Shallow depth tunnel support structure

Abstract

This invention discloses a method and structure for excavation and support of shallow-buried deep tunnels crossing water-rich strata, relating to the field of tunnel engineering. The aim is to improve the efficiency of pre-drainage and enhance the stability of the support structure. The technical solution adopted in this invention is as follows: For shallow-buried deep tunnel excavation and support, boreholes are drilled at the working face directly above the tunnel. These boreholes serve as drainage wells to lower the groundwater level. Afterward, the tunnel is excavated, and tie rod holes are drilled. A steel reinforcement cage and tie rod reinforcement are placed in the boreholes and tie rod holes, and concrete is poured to form an integral support structure. The support structure is arranged at intervals along the tunnel axis. The shallow-buried deep tunnel support structure is constructed using the above-described method. This invention utilizes boreholes as drainage wells, resulting in high pre-drainage efficiency and no impact on the straight-line construction period. The support structure is embedded in the soil, ensuring safety and stability. This invention is used for the excavation and support of shallow-buried deep tunnels crossing water-rich strata.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering, specifically to a method and structure for excavation and support of shallow-buried deep tunnels traversing water-rich strata. Background Technology

[0002] Excavation of shallow-buried deep tunnels through water-rich strata is challenging, with complex construction techniques and a high risk of tunnel collapses and other safety accidents. Currently, the main construction technique employed is a combination of pre-drainage and pre-support. Pre-drainage holes are drilled at the tunnel face to pre-drain groundwater, and after tunnel excavation, initial support is provided using steel supports, steel mesh, and shotcrete to ensure smooth excavation.

[0003] The above construction techniques have the following shortcomings: First, the effect of advance drainage is limited, especially in tunnel sections rich in groundwater. Advance drainage at the tunnel face is time-consuming and the timing of groundwater discharge cannot be accurately determined, leading to delays in construction progress and increased construction costs. Second, advance support construction occupies the straight-line construction period, slowing down the construction progress. Third, steel supports need to be prefabricated to the designed shape and size, and the steel supports often cannot fit tightly with the tunnel excavation outline, resulting in poor support effect. Fourth, the steel mesh is laid on the outside of the steel supports, with large gaps between it and the surrounding rock, which is not conducive to the long-term stability of the surrounding rock at the tunnel top. Fifth, when the tunnel is excavated by blasting, the steel supports near the tunnel face are easily damaged, causing damage to the support structure and leading to safety hazards. Sixth, under the soaking of groundwater and the crushing of muck trucks, the bottom of the steel supports is easily hollowed out, causing significant safety hazards. Summary of the Invention

[0004] This invention first provides a method for excavation and support of shallow-buried deep tunnels, with the aim of improving the efficiency of advance drainage and enhancing the stability of the support structure.

[0005] The technical solution adopted by the present invention to achieve the above objectives is: a method for excavation and support of shallow-buried deep tunnels, comprising the following steps:

[0006] S1. Leveling the site and determining the drilling points: Clear the working face on the ground directly above the tunnel, and arrange the drilling points along the outside of the projection of the working face on the tunnel sidewall.

[0007] Specifically: there should be at least two rows of drilling points, both rows of drilling points should be arranged along the axis of the tunnel, the distance between each row of drilling points and the vertical plane of the adjacent tunnel sidewall should be 20-40cm, and the horizontal spacing between each row of drilling points should be 50-150cm.

[0008] S2. Install casings at each drilling point and use static mud wall drilling technology for drilling. The bottom elevation of the borehole is lower than the elevation of the tunnel floor.

[0009] For example, the inner diameter of the casing is 20-40cm larger than the pile diameter, and the burial depth of the casing is 200-400cm.

[0010] S3. Clean the borehole and lower the water level: Clean the borehole and then use it as a drainage well to drain water and lower the water level.

[0011] For example: after the borehole reaches the designed depth, the depth and position of the borehole are checked and the borehole is cleaned. The borehole is cleaned by pumping. After cleaning, the well pipe is put into the borehole, and then the drain pipe is put into the well pipe. A water pump is connected to the outside of the drain pipe to drain the water.

[0012] S4. Tunnel excavation construction: After the water level in all boreholes within the single-cycle excavation length of the tunnel is lower than the elevation of the tunnel floor, single-cycle excavation of the tunnel will be carried out until the designed cross-sectional dimensions are reached.

[0013] S5. Select one borehole on each side of the tunnel axis and form a group. Select at least one group of boreholes in the tunnel section with single-cycle excavation, and put a steel reinforcement cage in each group of boreholes.

[0014] Furthermore, the centerlines of the two boreholes in the same group are equidistant from the tunnel axis.

[0015] Furthermore, the vertical plane containing the centerlines of the two boreholes in the same group is perpendicular to the tunnel axis.

[0016] Furthermore, each group of boreholes is arranged at equal horizontal intervals along the tunnel axis.

[0017] For example, a steel reinforcement cage includes vertically arranged main bars and horizontally arranged stirrups. The steel reinforcement cage is rectangular in horizontal cross-section, and the long side of the rectangle is parallel to the vertical plane containing the center lines of the two boreholes.

[0018] Specifically: the length of the longer side of the rectangle should be 50-100mm smaller than the diameter of the drill hole.

[0019] S6. Drill tie rod holes and install tie rod reinforcement in the tunnel: Drill tie rod holes on the tunnel wall along the corresponding cross-sections of two drilling points in the same group. Drill the tie rod holes to the drainage well on the corresponding side, and then put the tie rod reinforcement into the tie rod hole. The front end of the tie rod reinforcement is fixedly connected to the reinforcement cage, and the rear end of the tie rod reinforcement is located outside the hole opening. After the tie rod reinforcement is installed, seal the hole opening corresponding to the rear end of the tie rod reinforcement.

[0020] Furthermore, the tie rod holes on the same cross section of the tunnel are arranged symmetrically along the vertical centerline of the tunnel, and the extension lines of the centerlines of the tie rod holes on the same cross section of the tunnel all pass through the center of the tunnel arch.

[0021] For example, the front end of the tie rod is set with a hook to connect with the steel reinforcement cage, and the rear end of the tie rod is welded to the steel mesh. The number of tie rod holes in the same section of the tunnel is 4 to 8, and is an even number.

[0022] S7. Tunnel support construction: A steel mesh is installed on the inner wall of the tunnel. The steel mesh is fixedly connected to the rear end of the tie rod steel bar. After the steel mesh is installed, the initial support construction is carried out, such as shotcrete.

[0023] S8. After the initial support reaches the design strength, concrete is poured into the borehole in the working face, and the borehole and tie rod hole form an integral support structure.

[0024] S9. After the support structure reaches the design strength, proceed with the next cycle of construction according to steps S4 to S8 until the tunnel passes through water-rich strata.

[0025] This invention also provides a support structure for shallow-buried deep tunnels, constructed using the aforementioned shallow-buried deep tunnel excavation and support method. The purpose is also to improve the efficiency of advance drainage and enhance the stability of the support structure. In the shallow-buried deep tunnel support structure, a vertical pile hole is set on the outer side of each of the two sidewalls of the tunnel. The upper end of the pile hole extends above the ground surface, and the lower end is below the elevation corresponding to the tunnel floor. At least two tie rod holes are set between the tunnel wall and the pile hole on the same side. The centerline of the tie rod holes is located in the vertical plane containing the two pile holes. A steel reinforcement cage is set inside the pile hole, and tie rod reinforcement bars are set inside the tie rod holes. The front ends of the tie rod reinforcement bars are connected to the steel reinforcement cage. Concrete is poured into the drilled holes and tie rod holes to form an integral support structure. The support structure is arranged at intervals along the tunnel axis. A steel mesh is hung on the inner wall of the tunnel, and the steel mesh is fixedly connected to the rear end of the tie rod reinforcement bars. The steel mesh area constitutes the initial support structure of the tunnel.

[0026] Furthermore, the centerlines of two pile holes in the same support structure are equidistant from the tunnel axis. For example, the distance between the pile hole and the vertical plane containing the adjacent tunnel sidewall is 20–40 cm.

[0027] Furthermore, the vertical planes of each support structure are parallel to each other.

[0028] Furthermore, the plane containing the centerlines of the two pile holes of the same support structure is perpendicular to the tunnel axis.

[0029] Furthermore, the various support structures are arranged at equal intervals along the tunnel axis. For example, the spacing between adjacent support structures is 50–150 cm.

[0030] Specifically: The steel reinforcement cage inside the pile hole includes vertically arranged main bars and horizontally arranged stirrups. The steel reinforcement cage is rectangular in horizontal section, and the long side of the rectangle is parallel to the vertical plane where the center lines of the two pile holes are located.

[0031] Specifically: the front end of the tie rod is equipped with a hook to connect with the steel reinforcement cage, and the rear end of the tie rod is welded to the steel mesh.

[0032] Furthermore, the tie rod holes of the support structure are arranged symmetrically along the vertical centerline of the tunnel, and the extension of the centerline of the tie rod holes all pass through the center of the tunnel arch.

[0033] Specifically: the number of tie rod holes in the same support structure is 4 to 8, and is an even number.

[0034] Specifically: the initial support structure is a structure formed by shotcrete.

[0035] The beneficial effects of this invention are as follows: This invention drills holes directly above the working face of the tunnel, using these holes as drainage wells to lower the groundwater level within the single-cycle excavation length of the tunnel. This pre-drainage method is highly efficient and does not interfere with the straight-line construction period. Later, a steel reinforcement cage is inserted into the drilled holes, tie rod holes are drilled, and tie rod reinforcement bars are installed within these holes. Concrete is then poured into the drilled holes and tie rod holes to form an integral reinforced concrete support structure. This structure avoids the problem of the bottom being hollowed out by muck trucks, improving its stability. Simultaneously, the support structure is embedded in the soil, avoiding or mitigating damage from blasting excavation, thus improving its quality and construction efficiency. This invention also directly hangs and fixes steel mesh on the inner wall of the tunnel. The steel mesh is tightly bonded to the surrounding rock, and there are no gaps between the initial support steel mesh and the surrounding rock, which is beneficial for the long-term stability of the tunnel's surrounding rock.

[0036] The tie rod holes on the same cross section of the tunnel are arranged symmetrically along the vertical centerline of the tunnel, which means that the tie rod holes of the support structure are also arranged symmetrically along the vertical centerline of the tunnel. The extension of the centerline of the tie rod hole on the same cross section of the tunnel passes through the center of the arch, which means that the extension of the centerline of the tie rod hole of the support structure passes through the center of the tunnel arch. Both of these constraints help to balance the forces on both sides of the support structure and improve the stability of the support structure. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the shallow-buried deep tunnel support structure of the present invention.

[0038] Figure 2 yes Figure 1 A schematic diagram of the steel reinforcement cage on the horizontal section.

[0039] Attached reference numerals: 1. Working face; 2. Drainage well; 3. Reinforcing steel cage; 4. Tie rod hole; 5. Tie rod reinforcement; 6. Initial support. Detailed Implementation

[0040] This invention is applicable to the excavation and support of shallow-buried deep tunnels traversing water-rich strata, generally suitable for tunnel sections with a burial depth of less than 50m, where the water-rich strata are rich in groundwater and the surrounding rocks are soft and fractured, such as carbonaceous slate and mudstone. The invention will be further described below with reference to the accompanying drawings.

[0041] See Figure 1 The present invention provides a method for excavation and support of shallow-buried deep tunnels, comprising the following steps:

[0042] S1. Leveling the site and determining the drilling points: Clear the working face 1 on the ground directly above the tunnel, and arrange the drilling points along the tunnel sidewall on the outside of the projection of the working face 1.

[0043] Working face 1 is generally planar and is used for drilling and subsequent concrete pouring. Measurements are taken on working face 1 to determine the location of each drilling point. Each drilling point corresponds to one borehole for pre-drainage. All boreholes are first used for drainage, then the entire steel reinforcement cage 3 is lowered and concrete is poured to form the support structure; alternatively, all boreholes are first used for drainage, then a portion of the boreholes are selected for subsequent lowering of the steel reinforcement cage 3 and concrete pouring to form the support structure.

[0044] Since the support structure needs to span both sides of the tunnel, it is distributed along both sides of the tunnel. For example, there are two rows of boreholes, both arranged along the tunnel's axis, meaning the line connecting the two rows is parallel to the tunnel's axis. The boreholes corresponding to the two rows are used to form the support structure. The distance between each row of boreholes and the adjacent tunnel sidewall in the vertical plane is 20–40 cm, and the horizontal spacing between each row of boreholes is 50–150 cm. In addition to these two rows of boreholes, additional boreholes can be appropriately arranged; these boreholes are solely for drainage.

[0045] S2. Install casings at each drilling point and use static mud wall drilling technology for drilling. The bottom elevation of the borehole is lower than the elevation of the tunnel floor.

[0046] The bottom elevation of the borehole is lower than the elevation of the tunnel floor, ensuring that groundwater in the tunnel excavation area is reduced below the tunnel floor. Step S2 is carried out according to existing technology, following the approved construction plan and operating procedures, until the designed depth is reached.

[0047] For example, for boreholes forming support structures, the inner diameter of the casing should be 20-40 cm larger than the pile diameter, and the casing depth should be 200-400 cm. The centerline of the casing should be vertical and coincide with the centerline of the borehole. Unless otherwise specified in the design, the permissible error in plane is 50 mm, and the vertical inclination should not exceed 1%. When the drilling rig is in place, measures should be taken to ensure that the center of the drilling tool and the center of the borehole coincide, and the deviation should not exceed 20 mm. After the drilling rig is in place, it should be level and stable, and measures should be taken to fix it to ensure that it does not shift or shake during drilling. The drilling mud is mainly composed of water, clay, and additives in a certain proportion. It can be mechanically stirred evenly in the mud pit and borehole, and the mud specific gravity should be controlled between 1.15 and 1.20. Before drilling, the centerline and verticality should be aligned, and the casing should be pressed in place. When filling the borehole with mud, always keep the mud level 1.5 to 2.0 meters above the groundwater level and 0.3 meters below the top of the casing to prevent overflow.

[0048] S3. Clean the borehole and lower the water level: Clean the borehole and then use it as drainage well 2 to drain water and lower the water level.

[0049] Once the borehole reaches the designed depth, the depth and position are checked, and the borehole is cleaned. For example, a mud pump is used to remove mud from the borehole, along with drill cuttings. After cleaning, the pre-fabricated well casing is connected to the surface and placed into the borehole. When lowering it, it should be aligned with the center of the borehole and inserted vertically, taking care not to touch the borehole wall. The well casing should be lowered slowly, steadily, and continuously. After installation, a drain pipe is placed inside the well casing, and a water pump is used to drain any seepage into a surface drainage ditch.

[0050] Drainage can be achieved by drilling holes, either within the single-cycle excavation length of the tunnel and its surrounding area, or by drilling all the boreholes.

[0051] S4. Tunnel Excavation Construction: After the water level in all boreholes within the single-cycle excavation length of the tunnel is lower than the elevation of the tunnel floor, single-cycle excavation of the tunnel will commence, proceeding to the designed cross-sectional dimensions. The single-cycle excavation length will be determined comprehensively based on the working conditions, and the tunnel excavation will be carried out according to existing processes.

[0052] S5. Select one borehole on each side of the tunnel axis and form a group. Select at least one group of boreholes in the tunnel section with single-cycle excavation, and put the steel reinforcement cage 3 into each group of boreholes.

[0053] Two boreholes forming a group are used to create an integral reinforced concrete support structure; therefore, the two boreholes in the same group are located on opposite sides of the tunnel axis. The centerlines of the two boreholes in the same group are vertical, and the distances between the centerlines of the two boreholes and the tunnel axis may be equal or unequal. To ensure that the stress on both sides of the support structure is consistent, the distances between the centerlines of the two boreholes and the tunnel axis are preferably equal.

[0054] The centerlines of the two boreholes in the same group are both vertical, thus forming a vertical plane that is either oblique or perpendicular to the tunnel axis. When the plane is perpendicular, the size of a single support structure is relatively small, and the tunnel penetrates a certain length of water-rich strata, resulting in a larger number of support structures. When the plane is oblique, the size of a single support structure is relatively large, and the tunnel penetrates an equal length of water-rich strata, resulting in a relatively smaller number of support structures.

[0055] The boreholes in each group can be arranged at equal or unequal intervals. When the water-rich strata are homogeneous, the support structure can be arranged at equal intervals along the tunnel axis; otherwise, the support structure can be appropriately densified at weak points. Generally, the vertical plane containing the centerlines of two boreholes in the same group is perpendicular to the tunnel axis, and the boreholes in each group are arranged at equal horizontal intervals along the tunnel axis. For example, the horizontal distance between two adjacent groups of boreholes is 100–200 cm.

[0056] The reinforcing steel cage 3 can be prefabricated. Before placing the reinforcing steel cage 3 into the borehole, the drainage device inside the borehole needs to be removed, for example, the drainage pipe and well pipe need to be removed from the borehole in sequence, and then the prefabricated reinforcing steel cage 3 is hoisted into the borehole. Based on the stress of the support structure, the reinforcing steel cage 3 preferably adopts the following structure. See [link / reference] Figure 2 The reinforcing cage 3 includes vertically arranged main bars and horizontally arranged stirrups. The reinforcing cage 3 is rectangular in horizontal cross-section, and the long side of the rectangle is parallel to the vertical plane containing the center lines of the two boreholes in the same group. To ensure that the reinforcing cage 3 can be smoothly inserted into the borehole, the long side of the reinforcing cage 3 is 50-100mm smaller than the diameter of the borehole.

[0057] S6. Drill tie rod holes 4 inside the tunnel and install tie rod reinforcement bars 5.

[0058] Inside the tunnel, the tunnel wall is measured and positioned. Tie rod holes 4 are then drilled along the corresponding cross-sections of the two boreholes in the same group. Drilling of tie rod holes 4 stops when they reach the drainage well 2 on the corresponding side. Tie rod holes 4 and the two boreholes in the same group are located on the same plane. (See [reference]). Figure 1 The tie rod hole 4 is drilled into the drainage well 2 on the corresponding side; that is, the tie rod hole 4 only needs to be connected to the two holes in the same group. To balance the stress on the support structure, the tie rod holes 4 on the same cross-section of the tunnel are arranged symmetrically along the vertical centerline of the tunnel. The extension lines of the centerlines of the tie rod holes 4 on the same cross-section of the tunnel all pass through the center of the tunnel arch. See [reference needed]. Figure 1 The support structure corresponding to tie rod hole 4 mainly bears tensile force, and the diameter of tie rod hole 4 is smaller than the diameter of the two boreholes in the same group. The number of tie rod holes 4 is generally 4 to 8, and preferably an even number, to achieve an axisymmetric arrangement.

[0059] After drilling the tie rod hole 4, insert the tie rod reinforcement 5 into the tie rod hole 4. The front end of the tie rod reinforcement 5 is fixedly connected to the reinforcement cage 3, for example, by setting a hook at the front end of the tie rod reinforcement 5 to connect it to the reinforcement cage 3; the rear end of the tie rod reinforcement 5 is located outside the opening of the tie rod hole 4. One or more tie rod reinforcements 5 are placed in each tie rod hole 4. After the tie rod reinforcements 5 are installed, seal the opening corresponding to the rear end of the tie rod reinforcement 5.

[0060] S7. Tunnel Support Construction: A steel mesh is installed on the inner wall of the tunnel. The steel mesh is fixedly connected to the rear end of the tie rod 5, for example, by welding the steel mesh to the rear end of the tie rod 5. After the steel mesh is installed, initial support 6 is constructed at the steel mesh location, for example, by spraying concrete.

[0061] S8. After the initial support 6 reaches its design strength, concrete is poured into each group of boreholes at the working face 1 to form an integral support structure with the boreholes and tie rod holes 4. Concrete pouring is performed on the boreholes corresponding to each group of boreholes within the single-cycle excavation length. The concrete fluidity should meet construction requirements to ensure dense filling of the boreholes and tie rod holes 4. Boreholes used only for drainage in the excavated tunnel sections can be backfilled.

[0062] S9. After the support structure reaches the design strength, proceed with the next cycle of construction according to steps S4 to S8 until the tunnel passes through water-rich strata.

[0063] This invention also provides a support structure for shallow-buried deep tunnels, which is constructed using the aforementioned shallow-buried deep tunnel excavation and support method. See also... Figure 1 For the support structure of shallow-buried deep tunnels, a vertical pile hole is set on the outer side of each of the two sidewalls of the tunnel. The upper end of the pile hole protrudes above the ground surface, and the lower end is below the elevation corresponding to the tunnel floor. The two pile holes are a set of boreholes determined in step S5 above. At least two tie rod holes 4 are set between the tunnel wall and the pile holes on the same side. At least one tie rod hole 4 connects the tunnel to one pile hole, and at least one tie rod hole 4 connects the tunnel to another pile hole. The centerline of the tie rod hole 4 is located in the vertical plane where the two pile holes are located, that is, the tie rod hole 4 and the pile hole are located in the same vertical plane.

[0064] A steel reinforcement cage 3 is installed inside the pile hole. See, for example... Figure 2 The reinforcing cage 3 includes vertically arranged main bars and horizontally arranged stirrups. The reinforcing cage 3 is rectangular in horizontal cross-section, with the long side of the rectangle parallel to the vertical plane containing the center lines of the two pile holes. Tie rods 5 are installed in the tie rod holes 4, and the front end of the tie rods 5 is connected to the reinforcing cage 3. For example, the front end of the tie rods 5 is provided with a hook to connect to the reinforcing cage 3, and there is at least one tie rod 5 in each tie rod hole 4.

[0065] Concrete is poured into the drilled holes and tie rod holes 4 to form an integral support structure, which is arranged at intervals along the tunnel axis. To balance the stress on individual support structures, the centerlines of the two pile holes of the same support structure are equidistant from the tunnel axis. Specifically, the distance between the pile hole and the vertical plane of the adjacent tunnel sidewall is 20-40 cm.

[0066] To optimize the stress distribution of a single support structure, the tie rod holes 4 of the support structure are arranged symmetrically along the vertical centerline of the tunnel. For example, the number of tie rod holes 4 in the same support structure is 4 to 8, and always an even number. To further optimize the stress distribution of a single support structure, the extension of the centerline of each tie rod hole 4 passes through the center of the tunnel arch.

[0067] Each support structure is arranged along the tunnel axis, and the vertical planes in which each support structure is located are generally parallel to each other and perpendicular to the tunnel axis. For example, the support structures are arranged at equal intervals along the tunnel axis, with a spacing of 50 to 150 cm between adjacent support structures.

[0068] A steel mesh is installed on the inner wall of the tunnel. The steel mesh is fixedly connected to the rear end of the tie rod 5, for example, by welding the rear end of the tie rod 5 to the steel mesh. The steel mesh area forms the initial support structure 6 of the tunnel. The initial support structure 6 is generally a structure formed by shotcrete, and the steel mesh is part of the initial support structure 6.

Claims

1. A support structure for shallow-buried deep tunnels, characterized in that: A vertical pile hole is set on the outer side of each of the two sidewalls of the tunnel. The upper end of the pile hole extends to the ground surface, and the lower end of the pile hole is lower than the elevation corresponding to the tunnel floor. At least two tie rod holes (4) are set between the tunnel wall and the pile hole on the same side. The center line of the tie rod hole (4) is located on the vertical plane where the two pile holes are located. The tie rod holes (4) on the same section of the tunnel are arranged symmetrically along the vertical center line of the tunnel. A steel reinforcement cage (3) is set in the pile hole, and tie rod reinforcement (5) is set in the tie rod hole (4). The front end of the reinforcing bar (5) is connected to the reinforcing bar skeleton (3). Concrete is poured into the drilled holes and tie rod holes (4) to form an integral support structure. The center lines of the two pile holes of the same support structure are equidistant from the tunnel axis. The support structure is arranged at intervals along the tunnel axis. A steel mesh is hung on the inner wall of the tunnel. The steel mesh is fixedly connected to the rear end of the tie rod reinforcing bar (5). The steel mesh is the initial support (6) structure of the tunnel. The initial support (6) structure is a structure formed by shotcrete.

2. The shallow-buried deep tunnel support structure as described in claim 1, characterized in that: The vertical planes of each support structure are parallel to each other.

3. The shallow-buried deep tunnel support structure as described in claim 2, characterized in that: The plane containing the centerlines of the two pile holes of the same support structure is perpendicular to the axis of the tunnel.

4. The shallow-buried deep tunnel support structure as described in claim 2, characterized in that: Each support structure is arranged at equal intervals along the tunnel axis.

5. The shallow-buried deep tunnel support structure as described in any one of claims 1 to 4, characterized in that: The steel reinforcement cage (3) inside the pile hole includes vertically arranged main bars and horizontally arranged stirrups. The steel reinforcement cage (3) is rectangular in the horizontal section, and the long side of the rectangle is parallel to the vertical plane where the center lines of the two pile holes are located.

6. The shallow-buried deep tunnel support structure as described in any one of claims 1 to 4, characterized in that: The front end of the tie rod (5) is provided with a hook to connect with the steel reinforcement cage (3), and the rear end of the tie rod (5) is welded to the steel mesh.

7. The shallow-buried deep tunnel support structure as described in any one of claims 1 to 4, characterized in that: The tie rod holes (4) of the support structure are arranged symmetrically along the vertical centerline of the tunnel, and the extension of the centerline of the tie rod holes (4) all pass through the center of the tunnel arch.

8. The shallow-buried deep tunnel support structure as described in claim 7, characterized in that: The number of tie rod holes (4) in the same support structure is 4 to 8, and is an even number.

9. The shallow-buried deep tunnel support structure as described in any one of claims 1 to 4, characterized in that: The distance between the pile hole and the vertical plane of the adjacent tunnel sidewall is 20-40cm, and the spacing between adjacent support structures is 50-150cm.

Images