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.