Tunnel supporting device and method for crossing tunnel bottom large underground river and large-span cavern

Abstract

The invention discloses a tunnel supporting device penetrating through a tunnel bottom large underground river and a large-span cavern, which comprises a dome reticulated shell structure, the dome reticulated shell structure is fixedly connected to the inner wall of an upper cavern tunnel, and an anti-seepage geomembrane layer and a light foam concrete filling layer are arranged between the dome reticulated shell structure and the inner wall of the upper cavern tunnel. The system further comprises a multi-support cable assembly steel bridge, the multi-support cable assembly steel bridge is arranged above the underground river, and the multi-support cable assembly steel bridge is fixedly connected to the dome reticulated shell structure and the lower rock stratum. The invention further discloses a tunnel supporting method penetrating through the tunnel bottom large underground river and the large-span cavern. According to the tunnel supporting device and method penetrating through the tunnel bottom large underground river and the large-span cavern, the stability and safety needed by a tunnel structure are guaranteed, and meanwhile the cost needed by engineering is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of tunnel support construction, and specifically relates to a tunnel support device for crossing a large underground river and a large-span karst cavity at the bottom of a tunnel, and also relates to a tunnel support method for crossing a large underground river and a large-span karst cavity at the bottom of a tunnel. Background Art

[0002] With the rapid development of my country's economy, the number of underground infrastructure projects such as railways and highways has increased rapidly, and the special geological conditions they face are becoming more and more complex. In karst areas, tunnels inevitably pass through karst strata, which are complex and changeable, and difficult to construct. At the same time, when passing through large-span cavities in tunnels, they may encounter geological conditions that require consideration of the environment and hydrogeology, such as large underground rivers at the bottom of the tunnel, which pose a serious threat to the safety of engineering construction, resulting in slow construction progress and increased safety factors. For the support problem of cavities, traditional technical methods use direct concrete injection to achieve a close combination of the concrete layer and the cavity wall to achieve a good support effect, but direct concrete injection has high requirements for the engineering foundation. If the geology is poor, the construction will be restricted. At the same time, the scope of application of direct concrete injection is limited. It is more suitable for cavities with smaller spans and poorer stability. Summary of the invention The purpose of the present invention is to provide a tunnel support device for crossing a large underground river and a large-span solution cavity at the bottom of the tunnel, thereby ensuring the stability and safety required by the tunnel structure and reducing the cost required for the project.

[0003] Another object of the present invention is to provide a tunnel support method for crossing a large underground river and a large-span cavities at the bottom of the tunnel.

[0004] The technical solution adopted by the present invention is a tunnel support device for crossing a large underground river and a large-span karst cavity at the bottom of a tunnel, including a dome lattice shell structure, which is fixedly connected to the inner wall of the upper karst cavity tunnel, and an anti-seepage geomembrane layer and a lightweight foam concrete filling layer are provided between the dome lattice shell structure and the inner wall of the upper karst cavity tunnel. It also includes a multi-support cable-assembled steel bridge, which is arranged above the underground river and is respectively fixedly connected to the dome lattice shell structure and the lower rock layer.

[0005] The present invention is also characterized in that: The anti-seepage geomembrane layer is laid on the inner wall of the upper cavity tunnel, and the lightweight foam concrete filling layer is filled between the dome reticulated shell structure and the anti-seepage geomembrane layer.

[0006] Assembled steel bridge cables are fixedly connected at the four corners at both ends of the multi-support cable-assembled steel bridge, and the other ends of the four assembled steel bridge cables are fixedly connected to the dome lattice shell structure. A pad is provided between the multi-support cable-assembled steel bridge and the underlying rock formation.

[0007] The dome lattice shell structure includes a plurality of steel beams, which are arranged along the radial direction, one end of the plurality of steel beams is fixed by hexagonal sleeve bolts, the other ends of the plurality of steel beams are fixed with locking anchor rods, the other ends of the plurality of locking anchor rods are fixed to the inner wall of the upper cavity tunnel, small fiber optic Bragg grating sensors are provided at the contact positions of the plurality of locking anchor rods with the inner wall of the upper cavity tunnel and at the contact positions of the plurality of locking anchor rods with the hexagonal sleeve bolts, the plurality of locking anchor rods penetrate the lightweight foam concrete filling layer and the anti-seepage geomembrane layer, and also includes a plurality of inner ring beams, the plurality of inner ring beams are fixed to the plurality of steel beams along the circumference of concentric circles, and the intersections of the plurality of inner ring beams and the plurality of steel beams are fixed by bolts.

[0008] The multi-support cable-assembled steel bridge is composed of a number of standard trusses and a number of high-shear multilateral trusses, which are arranged alternately. The multi-support cable-assembled steel bridge is arranged along an "I" shape, and the outer walls of the number of standard trusses and the number of high-shear multilateral trusses are coated with an anti-slip paint layer.

[0009] The standard truss includes a standard truss inner ring beam, the cross-section of the standard truss inner ring beam is diamond-shaped, and a standard truss outer ring beam is fixedly connected to the outer side of the standard truss inner ring beam, and the cross-section of the standard truss outer ring beam is rectangular; the high shear polygonal truss includes a scissors brace, the cross-section of the scissors brace is "X"-shaped, and a high shear polygonal truss inner ring beam is fixedly connected to the scissors brace, and the cross-section of the high shear polygonal truss inner ring beam is rectangular, and two straight lines of the scissors brace coincide with the rectangular diagonals of the high shear polygonal truss inner ring beam, and a high shear polygonal truss outer ring beam is fixedly connected to the outer side of the scissors brace, and the cross-section of the high shear polygonal truss outer ring beam is rectangular, and two straight lines of the scissors brace coincide with the rectangular diagonals of the high shear polygonal truss outer ring beam.

[0010] Another technical solution adopted by the present invention is a tunnel support method for crossing a large underground river and a large-span cavities at the bottom of the tunnel, comprising the following steps: S1. Install multi-support cable-assembled steel bridge; S2. Lay an anti-seepage geomembrane layer on the inner wall of the upper cavity tunnel; S3, install the dome lattice shell structure on the inner wall of the upper cavity tunnel through the locking anchor rod; S4, filling a lightweight foam concrete filling layer between the dome reticulated shell structure and the anti-seepage geomembrane layer; S5. Check the stress condition of the dome lattice shell structure and complete the tunnel support.

[0011] Another technical solution of the present invention is also characterized in that: The specific process of S1 is as follows: In the early stage of construction, inclined guide tunnels are excavated at a ratio of 1:1.5 on both sides of the large underground river at the bottom of the tunnel, so that the guide tunnels on both sides are connected with the multi-support cable-assembled steel bridge. At the same time, horizontal areas are left at the end of the slope of the guide tunnel and the cliff. The bearing capacity of the ground in the horizontal area is tested by placing a static penetration instrument on the horizontal area, and points with a bearing capacity greater than 20,000 PSF are selected as fixed points. Pads are laid on the fixed points, holes are drilled around the pads and expansion plugs are driven in, and bolts and nuts are used to connect the multi-support cable-assembled steel bridge to the pads on the lower rock layer with expansion plugs. At the same time, assembled steel bridge cables are arranged around the upper dissolution cavity tunnel to pull up the multi-support cable-assembled steel bridge and fix it on the lower pad. Subsequently, the gaps between the guide tunnels on both sides and the upper and lower parts of the slope of the excavated guide tunnels are poured with concrete.

[0012] The specific process of S3 is: S3.1. Use ultrasonic sensors to detect the front, top, bottom, left and right dimensions of the upper cavity tunnel; S3.2. According to the size of the upper cavity tunnel, the center of the dome lattice shell structure is set directly above the center of the multi-support cable assembly steel bridge. According to the center point, a circle of tunnel walls in the same plane of the upper cavity tunnel is divided into several basic points with the center point as the symmetry axis. According to the center point, several steel beams are embedded into the inner wall of the upper cavity tunnel through locking anchor rods in a diagonally connected form. Locking anchor rods are extended from the end of each steel beam into the surrounding rock. Hexagonal sleeve bolts are used to connect at the center point. At the same time, the assembled steel bridge cables arranged around the upper cavity tunnel are fixed to the ends of the locking anchor rods. S3.3. According to the shape of the bottom of the dome lattice shell structure, the height of the bottom and top of the dome lattice shell structure is divided into several equal parts. The inner ring beam of each layer adopts a proportionally reduced structure with the same shape as the bottom of the dome lattice shell structure. The inner ring beam gradually shrinks as the dome lattice shell structure goes up, and adjacent inner ring beams are connected by bolts.

[0013] The specific process of S5 is as follows: by setting up a number of small fiber grating sensors on the locking foot anchor rods and the hexagonal sleeve bolts, the surface stress changes of the set foundation points are continuously monitored; when the average stress change rate of the monitoring point exceeds 50% of the warning value for three consecutive days, the number of locking foot anchor rods is increased near the foundation point of the dome lattice structure to ensure that the tunnel stability requirements are met; when the average stress change rate of the monitoring point is lower than 50% of the warning value for three consecutive days, the dome lattice structure is arranged, and then concrete is poured around the multi-support cable-assembled steel bridge deck, so that the multi-support cable-assembled steel bridge deck can pass through the pilot tunnel, and also serve as the lining bottom plate for future tunnel construction work to complete the tunnel support.

[0014] The beneficial effects of the present invention are: The tunnel support device and method for crossing a large underground river and a large-span solution cavity at the bottom of a tunnel provided by the present invention can use a multi-support cable-assembled steel bridge to quickly and safely pass through a large underground river at the bottom of a tunnel, while being able to use a dome lattice structure based on locking foot anchors to timely support a large-span solution cavity with poor stability, and utilize the overlapping compression zones formed between adjacent locking foot anchors to form a compression belt to suppress deformation of the upper solution cavity tunnel and improve the stress state of the support structure, thereby improving the overall safety of the upper solution cavity tunnel and the bearing capacity of the structure; compared with traditional welding, adjacent steel beams are connected by assembled bolts, which can reduce maintenance costs and timely repair problematic components. Disassembly and repair can be carried out, which simplifies the maintenance process while providing precision; when filling the cavity above the dome lattice structure with lightweight foam concrete, an anti-seepage geomembrane layer is first added at the contact surface between the lightweight foam concrete and the upper cavity tunnel to enhance its anti-seepage effect; while significantly improving the anti-seepage performance, the lightweight characteristics of the lightweight foam concrete can reduce the pressure on the rock wall around the upper cavity tunnel, making the stress on the surrounding rock more uniform and relaxed, and reducing the stress concentration of the surrounding rock; it effectively copes with the situation of encountering a large underground river at the bottom of the tunnel and a large-span cavity with poor stability at the same time, and efficiently supports the large-span cavity with poor stability, reducing the support cost and ensuring the quality of engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the structure of a tunnel support device for crossing a large underground river and a large-span cavities at the bottom of a tunnel according to the present invention; Figure 2 It is a structural schematic diagram of the dome lattice shell structure of the present invention; Figure 3 It is a structural schematic diagram of a standard truss of the present invention; Figure 4 It is a structural schematic diagram of the high shear force multilateral truss of the present invention.

[0016] In the figure, 1. upper cavity tunnel, 2. anti-seepage geomembrane layer, 3. dome lattice shell structure, 4. lightweight foam concrete filling layer, 5. multi-support cable-assembled steel bridge, 6. underground river, 7. lower rock layer, 8. assembled steel bridge cable, 9. pad, 10. steel beam, 11. hexagonal sleeve bolt, 12. locking foot anchor rod, 13. inner ring beam, 14. bolt, 15. standard truss, 16. high shear multilateral truss, 17. standard truss inner ring beam, 18. standard truss outer ring beam, 19. scissors brace, 20. high shear multilateral truss inner ring beam, 21. high shear multilateral truss outer ring beam, 22. small fiber grating sensor. DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0018] The tunnel support device provided by the present invention for crossing a large underground river and a large-span cavities at the bottom of the tunnel is as follows: Figure 1 As shown, it includes a dome lattice shell structure 3, which is fixed to the inner wall of the upper cavity tunnel 1. An anti-seepage geomembrane layer 2 and a lightweight foam concrete filling layer 4 are arranged between the dome lattice shell structure 3 and the inner wall of the upper cavity tunnel 1. While significantly improving the anti-seepage performance, its lightweight characteristics can reduce the pressure on the surrounding rock wall, make the surrounding rock stress more uniform and relaxed, and reduce the stress concentration of the surrounding rock. It also includes a multi-support cable-assembled steel bridge 5, which is arranged above the underground river 6. The multi-support cable-assembled steel bridge 5 is fixedly connected to the dome lattice structure 3 and the lower rock layer 7 respectively; the anti-seepage geomembrane layer 2 is laid on the inner wall of the upper cavity tunnel 1, and the lightweight foam concrete filling layer 4 is filled between the dome lattice structure 3 and the anti-seepage geomembrane layer 2; the four corners of the two ends of the multi-support cable-assembled steel bridge 5 are fixedly connected with assembled steel bridge cables 8, and the other ends of the four assembled steel bridge cables 8 are fixedly connected to the dome lattice structure 3, and a pad 9 is provided between the multi-support cable-assembled steel bridge 5 and the lower rock layer 7. Figure 2 As shown, the dome lattice structure 3 includes a plurality of steel beams 10, which are arranged along the radial direction, one end of the plurality of steel beams 10 is fixed by a hexagonal sleeve bolt 11, and the other end of the plurality of steel beams 10 is fixed with a locking foot anchor rod 12, and the other end of the plurality of locking foot anchor rods 12 is fixed to the inner wall of the upper dissolution cavity tunnel 1 to ensure the stability and integrity of the structure. Small fiber optic Bragg grating sensors 22 are provided at the contact positions of several locking anchor rods 12 and the inner wall of the upper dissolution cavity tunnel 1 and at the contact positions of several locking anchor rods 12 and the hexagonal sleeve bolts 11. Several locking anchor rods 12 penetrate the lightweight foam concrete filling layer 4 and the anti-seepage geomembrane layer 2. The support system of the dome lattice structure 3 controls the stability and balance of the dome lattice structure 3 frame, and also includes several inner ring beams 13. Several inner ring beams 13 are fixedly connected to several steel beams 10 along the circumference of concentric circles. The intersections of several inner ring beams 13 and several steel beams 10 are fixedly connected by bolts 14. Improve the accuracy of components, facilitate disassembly, and quickly respond to geological conditions caused by large-span cavities; the multi-support cable-assembled steel bridge 5 is composed of a number of standard trusses 15 and a number of high-shear multilateral trusses 16, which are used to simultaneously meet the bridge's bending and shearing capabilities. A number of standard trusses 15 and a number of high-shear multilateral trusses 16 are interspersed, and the multi-support cable-assembled steel bridge 5 is arranged along an "I" shape. The outer walls of a number of standard trusses 15 and a number of high-shear multilateral trusses are coated with an anti-slip coating layer to ensure that the multi-support cable-assembled steel bridge can meet the stability and safety requirements required by the project. Figure 3 As shown, the standard truss 15 includes a standard truss inner ring beam 17, the cross section of the standard truss inner ring beam 17 is diamond-shaped, and the outer side of the standard truss inner ring beam 17 is fixedly connected to a standard truss outer ring beam 18, and the cross section of the standard truss outer ring beam 18 is rectangular; Figure 4As shown, the high shear force polygonal truss 16 includes a scissors brace 19, the cross section of the scissors brace 19 is "X" shaped, a high shear force polygonal truss inner ring beam 20 is fixedly connected to the scissors brace 19, the cross section of the high shear force polygonal truss inner ring beam 20 is rectangular, and two straight lines of the scissors brace 19 coincide with the rectangular diagonal of the high shear force polygonal truss inner ring beam 20, and a high shear force polygonal truss outer ring beam 21 is fixedly connected to the outside of the scissors brace 19, the cross section of the high shear force polygonal truss outer ring beam 21 is rectangular, and two straight lines of the scissors brace 19 coincide with the rectangular diagonal of the high shear force polygonal truss outer ring beam 21. The multi-support cable-assembled steel bridge and the dome lattice structure support system are used to deal with the situation of encountering a large underground river and a large-span cavities crossing the bottom of the tunnel at the same time, so as to achieve smooth crossing of the large underground river at the bottom of the tunnel, and at the same time, tunnels with large spans and cavities with poor stability can be efficiently supported and waterproofed.

[0019] Example 1 The tunnel support device proposed in this embodiment for crossing a large underground river and a large-span cavities at the bottom of the tunnel is as follows: Figure 1 As shown, it includes a dome lattice shell structure 3, which is fixed to the inner wall of the upper dissolution cavity tunnel 1. An anti-seepage geomembrane layer 2 and a lightweight foam concrete filling layer 4 are provided between the dome lattice shell structure 3 and the inner wall of the upper dissolution cavity tunnel 1. It also includes a multi-support cable-assembled steel bridge 5, which is arranged above the underground river 6 and is fixed to the dome lattice shell structure 3 and the lower rock layer 7 respectively.

[0020] Example 2 The tunnel support device proposed in this embodiment for crossing a large underground river and a large-span cavities at the bottom of the tunnel is as follows: Figure 1 As shown, it includes a dome lattice shell structure 3, which is fixedly connected to the inner wall of the upper cavity tunnel 1, and an anti-seepage geomembrane layer 2 and a lightweight foam concrete filling layer 4 are arranged between the dome lattice shell structure 3 and the inner wall of the upper cavity tunnel 1. It also includes a multi-support cable assembled steel bridge 5, which is arranged above the underground river 6, and the multi-support cable assembled steel bridge 5 is respectively fixedly connected to the dome lattice shell structure 3 and the lower rock layer 7; the anti-seepage geomembrane layer 2 is laid on the inner wall of the upper cavity tunnel 1, and the lightweight foam concrete filling layer 4 is filled between the dome lattice shell structure 3 and the anti-seepage geomembrane layer 2; assembled steel bridge cables 8 are fixedly connected at the four corners of both ends of the multi-support cable assembled steel bridge 5, and the other ends of the four assembled steel bridge cables 8 are fixedly connected to the dome lattice shell structure 3, and a pad 9 is arranged between the multi-support cable assembled steel bridge 5 and the lower rock layer 7.

[0021] Example 3 The tunnel support device proposed in this embodiment for crossing a large underground river and a large-span cavities at the bottom of the tunnel is as follows: Figure 1As shown, it includes a dome lattice shell structure 3, which is fixedly connected to the inner wall of the upper cavity tunnel 1. An anti-seepage geomembrane layer 2 and a lightweight foam concrete filling layer 4 are provided between the dome lattice shell structure 3 and the inner wall of the upper cavity tunnel 1. It also includes a multi-support cable-assembled steel bridge 5, which is arranged above the underground river 6 and is respectively fixedly connected to the dome lattice shell structure 3 and the lower rock layer 7; the anti-seepage geomembrane layer 2 is laid on the inner wall of the upper cavity tunnel 1, and the lightweight foam concrete filling layer 4 is filled between the dome lattice shell structure 3 and the anti-seepage geomembrane layer 2; assembled steel bridge cables 8 are fixedly connected to the four corners at both ends of the multi-support cable-assembled steel bridge 5, and the other ends of the four assembled steel bridge cables 8 are fixedly connected to the dome lattice shell structure 3, and a pad 9 is provided between the multi-support cable-assembled steel bridge 5 and the lower rock layer 7. As shown Figure 2 As shown, the dome lattice shell structure 3 includes a plurality of steel beams 10, which are arranged along the radial direction, one end of the plurality of steel beams 10 is fixed by a hexagonal sleeve bolt 11, and the other ends of the plurality of steel beams 10 are fixed with locking anchor rods 12, and the other ends of the plurality of locking anchor rods 12 are fixed to the inner wall of the upper dissolution cavity tunnel 1, and small fiber optic grating sensors 22 are provided at the contact positions of the plurality of locking anchor rods 12 and the inner wall of the upper dissolution cavity tunnel 1 and at the contact positions of the plurality of locking anchor rods 12 and the hexagonal sleeve bolts 11, and the plurality of locking anchor rods 12 all penetrate the lightweight foam concrete filling layer 4 and the anti-seepage geomembrane layer 2, and also include a plurality of inner ring beams 13, and the plurality of inner ring beams 13 are fixed to the plurality of steel beams 10 along the circumference of the concentric circle, and the intersections of the plurality of inner ring beams 13 and the plurality of steel beams 10 are fixed by bolts 14.

[0022] Example 4 The tunnel support device proposed in this embodiment for crossing a large underground river and a large-span cavities at the bottom of the tunnel is as follows: Figure 1 As shown, it includes a dome lattice shell structure 3, which is fixedly connected to the inner wall of the upper cavity tunnel 1. An anti-seepage geomembrane layer 2 and a lightweight foam concrete filling layer 4 are provided between the dome lattice shell structure 3 and the inner wall of the upper cavity tunnel 1. It also includes a multi-support cable-assembled steel bridge 5, which is arranged above the underground river 6 and is respectively fixedly connected to the dome lattice shell structure 3 and the lower rock layer 7; the anti-seepage geomembrane layer 2 is laid on the inner wall of the upper cavity tunnel 1, and the lightweight foam concrete filling layer 4 is filled between the dome lattice shell structure 3 and the anti-seepage geomembrane layer 2; assembled steel bridge cables 8 are fixedly connected to the four corners at both ends of the multi-support cable-assembled steel bridge 5, and the other ends of the four assembled steel bridge cables 8 are fixedly connected to the dome lattice shell structure 3, and a pad 9 is provided between the multi-support cable-assembled steel bridge 5 and the lower rock layer 7. As shown Figure 2As shown, the dome lattice structure 3 includes a plurality of steel beams 10, which are arranged along the radial direction, one end of each of the steel beams 10 is fixed by a hexagonal sleeve bolt 11, and the other end of each of the steel beams 10 is fixed with a locking anchor rod 12, and the other end of each of the locking anchor rods 12 is fixed to the inner wall of the upper dissolution cavity tunnel 1. Small fiber optic Bragg grating sensors 22 are provided at the contact positions between the several locking foot anchor rods 12 and the inner wall of the upper dissolution cavity tunnel 1 and at the contact positions between the several locking foot anchor rods 12 and the hexagonal sleeve bolts 11. The several locking foot anchor rods 12 penetrate the lightweight foam concrete filling layer 4 and the anti-seepage geomembrane layer 2, and also include several inner ring beams 13. The several inner ring beams 13 are fixedly connected with the several steel beams 10 along the circumference of concentric circles, and the intersections of the several inner ring beams 13 and the several steel beams 10 are fixedly connected by bolts 14; the multi-support cable-assembled steel bridge 5 is composed of several standard trusses 15 and several high-shear multilateral trusses 16, and the several standard trusses 15 and the several high-shear multilateral trusses 16 are interspersed. The multi-support cable-assembled steel bridge 5 is arranged along an "I" shape, and the outer walls of the several standard trusses 15 and the several high-shear multilateral trusses are coated with an anti-slip coating layer.

[0023] Example 5 The tunnel support device proposed in this embodiment for crossing a large underground river and a large-span cavities at the bottom of the tunnel is as follows: Figure 1 As shown, it includes a dome lattice shell structure 3, which is fixedly connected to the inner wall of the upper cavity tunnel 1. An anti-seepage geomembrane layer 2 and a lightweight foam concrete filling layer 4 are provided between the dome lattice shell structure 3 and the inner wall of the upper cavity tunnel 1. It also includes a multi-support cable-assembled steel bridge 5, which is arranged above the underground river 6 and is respectively fixedly connected to the dome lattice shell structure 3 and the lower rock layer 7; the anti-seepage geomembrane layer 2 is laid on the inner wall of the upper cavity tunnel 1, and the lightweight foam concrete filling layer 4 is filled between the dome lattice shell structure 3 and the anti-seepage geomembrane layer 2; assembled steel bridge cables 8 are fixedly connected to the four corners at both ends of the multi-support cable-assembled steel bridge 5, and the other ends of the four assembled steel bridge cables 8 are fixedly connected to the dome lattice shell structure 3, and a pad 9 is provided between the multi-support cable-assembled steel bridge 5 and the lower rock layer 7. As shown Figure 2As shown, the dome lattice structure 3 includes a plurality of steel beams 10, which are arranged along the radial direction, one end of each of the steel beams 10 is fixed by a hexagonal sleeve bolt 11, and the other end of each of the steel beams 10 is fixed with a locking anchor rod 12, and the other end of each of the locking anchor rods 12 is fixed to the inner wall of the upper dissolution cavity tunnel 1. Small fiber optic Bragg grating sensors 22 are provided at the contact positions between the several locking foot anchor rods 12 and the inner wall of the upper solution cavity tunnel 1 and at the contact positions between the several locking foot anchor rods 12 and the hexagonal sleeve bolts 11. The several locking foot anchor rods 12 penetrate the lightweight foam concrete filling layer 4 and the anti-seepage geomembrane layer 2, and also include several inner ring beams 13. The several inner ring beams 13 are fixedly connected with the several steel beams 10 along the circumference of concentric circles. The intersections of the several inner ring beams 13 and the several steel beams 10 are fixedly connected by bolts 14. The multi-support cable-assembled steel bridge 5 is composed of several standard trusses 15 and several high-shear multilateral trusses 16. The several standard trusses 15 and the several high-shear multilateral trusses 16 are interspersed. The multi-support cable-assembled steel bridge 5 is arranged along an "I" shape. The outer walls of the several standard trusses 15 and the several high-shear multilateral trusses are coated with an anti-slip coating layer. Figure 3 As shown, the standard truss 15 includes a standard truss inner ring beam 17, the cross section of the standard truss inner ring beam 17 is diamond-shaped, and the outer side of the standard truss inner ring beam 17 is fixedly connected to a standard truss outer ring beam 18, and the cross section of the standard truss outer ring beam 18 is rectangular; Figure 4 As shown, the high shear multilateral truss 16 includes a scissors brace 19, the cross-section of the scissors brace 19 is "X"-shaped, a high shear polygonal truss inner ring beam 20 is fixedly connected to the scissors brace 19, the cross-section of the high shear polygonal truss inner ring beam 20 is rectangular, two straight lines of the scissors brace 19 coincide with the rectangular diagonals of the high shear polygonal truss inner ring beam 20, and a high shear polygonal truss outer ring beam 21 is fixedly connected to the outer side of the scissors brace 19, the cross-section of the high shear polygonal truss outer ring beam 21 is rectangular, two straight lines of the scissors brace 19 coincide with the rectangular diagonals of the high shear polygonal truss outer ring beam 21.

[0024] Example 6 The tunnel support method proposed in this embodiment for crossing a large underground river and a large-span cavities at the bottom of a tunnel specifically comprises the following steps: S1. Install multi-support cable-assembled steel bridge; S2. Lay an anti-seepage geomembrane layer on the inner wall of the upper cavity tunnel; S3, install the dome lattice shell structure on the inner wall of the upper cavity tunnel through the locking anchor rod; S4, filling a lightweight foam concrete filling layer between the dome reticulated shell structure and the anti-seepage geomembrane layer; S5. Check the stress condition of the dome lattice shell structure and complete the tunnel support.

[0025] Example 7 The tunnel support method proposed in this embodiment for crossing a large underground river and a large-span cavities at the bottom of a tunnel specifically comprises the following steps: S1. Install multi-support cable-assembled steel bridge; The specific process is as follows: In the early stage of construction, inclined guide tunnels are excavated at a ratio of 1:1.5 on both sides of the large underground river at the bottom of the tunnel, so that the guide tunnels on both sides are connected with the multi-support cable-assembled steel bridge. At the same time, horizontal areas are left at the end of the slope of the guide tunnel and the cliff. The bearing capacity of the ground in the horizontal area is tested by placing a static penetration instrument on the horizontal area, and points with a bearing capacity greater than 20,000 PSF are selected as fixed points. Pads are laid on the fixed points, holes are drilled around the pads and expansion plugs are driven in. Bolts and nuts are used to connect the multi-support cable-assembled steel bridge to the pads on the lower rock layer with expansion plugs. At the same time, assembled steel bridge cables are arranged around the upper dissolution cavity tunnel to pull up the multi-support cable-assembled steel bridge and fix it on the lower pad. Subsequently, the gaps between the guide tunnels on both sides and the upper and lower parts of the slope of the excavated guide tunnels are poured with concrete; S2. Lay an anti-seepage geomembrane layer on the inner wall of the upper cavity tunnel; S3, install the dome lattice shell structure on the inner wall of the upper cavity tunnel through the locking anchor rod; The specific process is: S3.1. Use ultrasonic sensors to detect the front, top, bottom, left and right dimensions of the upper cavity tunnel; S3.2. According to the size of the upper cavity tunnel, the center of the dome lattice shell structure is set directly above the center of the multi-support cable assembly steel bridge. According to the center point, a circle of tunnel walls in the same plane of the upper cavity tunnel is divided into several basic points with the center point as the symmetry axis. According to the center point, several steel beams are embedded into the inner wall of the upper cavity tunnel through locking anchor rods in a diagonally connected form. Locking anchor rods are extended from the end of each steel beam into the surrounding rock. Hexagonal sleeve bolts are used to connect at the center point. At the same time, the assembled steel bridge cables arranged around the upper cavity tunnel are fixed to the ends of the locking anchor rods. S3.3. According to the shape of the bottom of the dome lattice shell structure, the height of the bottom and top of the dome lattice shell structure is divided into several equal parts. The inner ring beam of each layer adopts a proportionally reduced structure with the same shape as the bottom of the dome lattice shell structure. The inner ring beam gradually shrinks as the dome lattice shell structure moves upward, and adjacent inner ring beams are connected by bolts; S4, filling a lightweight foam concrete filling layer between the dome reticulated shell structure and the anti-seepage geomembrane layer; S5. Check the stress of the dome shell structure and complete the tunnel support; The specific process is as follows: by setting up a number of small fiber grating sensors on the locking foot anchor rods and the hexagonal sleeve bolts, the surface stress changes of the set foundation points are continuously monitored; when the average stress change rate of the monitoring point exceeds 50% of the warning value for three consecutive days, the number of locking foot anchor rods is increased near the foundation point of the dome lattice structure to ensure that the tunnel stability requirements are met; when the average stress change rate of the monitoring point is lower than 50% of the warning value for three consecutive days, the dome lattice structure is arranged, and then concrete is poured around the multi-support cable-assembled steel bridge deck, so that the multi-support cable-assembled steel bridge deck can pass through the pilot tunnel, and also serve as the lining bottom plate for future tunnel construction work to complete the tunnel support.

Claims

1. A tunnel support device for crossing a large underground river and a large-span cavities at the bottom of the tunnel, characterized in that: The invention comprises a dome lattice shell structure (3), wherein the dome lattice shell structure (3) is fixedly connected to the inner wall of an upper dissolution cavity tunnel (1), an impermeable geomembrane layer (2) and a lightweight foam concrete filling layer (4) are provided between the dome lattice shell structure (3) and the inner wall of the upper dissolution cavity tunnel (1), and further comprises a multi-support cable-assembled steel bridge (5), wherein the multi-support cable-assembled steel bridge (5) is provided above an underground river (6), and the multi-support cable-assembled steel bridge (5) is respectively fixedly connected to the dome lattice shell structure (3) and a lower rock layer (7).

2. The tunnel support device for crossing a large underground river and a large-span cavities at the bottom of a tunnel according to claim 1 is characterized in that: The anti-seepage geomembrane layer (2) is laid on the inner wall of the upper dissolution cavity tunnel (1), and the lightweight foam concrete filling layer (4) is filled between the dome reticulated shell structure (3) and the anti-seepage geomembrane layer (2).

3. The tunnel support device for crossing a large underground river and a large-span cavities at the bottom of a tunnel according to claim 2 is characterized in that: Assembly steel bridge cables (8) are fixedly connected at four corners at both ends of the multi-support cable assembly steel bridge (5); the other ends of the four assembly steel bridge cables (8) are fixedly connected to the dome lattice structure (3); and a pad (9) is provided between the multi-support cable assembly steel bridge (5) and the lower rock layer (7).

4. The tunnel support device for crossing a large underground river and a large-span cavities at the bottom of a tunnel according to claim 3 is characterized in that: The dome lattice shell structure (3) comprises a plurality of steel beams (10), wherein the plurality of steel beams (10) are arranged along a radial direction, one end of the plurality of steel beams (10) is fixedly connected by a hexagonal sleeve bolt (11), the other end of the plurality of steel beams (10) is fixedly connected to a locking foot anchor rod (12), and the other end of the plurality of locking foot anchor rods (12) is fixedly connected to the inner wall of the upper dissolution cavity tunnel (1). Small fiber optic grating sensors (22) are provided at the contact positions between the plurality of locking foot anchor rods (12) and the inner wall of the upper dissolution cavity tunnel (1) and at the contact positions between the plurality of locking foot anchor rods (12) and the hexagonal sleeve bolts (11). The plurality of locking foot anchor rods (12) penetrate the lightweight foam concrete filling layer (4) and the anti-seepage geomembrane layer (2). The plurality of inner ring beams (13) are fixedly connected to the plurality of steel beams (10) along the circumference of concentric circles. The intersections between the plurality of inner ring beams (13) and the plurality of steel beams (10) are fixedly connected by bolts (14).

5. The tunnel support device for crossing a large underground river and a large-span cavities at the bottom of a tunnel according to claim 4 is characterized in that: The multi-support cable-assembled steel bridge (5) is composed of a plurality of standard trusses (15) and a plurality of high-shear multilateral trusses (16), wherein the plurality of standard trusses (15) and the plurality of high-shear multilateral trusses (16) are arranged in an interlaced manner, and the multi-support cable-assembled steel bridge (5) is arranged along an "I" shape, and the outer walls of the plurality of standard trusses (15) and the plurality of high-shear multilateral trusses are coated with an anti-slip coating layer.

6. The tunnel support device for crossing a large underground river and a large-span cavities at the bottom of a tunnel according to claim 5 is characterized in that: The standard truss (15) comprises a standard truss inner ring beam (17), the cross section of the standard truss inner ring beam (17) is rhombus-shaped, and a standard truss outer ring beam (18) is fixedly connected to the outside of the standard truss inner ring beam (17), and the cross section of the standard truss outer ring beam (18) is rectangular; the high shear force polygonal truss (16) comprises a scissors brace (19), the cross section of the scissors brace (19) is "X"-shaped, and a high shear force polygonal truss inner ring beam (20) is fixedly connected to the scissors brace (19). The cross section of the high shear force polygonal truss inner ring beam (20) is rectangular, and the two straight lines of the scissors brace (19) coincide with the rectangular diagonal of the high shear force polygonal truss inner ring beam (20). The outer side of the scissors brace (19) is fixedly connected to the high shear force polygonal truss outer ring beam (21), and the cross section of the high shear force polygonal truss outer ring beam (21) is rectangular, and the two straight lines of the scissors brace (19) coincide with the rectangular diagonal of the high shear force polygonal truss outer ring beam (21).

7. A tunnel support method for crossing a large underground river and a large-span cavities at the bottom of the tunnel, characterized in that: The tunnel support device for crossing a large underground river and a large-span cavities at the bottom of a tunnel according to claim 6 specifically comprises the following steps: S1. Install multi-support cable-assembled steel bridge; S2. Lay an anti-seepage geomembrane layer on the inner wall of the upper cavity tunnel; S3, install the dome lattice shell structure on the inner wall of the upper cavity tunnel through the locking anchor rod; S4, filling a lightweight foam concrete filling layer between the dome reticulated shell structure and the anti-seepage geomembrane layer; S5. Check the stress condition of the dome lattice shell structure and complete the tunnel support.

8. The method for supporting a tunnel through a large underground river and a large-span cavities at the bottom of a tunnel according to claim 7, characterized in that: The specific process of S1 is as follows: in the early stage of construction, inclined guide tunnels are excavated at a ratio of 1:1.5 on both sides of the large underground river at the bottom of the tunnel, so that the guide tunnels on both sides are connected with the multi-support cable-assembled steel bridge. At the same time, horizontal areas are left at the end of the slope of the guide tunnel and the cliff. The bearing capacity of the ground in the horizontal area is tested by passing a static probe to the horizontal area, and points with a bearing capacity greater than 20000PSF are selected as fixed points. Pads are laid on the fixed points, holes are drilled around the pads and expansion plugs are driven in, and bolts and nuts are used to connect the multi-support cable-assembled steel bridge to the pads on the lower rock layer with expansion plugs. At the same time, assembled steel bridge cables are arranged around the upper dissolution cavity tunnel to pull up the multi-support cable-assembled steel bridge and fix it on the lower pad. Subsequently, the gaps between the guide tunnels on both sides and the upper and lower parts of the slope of the excavated guide tunnels are poured with concrete.

9. The method for supporting a tunnel through a large underground river and a large-span cavities at the bottom of a tunnel according to claim 7, characterized in that: The specific process of S3 is as follows: S3.

1. Use ultrasonic sensors to detect the front, top, bottom, left and right dimensions of the upper cavity tunnel; S3.

2. According to the size of the upper cavity tunnel, the center of the dome lattice shell structure is set directly above the center of the multi-support cable assembly steel bridge. According to the center point, a circle of tunnel walls in the same plane of the upper cavity tunnel is divided into several basic points with the center point as the symmetry axis. According to the center point, several steel beams are embedded into the inner wall of the upper cavity tunnel through locking anchor rods in a diagonally connected form. Locking anchor rods are extended from the end of each steel beam into the surrounding rock. Hexagonal sleeve bolts are used to connect at the center point. At the same time, the assembled steel bridge cables arranged around the upper cavity tunnel are fixed to the ends of the locking anchor rods. S3.

3. According to the shape of the bottom of the dome lattice shell structure, the height of the bottom and top of the dome lattice shell structure is divided into several equal parts. The inner ring beam of each layer adopts a proportionally reduced structure with the same shape as the bottom of the dome lattice shell structure. The inner ring beam gradually shrinks as the dome lattice shell structure goes up, and adjacent inner ring beams are connected by bolts.

10. The tunnel support method for crossing a large underground river and a large-span cavities at the bottom of a tunnel according to claim 7, characterized in that: The specific process of S5 is as follows: by setting a number of small fiber grating sensors on the locking foot anchor rods and the hexagonal sleeve bolts, the surface stress changes of the set foundation points are continuously monitored; when the average stress change rate of the monitoring point exceeds 50% of the warning value for three consecutive days, the number of locking foot anchor rods is increased near the foundation point of the dome lattice structure to ensure that the tunnel stability requirements are met; when the average stress change rate of the monitoring point is lower than 50% of the warning value for three consecutive days, the dome lattice structure is arranged, and then concrete is poured around the multi-support cable-assembled steel bridge deck, so that the multi-support cable-assembled steel bridge deck can pass through the pilot tunnel, and also serves as the lining bottom plate for future tunnel construction work to complete the tunnel support.

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