Treatment structure for large tiled karst cave at bottom of tunnel

Abstract

The utility model provides a treatment structure for a large tiled karst cave at the bottom of a tunnel, which comprises a supporting platform and a supporting foundation, and the supporting platform is used for being arranged below a tunnel bottom plate so as to bear load acting on the supporting platform; the supporting foundation is arranged below the supporting platform and used for supporting the supporting platform. The treatment structure system is clear in structural stress, has the advantages of being short in construction period, reliable in structure, high in practicability, good in stability, controllable in sedimentation, economical, practical and the like, and has good economic benefits.

Description

Technical Field

[0001] The utility model relates to the technical field of tunnel engineering, in particular to a treatment structure for a large flat karst cave at the bottom of a tunnel. Background Art

[0002] my country has a wide distribution of limestone formations and a very common karst phenomenon, such as caves and sinkholes, among which caves are the most common karst form. Tunnel construction is a project that is highly dependent on geological conditions. When it passes through a karst area, caves of various sizes and shapes, as well as their locations, filling conditions, and filling properties, will have a significant impact on tunnel construction. The hazards of caves to tunnel engineering are mainly manifested in the following aspects: 1) The existence of caves makes the building all or partly suspended in the air, which will greatly reduce the reliability of tunnel use. 2) Karst water, especially when CO3 2- When the content of soluble substances increases, the flow of water will cause great erosion to the tunnel structure, affecting the service life of the tunnel. 3) Cave deposits are soft and easy to collapse and sink, changing the stress distribution pattern around the cave and affecting the stability of the tunnel. 4) The loss of groundwater in the tunnel causes the karst collapse of the top of the tunnel, resulting in the destruction of environmental geology, which is also the reason for the instability of the tunnel structure.

[0003] Since the size, shape, location, filling material and groundwater of karst caves are ever-changing, the treatment methods for karst caves are also constantly changing due to adaptation. Taking reasonable treatment measures for different karst caves has become a key factor in karst cave management. At present, for karst caves that have stopped developing, have a small span and are waterless, they can be backfilled and closed with concrete, mortar-laid stone or dry-laid stone according to their intersection with the tunnel and their filling conditions, and whether the side wall foundation needs to be deepened can be determined based on the geological conditions.

[0004] When a narrow and deep cave is encountered on one side of the tunnel, the side wall foundation on that side can be deepened to pass through. When a large cave with flowing water is encountered at the bottom of the tunnel, a masonry support wall can be built below the bottom of the tunnel to support the tunnel structure, and a culvert can be installed inside the support wall to drain the cave water. When a large and deep cave is encountered at the side wall of the tunnel, and it is not appropriate to deepen the side wall foundation, an arch can be built at the side wall or below the tunnel bottom to cross it. When a deep and narrow cave is encountered in the middle and bottom of the tunnel, the foundations of both side walls can be strengthened, and abutments and beams can be set up to pass through it according to the situation.

[0005] There is currently no economically reasonable and technically reliable means to treat large flat caves with small depth and large area at the bottom of the tunnel. If conventional cave slag or mortar-laid stone backfilling scheme is adopted, for large flat caves with small depth but large span and water-containing fillings in the cavity, it is necessary to clean up the water-containing fillings before backfilling. In addition, the amount of filling materials is huge, the drainage channel is easily blocked, the construction period is long, and the post-construction settlement is large, which is difficult to meet the structural and operational safety requirements.

[0006] In summary, there is an urgent need for a treatment structure for large flat caves at the bottom of tunnels to solve the problems existing in the prior art. Utility Model Content

[0007] The utility model aims to provide a treatment structure for a large flat karst cave at the bottom of a tunnel, aiming to solve the problem of treating a large flat karst cave with a small depth and a large range at the bottom of a tunnel. The specific technical scheme is as follows:

[0008] A treatment structure for a large flat karst cave at the bottom of a tunnel comprises a support platform and a support foundation. The support platform is arranged below the tunnel floor to bear the load acting on the support platform; the support foundation is arranged below the support platform to support the support platform.

[0009] Preferably in the above technical solution, the support platform includes a beam and a raft, a plurality of beams are arranged at intervals along the longitudinal direction of the tunnel, and the raft is arranged between two adjacent beams, and at least one group of the support foundations is provided below the beams.

[0010] Preferably in the above technical solution, the supporting foundation includes a pier and a bottom foundation, the upper end of the pier is connected to the cross beam, and the lower end of the pier is arranged on the bottom foundation.

[0011] Preferably in the above technical solution, the bottom foundation is a stepped enlarged foundation, and a cushion layer is provided below the bottom foundation.

[0012] Preferably, the above technical solution further comprises a tie beam arranged along the longitudinal direction of the tunnel, wherein two ends of the tie beam are respectively connected to two adjacent piers in the longitudinal direction.

[0013] Preferably in the above technical solution, the elevation of the top surface of the raft is consistent with the elevation of the top surface of the beam.

[0014] The preferred technical solutions above are:

[0015] The crossbeam is a reinforced concrete structure, with a beam height of not less than 80 cm, a beam width of not less than 60 cm, a concrete grade of not less than C40, and a main force reinforcement of grade 3 steel bars with a diameter of not less than 22 mm;

[0016] The raft slab is a reinforced concrete structure with a slab thickness of not less than 35 cm and a concrete grade of not less than C35. The main force-bearing reinforcement is grade three steel and has a diameter of not less than 22 mm.

[0017] The preferred technical solutions above are:

[0018] The pier is a cylindrical reinforced concrete structure with a cross-sectional diameter of not less than 1.0m, a concrete grade of not less than C35, and a main force reinforcement of grade 3 steel bars with a diameter of not less than 22mm;

[0019] The tie beam is a reinforced concrete structure with a beam height of not less than 50 cm, a beam width of not less than 50 cm, a concrete grade of not less than C40, and main stress-bearing reinforcement of grade 3 steel bars with a diameter of not less than 22 mm.

[0020] In the above technical solution, the buried depth of the bottom foundation is not less than 1.0m, the maximum width is not less than 3.0m, the concrete grade is not less than C30, the lower part is equipped with a steel mesh, the diameter of the main force is not less than 12mm, the height of each step is 30-50cm, and the width of each side of the next step is not less than 50cm compared with the previous step;

[0021] The concrete grade of the cushion layer shall not be lower than C10, and its thickness shall not be less than 70mm.

[0022] Preferably in the above technical solution, the supporting foundation further includes a diagonal bracing beam, and two ends of the diagonal bracing beam are respectively connected to the pier column and the cross beam.

[0023] The application of the technical solution of the utility model has the following beneficial effects:

[0024] The treatment structure forms a large-scale flat-paved cave spanning structure system by arranging crossbeams, rafts, piers, tie beams and bottom foundations. It can avoid the problems caused by traditional cave slag or mortar-laid stone backfilling schemes, such as huge amount of filling materials, easy blocking of drainage channels, long construction period, large post-construction settlement, and difficulty in meeting structural and operational safety needs. The treatment structure system structure of the utility model has clear force, and has the advantages of short construction period, reliable structure, strong practicality, good stability, controllable settlement, economy and practicality, and has good economic benefits.

[0025] In addition to the above-described purposes, features and advantages, the present invention has other purposes, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of this application are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0027] Figure 1 It is a cross-sectional view of the treatment structure of the utility model along the transverse direction;

[0028] Figure 2 It is a cross-sectional view of the treatment structure of the utility model along the longitudinal direction;

[0029] Among them, 1. bottom foundation, 2. tie beam, 3. pier, 4. cross beam, 5. cave, 6. tunnel lining, 7. raft. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0032] Example:

[0033] See also Figure 1-Figure 2 This embodiment provides a treatment structure for a large flat cave at the bottom of a tunnel, including a support platform and a support foundation. The support platform is used to be arranged below the tunnel floor to withstand the load acting on the support platform, and the load includes the pressure generated by permanent loads such as the deadweight of the support platform, the deadweight of the tunnel structure, the water and soil pressure behind the tunnel lining 6, and the variable load generated by vehicles and pedestrians; the support foundation is arranged below the support platform to support the support platform.

[0034] Specifically, the support platform includes a crossbeam 4 and a raft 7. A plurality of crossbeams 4 are arranged at intervals along the longitudinal direction of the tunnel, and the raft 7 is arranged between two adjacent crossbeams 4 (the raft 7 is connected to the crossbeam 4), and at least one group of the support foundation is arranged below the crossbeam 4. The main function of the crossbeam 4 is to bear the self-weight of the crossbeam and the vertical load and horizontal load transmitted from the raft, and transfer the load to the support foundation; the main function of the raft 7 is to bear the pressure generated by permanent loads such as the self-weight of the raft, the self-weight of the tunnel structure, and the water and soil pressure behind the tunnel lining 6, as well as the variable loads generated by vehicles and pedestrians, and transfer the loads received to the crossbeam; at the same time, the effect of improving the structural rigidity is achieved.

[0035] Furthermore, the elevation of the top surface of the raft slab 7 is consistent with the elevation of the top surface of the cross beam 4, that is, the top surface of the raft slab 7 is flush with the top surface of the cross beam 4, so that the upper surface of the support platform is a flat surface, ensuring that the support platform is evenly stressed.

[0036] Specifically, the supporting foundation includes a pier 3 and a bottom foundation 1, wherein the upper end of the pier 3 is connected to the cross beam 4, and the lower end thereof is arranged on the bottom foundation 1. The main function of the pier 3 is to support the cross beam 4 and transfer the load of the supporting platform to the bottom foundation 1; the main function of the bottom foundation 1 is to directly transfer the load transferred by the pier and the upper structure to the supporting foundation, increase the bearing capacity of the supporting foundation, improve the overall stiffness of the structural system, enhance the symmetry of the structural deformation, reduce the unbalanced force in the foundation, and enhance the overall stability of the structural system.

[0037] Preferably, the bottom foundation 1 in this embodiment is a stepped enlarged foundation, and a cushion layer is provided below the bottom foundation 1.

[0038] Specifically, the treatment structure for the large flat cave at the bottom of the tunnel also includes a tie beam 2 arranged along the longitudinal direction of the tunnel, and the two ends of the tie beam 2 are respectively connected to two piers 3 adjacent in the longitudinal direction, that is, the tie beam 2 is provided between the piers adjacent in the longitudinal direction. Among them, the main function of the tie beam 2 is to connect the front and rear piers to form an integral force, improve the force mode of the piers, and strengthen the overall rigidity of the structure to ensure the stability and safety of the entire system. Preferably, when the longitudinal spacing between two adjacent piers 3 is not large, the tie beam 2 may not be provided, and those skilled in the art may consider whether it is necessary to provide a tie beam to improve the stability and safety of the structural system according to the actual layout.

[0039] Preferably, in this embodiment, two groups of support foundations are provided under the cross beam 4, and the two groups of support foundations are respectively located at the two ends of the cross beam. Of course, in some embodiments, only one group of support foundations may be provided under the cross beam, or more than three groups of support foundations may be provided, depending on the span of the cross beam 4.

[0040] Preferably in this embodiment, the cross beam 4 is a reinforced concrete structure, with a beam height of not less than 80 cm, a beam width of not less than 60 cm, a concrete grade of not less than C40, and main stress-bearing reinforcement of grade 3 steel bars with a diameter of not less than 22 mm; further preferably, the longitudinal spacing between adjacent cross beams 4 is 4 to 6 m.

[0041] Preferably, in this embodiment, the raft slab 7 is a reinforced concrete structure, the slab thickness is not less than 35 cm, the concrete grade is not less than C35, and the main force-bearing reinforcement is grade 3 steel bar with a diameter of not less than 22 mm.

[0042] Preferably, in this embodiment, the pier 3 is a cylindrical reinforced concrete structure, the cross-sectional diameter of which is not less than 1.0m, the concrete grade of which is not less than C35, and the main force-bearing reinforcement is grade three steel bar with a diameter of not less than 22mm.

[0043] Preferably, in this embodiment, the tie beam 2 is a reinforced concrete structure, with a beam height of not less than 50 cm, a beam width of not less than 50 cm, a concrete grade of not less than C40, and main force-bearing reinforcement of grade 3 steel bars with a diameter of not less than 22 mm.

[0044] In this embodiment, the buried depth of the bottom foundation 1 is preferably not less than 1.0m, the maximum width is not less than 3.0m, the concrete grade is not less than C30, the lower part is provided with a steel mesh, the diameter of the main force is not less than 12mm, the height of each step is 30-50cm, and the width of each side of the next step is increased by not less than 50cm compared with the previous step;

[0045] Preferably, in this embodiment, the concrete grade of the cushion layer is not less than C10, and its thickness is not less than 70 mm.

[0046] Preferably, in some embodiments, the support foundation may further include a diagonal bracing beam (not shown), the two ends of which are respectively connected to the pier column 3 and the cross beam 4. Specifically, the diagonal bracing beam may be symmetrically arranged on both sides of the pier column 3, or may be arranged only on one side of the pier column. The diagonal bracing beam, the pier column and the cross beam form a stable triangular structure, further increasing the stability and safety of the structural system.

[0047] The technical solution of this embodiment is specifically:

[0048] (1) Construction process:

[0049] Comprehensively explore all information about the cave - determine the size and position of each component in the structure - bottom foundation construction - pier construction - tie beam construction - cross beam and raft construction - tunnel structure construction.

[0050] (2) Construction plan:

[0051] ① When a karst cave appears below the planned tunnel route during tunnel excavation, the next step is taken after confirming that karst cave 5 passes below the planned tunnel route and is a large flat-type karst cave with a small depth but a large range.

[0052] ② According to the size and depth of the cave and its relative position to the tunnel, determine the design scheme including the size of the beam, the spacing and position of the beams, the thickness of the raft, the diameter and position of the piers, whether tie beams are needed and their size and position, the size of the stepped expanded foundation, the height of the steps, the spacing of the steel meshes and the burial depth.

[0053] ③Construct the stepped foundation. First, excavate to the foundation embedding depth, construct the cushion layer, and tie the steel mesh after the cushion layer concrete reaches 1.2MPa. Make each step formwork according to the size of the stepped foundation, and install it layer by layer from bottom to top. Pour the concrete layer by layer continuously, and the interval time should not exceed the initial setting time of the concrete. Cover and water the poured concrete after about 12 hours of curing. After the curing is completed, proceed to the next process.

[0054] ④ Construct piers. Construct full-floor scaffolding according to the position and size of the piers. The scaffolding should be strong and reliable. Tie the steel bars according to the design requirements and keep the tie beam steel bar interface. Install the formwork according to the size of the piers, and install it layer by layer from bottom to top. Pour the concrete layer by layer continuously, and the interval time should not exceed the initial setting time of the concrete. Cover and water the poured concrete after curing for about 12 hours. After curing, proceed to the next process.

[0055] ⑤ Construct tie beams. Determine the tie beam position according to the design, and install the bottom formwork and side formwork according to the tie beam size. Tie the steel bars according to the design requirements. Pour the concrete layer by layer continuously, and the interval time should not exceed the initial setting time of the concrete. Curing the poured concrete should be covered and watered in about 12 hours. After the curing is completed, proceed to the next process.

[0056] ⑥ Construct beams and rafts. Construct full-floor scaffolding according to the position and size of beams and rafts. The scaffolding should be strong and reliable. Install bottom formwork and side formwork according to the size of beams and rafts. Tie steel bars according to design requirements. Pour concrete layer by layer continuously, with the interval time not exceeding the initial setting time of concrete. Cover and water the poured concrete after about 12 hours of maintenance.

[0057] ⑦ After the structural maintenance is completed, remove the formwork and scaffolding.

[0058] ⑧ During the construction of the main tunnel, the initial support of the tunnel arch wall and the lining structure fall on the raft.

[0059] Applying the technical solution of this embodiment has the following effects:

[0060] The treatment structure forms a large flat cave spanning structure system by setting up beams, rafts, piers, tie beams and bottom foundations. It can avoid the problems caused by traditional cave slag or mortar-laid stone backfilling schemes, such as huge amount of filling materials, easy blocking of drainage channels, long construction period, large post-construction settlement, and difficulty in meeting structural and operational safety needs. This structural system has clear force structure and has the advantages of short construction period, reliable structure, strong practicality, good stability, controllable settlement, economy and practicality, and has good economic benefits.

[0061] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A treatment structure for a large flat cave at the bottom of a tunnel, characterized in that: It includes a support platform and a support foundation, wherein the support platform is used to be arranged below the tunnel floor to bear the load acting on the support platform; The support base is arranged below the support platform and is used to support the support platform; The support platform comprises a cross beam (4) and a raft (7); a plurality of cross beams (4) are arranged at intervals along the longitudinal direction of the tunnel, and the raft (7) is arranged between two adjacent cross beams (4); and at least one group of the support foundations is arranged below the cross beams (4).

2. The treatment structure for large flat caves at the bottom of a tunnel according to claim 1 is characterized in that: The supporting foundation comprises a pier column (3) and a bottom foundation (1); the upper end of the pier column (3) is connected to the cross beam (4), and the lower end of the pier column (3) is arranged on the bottom foundation (1).

3. The treatment structure for a large flat cave at the bottom of a tunnel according to claim 2 is characterized in that: The bottom foundation (1) is a stepped enlarged foundation, and a cushion layer is provided below the bottom foundation (1).

4. The treatment structure for a large flat cave at the bottom of a tunnel according to claim 2, characterized in that: It also comprises a tie beam (2) arranged in the longitudinal direction of the tunnel, wherein two ends of the tie beam (2) are respectively connected to two piers (3) adjacent in the longitudinal direction.

5. The treatment structure for large flat caves at the bottom of a tunnel according to claim 2, characterized in that: The elevation of the top surface of the raft (7) is consistent with the elevation of the top surface of the crossbeam (4).

6. The treatment structure for a large flat cave at the bottom of a tunnel according to claim 2, characterized in that: The crossbeam (4) is a reinforced concrete structure, with a beam height of not less than 80 cm, a beam width of not less than 60 cm, a concrete grade of not less than C40, and a main force-bearing reinforcement of grade 3 steel bars with a diameter of not less than 22 mm; The raft slab (7) is a reinforced concrete structure, the slab thickness is not less than 35 cm, the concrete grade is not less than C35, and the main force-bearing reinforcement is grade 3 steel bar with a diameter of not less than 22 mm.

7. The treatment structure for large flat caves at the bottom of a tunnel according to claim 4, characterized in that: The pier column (3) is a cylindrical reinforced concrete structure, the cross-sectional diameter of which is not less than 1.0m, the concrete grade of which is not less than C35, and the main force-bearing reinforcement of which is grade 3 steel and has a diameter of not less than 22mm; The tie beam (2) is a reinforced concrete structure, with a beam height of not less than 50 cm, a beam width of not less than 50 cm, a concrete grade of not less than C40, and main reinforcements of the tie beams made of grade 3 steel bars with a diameter of not less than 22 mm.

8. The treatment structure for a large flat cave at the bottom of a tunnel according to claim 3, characterized in that: The buried depth of the bottom foundation (1) is not less than 1.0m, the maximum width is not less than 3.0m, the concrete grade is not less than C30, a steel mesh is arranged at the bottom, the diameter of the main reinforcement is not less than 12mm, the height of each step is 30-50cm, and the width of each side of the next step is not less than 50cm compared with the previous step; The concrete grade of the cushion layer shall not be lower than C10, and its thickness shall not be less than 70mm.

9. The treatment structure for a large flat cave at the bottom of a tunnel according to any one of claims 2 to 8, characterized in that: The supporting foundation also includes a diagonal bracing beam, the two ends of which are respectively connected to the pier column (3) and the cross beam (4).

Images