1 project overview
Design overview of 1. 1
XXX tunnel is a small clear distance tunnel, with a single tunnel length of 582m ... and a maximum buried depth of 48 m, the entrance wall is poured with C20 concrete, and the pavement in the tunnel is made of 240 mm thick cement concrete.
1.2 tunnel geology
(1) engineering geology
The surrounding rocks at the import and export are mainly loose low liquid limit clay and strongly weathered mudstone, with loose and broken lithology; The surrounding rock in the middle is argillaceous siltstone and mudstone mixed with fine siltstone, which belongs to soft rock and is less affected by structure. The rock is weakly weathered, with relatively developed-undeveloped cracks. The rock mass is complete and partially broken, showing block stone structure and block stone mosaic structure.
(2) Hydrogeology
The groundwater activity at the entrance and exit of XXX tunnel is seepage, and the surrounding rock is unstable and easy to collapse. During construction, the low liquid limit clay on the uphill slope should be completely removed to ensure the construction safety; Mudstone in the middle is mainly seepage and dripping, and argillaceous siltstone and siltstone occur in cracks, interlayer lines or small strands. The surrounding rock is basically stable. Because of the gentle dip angle of rock strata, poor interlayer bonding and fracture cutting, the arch of the cavern is easy to collapse along the plane without support after excavation, and the side wall is basically stable.
1.3 structural form and supporting parameters
The tunnel structure is designed according to NATM principle. In the construction, composite lining is adopted, with cartridge anchor, pipe shed and small grouting pipe as the advanced support, anchor rod, hanging steel mesh and wet sprayed concrete as the initial support, and steel arch, hollow grouting anchor rod, cartridge anchor rod and self-propelled anchor rod as the auxiliary support measures. Fully mobilize and give play to the self-supporting capacity of surrounding rock, and implement initial support and secondary forming lining under the guidance of monitoring and measurement information.
XXX Tunnel Lining Length Table
Number, lining type, lining length (m), applicable section and main supporting measures.
1Ⅱ pipe is shallowly buried, and the surrounding rock of Grade 20 Ⅱ is shallowly buried, and the arch part is mainly mudstone strongly weathered zone (pipe shed advanced support, totally enclosed steel frame of public security steel).
2 Ⅱ ultra-shallow 86 Ⅱ surrounding rock shallow buried section, the arch part is mainly the strongly weathered zone of bedrock (pre-supported with small conduit and inverted arch without grid steel frame).
3 Ⅲ ultra-shallow 65 Ⅲ surrounding rock shallow buried section, the arch is mainly the strongly weathered zone of bedrock (pre-supported with cartridge bolt, inverted arch without grid steel frame).
4 Ⅲ lattice 120 tunnel body is deeply buried in Ⅲ surrounding rock, and the arch stability is poor (with inverted arch and grid steel frame).
Note: Wet shotcrete is used for initial support, and dry shotcrete is strictly prohibited.
2 construction organization arrangement
2. 1 schedule
The preparation for the tunnel started on May 2005 10 and was completed on July 3, 20061. Construction preparation: May 2005 10 to July 3, 20051. The time limit for each sub-item is as follows:
Construction of entrance section: August 2005 1 to August 3, 20051;
Tunnel excavation and support: September 2005 1 to May 3, 20061;
Waterproofing and drainage of tunnel body: from October 20th, 2005 to May 30th, 2006,11;
Tunnel lining: February 5, 2005 to June 5, 2005;
Tunnel entrance: from August, 2005 1 day to October, 2005 16;
Pavement and accessories in tunnel: June 5, 2006 ~ July 3, 20061.
2.2 labor organization
The XXX tunnel is under the responsibility of the tunnel construction team (240 people). The team has a construction team, and each team includes three shifts: excavation, lining and integration. The tunneller is responsible for tunnel excavation, support, slag discharge and transportation. Lining workers are responsible for lining, including the production, transportation and pouring of concrete; Maintenance of wind, water, electricity and equipment. The comprehensive class is responsible for the transshipment of off-site materials. Organize the construction according to the three-shift system. When arranging personnel, the working time of each person shall not exceed 8 hours per day. See the following table for the specific labor arrangement of the construction team:
Table of tunnel construction organization and division of labor
Number of names, responsibilities and responsibilities
1 Team leader 5 is responsible for the construction organization and command.
2 security officer 6 is responsible for safety work, finding and eliminating the signs of accidents.
Electrician 6 is in charge of the circuit.
4 drill 40 is responsible for drilling.
5 Blasting 16 is responsible for initiating explosive cartridge, transporting explosives, charging, connecting and initiating.
6 slag loading 12 is responsible for slag loading.
7 Slagging (in the hole) 12 is responsible for slagging in the hole.
8 slag transportation 9 responsible for slag transportation
9 Support 18 is responsible for supporting, grouting, water plugging and stratum reinforcement.
10 two warehouse keepers will guard the detonator and explosive magazine, and keep and distribute the initiating explosive device.
1 1 repairman 3 general maintenance work
12 assistant worker 2
Total 13 1
Li Ning's labor organization and division of labor table
Number of names, responsibilities and responsibilities
1 Team leader 4 is responsible for the construction organization and command.
2 Mixing Station 12 Operation Mixing Station
3 Loader 6 loads aggregate and admixture
4 concrete pump driver and assistant worker 10 operate concrete pump, load and unload pipes, and concrete truck transports concrete.
5 Waterproofing workers 10 Install waterproof boards and lay blind ditches.
6 trolley in place and assistant worker 12 trolley moving, positioning and template outline size
7 concrete rammer 6 tamp concrete
Repairman 5 is responsible for equipment maintenance.
9 electricians 4
A total of 69 people
Labor organization of the whole class (wind, water and electricity equipment and safety outside the tunnel)
Number of names, responsibilities and responsibilities
1 Team leader 3 is responsible for organizing and commanding.
2 wind and hydropower 4 high-pressure wind and hydropower supply management, high-pressure wind and water pipe installation
3 ventilation and smoke exhaust, etc. 4 Installation and maintenance of ventilator, air duct and drainage pipe.
4 The main maintenance work of the repairman 5 in the operation area
5 Processing 6 All processing work in the operation area.
Six welders and four welding operators
7 holes external transportation 7 holes external material transportation
8 auxiliary workers outside the hole, 7 auxiliary work such as material loading and unloading outside the hole.
Total 40
2.3 Site layout
The setting of construction site and team station mainly considers factors such as proximity to the entrance of the cave, convenience for commuting, shelter from the wind, flood control and environmental protection requirements.
2.4 Temporary Works
(1) construction access road
When the tunnel enters the tunnel from the entrance, it needs to be built 0.4Km to the entrance of the tunnel, and the road surface is treated with mud and gravel. The construction standard is the pavement width of 4.5 meters. Designate a special person to be responsible for the daily inspection, maintenance and repair of the construction access road, so that someone will clear the ditch and drain water in rainy days, and a car will be sprinkled with water to remove dust in sunny days to ensure smooth road surface, comfortable driving and all-weather traffic. See "XXX Tunnel Entrance Construction Layout" for the site layout of the tunnel.
(2) Layout of high-pressure gas supply system
Two 20m/min electric air compressors are set at the entrance of the cave, and the high-pressure air duct adopts φ 120mm seamless steel pipe, which is set at the foot of the wall on the same side as the ventilation duct. Strictly strengthen management during construction to ensure no air leakage.
XXX tunnel entrance construction layout
(3) Layout of water supply system
A 60m3 high-level pool will be built on Dongkou Mountain, which is about 30m higher than the vault elevation of Dongkou. Water pipes will be laid and high-pressure pumps installed.
(4) Layout of power supply system
High-voltage wires are connected to the tunnel entrance nearby, and transformers with sufficient capacity are set, and internal combustion generator sets are reserved at the tunnel entrance to ensure construction electricity consumption.
(5) Construction ventilation system layout
Adopt long pipe pressure ventilation. The tunnel ventilation system consists of SDA 1 10AD ventilator with power of 1200m/min and antistatic flame retardant reinforced PVC flexible duct (φ 1.4m).
The ventilator is located 30m away from the hole, so as to prevent the dirty air flowing out of the hole from entering the hole again. The air outlet of the air duct is 30 ~ 40m away from the excavation face, and the air duct is hung at the vault. In order to solve the problem of wind resistance of the air duct at the trolley, a hard pipe is arranged at the top of the trolley, so that the air duct can pass smoothly and the hose can be prevented from shrinking, bending and deformation. See "Schematic Diagram of Pipeline Layout in Tunnel".
2.5 Main mechanical equipment arrangement
Tunnel construction adopts pipe-shed drilling rig (MGJ-50). For the construction methods of slag transportation by loader's slag dump truck, initial support of wet sprayed concrete, injection molding of integral lining platform, mixing by concrete mixing station, transportation by concrete transport vehicle and pumping by concrete delivery pump, see the "List of Main Construction Machinery and Equipment to be put into this Contract Project" in the previous table for the machinery and equipment required for construction.
3 overall construction scheme
The tunnel opens from the entrance. Tunnel construction follows the basic principles of NATM, with the guidance of "early prediction, diligent measurement, leading pipe, weak blasting, short footage, strong support, quick closure and tight lining", and adopts trackless transportation and forced ventilation. For drilling and blasting tunnel excavation, see "New Austrian Tunneling Method Construction Process Block Diagram". In order to improve the state of surrounding rock, improve its self-stabilizing ability and prevent possible collapse, grouting small pipes are used to pre-reinforce the surrounding rock of tunnel entrance, entrance reinforcement section and fault fracture zone. According to the geological conditions, advance support shall be carried out for type II small clear distance section before excavation; Strengthen the rock pillar first, and then carry out full-face construction; Excavation work from top to bottom, lining construction from bottom to top, closed inverted arch in time. Generally, the excavation of the upper step in the left half of the right tunnel (back tunnel) should be 5 ~ 10m behind the lower step in the right half of the left tunnel (first tunnel). The rock pillar between the two tunnels is reinforced by φ27 self-propelled anchor rods, each of which is 5m long. Before excavation, pre-support the ground section with small net distance of Class III surrounding rock; First, the left hole is constructed to reinforce the rock pillar, and then the right hole is excavated to further strengthen the rock pillar; Excavation is from top to bottom, lining construction is from bottom to top, and secondary lining (inverted arch) is constructed in time. Generally, the excavation of the upper step in the left half of the right tunnel (back tunnel) should be 5 ~ 10m behind the lower step in the right half of the left tunnel (first tunnel). The rock pillar between the two tunnels is reinforced by φ25 hollow grouting anchor rods, each of which is 4m long. Among them, the upper steps are excavated circularly, and the core soil is reserved in the arch. The length of steps should be controlled at about 4 meters. The lower step of bench method is drilled by a rock drill. Slag is discharged by side dump loaders and dump trucks. When the bench method is adopted, the slag is turned to the lower step manually. Lining adopts lining trolley, concrete is mixed by mixing station, transported by car, pumped into mould by concrete delivery pump, and the whole section of secondary lining is constructed at one time. The circulating footage should be controlled within 1.0m, so as to close the initial support as soon as possible. In these areas, the arch is inverted first, and the secondary lining is constructed in time to ensure safety.
This tunnel was built by drilling and blasting. Hydraulic drilling rig and air gun are used to drill holes, smooth blasting of arch and side wall blasting, and the excavation contour is controlled to reduce over-excavation and under-excavation. In the early stage, anchor rod, steel mesh and wet shotcrete were used for combined support, and I-steel steel frames were added to the reinforcement section of the hole and fault fracture zone for reinforcement; Waterproof board adopts back hanging nail-free laying technology to ensure no top hole and prevent water leakage; Ballast shall be loaded by ZC50 loader and transported by dump trucks over 15t. The lining is supplied by the 30-60m/h automatic metering mixing station outside the tunnel, transported by 6m concrete delivery truck, poured by 30-60m/h concrete delivery pump and equipped with 12m lining steel formwork trolley; Construction drainage: temporary drains on both sides are used for drainage along the slope in the inlet work area, and reverse slope construction is used in the outlet work area, and water is pumped out of the tunnel step by step by using ditches on both sides; Pipeline forced ventilation is adopted for construction ventilation, and two SDA110AD (1200m/min) adjustable-speed axial fans are arranged outside each tunnel.
4 Main construction methods and technologies
4. 1 hole construction
The entrance construction includes earthwork excavation, entrance drainage system construction and entrance slope protection. Tunnel entry scheme includes protective measures, excavation methods and support types when entering the tunnel.
(1) intercepting ditch construction. Before the excavation of the tunnel entrance, a intercepting ditch shall be built 5 meters away from the excavation slope line of the entrance, and the intercepting ditch leads to the subgrade side ditch to prevent the slope from being washed by accumulated water in rainy season. The intercepting ditch is excavated manually and laid firmly with 7.5# mortar rubble (the picture shows soil). The intercepting ditch is built according to trapezoidal section, with a bottom width of 60cm and a depth of 60cm. The upstream water inlet of the intercepting ditch is closely connected with or slightly lower than the original ground, and the downstream water outlet is connected with the cutting drainage system.
(2) the hole earthwork construction. First, remove the ground plants that affect the construction, such as the vegetation on the ground. Step 2: Carry out construction survey according to the slope of the design drawing, and accurately set out the excavation contour lines of the edge and uphill. Step 3, the crawler excavator enters the construction site and repairs roads for vehicles along the road. Fourth, carry out excavation work. Residual loam, residual sandy cohesive soil and other soils are directly excavated by excavators, and slopes are brushed from top to bottom, loaded by loaders and transported by cars. In the rock blasting excavation section, smooth blasting with dense holes and less explosives is adopted to reduce the disturbance to the imported surrounding rock. Step 5, clean up the floating mud and ballast on the slope and trim the uneven part of the slope.
(3) Protection of the slope at the entrance. The slope protection is of anchor net shotcrete structure, and φ 22 ordinary mortar anchor is drilled on the cleaned rock slope, with a length of 3.5m and a row spacing of1.5m; : Then hang a φ6.5 steel mesh with a spacing of 30×30cm, which is welded with the anchor head. After hanging the steel mesh, the steel mesh and anchor head will be covered with 10cm thick wet sprayed C20 concrete and maintained in time.
(4) Tunnel entry method: step method is adopted for construction. Before entering the tunnel, pre-grouting small ducts are used to pre-reinforce the surrounding rock according to the surrounding rock conditions, that is, a circle of grouting small ducts is constructed 20cm away from the excavation contour line. The pipeline is made of hot-rolled seamless steel pipe, with an outer diameter of φ42mm, a wall thickness of 4mm and a length of 3.5m m. The front end of the steel pipe is processed into a cone shape, and the grouting hole is not drilled at the tail 30cm as the slurry stop section. Four rows of φ8mm grouting holes are drilled around the pipe wall, and the grouting holes are arranged in plum blossom shape. During the construction, the conduit is driven into the surrounding rock along the periphery of the tunnel at an extrapolation angle of 5- 10 degrees. The circumferential spacing of the conduits is 40 cm. After the conduit is driven into the stratum, the corresponding section is grouted, and the loose soil layer at the mouth of the cave is consolidated into a rock mass with strong integrity through the injected cement slurry. Pure cement slurry (w/c= 1.0) is often used for grouting, and cement-sodium silicate double slurry is used when local water is heavy. Its parameters are: cement slurry/water glass = 1: 0.8 (volume ratio), cement slurry w/c= 1.0, water glass modulus m=2.6, concentration be = If the cracks in surrounding rock are not developed and the integrity is good, it is estimated that grouting reinforcement is difficult to work, and only cement mortar (w/c = 0.5 ~) The end of the leading small catheter is welded with the steel bracket. If the surrounding rock of the upward slope of the portal is loose, a circle of grouting small ducts will be added around the leading small ducts to increase the consolidation range of the surrounding rock of the portal. When all advanced pre-support construction is completed, wet sprayed concrete will wrap the grouting small pipe and steel arch frame. After the above advanced support is completed, the bench drilling and blasting excavation can be carried out.