Tunnel structure crossing karst cave and construction method thereof

Abstract

The invention relates to the field of tunnels, in particular to a tunnel structure crossing a karst cave and a construction method thereof. The tunnel structure crossing the karst cave comprises a combined arch supporting structure and a light combined protection structure. The combined arch supporting structure comprises a steel arch, a concrete arch and a filler area. The steel arch is an arched corrugated steel plate and serves as a permanent and temporary combined structure. The steel arch serves as a temporary formwork of the concrete arch and also serves as an arch structure permanently stressed in the later period. The filling area is used for filling to form a tunnel foundation. According to the scheme, the form of a new karst cave crossing structure is adopted, and the problems that an original karst cave drainage channel is backfilled and a girder bridge difficultly crosses a karst cave are solved. The light combined protection structure comprises a corrugated steel protection arch built on a tunnel foundation, a buffer layer and an inner lining. According to the combined protection structure, the safety and durability of the tunnel are improved, lining outer formworks are saved, the lining thickness is reduced, construction is convenient and fast, and cost is saved. The effects of environmental protection, safety and convenience are achieved through the combined arch supporting structure and the combined protection structure.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel structure construction, and particularly relates to a tunnel structure spanning a karst cave and a construction method thereof. Background Art

[0002] In karst areas of China, especially in Guangxi, Guizhou, Yunnan and other places, large hall karst caves are often encountered in tunnel engineering construction. When a tunnel passes through a hall karst cave, the structural design should consider not only the impact load dropped from the top of the karst cave and the vehicle load, but also the protection of the natural drainage channel of the karst cave and the problem of whether the bottom structure is strong enough to bear the load; it should consider not only the safety factors during construction, but also the long-term operation safety, structural durability and maintenance convenience. In current tunnel construction, when encountering a hall-type karst cave, generally, the bottom of the karst cave is backfilled or a beam bridge is set up to span the karst cave; a reinforced concrete shed tunnel or open tunnel structure is set outside the tunnel contour. However, the treatment plan of backfilling at the bottom of the karst cave has a great impact on the natural drainage channel of the karst cave, destroys the original drainage channel of the karst cave, and is difficult to backfill densely, with a large backfill volume and high cost; the treatment plan of setting up a cast-in-situ beam bridge to span the karst cave by setting up a scaffolding formwork support system in the karst cave has problems such as difficult construction of the formwork support and difficult demolition in the later stage; when using a precast beam bridge to span the karst cave, there are problems such as difficult hoisting and erection of precast beams and mismatched spans of precast beams. Setting a reinforced concrete shed tunnel or open tunnel structure outside the tunnel contour has the following disadvantages: ① The construction period is long, and construction workers need to work without protection for a long time, with high safety risks; ② The bearing capacity of the clay layer at the bottom of most karst caves is low and does not meet the requirements of the reinforced concrete structure for the bearing capacity of the foundation, and complex foundation reinforcement or pile foundation construction is required. However, the impact vibration generated during the process of foundation reinforcement or pile foundation construction may cause the collapse of the rock layer on the top of the karst cave, and the implementation of the plan has high safety risks; ③ The reinforced concrete structure belongs to a rigid structure, and the impact force of the rock layer collapse is likely to cause great damage to the rigid structure, thereby affecting the force of the tunnel lining structure. At the same time, there are difficulties in operation and durability problems in setting a buffer layer in the karst cave; ④ The construction of the reinforced concrete structure requires large equipment, but the operation space and traffic conditions in the tunnel are limited, increasing the construction difficulty. Summary of the Invention

[0003] The purpose of the present invention is to overcome the problems existing in the prior art in tunnel construction, that is, when encountering a hall-type karst cave, the traditional treatment plans of backfilling at the bottom of the karst cave or setting up a beam bridge to span the karst cave have problems such as destroying the original drainage channel of the karst cave, difficult construction and demolition of the formwork support, difficult hoisting and erection of precast beams and mismatched spans, and provide a tunnel structure spanning a karst cave and a construction method thereof.

[0004] In the first aspect, the present invention provides a tunnel combined arch support structure spanning a karst cave, including: Steel arch, the arch feet of the steel arch are connected to the cave wall of the karst cave, the steel arch is located below the tunnel, the steel arch is an arched corrugated steel plate, the corrugated steel plate has a corrugated cross-section, in the cross-section, the corrugation extension direction is the width direction of the corrugated steel plate, the direction perpendicular to the corrugation extension direction is the length direction of the corrugated steel plate, the corrugated steel plate is bent into an arch shape along the length direction, and the width direction of the corrugated steel plate is consistent with the width direction of the tunnel.

[0005] Concrete arch, the concrete arch is arranged above the steel arch.

[0006] Filling area, the filling area is arranged above the concrete arch, and the filling area is used for filling to form the tunnel foundation.

[0007] The present invention provides a tunnel composite arch support structure for spanning a karst cave. The steel arch is an arched corrugated steel plate. The corrugated steel plate is light in weight, and it can be conveniently erected and constructed with general hoisting equipment. The corrugated steel plate is usually processed into various corrugated plates through a roll-forming cold bending process. This corrugated design can increase the sectional moment of inertia of the steel plate, thereby improving its flexural stiffness, and further enabling the steel arch to have a high bearing capacity, so that no additional steel structure needs to be used as a support skeleton. In the cross-section, the corrugation extension direction is the width direction of the corrugated steel plate, the direction perpendicular to the corrugation extension direction is the length direction of the corrugated steel plate, the corrugated steel plate is bent into an arch shape along the length direction, and the width direction of the corrugated steel plate is consistent with the width direction of the tunnel. This method ensures that the corrugation extension direction of the corrugated steel plate is the arch width direction of the steel arch, ensures that both ends of the corrugated steel plate along its length direction (the end faces with corrugated cross-sections) can be used as arch feet to support on the cave wall of the karst cave, and further ensures that the corrugated steel plate has stronger stability when forming the steel arch. Connecting the arch feet of the steel arch to the cave wall of the karst cave enables the steel arch to be used as a temporary stress-bearing structure for spanning the karst cave. The steel arch can be used as the bottom formwork for the steel bar binding and concrete pouring of the concrete arch, bearing the self-weight load of the concrete arch before reaching the design strength, and can also be used as a temporary platform for operators, small equipment, materials, etc. At the same time, the steel arch is located at the bottom of the concrete arch. After the concrete arch reaches the design strength, the tunnel composite arch support structure formed by the steel arch and the concrete arch is used to bear the self-weight of the structure, the upper structure load, the dynamic load, etc. This scheme can improve the mechanical properties of the overall structure and further reduce the thickness of the concrete arch, saving construction costs. The filling area is used for filling to form the tunnel foundation.

[0008] The corrugated steel plate of the arch is used as a steel arch to span the karst cave. At the same time, the steel arch also serves as a formwork (temporary load-bearing structure) for the concrete arch and forms a tunnel composite arch support structure (permanent load-bearing structure) with the concrete arch. Compared with the treatment scheme of backfilling at the bottom of the karst cave in the prior art, there is no need to backfill and treat the karst cave, avoiding the damage to the original water drainage channel of the karst cave. At the same time, compared with the treatment scheme of setting a beam bridge to span the karst cave in the prior art, it avoids the problems of difficult construction of the formwork support of the cast-in-place beam bridge and difficult demolition in the later stage, as well as the problems of difficult hoisting and erection of precast beams and mismatched span diameters.

[0009] There are various connection methods between the arch feet of the steel arch and the cave wall of the karst cave. For example, the arch feet are directly connected to the cave wall through anchor bolts. For example, grooves or holes for placing the arch feet can be chiseled on the cave wall, and the arch feet are connected to the cave wall through the grooves or the holes.

[0010] The strength of the filler in the filler area is not less than 0.5 MPa. Lightweight aggregate concrete or pumice concrete can be used, which can reduce the self-weight of the structure, improve the construction safety and speed, and save the construction cost. The height of the filler in the filler area can be flush with the top of the concrete arch or higher than the top of the concrete arch.

[0011] Temporary formwork or permanent formwork can be set on the sides of the concrete arch and the filler area to facilitate smooth shaping during concrete pouring or filler pouring. The temporary formwork can be made of wooden formwork, and the permanent formwork can be made of metal formwork.

[0012] Preferably, the steel arch includes a plurality of arch segments, and all the arch segments are corrugated steel plates in an arch shape. The plurality of arch segments are arranged along the width direction of the corrugated steel plate, and adjacent two arch segments are connected to each other. This scheme can reduce the size and weight of a single arch component, facilitate the transportation of a single arch component to the edge of the karst cave through the already built tunnel, and also facilitate the hoisting, transfer and installation construction of a single arch component. The connection method between adjacent two arch segments can be bolt connection, rivet connection or welding, etc.

[0013] Preferably, shear studs are provided on all the arch segments, and the shear studs are welded to the arch segments. The shear studs are used to be embedded in the concrete arch, playing a role in strengthening the connection between the corrugated steel plate and the concrete arch and improving the integrity between the two.

[0014] Preferably, baffles are provided on both sides of the steel arch, and anti-deformation components are provided on both baffles. The baffles are used as lateral formworks during the casting of the concrete arch and during the filling construction of the filling area. The baffles can be made of aluminum plates, steel plates, etc. The bottom edge of the baffle is connected to the steel arch by bolts or welding. The anti-deformation components can be arranged between the baffle and the arch surface of the steel arch, such as triangular rib plates, or can be arranged between the baffles on both sides respectively, such as tie rods. The anti-deformation components can improve the ability of the baffle to resist lateral deformation. The tie rods can be steel bars, screw rods or high-strength plastic rods, and their two ends are respectively fixedly connected to the baffles on both sides.

[0015] Preferably, grooves are provided on the wall of the karst cave, and the arch feet of the steel arch are connected at the grooves. The grooves are formed by grooving on the wall of the karst cave. The grooves can make the originally uneven cave wall relatively flat, facilitating the connection between the arch feet of the steel arch and the cave wall. At the same time, the grooves can also play a role in positioning and restricting the sliding of the arch feet, improving the safety of installing the steel arch.

[0016] Preferably, the filling area is provided with hollow structures, and the filling area is filled with ceramsite concrete or pumice concrete. The hollow structures can reduce the amount of filling materials, further reduce the self-weight of the structure, save costs. The hollow structures can be PVC pipes, corrugated pipes or hollow spheres. Using ceramsite concrete or pumice concrete can further reduce the self-weight of the filling area, and thus reduce the self-weight of the overall structure, saving costs.

[0017] In a second aspect, the present invention provides a tunnel structure spanning a karst cave, including a tunnel lightweight combined protection structure. The tunnel lightweight combined protection structure is located above the tunnel combined arch support structure for spanning a karst cave. The tunnel lightweight combined protection structure includes a corrugated steel protection arch, a buffer layer and an inner tunnel lining. The bottom of the corrugated steel protection arch is connected to the tunnel combined arch support structure. The buffer layer is arranged inside the corrugated steel protection arch, and the inner tunnel lining is arranged inside the buffer layer.

[0018] The present invention provides a tunnel structure spanning a karst cave. The corrugated steel protective arch, as an impact protection structure (to avoid the impact damage of falling rocks above the karst cave on the tunnel), has the following advantages: The corrugated steel protective arch is convenient for construction, can quickly form a safety protection structure, and improves the safety guarantee during construction; The corrugated steel protective arch has high strength and high toughness properties, and has a better protective effect on bearing the impact load of falling rocks; The corrugated steel protective arch has a lower self-weight compared to the concrete structure, can reduce the self-weight of the protective structure, and can achieve the purpose of quick and convenient repair by replacing or stacking the corrugated steel plates of the protective arch; The corrugated steel protective arch can also serve as the structural support framework of the buffer layer.

[0019] The buffer layer, as a protection structure, mainly functions to further disperse the impact load and protect the structures or vehicles inside it. The combination of the corrugated steel protective arch and the buffer layer has the following advantages: Compared with the traditional heavy concrete arch + backfill anti-impact layer on the top structure, it saves more project costs and improves the safety and durability of the tunnel; It can be used as the external formwork for the inner lining of the tunnel, solves the difficulty of setting up the external formwork for the inner lining of the tunnel, further saves the cost of the external formwork, and also increases the construction convenience; It can reduce the designed thickness of the inner lining of the tunnel, further reduce the weight of the protective structure, and save construction costs.

[0020] There can be various materials for the buffer layer, such as rubber, foam plastic, or spring pads. The buffer layer is arranged inside the corrugated steel protective arch. Compared with the scheme of arranging the buffer layer outside the corrugated steel protective arch, this scheme only needs to install and construct the buffer layer inside the corrugated steel protective arch, thus making the construction process simpler and more efficient.

[0021] The inner lining of the tunnel, as the safety protection reserve of the tunnel, can be a steel structure or a concrete structure. The inner lining of the tunnel can be optimized or cancelled according to the structural force analysis, further reducing the self-weight of the structure and saving construction costs.

[0022] Preferably, the buffer layer is a rubber block or a foam plastic block. The rubber block and the foam plastic block are convenient for fixing to the corrugated steel protective arch. For example, they can be fixed by bolts, screws, binding straps, or adhesives.

[0023] Preferably, the buffer layer is fixed to the corrugated steel protective arch by bolts. The bolt connection method ensures firm connection and can also achieve the purpose of convenient replacement.

[0024] Preferably, the inner lining of the tunnel is a reinforced concrete structure, and the thickness of the reinforced concrete structure is 300 mm - 600 mm.

[0025] In a third aspect, the present invention provides a construction method for a tunnel structure spanning a karst cave, comprising the following steps: S1: Use a truck crane to hoist the steel arch that needs to span the karst cave to the designated installation position of the karst cave, and install the arch feet of the steel arch on the cave wall of the karst cave; S2: Conduct steel bar layout and binding operations on the steel arch, and then pour concrete to form a concrete arch; S3: Carry out filling construction on the filling area and fill it to a predetermined elevation to form a tunnel foundation; S4: Hoist and place the corrugated steel protection arch on the tunnel foundation, and fixedly connect the corrugated steel protection arch to the tunnel foundation; S5: Fix the buffer layer to the inner side of the corrugated steel protection arch by bolts; S6: Use the buffer layer as a formwork to construct the inner lining of the tunnel on the inner side of the buffer layer to complete the construction.

[0026] The present invention provides a construction method for a tunnel structure spanning a karst cave. By erecting the steel arch on the karst cave of the tunnel and pouring a concrete arch to form a tunnel combined arch support structure, it is not necessary to backfill and treat the karst cave, avoiding the destruction of the original water drainage channel of the karst cave. At the same time, compared with the treatment scheme of setting a beam bridge to span the karst cave in the prior art, it avoids the problems of difficult construction of the formwork support of the cast-in-place beam bridge and difficult demolition in the later stage, as well as the problems of difficult hoisting and erection of precast beams and mismatched span diameters, improving the construction safety and operation durability of the tunnel. At the same time, the steel arch can be used as a combined temporary and permanent stress-bearing structure. During the construction stage, the steel arch serves as the formwork (temporary stress-bearing structure) of the concrete arch. After the concrete arch reaches the design strength, the steel arch and the concrete arch form a tunnel combined arch support structure (permanent stress-bearing structure), thus having the advantages of saving project costs and shortening the construction period. And by constructing the corrugated steel protection arch and the buffer layer to form a tunnel lightweight combined protection structure, it can quickly form a safety protection structure, improve the safety guarantee during construction, and reduce the self-weight of the protection structure. At the same time, the tunnel lightweight combined protection structure can be used as the outer formwork of the inner lining of the tunnel, solving the difficulty of erecting the outer formwork of the inner lining of the tunnel, further saving the cost of the outer formwork, and also increasing the construction convenience.

[0027] Compared with the prior art, the beneficial effects of the present invention are: 1. The present invention provides a tunnel composite arch support structure for spanning a karst cave. The corrugated steel plate in an arch shape is used as a steel arch to span the karst cave. At the same time, the steel arch also serves as a formwork (temporary load-bearing structure) for the concrete arch and forms a tunnel composite arch support structure (permanent load-bearing structure) with the concrete arch. Compared with the treatment scheme of backfilling at the bottom of the karst cave in the prior art, there is no need to carry out backfilling treatment on the karst cave, avoiding the damage to the original water drainage channel of the karst cave. At the same time, compared with the treatment scheme of setting a beam bridge to span the karst cave in the prior art, it avoids the problems of difficult construction of the formwork support for the cast-in-place beam bridge and difficult demolition in the later stage, as well as the problems of difficult hoisting and erection of precast beams and mismatched span diameters. The tunnel composite arch support structure formed by the steel arch and the concrete arch can improve the mechanical properties of the overall structure and further reduce the thickness of the concrete arch, saving construction costs.

[0028] 2. The present invention provides a tunnel structure for spanning a karst cave, and the corrugated steel protection arch achieves the following advantages: The construction of the corrugated steel protection arch is convenient, and it can quickly form a safety protection structure, improving the safety guarantee during construction; The corrugated steel protection arch has high strength and high toughness properties, and has a better protection effect on bearing the impact load of falling rocks; The corrugated steel protection arch has a relatively low self-weight compared with the concrete structure, which can reduce the self-weight of the protection structure. At the same time, the purpose of rapid and convenient repair can be achieved by replacing or superimposing the corrugated steel plates of the protection arch; The corrugated steel protection arch can also be used as the structural support framework of the buffer layer. The combination of the corrugated steel protection arch and the buffer layer achieves the following advantages: Compared with the traditional structure of a thick concrete arch + a top backfill impact protection layer, it saves more project costs and improves the safety and durability of the tunnel; It can be used as the external formwork for the inner lining of the tunnel, solving the difficulty of setting the external formwork for the inner lining of the tunnel, further saving the cost of the external formwork, and also increasing the construction convenience; It can reduce the designed thickness of the inner lining of the tunnel, further reducing the weight of the protection structure and saving construction costs.

[0029] 3. The present invention provides a construction method for a tunnel structure spanning a karst cave. By erecting the steel arch on the karst cave of the tunnel and pouring a concrete arch to form a tunnel combined arch support structure, it is not necessary to backfill and treat the karst cave, avoiding the damage to the original water drainage channel of the karst cave. At the same time, compared with the treatment scheme of setting a beam bridge to span the karst cave in the prior art, it avoids the problems of difficult construction of the formwork support for the cast-in-place beam bridge and difficult demolition in the later stage, as well as the problems of difficult hoisting and erection of precast beams and mismatched span diameters, improving the construction safety and operation durability of the tunnel. At the same time, the steel arch can be used as a combined temporary and permanent stress-bearing structure. During the construction stage, the steel arch serves as the formwork (temporary stress-bearing structure) of the concrete arch. After the concrete arch reaches the design strength, the steel arch and the concrete arch form a tunnel combined arch support structure (permanent stress-bearing structure), thus having the advantages of saving project costs and shortening the construction period. And by constructing the corrugated steel protection arch and the buffer layer to form a tunnel lightweight combined protection structure, it can quickly form a safety protection structure, improve the safety guarantee during construction, and reduce the self-weight of the protection structure. At the same time, the tunnel lightweight combined protection structure can be used as the external formwork of the inner lining of the tunnel, solving the difficulty of erecting the external formwork of the inner lining of the tunnel, further saving the cost of the external formwork, and increasing the construction convenience. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. is a schematic diagram of a tunnel structure spanning a karst cave.

[0031] Figure 2 is Figure 1 the sectional view along the cutting line A-A in FIG.

[0032] Figure 3 is Figure 1 the sectional view along the cutting line B-B in FIG.

[0033] Figure 4 is the three-dimensional schematic diagram of the steel arch.

[0034] Markings in the figure: 1 - steel arch, 2 - concrete arch, 3 - filling area, 4 - hollow structure, 5 - groove, 6 - karst cave, 7 - corrugated steel protection arch, 8 - buffer layer, 9 - inner lining of the tunnel, 10 - baffle. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0035] The following further describes the present invention in detail with reference to specific embodiments. However, this should not be construed as limiting the scope of the above-mentioned subject matter of the present invention to the following embodiments. All technologies implemented based on the content of the present invention belong to the scope of the present invention.

[0036] Unless otherwise specified, in the description of the specific embodiments of the present invention, the expression terms indicating the orientation or positional relationship such as "upper", "lower", "left", "right", "center", "inner", "outer", etc. are all based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the invention product / device / device is commonly used. These terms of orientation or positional relationship are only for the convenience of describing the solution of the present invention or simplifying the description in the specific embodiments, so as to facilitate technicians to quickly understand the solution, rather than indicating or implying that a specific device / component / element must have a specific orientation, or be constructed and operated in a specific positional relationship. Therefore, it should not be construed as a limitation to the present invention.

[0037] In addition, if terms such as "horizontal", "vertical", "hanging", "parallel" appear, it does not mean that the corresponding device / component / element is required to be absolutely horizontal or vertical or hanging or parallel, but can be slightly inclined or have a deviation. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but can be slightly inclined. Or, it can be simply understood that the corresponding device / component / element is arranged in the directions of "horizontal", "vertical", "hanging", "parallel", etc., and can have an error / deviation of ±10% relative to the corresponding direction setting, more preferably within ±8%, more preferably within ±6%, more preferably within ±5%, more preferably within ±4%. As long as the corresponding device / component / element is within the error / deviation range, it can still perform its function in the solution of the present invention.

[0038] In addition, the expressions "first", "second", "third", etc. in the terms are only used to distinguish the description of the same or similar components, and should not be understood as emphasizing or implying the relative importance of a specific component.

[0039] In addition, in the description of the embodiments of the present invention, "several", "multiple", "a plurality of" represent at least 2. It can be any situation such as 2, 3, 4, 5, 6, 7, 8, 9, etc., or even more than 9.

[0040] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, where terms such as "set", "installed", "connected", "connected", "provided with", "laid", "arranged" appear, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection. It can be a connection means commonly used in the art such as welding, riveting, bolting, threaded connection, etc. This connection can be a mechanical connection, an electrical connection or a communication connection; it can be directly connected, or indirectly connected through an intermediate medium, and can be the communication inside two components.

[0041] Example 1 As shown Figures 1 to 3 in the figure, a combined arch support structure for a tunnel spanning a karst cave includes a steel arch 1, a concrete arch 2, and a filling area 3.

[0042] The arch feet of the steel arch 1 are connected to the cave wall of the karst cave 6. The steel arch 1 is located below the tunnel. The steel arch 1 is an arched corrugated steel plate, and the corrugated steel plate has a corrugated cross-section. Specifically, the cross-sectional shape of the corrugated steel plate can be a continuous sine wave shape. In the cross-section, the corrugation extension direction is the width direction of the corrugated steel plate, and the direction perpendicular to the corrugation extension direction is the length direction of the corrugated steel plate. The corrugated steel plate is bent into an arch shape along the length direction, and the width direction of the corrugated steel plate is consistent with the width direction of the tunnel. The arch width direction of the steel arch 1 is consistent with the width direction of the tunnel, and the span direction of the steel arch 1 is consistent with the length direction of the tunnel. As shown Figure 4 in the figure, a three-dimensional schematic diagram of the arched corrugated steel plate as the steel arch 1 is shown. The arrow direction in the figure is the corrugation extension direction of the corrugated steel plate, and this direction is also the arch width direction of the steel arch 1.

[0043] The concrete arch 2 is arranged above the steel arch 1. During the construction of the concrete arch 2, the steel arch 1 can be used as a bottom formwork so that the bottom shape of the concrete arch 2 fits with the steel arch 1.

[0044] The filling area 3 is arranged above the concrete arch 2. The filling area 3 is used for filling to form a tunnel foundation. The filling can specifically adopt ceramsite concrete or pumice concrete.

[0045] In an optional implementation manner, the steel arch 1 can include several arch segments. All the arch segments are arched corrugated steel plates. The several arch segments are arranged along the width direction of the corrugated steel plate, and adjacent two arch segments are connected to each other. Specifically, adjacent two arch segments can be connected by bolts, rivets or welding. The width of the arch segment can be 1.0 m - 2.0 m, and the specific width can be 1.0 m, 1.2 m, 1.5 m, 1.8 m or 2.0 m.

[0046] In an optional implementation manner, shear studs can be provided on several of the arch segments. The shear studs are welded to the arch segments. The shear studs can be arranged at 10 - 25 per square meter, and specifically can be 10, 12, 16, 18, 20 or 25 per square meter.

[0047] In an alternative embodiment, baffles 10 may be provided on both sides of the steel arch 1. The baffles 10 may specifically be steel plates. The bottom edge of the steel plate is welded to the steel arch 1, and the top edge of the steel plate is flush with the top of the filling area 3. Resistance to deformation components may be provided on both of the baffles 10. The resistance to deformation components may be tie rods arranged between the two baffles 10 on both sides. The tie rods may specifically be steel bars or screws. The two ends of the steel bar are welded to the steel plate, and the two ends of the screw are bolted to the steel plate. The diameter of the steel bar or the screw may be selected from 6 mm to 22 mm according to the actual situation, and the specific diameters may be 6 mm, 8 mm, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, and 22 mm.

[0048] In an alternative embodiment, grooves 5 may be provided on the wall of the karst cave 6, and the arch feet of the steel arch 1 are connected to the grooves 5. Embedded bolts may be provided in the grooves 5, and the embedded bolts can be connected to the arch feet of the steel arch 1.

[0049] In an alternative embodiment, hollow structures 4 may be provided in the filling area 3. The hollow structures 4 may specifically be PVC pipes, and the axial direction of the PVC pipes is the same as the arch width direction of the steel arch 1. The diameter of the PVC pipe is 100 mm - 200 mm, and the specific diameters may be 100 mm, 110 mm, 125 mm, 160 mm, or 200 mm. The distance between two adjacent PVC pipes in the horizontal and vertical directions is 0.4 m - 0.6 m, and the specific distances may be 0.4 m, 0.5 m, or 0.6 m.

[0050] Example 2 As Figures 1 to 3 shown, a tunnel structure spanning a karst cave includes a tunnel lightweight combined protection structure. The tunnel lightweight combined protection structure is located above the tunnel combined arch support structure described in Example 1. The tunnel lightweight combined protection structure includes a corrugated steel protection arch 7, a buffer layer 8, and a tunnel inner lining 9. The bottom of the corrugated steel protection arch 7 is connected to the tunnel combined arch support structure. The buffer layer 8 is provided inside the corrugated steel protection arch 7, and the tunnel inner lining 9 is provided inside the buffer layer 8.

[0051] In an alternative embodiment, the buffer layer 8 may be a rubber block or a foam plastic block.

[0052] In an alternative embodiment, the buffer layer 8 may be fixed to the corrugated steel protection arch 7 by bolts.

[0053] In an optional embodiment, the inner lining 9 of the tunnel may be a reinforced concrete structure. The thickness of the reinforced concrete structure may be 300 mm-600 mm, and the specific thickness may be 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, 550 mm, or 600 mm.

[0054] Example 3 The present invention provides a construction method for a tunnel structure across a karst cave, and specifically describes the construction steps of a tunnel structure across a karst cave described in Example 2, which includes the following steps: S1: grooves 5 are cut at predetermined positions on the wall of the cave 6, and embedded bolts are installed. A truck crane is used to hoist several arch pieces to the designated installation positions of the cave 6, all the arch pieces are arranged along the arch width direction of the steel arch 1, and the arch feet of the arch pieces are installed in the grooves 5, and the arch feet are connected to the embedded bolts. Two adjacent arch pieces are connected by bolts to form a steel arch 1.

[0055] S2: Install baffles 10 on both sides of the steel arch 1. The baffles 10 are made of steel plates. The bottom of the steel plates is welded to the steel arch 1. Tie rods are used to tie the steel plates on both sides. The tie rods can be made of steel bars with a diameter of 22 mm. Arrange and tie steel bars on the steel arch 1, and then pour concrete to form a concrete arch 2.

[0056] S3: Filling construction is performed using ceramsite concrete to fill the filling area 3. During the filling process, several PVC pipes with a diameter of 110 mm are placed in the filling area 3. The axial direction of the PVC pipe is consistent with the arch width direction of the steel arch 1. The ceramsite concrete is filled to a level with the top of the concrete arch 2 to form a tunnel foundation. At the same time, embedded parts that can be connected to the corrugated steel protective arch 7 are constructed on the tunnel foundation.

[0057] S4: The corrugated steel protective arch 7 is hoisted section by section at the edge of the cave 6 and assembled, the assembled corrugated steel protective arch 7 is hoisted onto the tunnel foundation, and the corrugated steel protective arch 7 is connected to the embedded parts on the tunnel foundation with bolts.

[0058] S5: Fix the buffer layer 8 to the inner side of the corrugated steel protective arch 7 by bolts. The buffer layer 8 is specifically made of rubber blocks. The corrugated steel protective arch 7 and the rubber blocks are both pre-reserved with corresponding screw holes for easy and quick installation.

[0059] S6: constructing the tunnel inner lining 9 on the inner side of the buffer layer 8. The tunnel inner lining 9 is a reinforced concrete structure. The buffer layer 8 is used as an outer mold when pouring the tunnel inner lining 9 to complete the construction.

[0060] The tunnel structure spanning a karst cave and its construction method provided by the present invention further have the following advantages: By using corrugated steel plates as the main structure of the steel arch 1, the effect of quickly spanning the karst cave 6 is achieved, making the construction of the arch bridge structure more convenient, shortening the construction period, and reducing safety risks.

[0061] The use of large-scale mechanical equipment and the large formwork support system at the lower part of the construction are eliminated. At the same time, the steel arch 1 and the concrete arch 2 form a combined arch support structure for the tunnel to jointly bear the load, reducing the thickness of the concrete arch 2, thus achieving the effect of cost savings. After the combined arch support structure of the tunnel is formed, the corrugated steel protection arch 7 can be conveniently and quickly transported to the location of the karst cave 6 for installation construction, and a protection structure during the construction period can be quickly formed. Construction workers can then construct inside the corrugated steel protection arch 7, reducing the harm of falling rocks from the top of the karst cave 6 to the construction workers. The tunnel lightweight combined protection structure composed of the corrugated steel protection arch 7 and the buffer layer 8, as a buffer structure, can make the impact load outside the tunnel act on the corrugated steel protection arch 7 and the buffer layer 8, thereby weakening the impact load that the inner lining 9 of the tunnel needs to bear, and thus the designed thickness of the inner lining 9 of the tunnel can be reduced, effectively reducing the overall project cost. The tunnel lightweight combined protection structure can also continue to be used as the outer formwork on the outside of the inner lining 9 of the tunnel. This solution overcomes the technical problem of installing external formwork on the outside of the inner lining 9 of the tunnel in a karst cave environment, and at the same time eliminates the step of separately building the external formwork, thus effectively saving the cost of setting up the external formwork and further promoting the reduction of the overall project cost.

[0062] The original drainage channel of the karst cave 6 below is reserved to avoid the erosion of the tunnel structure by the water flow in the karst cave 6, thus achieving the durability effect.

[0063] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A combined arch support structure for a tunnel spanning a karst cave, characterized in that, Comprising: A steel arch (1), the arch feet of the steel arch (1) being connected to the cave wall of the karst cave (6), the steel arch (1) being located below the tunnel, the steel arch (1) being an arched corrugated steel plate, the corrugated steel plate having a corrugated cross-section, in the cross-section the corrugation extending direction being the width direction of the corrugated steel plate, the direction perpendicular to the corrugation extending direction being the length direction of the corrugated steel plate, the corrugated steel plate being bent into an arch along the length direction, the width direction of the corrugated steel plate being consistent with the width direction of the tunnel; A concrete arch (2), the concrete arch (2) being arranged above the steel arch (1); A filling area (3), the filling area (3) being arranged above the concrete arch (2), the filling area (3) being used for filling to form a tunnel foundation.

2. The combined arch support structure for a tunnel spanning a karst cave according to claim 1, characterized in that, The steel arch (1) comprises a plurality of arch segments, all of the plurality of arch segments being arched corrugated steel plates, the plurality of arch segments being arranged along the width direction of the corrugated steel plate, and adjacent two of the arch segments being connected to each other.

3. The combined arch support structure for a tunnel spanning a karst cave according to claim 2, characterized in that, A plurality of shear studs are provided on the plurality of arch segments, and the shear studs are welded to the arch segments.

4. A combined arch support structure for a tunnel spanning a karst cave according to claim 1, characterized in that, Baffles (10) are provided on both sides of the steel arch (1), and deformation resistance components are provided on both of the baffles (10).

5. The combined arch support structure for a tunnel spanning a karst cave according to claim 1, characterized in that, A groove (5) is provided on the cave wall of the karst cave (6), and the arch feet of the steel arch (1) are connected to the groove (5).

6. The combined arch support structure for a tunnel spanning a karst cave according to claim 1, characterized in that, A hollow structure body (4) is provided in the filling area (3), and the filling area (3) is filled with ceramsite concrete or pumice concrete.

7. A tunnel structure spanning a karst cave, characterized in that, Comprising a tunnel light composite protection structure, the tunnel light composite protection structure being located above a tunnel composite arch support structure according to any one of claims 1-6 for a tunnel spanning a karst cave, the tunnel light composite protection structure comprising a corrugated steel protection arch (7), a buffer layer (8) and a tunnel inner lining (9), the bottom of the corrugated steel protection arch (7) being connected to the tunnel composite arch support structure, the buffer layer (8) being arranged inside the corrugated steel protection arch (7), and the tunnel inner lining (9) being arranged inside the buffer layer (8).

8. A tunnel structure spanning a karst cave according to claim 7, characterized in that, The buffer layer (8) is a rubber block or a foam plastic block.

9. A tunnel structure spanning a karst cave according to claim 8, characterized in that, The buffer layer (8) is fixed to the corrugated steel protection arch (7) by bolts.

10. A tunnel structure spanning a karst cave according to claim 7, characterized in that, The tunnel inner lining (9) is a reinforced concrete structure, and the thickness of the reinforced concrete structure is 300 mm - 600 mm.

11. A construction method for a tunnel structure spanning a karst cave, characterized in that, Applied to a tunnel structure for spanning a karst cave according to any one of claims 7-10, comprising the following steps: S1: Using a truck crane to hoist the steel arch (1) that needs to span the karst cave (6) to the designated installation position of the karst cave (6), and installing the arch feet of the steel arch (1) on the cave wall of the karst cave (6); S2: Conducting steel bar layout and binding operations on the steel arch (1), and then pouring concrete to form the concrete arch (2); S3: Conducting filling construction on the filling area (3) and filling to a predetermined elevation to form a tunnel foundation; S4: Hoisting and placing the corrugated steel protection arch (7) on the tunnel foundation, and fixedly connecting the corrugated steel protection arch (7) to the tunnel foundation; S5: Fix the buffer layer (8) to the inner side of the corrugated steel protection arch (7) by bolts; S6: Use the buffer layer (8) as a formwork to construct the inner lining (9) of the tunnel on the inner side of the buffer layer (8) to complete the construction.

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