions.

Trackless transportation uses dump trucks as a means of transportation and is mostly used in the construction of large-section tunnels and short-distance tunnels. The advantage is that it is mobile and flexible, and the waste slag is not allowed to be transported twice and can be transported directly to the waste slag yard. The disadvantages are serious exhaust gas and noise pollution in the tunnel, serious damage to the invert of the tunnel bottom, high tire consumption, and greater restriction in the construction of small-section tunnels.

Rail transportation Laying tracks in the tunnel, using battery trucks to pull the slag truck and feed truck for transportation. Its advantages are no waste gas and noise pollution, good ventilation effect, and no damage to the invert of the tunnel bottom. The disadvantages are poor maneuverability, large one-time investment, complicated construction management, and long distance from the waste slag field, requiring a secondary waste slag transfer station outside the cave.

Support lining equipment

Initial support equipment. In tunnel construction, the initial support adopts sprayed concrete with anchor rods, hanging nets, and steel arches. Concrete spraying machines are divided into dry spraying and wet spraying, according to the structure can be divided into rotor type and piston type. The rotor type structure is simple and the price is low. The piston type is mainly used as a wet jet, with high jet quality, and can be used for steel fiber jetting, and the price is relatively high.

Secondary lining equipment. In tunnel construction, the mechanical equipment used for concrete injection lining has a variety of configurations according to different construction techniques. The main machinery includes concrete mixing station, concrete transport tanker, concrete delivery pump, lining formwork trolley and other equipment.

Taking into account the construction period and overall economic benefits of the tunnel, a multi-functional excavation trolley is used for operation. The waste slag yard is far away from the entrance of the cave and is restricted by the conditions of the entrance. The dump truck is used to discharge the slag and transported to the waste slag yard at one time. The initial support adopts wet spraying machine for concrete spraying. The secondary lining is supported by a lining template, and the concrete pump is used for construction.

All in all, the configuration of tunnel construction machinery and equipment is not as advanced as possible. It should be considered from the overall rational configuration. In addition to the social environment and safety production needs, the first consideration is technical and economic conditions. When the economic conditions are met, the need for technical conditions must be considered.

Six methods of tunnel construction

In the current tunnel construction practice, considering the construction cost and construction speed, the selection sequence of the construction method is: full-section method one→bench method→circular excavation method with core soil method→intermediate wall method (CD method)→cross middle wall method (CRD method)→Double-side-side pilot pit method is considered from the perspective of construction safety, and the order of selection should be reversed.

How to make the right choice should be comprehensively considered based on the actual situation, but it must meet the requirements of safety, speed, quality and environmental protection, so as to achieve the purpose of avoiding risks, accelerating progress and saving investment.

Full-face excavation

The full-section excavation method is a construction method in which the lining is constructed by blasting the shape at one time according to the design contour.

1. Applicable conditions:

(1) The surrounding rock of Grade 1~IV, when used in Grade IV surrounding rock, the surrounding rock should have the conditions to maintain its own stability during the period from full-face excavation to the initial support.

(2) There are drilling rigs or self-made work benches and high-efficiency shipping machinery and equipment.

(3) The length of the tunnel or the length of the construction section should not be too short. According to experience, it should not be less than 1km. Otherwise, large-scale mechanized construction is used, which is less economical.

2. The tunnel mechanized construction has three main operation lines:

(1) Excavation line: drilling trolley, charging trolley, loader with dump truck (trackless transportation), slag loading machine with mining car and battery car or diesel locomotive (tracked transportation).

(2) Anchor shotcreting line: concrete spraying machine, concrete spraying manipulator, anchoring shotcreting work platform, feeding and transportation equipment and bolt grouting equipment.

(3) Mould building and village masonry work line: concrete mixing equipment, concrete truck and pump, waterproof layer working platform, lining steel mould trolley.

3. Construction features of full-face method:

(1) Excavation section and work space are large and interference is small;

(2) Conditions to make full use of machinery and reduce manpower;

(3) There are few procedures, which is convenient for construction organization and management, and improves working conditions;

(4) Excavation takes shape at one time, which has less disturbance to surrounding rock and is beneficial to the stability of surrounding rock.

Step method construction

The step method is to excavate the upper half of the section first, and then excavate the lower half of the section at the same time after the excavation reaches a certain length, and the upper and lower half of the section go in parallel at the same time; according to the length of the steps, there are three types: long steps, short steps and ultra-short steps . In recent years, due to the design of large-section tunnels, there have been three-step temporary inversion methods and even multi-step methods.

1. As for which step method should be used in construction, it should be decided according to the following two conditions:

(1) The time required for the initial support to form a closed section. The worse the surrounding rock, the shorter the closing time.

Two-lane highway lining trolley

(2) Requirements for the size of the construction site for the excavation, support, and ballasting of mechanical equipment used in the construction of the upper section.

In the weak surrounding rock, the former should be the main one, while the latter should be taken into consideration to ensure construction safety. When the surrounding rock conditions are good, the main consideration is how to better exert the mechanical efficiency and ensure the economic efficiency of construction, so only the latter condition should be considered.

2. The advantages and disadvantages of the step excavation method:

The step excavation method can have enough working space and considerable construction speed. However, the upper and lower operations have interference: although step excavation increases the number of disturbances to the surrounding rock, the step is conducive to the stability of the excavation surface. Especially after the upper part is excavated and supported, the lower part is safer, but attention should be paid to the influence of the lower part on the stability of the upper part.

3. Pay attention to the following points when excavating steps:

(1) Solve the problem of mutual interference between upper and lower half section operations. The micro steps are basically combined into one working face for simultaneous excavation; the long steps are basically opened, and the interference is small: the short steps have greater interference, and attention should be paid to the work organization. For tunnels with a short length, the upper half of the section can be penetrated before the lower half of the section is constructed.

(2) When excavating the lower part, attention should be paid to the stability of the upper part. If the stability of the surrounding rock is good, it can be excavated in stages; if the stability of the surrounding rock is poor, the lower excavation cycle length should be shortened; if the stability is worse, it can be staggered to the left and right, or the middle trough can be pulled first before digging Side gang.

(3) After the excavation of the lower side wall, the concrete must be sprayed immediately and the initial support shall be made according to the regulations.

(4) The measurement work must be timely to observe the displacement value of the vault, the arch foot and the middle of the side wall. When the speed is found to increase, the invert arch should be closed immediately.

The core soil method for annular excavation

The tunnel concrete maintenance formwork

The following points should be paid attention to in the ring excavation and core soil method:

(1) The circular excavation footage should be such that the core soil area should not be less than 50% of the entire section area.

(2) Spray anchor support and steel frame support should be constructed in time after excavation. Adjacent steel frames must be connected by steel bars, and the angle lock anchors should be designed and constructed according to construction requirements.

(3) When the surrounding rock geological conditions are poor and the self-stabilization time is short, advance support should be carried out according to the design requirements before excavation.

(4) The excavation of the core soil and the lower steps should be completed and the shotcrete shall reach 70% of the design strength.

The next door method (CD method)

The CD method is a construction method in which one side of the tunnel is first excavated in a large-span tunnel with weak surrounding rock, and the middle wall is constructed, and then the other side is excavated. It is mainly used in double-line tunnels with deep-buried hard rock in Class IV surrounding rock Lots and old loess tunnels (Class IV surrounding rock).

Cross-in-neighbor method (CRD method)

The cross-intersection method is to first excavate one or two parts of one side of the tunnel in a large-span tunnel with weak surrounding rock, apply part of the middle partition and diaphragm, and then excavate one or two parts on the other side of the tunnel to complete Diaphragm construction; then excavate the last part of the first construction side, extend the middle wall, and finally excavate the remaining part. When the short step method is difficult to ensure the stability of the face, it is advisable to use the CRD method with a small section size, which is more advantageous for controlling deformation.

The CD law is the abbreviation of “Center Diaphragm”, and the CRD law is the abbreviation of “Cross Diaphragm”. The two are both related and different. They are used in relatively weak stratum and are large section tunnels. The former is a method of excavating by dividing the partition with steel support and shotcrete; the latter is a method of using the partition and invert to divide the section up and down, left and right to excavate, and the geological conditions require the section section The method adopted under timely closed conditions.

Therefore, the only difference between the CRD method and the CD method is that each step in the construction process requires the use of temporary inverts to close the section. In the CRD method or the CD method, a key issue is the removal of the middle wall. Generally speaking, the middle wall should be removed only after the full section is closed and the displacement of each section is sufficiently stable.

Tunnel waterproof board laying formwork

Double side wall pilot pit method

Generally, the section is divided into four parts: the left and right side pilot pits, the upper core soil and the lower steps. The principle is to use two intermediate walls to divide the large section of the tunnel into three small sections on the left, middle and right for construction. The left and right pilot tunnels go first, and the middle section follows immediately; after the initial supporting inverted arch is formed into a ring, the two pilots are removed. The hole is temporarily supported to form a full section. The pilot holes on both sides are inverted oval shape, which is conducive to controlling the sinking of the vault.

When the tunnel span is large, the surface subsidence requirements are strict, the surrounding rock conditions are particularly poor, and the single-side pilot method is difficult to control the surrounding rock deformation, the double-side pilot method may be used. Field measurements show that the surface subsidence caused by the double-side pilot method is only 1/2 of the short-step method.

Although the double-side-wall pilot method has many sections in the excavation section, large disturbances, and a long time for the full section of the first support to be closed, each section is closed immediately after excavation, so there is almost no deformation during construction. development of. The double-side pilot tunnel method is safe to construct, but the speed is slower and the cost is higher. This method is mainly applicable to formations such as cohesive soil layer, sand layer and sand egg layer.

1. The construction sequence of the double-side pilot tunnel method is:

(1) Excavate a pilot pit on one side and close it in time for the initial support.

(2) Excavate the pilot pit on the other side after a proper distance, and construct the primary support.

(3) Excavate the upper core soil to construct the primary support of the arch, and the arch foot is supported on the primary support of the pilot pit on both sides.

(4) Excavate the lower steps, construct the first support at the bottom, and close the full section of the first support.

(5) Remove the first support of the empty part of the pilot pit.

(6) Construct the inner lining.

2. Pay attention to the following points in the double-sided pilot pit method:

(1) The next step of excavation can be carried out only after the sidewall pilot pit is excavated. When the geological conditions are poor, a temporary steel frame or temporary inverted arch shall be installed at the bottom of each step according to the design requirements.

(2) When each part is excavated, the peripheral contour should be as smooth as possible.

(3) Excavation should be carried out on the other side after the strength of the shotcrete on the first excavation side reaches the design requirements.

(4) The longitudinal spacing of the excavation face of the pilot pits on the left and right sides should not be less than 15 meters.

(5) When the excavation forms a full section, the initial support closure of the full section should be completed in time.

(6) The partition wall and temporary supports shall be removed section by section when the secondary lining is poured.

Construction technology of special grouting machine with mould for tunnel lining

Tunnel lining special grouting machine vault with mold grouting construction technology is to open a hole on the top of the lining trolley, and then set the RPC grouting pipe on the vault. After the lining is finished, the grouting integrated machine with mold High pressure injects micro-expansion mortar to treat vault voids, ensure the thickness of tunnel lining, and prevent tunnel lining vaults from voiding.

Technical advantages of special grouting machine for tunnel lining

1. By simplifying the embedded pipe and grouting construction technology, improving the grouting tooling and repairing grouting binder, the hidden project of the lining vault pouring is transformed into a “visible” project to prevent the defects of the lining vault; adopt micro-expansion grouting The grout binder has defects such as repairing construction gap joints, cold joints and imperfect concrete.

2. Through the penetration of the slurry, the damage of the waterproof board is blocked, forming a “mushroom” type plug, which has a water blocking function.

3. The tunnel lining special grouting machine is used for grouting. The equipment integrates the functions of slurry preparation, storage and grouting, and has a high grouting pressure, which can fully overcome the pipeline resistance and the low water-to-material ratio slurry. The resistance to vertical conveyance of the slurry.

4. Utilize the support of the lining trolley, adopt higher grouting pressure, and implement low water-to-material ratio grouting, which is fully dense, safe and reliable.

5. Use the special grouting machine for tunnel lining to grouting. The equipment is small in size and does not occupy space. In addition, the lining construction gap grouting does not affect other processes.

The principle of grouting with mold for tunnel lining

Through the transformation of the lining trolley, a certain number of grouting holes are set along the longitudinal direction of the trolley at the center line of the lining trolley formwork, and fixed flanges for grouting are installed, and the reactive powder concrete (RPC) is embedded before the concrete is poured. Grouting pipe, grouting from the embedded grouting pipe in time after concrete pouring.

Grouting with mold

The characteristics of the grouting process of the tunnel lining with a mold

1. By simplifying the pre-embedded pipe and grouting construction process, improving the grouting tooling and the lining micro-expansion grouting binder, the concealed project of the lining vault pouring is transformed into a “visible” project, preventing the defects of the lining vault and avoiding lining If the thickness is insufficient, carry out secondary backfill grouting or destroy and rebuild.

2. The micro-expansion grouting binder has the function of repairing construction gaps, cold joints, and concrete imperfections, lack of edges and corners, etc.; through the penetration of the slurry, the damage of the waterproof board is blocked, forming a “mushroom” type plug, which has water blocking Function to reduce leakage at the top of the arch.

3. Special grouting machine for tunnel lining is used for grouting. This equipment integrates grouting, grouting, and grouting as a whole, and has a high grouting pressure, which can fully overcome the pipeline resistance and the low water-to-material ratio slurry. The resistance to vertical conveyance of the slurry.

4. With the support of the lining trolley, grouting is done in time after the concrete is poured. The construction period does not affect other processes.

5. Count the lining grouting volume of each ring, implement process management and assessment, and force the construction team to improve the quality of lining grouting.

The key points of the construction of tunnel lining with mold grouting

Grouting with mold

Generally, 1 to 2 hours after the completion of concrete pouring, grouting with a mold is started.

1. Grouting process

Carry out grouting to the main grouting hole #1, and control the water-to-material mass ratio to 0.18. Stop grouting when the grouting hole of the #2 grouting hole or the reading of the pressure gauge exceeds 1.0MPa, and inject 2# and 3# in sequence. The grout hole is grouted, and the grouting is finished when the grout comes out from the end mold of the secondary lining. The 4# grouting hole is a spare, which can be selected according to the grouting situation.

2. Key points of grouting

① The grouting sequence is from the main grouting hole to the end mold grouting hole.

② Each grouting hole needs to be grouted, but when the grouting hole of other holes is grouted during the grouting process, when the grouting hole reaches the same density, the hole can be closed without grouting.

③ The end of grouting marks the end of grouting when the thick grouting out of the exhaust hole and end template. If the grout pressure at the trolley template reaches 1.0MPa and no thick grout is produced, the grout hole should be replaced for grouting until the end mold exhaust hole flows out of the thick grout. The RPC grouting pipe must be full, and the RPC grouting pipe should be sealed in time when the grouting connector is replaced after the grouting is completed.

④ Record the total amount of grouting, the start time and end time of grouting.

3. Pipeline cleaning

After the grouting is finished, close the grouting valve, remove the hose and grouting pipe fittings of the grouting machine, block the RPC grouting pipe in time, and rinse the grouting equipment repeatedly with clean water to ensure the smooth flow of the pipeline. After the strength of the lining concrete reaches 8.0MPa, knock out the RPC grouting pipe, and the trolley will be demoulded and enter the next cycle construction process.

Grouting with mold

Precautions for the operation of grouting with mold

1. Before the concrete is poured, analyze the embedded length of the grouting pipe, and basically judge the flatness of the lining and the condition of over-under-excavation through the length of 4 grouting pipes embedded in each cycle. Especially if the length of the embedded pipe is significantly smaller than the design thickness, it is necessary to exit the trolley, remove the waterproof board, and reprocess the support to avoid leaving hidden dangers.

2. During the concrete pouring process, observe the grouting condition of the grouting pipe. In principle, it is required that each grouting pipe can produce grout. In this case, it can ensure that the vault concrete is full, without quality defects, and the amount of grouting is small. In the case of uneven support, it should also be ensured that 1-2 grouting pipes are grouting, especially the remote grouting pipes.

3. After the concrete is poured, analyze the amount of grouting with mold in time. The amount of grouting per 12m lining vault is 0.5~1m3 (according to the grade of surrounding rock, the void volume is 0.5~1m3).

4. Under the condition that the support flatness meets the requirements, if the grouting material exceeds the normal dosage, the reason must be analyzed in time, and the next cycle lining concrete mix ratio and pouring process must be adjusted to improve the lining concrete pouring quality.

5. Due to uneven support, the end template is easy to leak. If the end template leaks at a low position, it is easy to fail to maintain pressure and the vault is full. Therefore, the end template should be closed, such as placing an arc to prevent leakage. Waterproof board or waterproof cloth, etc.

Detailed description of each component of the lining trolley

Lining trolley generally consists of template assembly, bracket assembly, translation mechanism, mast assembly, master-slave travel mechanism, lateral hydraulic cylinders, lateral support jacks, bracket support jacks, and gantry support jacks.

1. Template assembly

The template consists of 1~2 top molds and 2~4 side molds to form a cross section. The top mold and the top mold are connected as a whole by bolts, and the side mold and the top mold are connected by hinge trunnions. Each section of the template is made 1.5 meters wide, composed of multiple sections, and the templates are connected by bolts. There are working windows arranged in a product shape on the template, and a grouting device connected with the delivery pump Φ125 is installed on the top.

The tunnel concrete maintenance formwork

2. Bracket assembly

The bracket mainly bears the weight of the upper concrete and formwork during casting. It supports the formwork, and the lower part transmits the force to the mast through a hydraulic cylinder and a supporting jack. The bracket is composed of two longitudinal beams, two side beams, multiple middle beams and uprights. The longitudinal beams are welded by steel plates into an I-shaped section; the side beams and multiple middle beams are made of I-steel; the columns are made of I-steel.

3. Translation mechanism

A hydraulic trolley, one set of translation mechanism at the front and rear, is supported on the side beam of the mast. The hydraulic cylinder (GE160/90─300) on the translation trolley is connected to the bracket longitudinal beam, and the vertical positioning and demolding of the template are adjusted through the contraction of the cylinder. The adjustment stroke is 300mm; and the horizontal cylinder (GE90 /50─200) It is used to adjust whether the center of the lining of the template is aligned with the center of the tunnel. The left and right adjustable stroke is 100mm.

4. The door frame assembly

The mast is the main load-bearing component of the entire trolley. It is made up of beams, columns and longitudinal beams connected by bolts, and each beam and column are connected by connecting beams and diagonal tie rods. The main structure of the hydraulic trolley is welded by steel plates, and the entire mast is guaranteed to have sufficient strength, rigidity and stability. The mast beams are welded by steel plates into I or II-shaped cross-sections; the columns are also welded by I-beams into I or II-shaped cross-sections; the longitudinal beams are welded by steel plates; the oblique supports are made of I-beam or channel steel; each connecting beam adopts grooves Steel, I-beam or angle steel.

Tunnel waterproof board laying formwork

5. Master-slave walking mechanism

The hydraulic trolley has two master and slave walking mechanisms, which are hinged on the longitudinal beam of the mast. The main traveling mechanism is decelerated by a Y-type motor driven by a first-stage gear, and then decelerated by a two-stage chain. The traveling speed is 8m/min and the traveling wheel diameter is φ350mm;

6. Lateral hydraulic cylinder

The lateral hydraulic cylinder is mainly used for demolding the side template, and at the same time it plays the role of supporting the template. The lateral cylinder (GE100/63-400) selects 4 cylinders according to the length of the lining, and the adjustment stroke is 250mm.

7. Lateral screw jack

The screw jacks installed on the portal frame are used to support and adjust the position of the formwork and bear the pressure generated when concrete is poured. The screw diameter is 65mm, and its adjustment stroke is 250mm. Consider that the special screw of this trolley is a single screw.

Pipeline municipal lining trolley

8. Bracket supporting weight

It is mainly to improve the stress conditions of the bracket longitudinal beam when concrete is poured, and to ensure the reliability and stability of the bracket. The screw diameter is 65mm, and its adjustment stroke is 150mm.

9. The support of the door frame

It is connected under the longitudinal beam of the gantry. When the trolley is working, it bears the weight of the trolley and concrete, which improves the stress condition of the longitudinal beam of the gantry and ensures the stability of the gantry when the trolley is working. The screw diameter is 65mm and its adjustment stroke is 200mm.

The above is a detailed introduction of the various components of the lining trolley. Only by clearly grasping the working principle of each component can the lining trolley be better operated.

What are the secondary lining standards for tunnels?

The secondary lining is a moulded concrete or reinforced concrete lining applied on the inner side of the initial support during the tunnel construction, and it forms a composite lining with the initial support.

Relatively speaking, the secondary lining and the initial support refer to the inner lining constructed with concrete and other materials under the condition of the initial support of the tunnel, so as to achieve reinforcement support, optimize the route waterproof and drainage system, beautify the appearance, and facilitate installation The functions of communication, lighting, monitoring and other facilities can meet the requirements of modern highway tunnel construction. So what are the standards for the secondary lining of the tunnel?

The tunnel concrete maintenance formwork

1. In order to ensure the quality of the lining project, the second lining construction of the general section of the tunnel (including the tunnel body, the open tunnel, and the widened section) should adopt the full-section formwork trolley and pumping operation.

2. The secondary lining of the tunnel entrance section should be constructed in time. If the excavation exceeds 50m, the excavation should be stopped and the secondary lining construction should be stopped; the secondary lining of the tunnel entrance and the soft rock section in the tunnel should be constructed as soon as possible. Under circumstances, the distance between the second lining and the tunnel face is not more than 200m; the distance between the second lining work surface and the bottom paving work surface is generally 30m, and the distance from the low side wall work surface is generally 50m to ensure the normal construction progress of the second lining.

The tunnel concrete maintenance formwork

3. Before the construction of the second lining, laser measurement should be carried out on the initial support section, and the non-compliant ones should be dealt with.

4. When the underground water in the cave is confirmed to be corrosive to the lining structure through laboratory tests, different types of corrosion-resistant concrete should be used for different types of corrosion according to the requirements of the drawings. When there is no design requirement, the change shall be reported in time.

5. When the grade of surrounding rock changes, the grade of the lining section should also be changed accordingly, but the supervisor’s approval is required. The lining of the section with poor surrounding rock should be extended to the section with good surrounding rock, and the general extension is 5m.

Tunnel waterproof board laying formwork

6. The installation quality of tunnel waterproof and drainage facilities, embedded parts and reserved cavern templates, etc. must meet the design and specification requirements.

7. The construction unit shall entrust a qualified professional inspection unit to inspect the secondary lining steel bar, the thickness of the protective layer, and the void condition. The contractor shall carry out rectification and treatment of items that fail to pass the inspection.

8. In order to ensure that the lining does not invade the boundary of the tunnel construction, the designed contour line can be appropriately expanded when setting out.

9. For the completed lining section, continue to observe the stability of the second lining, pay attention to phenomena such as deformation, cracking, and intrusion into the clear space, and record in time.

What are the steel reinforcement installation requirements of the tunnel lining trolley?

Tunnel trolley is a relatively common product on highways. The installation of tunnel lining trolleys is relatively complicated. First, choose the installation location, and then install the walking wheel frame assembly, various accessories, accessories and systems. And so on, but the installation of steel bars is more important in the entire installation and use process, because it is related to the subsequent use. Then, what are the installation requirements of the lining trolley, let’s take a closer look!

1) Each node of the transverse reinforcement and the longitudinal reinforcement should be tied or welded;

2) The welded lap length of the steel bar shall meet the design and specification requirements, the lap joint of the stressed main bar shall be welded, and the welded lap length and weld shall meet the requirements of the specification;

Double-track railway lining trolley

3) The overlapping positions of adjacent main bars should be staggered, and the staggered distance should not be less than 1000mm;

4) The two overlapping distances of the same stressed steel bar should not be less than 1500mm;

5) The connection point of the stirrup should be at the cross connection of the longitudinal and longitudinal ribs, and should be tied or welded;

6) Other connection methods of steel bars should comply with relevant specifications;

7) When installing steel bars, the length, spacing, position and thickness of the protective layer of the steel bars should meet the design requirements.

Tunnel waterproof board laying formwork

Reinforcing steel bars should be positioned according to the design outline. In order to ensure that the positioning of the secondary lining steel bars is accurate and the thickness of the steel protection layer meets the requirements, the following measures should be taken:

(1) First, the surveyor uses coordinates to set out the center points of the front and rear two steel bars within the scope of the self-made trolley on the leveling layer and the vault waterproof layer, and determine the normal direction to ensure the verticality and verticality of the positioning steel bars. The accuracy of the arch reserved steel connection. The verticality of steel tying is determined by the method of three-point hanging ball.

(2) Use a level to measure the elevation of the center point of the positioning steel bar on the leveling layer, calculate the height difference between the center of the mileage and the center point on the leveling layer, and use a self-made tripod to determine the center of the circle.

(3) After the center of the circle is determined, use the ruler method to check whether the size of the positioning steel bar meets the design requirements, re-adjust the positions that do not meet the requirements, and fix the steel bars after all meet the requirements. The steel bar is fixed by the adjustable support rod welded by steel pipe on the self-made trolley.

(4) After the positioning steel bars are fixed, use chalk to mark the location of the circumferential main reinforcing bars on the support rods according to the design steel bar spacing, mark the installation positions of the longitudinally distributed ribs on the positioning steel bars, and then start binding the steel bars within this section. The intersection of steel bars should be tied.

In short, the tunnel lining trolley manufacturer specially reminded that the steel protection layer should be controlled by high-strength mortar pads, and plastic pads should not be used. It is required that the longitudinal spacing of the main ribs, the circumferential spacing of the distributed ribs, the horizontal spacing of the inner and outer layers, and the thickness of the protective layer meet the design requirements.

Introduction to the Structural Features of Tunnel Lining Trolley

The tunnel lining jumbo has low cost, high construction efficiency and good effect. It is mainly used in the construction of highways and various tunnels. Tunnel lining trolleys mainly include simple lining trolleys, fully hydraulic automatic walking lining trolleys and net-frame lining trolleys. Full hydraulic lining trolley can be divided into side-top arch type, full circle needle beam type, bottom mold needle beam type, full circle travel type, etc. So, what are the structural characteristics of the tunnel lining trolley?

1. Trolley structure

Both hydraulic and mechanical types are available. The hydraulic type has low rigidity requirements for the trolley frame, flexible structure type, light weight, low processing requirements and low elevation requirements for the track laying in the construction, and easy to use, but it has high requirements for the self-locking of the hydraulic cylinder, and the hydraulic cylinder in the lining is not allowed to retract . The mechanical type is the opposite. Because one motor must drive several lead screws, the coaxiality of each drive shaft is required to be high, and the trolley frame must have greater rigidity, and the structure and size must be accurate.

Due to the heavy structure and high processing requirements, And because the lead screw is synchronized action (unlike hydraulic transmission, each hydraulic cylinder can be synchronized or independently), when the track elevation error (each point is not at the same elevation) is large, it will directly affect the template position, thereby affecting the lining quality. After analysis and comparison, the hydraulic transmission scheme is selected, and measures such as hydraulic lock and balance valve are adopted for the hydraulic cylinder to make the hydraulic cylinder self-locking; at the same time, the screw mechanism is used for mechanical locking, and the support of the template is strengthened to ensure that the template does not return during lining. Shrink without deformation.

Tunnel formwork channel

2. Frame structure

The trolley adopts hydraulic transmission, which simplifies the structure of the trolley frame and reduces the weight. At the same time, it also improves the flexibility and diversity of the structure. After the analysis and comparison of various trolley frame structure schemes, the strength calculation and optimization select 9m four-door frame 12m The main door frame structure scheme reduces the structural weight by more than 40% compared with the mechanical type, and reduces the production cost by more than 25%.

Tunnel waterproof board laying formwork

3. Steel mold structure

The steel mold is the working device of the trolley. Its appearance quality and dimensional accuracy directly determine the quality of the concrete lining. At the same time, it is the most difficult part to process. A reasonable processing and welding process has been formulated, and a special assembled welding tire mold has been designed and processed. In order to ensure the accuracy of the overall dimensions, minimize welding distortion, and ensure that the outer surface is smooth and free of defects such as unevenness. In order to control the misalignment of adjacent formwork, the stabilizing pin of interference fit is used to fix the connecting plate of adjacent formwork as a whole, which effectively controls the misalignment of adjacent formwork caused by the gap between bolt holes and ensures the quality of concrete lining .

Tunnel formwork channel

4. Support structure

The entire mass of the lining concrete is transmitted to the supporting mechanism through the steel mold of the trolley, and then to the portal frame. The lining concrete is in a solid-liquid state, which produces large vertical pressure and lateral pressure on the top and side directions, and at the same time produces a large buoyancy. When the buoyancy exceeds the vertical pressure and the weight of the trolley, the trolley will float. Will not work properly. In order to solve this technical problem, after careful calculation, optimized design, and reasonable selection of each supporting position. That is, the lower longitudinal beams on the inner side of the mast are supported with the ground to avoid lateral pressure to cause the mast columns to retract, and there are several horizontal supports on the outer side of the mast and the longitudinal beams of the side form, at the upper beam and the upper longitudinal beam of the mast It adopts several vertical supports (the top hydraulic cylinders are arranged on the horizontal part of the gantry at both ends, and the middle is the vertical supporting screw), which is uniformly distributed in the longitudinal direction of the trolley.

The tunnel lining trolley is a special equipment that must be used in the secondary lining of the tunnel construction process, and is used for the concrete lining construction of the inner wall of the tunnel. The above is the specific description of the structural characteristics of the tunnel lining trolley. I hope it can help everyone to know more about the tunnel lining trolley.

What are the operating procedures and precautions for tunnel lining trolleys?

During the secondary lining construction of the tunnel, the tunnel lining trolley is an indispensable professional equipment. The tunnel lining jumbo is generally designed as a steel arch type, which is mainly used in the construction of medium and long tunnels to improve construction efficiency. Then, in the actual operation process, what are the operating procedures and precautions for the tunnel lining trolley? Here is a brief introduction:

Operating procedures

Lining trolley plug steel template

1. Operator job requirements

① The operator should have received good safety technology and skill training. Work with a certificate.

② The operator shall do the inspection and maintenance of the daily use of the lining trolley, and make necessary records.

③ Strictly follow the technical explanations and the corresponding operating procedures.

2. Work preparation before operation

① After the assembling of the trolley is completed, each connecting screw shall be checked and tightened one by one, and it can be put into use after the joint inspection and acceptance by all parties.

② Wear belts when constructing on the trolley, and cover the operation area with 5cm wooden boards to prevent the operator from falling from a height. The two trolleys are equipped with eye-catching reflective strips.

3. Specific operating procedures

① The base surface of the trolley track should be solid and flat. It is strictly forbidden to have soft sides and hard sides. The top surface of the track should be on the same plane, and the track spacing should be consistent with the wheel flange of the trolley.

② The top surface of the trolley track is basically parallel to the longitudinal excavation surface of the tunnel. When the slope is large, a track clamp should be set at a place not less than 3m at the head of the track to prevent the trolley from derailing during operation.

③ When the trolley moves to its place, when the trolley slides down automatically, the operator should send people on both sides of the forward direction to check the operation at the same time. When an abnormal situation occurs, the operator should be notified at any time to brake the trolley immediately. When the trolley moves with external forces (loaders, excavators), a qualified wire rope must be used to drag the trolley along the uphill direction of the tunnel, and move slowly, allowing the trolley to move under its own gravity. It is strictly forbidden to follow the direction of the slope Go trolley.

④ The trolley should be moved slowly and smoothly. When it is difficult to move, carefully check whether there are hard objects stuck on the sides or bottom of the trolley. Check whether there are steel bars on both sides and the top surface that hinder the operation of the trolley. The trolley should be stopped to advance, and the steel frame may collapse easily.

⑤ After the trolley is positioned, the operator should first wedge the trolley wheel with a wooden wedge, and then perform the positioning adjustment of the trolley under the command of the surveyor. When the trolley has a large deviation, the cylinder should be adjusted symmetrically. The position of the trolley meets the balance requirement. When the positioning of the trolley meets the requirements, the screw jacks at the bottom of the trolley should be tightened first, and then the jacks on both sides of the trolley should be tightened symmetrically. When the tops of the screw jacks of the trolley are tightened in place, loosen the hydraulic cylinder jacks. Open to protect the cylinder.

⑥ Before pouring the concrete, the operator should repeatedly check the jacks one by one to ensure that each screw jack has been tightened, and the top of each hydraulic jack is depressurized. In the process of concrete pouring, it should be placed strictly symmetrically, and the height difference between the two sides of the mold concrete should not exceed 1 meter, preferably 0.5-0.8 meters, and someone should be sent to check the jack. When the molded concrete structure is thick and large in volume, the pouring speed should be slowed down in a timely manner, and the frequency of the mold should be checked closely to prevent accidents caused by running, rising, and collapse of the mold
.
⑦ The power supply control box of the trolley should be placed on the base of the tunnel. It is strictly forbidden to install the control box on the trolley. All power cables must pass through a leakage protector. The operating current should not exceed 30 amperes and the operating time should not exceed 0.1 seconds. The cable must use rubber flexible cable, and there must be no joints or damage in the middle, and the trolley frame body must have a reliable protective zero connection.

⑧ The lighting on the trolley should use safe voltage or flashlight.

Other matters needing attention

Concrete diversion groove

1. When a vehicle passes under the trolley clearance during the construction period, a person should be assigned to conduct traffic command and management to prevent the vehicle from colliding with the trolley.

2. Strictly control the center line of the steel rail to avoid excessive deviation between the center of the backstage car and the center of the tunnel.

3. During the rail laying process, the rails must be firmly connected to each other to avoid crushing the rails or derailing the trolley due to the excessive weight of the trolley.

4. Remove the virtual ballast under the sleepers to avoid sinking due to the weight of the concrete and the trolley during the lining process.

5. The baffle plate bears a lot of force, and must be reinforced firmly during the erection process. During the concrete pouring process, it must be inspected and reinforced at any time.

6. The second lining concrete pouring takes a long time. In order to facilitate the simultaneous construction of the second lining and the ballast discharge, the delivery pump is placed far away from the lining trolley.

7. The concrete conveying pipe is firmly fixed on the bench, and the pipe should not be in contact with the template, so as to avoid strong vibration at the nozzle when the concrete is pressed out and the template will be deformed and run. The joint pipe clamp should be connected firmly to avoid bursting off, and the pipe 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.

Tunnel lining trolleys are widely used in the construction of concrete secondary lining of highways, railway tunnels and underground caverns due to their good performance, reasonable structure, and good lining quality. The above is a specific description of the operating rules and precautions of the tunnel lining trolley. I hope it can help everyone to have more understanding of the tunnel lining trolley. Luoyang Gaofei Bridge Tunnel Machinery Co., Ltd. has been specializing in the production and research and development of tunnel lining trolleys for many years. The series of products are spread all over the country and are well received by customers. Interested parties are welcome to consult.

Installation of tunnel lining trolley, specific steps are introduced

The tunnel lining trolley is a special equipment that must be used in the secondary lining of the tunnel construction process, and is used for the concrete lining construction of the inner wall of the tunnel. Tunnel lining trolleys are widely used in the construction of various highways, railway tunnels and underground caverns due to their low production cost, high construction efficiency, and good effects. So, how does the installation of the tunnel lining trolley proceed in the actual construction of the project? Let me introduce you step by step.

Choose the installation location

The combination of the tunnel lining trolley must first be combined with the actual situation on the site, and the appropriate installation site should be selected. The site should be as flat and wide as possible so that the trolley can enter the tunnel or work surface smoothly. According to the specific venue, it is roughly divided into two situations:

1. Install outside the cave, with large space, suitable for crane operation.

2. Installation in the cave, small space, requires anchor rod lifting operations.

The specific installation steps

The tunnel concrete maintenance formwork

1. Level the site and lay the track. The site should be as flat and open as possible to facilitate installation work. According to the actual situation of the site, the site should generally be 20×30 meters. (If the hole is installed inside, it needs to have the top 50 cm outside and the side 30 cm outside. The length of the trolley is increased by 3 meters to facilitate the lifting operation. In order to successfully complete the installation task, it is necessary to keep the site twice the length of the trolley.)

2. Install anchor rods: The track will be laid according to the requirements of the trolley gauge. The track will be straight, without obvious triangular pits, and no staggered seams. The height difference between the front, rear, left and right will be less than 5 mm, and the center line will be as close as possible The centerline of the tunnel coincides, the error will be less than 15 mm, the track sleeper spacing will usually be less than or equal to 0.5 meters, and nailed, the steel rail is 38 kg/m.

3. Install the walking wheel frame assembly: use a lifting device (chain block or crane) to place the driving wheel frame and the driven wheel frame on the laid track, and make temporary support, adjust the front and rear wheels according to the center line of the bottom longitudinal beam The distance between the frames shall be adjusted to the correct position of the wheel frames based on the principle of equal diagonals, leveled and fixed.

4. Install the bottom longitudinal beam: Lift the bottom longitudinal beam above the installed wheel frame and use bolts to add temporary support to check whether the diagonal has changed. If it is within the correct value, you can install the door frame.

5. Installation of portal frame: Generally speaking, the overall assembly of portal frame is first assembled on site. Then, they were suspended one by one at the relative position of the bottom longitudinal beams and temporarily fixed with bolts.

6. Install lock beams and scissor braces: install door frames, and then install lock beams and scissor braces in each space. Adjust and align by vertical ball or eye view. And tighten all bolts in time to form a complete skeleton. Make it an organic whole as soon as possible.

7. Install the jacking cylinder and other parts of the tunnel lining trolley.

8. Lift the lifting beam and install the platform beam: first lift the platform beam on the top of the jacking shaft cylinder, adjust the center distance and diagonal, and then add temporary support, lift the lifting beam on the top of the platform beam and fasten it with bolts.

9. Install hanging beams and columns and top templates. When installing the top mold, start from the middle and extend to both ends to reduce the accumulated error. Install the first top mold in the middle, and install other top molds after checking that the chord length and height meet the design standards, until the top mold installation task is completed .

10. In order to ensure the stability of the trolley, various supports and supports on the suspension beam will be checked and tightened at this time.

11. Installation of side mold (using crane or chain block): The top mold can be installed after inspection. The side mold should be installed symmetrically to prevent tilting. If the side mold is installed in the hole, the side mold should be installed before installation. Transport to the hole, and the side mold should be placed on the side wall for easy hoisting. After adjusting the installation of the side mold, the surface is smooth and flat, there is no misalignment at the joint, and the geometric size meets the design requirements, and the beam can be installed.

12. Install the beam and support system of the tunnel lining trolley.

13. Install hydraulic and electrical systems: When installing in a small hole, you must install mobile electrical appliances before the trolley can move back and forth.

14. Install accessories, such as railings, ladders, working platforms, and slats.

15. Check all fastening bolts.

16. During the no-load test, the electro-hydraulic system works normally.

The tunnel lining trolley has light weight, high strength, large span, wide application range, and is beneficial to overall construction control. In construction, it is necessary to use different models for operation according to different situations, so it is very necessary to understand the installation steps of tunnel lining trolleys. Luoyang Gaofei Bridge Tunnel Machinery Co., Ltd. has specialized in the production and research and development of tunnel lining trolleys for many years. The series of products are spread all over the country and are well received by customers. Interested parties are welcome to come to consult.

Introduction of tunnel construction method

Attention should be paid to the following points when excavating steps: With the implementation of information technology, the impact of tunnel construction on the surrounding environment has been minimized, and the construction efficiency has been greatly improved. Various integrated pipeline corridors, subway tunnels, and highway tunnels are constructed everywhere. It can be seen that, especially in subway and high-speed rail construction in recent years, various tunnel projects have emerged one after another, and there are more and more construction techniques and methods. The relevant personnel of tunnel construction manufacturers have summarized and shared 6 commonly used tunnel construction methods for us, let’s take a look. Right.

1. Full-face excavation method

The full-face excavation method is a construction method in which the lining is formed by blasting at one time according to the design contour.

Applicable conditions:

(1) I~IV class surrounding rock, when used in class IV surrounding rock, the surrounding rock should have the conditions to maintain its own stability during the period from full-face excavation to the initial support.

(2) There are drilling rigs or self-made work benches and high-efficiency shipping machinery and equipment.

(3) The length of the tunnel or construction section should not be too short. According to experience, it should not be less than 1km. Otherwise, large-scale mechanized construction is adopted, which is less economical.

The tunnel mechanized construction has three main lines:

Excavation line: drilling trolley, charging trolley, loader with dump truck (trackless transportation), slag loading machine with mining garbage battery car or diesel locomotive (track transportation).

Anchor shotcreting line: concrete shotcrete machine, concrete shot manipulator, anchor shotcrete work platform, feeding and transportation equipment and bolt grouting equipment.

Moulding and lining work line: concrete mixing equipment, concrete truck and pump, waterproof layer working platform, lining steel mould trolley. Construction features of full-face method:

(1) Excavation section and working space are large and interference is small;

(2) Conditions to make full use of machinery and reduce manpower;

(3) There are few procedures, which is convenient for construction organization and management, and improves working conditions;

(4) Excavation takes shape at one time, which has less disturbance to surrounding rock and is beneficial to the stability of surrounding rock.

2. Step method construction

The step method is to excavate the upper half of the section first, and after the excavation reaches a certain length, the lower half of the section is excavated at the same time, and the upper and lower half of the section are simultaneously advanced; according to the length of the step, there are three types of long steps, short steps and ultra-short steps. . In recent years, due to the design of large-section tunnels, there have been three-step temporary inversion methods and even multi-step methods.

As for which step method should be used in construction, it should be decided according to the following two conditions:

(1) The time required for the initial support to form a closed section. The worse the surrounding rock, the shorter the closing time.

(2) Requirements for the size of the construction site for the excavation, support, and ballasting of mechanical equipment used in the construction of the upper section.

In the weak surrounding rock, the former should be the main one, while the latter should be taken into consideration to ensure construction safety. When the surrounding rock conditions are better, the main consideration is how to better exert the mechanical efficiency and ensure the economic efficiency of construction, so only the latter condition is considered.

The advantages and disadvantages of the step excavation method:

The step excavation method can have enough working space and considerable construction speed. However, the upper and lower operations have interference; although step excavation increases the number of disturbances to the surrounding rock, the step is conducive to the stability of the excavation surface. Especially after the upper excavation and support, the lower operation is safer, but attention should be paid to the influence of the lower operation on the upper stability.

(1) Solve the problem of mutual interference between upper and lower half section operations. The micro steps are basically combined into a working face for simultaneous excavation; the long steps are basically opened, and the interference is small; while the short steps have greater interference, and attention should be paid to the work organization. For tunnels with a shorter length, the upper half of the section can be penetrated before the lower half of the section is constructed.

(2) When excavating the lower part, pay attention to the stability of the upper part. If the stability of the surrounding rock is good, it can be excavated in stages; if the stability of the surrounding rock is poor, the lower excavation cycle should be shortened; if the stability is worse, it can be staggered to the left and right, or the middle groove can be pulled first and then dig Side gang.

(3) After the excavation of the lower side wall, the concrete must be shot immediately, and the initial support must be made according to the regulations.

(4) The measurement work must be timely to observe the displacement value of the vault, the arch foot and the middle of the side wall. When the speed is found to increase, the invert arch should be closed immediately.

3. Ring excavation to retain core scholars

The following points should be paid attention to in the ring excavation and core soil method:

(1) The circular excavation footage should be 0.5-1.0m, and the core soil area should not be less than 50% of the entire section area.

(2) Spray anchor support and steel frame support should be constructed in time after excavation. Adjacent steel frames must be connected by steel bars, and the angle lock anchors should be designed and constructed according to construction requirements.

(3) When the surrounding rock geological conditions are poor and the self-stabilization time is short, advance support should be carried out according to the design requirements before excavation.

(4) The excavation of the core soil and the lower steps should be completed after the upper step support is completed, and the sprayed concrete reaches 70% of the design strength.

4. The next door method (CD method)

The CD method is a construction method in which one side of the tunnel is first excavated in a large-span tunnel with weak surrounding rock, and the middle side wall is constructed, and then the other side is excavated. It is mainly used in double-line tunnels with deep buried hard rock in the IV-level surrounding rock Lots and old loess tunnels (Class IV surrounding rock) lots.

5. Double side wall pilot pit method

The double-sided pilot pit method generally divides the section into four sections: the left and right side pilot pits, the upper core soil and the lower steps. The principle is to use two intermediate walls to divide the entire large section of the tunnel into three small sections on the left, middle and right for construction. The left and right pilot tunnels go first, and the middle section immediately follows; after the initial supporting inverted arch is formed into a ring, the two sides of the pilot are removed. The hole is temporarily supported to form a full section. The pilot holes on both sides are inverted oval-shaped, which is beneficial to control the sinking of the vault.

When the tunnel span is large, the surface subsidence requirements are strict, the surrounding rock conditions are particularly poor, and the single-side pilot method is difficult to control the surrounding rock deformation, the double-side pilot method can be used. Field measurements show that the surface subsidence caused by the double-side pilot method is only 1/2 of the short-step method. Although the double-wall pilot tunnel method has many excavation sections and large disturbances, it takes a long time to close the full section of the first support, but each section is closed immediately after excavation, so the deformation is almost Does not develop. The construction of the double-side pilot tunnel method is safe, but the speed is slow and the cost is higher. This method is mainly applicable to formations such as cohesive soil layer, sand layer and sand egg layer.

The construction sequence of the double-side pilot pit method is:

(1) Excavate a pilot pit on one side and close it for the first time in time.

(2) Excavate the pilot pit on the other side after a proper distance, and construct the primary support.

(3) Excavate the upper core soil to construct the primary support of the arch, and the arch foot is supported on the primary support of the pilot pit on both sides.

(4) Excavate the lower steps and construct the first support at the bottom, so that the full section of the first support is closed.

(5) Remove the first support of the empty part of the pilot pit.

(6) Construct the inner lining.

Pay attention to the following points in the double-sided pilot pit method:

(1) The next excavation can be carried out only after the sidewall pilot pit is excavated. When the geological conditions are poor, a temporary steel frame or temporary inverted arch should be installed at the bottom of each step according to the design requirements.

(2) When each part is excavated, the peripheral contour should be as smooth as possible.

(3) Excavation should be carried out on the other side after the strength of the shotcrete on the excavation side reaches the design requirements.

(4) The longitudinal spacing of the excavation face of the pilot pits on the left and right sides should not be less than 15 meters.

(5) When the excavation forms a full section, the initial support closure of the full section should be completed in time.

(6) The partition wall and temporary supports shall be removed section by section when the secondary lining is poured.

6. Fork in the next door method (CRD method)

Fork-in-the-next-wall method is to excavate one or two parts of one side of the tunnel in a large-span tunnel with weak surrounding rock, apply the partition and diaphragm in the part, and then excavate one or two parts on the other side of the tunnel to complete the horizontal Diaphragm construction; then excavate the last part of the first construction side, extend the middle wall, and finally excavate the remaining part. When the short-step method is difficult to ensure the stability of the tunnel face, the CRD method with a small section size should be used, which is more advantageous for controlling deformation.

The CD law is the abbreviation of “Center Diaphragm”, and the CRD law is the abbreviation of “Cross Diaphragm”. The two are both related and different. They are used in relatively weak stratum and are large section tunnels. The former is a method of excavating by dividing the partition with steel support and shotcrete; the latter is a method of using the partition and invert to divide the section up and down, left and right to excavate, and the geological conditions require the section section The method adopted under timely closed conditions. Therefore, the only difference between the CRD method and the CD method is that each step in the construction process requires the use of temporary inverts to close the section.

In the CRD method or the CD method, a key issue is the removal of the middle wall. Generally speaking, the middle wall should be removed only after the full section is closed and the displacement of each section is fully stabilized.