Construction method of tunnel crossing large-span water-rich karst cave

Abstract

This invention relates to a construction method for tunneling through a large-span water-rich karst cave. It employs a technical solution where an escape passage intersects with the tunnel within the karst cave, facilitating the entry and exit of construction equipment, materials, and personnel. This enables the excavation and support construction of a two-way tunnel within the karst cave, and allows for the orderly filling of the rubble generated during the two-way tunnel excavation into the bottom of the karst cave. This not only improves the construction efficiency of tunneling through the karst cave but also simultaneously solves the problem of efficient rubble disposal. It reduces the cost and time of rubble disposal and, to a certain extent, improves the load-bearing capacity of the double-row support structure and the stability of the karst cave. The direct use of prestressed panels as the tunnel invert arch for the karst cave avoids redundant invert arch construction and provides a better load-bearing foundation for the tunnel section through the piers and double-row support structure.

Description

Technical Field

[0001] This invention belongs to the field of tunnel construction through karst caves, and particularly relates to a construction method for tunnels through large-span water-rich karst caves. Background Technology

[0002] When large or long-span karst caves exist within the surrounding rock of a mountain, tunneling through these caves presents a series of technical challenges. This is particularly true when traversing large, water-rich karst caves, where fluctuations in the water level directly impact the tunnel's construction progress. To address this issue, CN108979644A discloses a method for handling karst cave collapses and excavating tunnels in water-rich areas. This method successfully drains a large amount of water from the karst cave using a water diversion tunnel and device, thus providing construction space for the tunnel. However, this method is prone to causing excessive water loss from the karst cave, affecting its stability. The design deteriorates and does not consider the harm caused by rising water levels during later tunnel operation. In addition, the technologies disclosed in CN109812270A, CN114876568A, CN216518044U and CN201110260206.4 are mostly achieved by grouting, sealing or filling the karst caves to enable tunnels to pass through them. However, these technologies are somewhat inadequate when facing large-span water-rich karst caves. Therefore, they can only be used for temporary treatment of small karst caves and cannot be used as technical measures for tunnels to pass through large-span water-rich karst caves.

[0003] Therefore, there is an urgent need to find a technical measure for tunneling through large-span water-rich karst caves, to solve the problem of water level changes within the caves, and to comprehensively consider the stability of the caves and the safety of tunnel operation in the later stages. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a construction method for tunneling through a large-span water-rich karst cave.

[0005] This construction method for tunneling through a large-span, water-rich karst cave includes the following steps:

[0006] Step 1: Determine the tunnel route through the water-rich karst cave; then design the escape route and the water diversion tunnel route.

[0007] Step 2: Construct an escape tunnel. The escape tunnel uses a boom to lower a drainage pipe connected to a water pump into the water body in the water-rich cave to drain the water from the cave.

[0008] Step 3: Set up a frame on the side wall of the water-rich karst cave and set up a lower platform and an upper platform; construct the water diversion tunnel from the outside into the water-rich karst cave, and install a water-permeable protective head at the water-rich karst cave end of the water diversion tunnel;

[0009] Step 4: Dismantle the lower platform, set up floating boxes in the water-rich karst cave, use drainage pipes to recharge the water, assemble the steel trestle bridge using the floating boxes, and then dismantle the floating boxes and drainage pipes.

[0010] Step 5: Using the steel trestle bridge as a construction platform, the tunnel is constructed from the inside out in both directions. The generated gravel is loaded into gabions and hoisted to the bottom of the water-rich karst cave; the steel trestle bridge is dismantled; and then the prestressed panels are constructed at the bottom of the tunnel.

[0011] Step Six: The tunnel within the surrounding rock of the mountain is completed. The tunnel section is then constructed on the prestressed panel, and the escape passage and tunnel are connected.

[0012] As a preferred option, in step one, the tunnel crossing path is first determined based on the spatial location of the water-rich karst cave within the surrounding rock of the mountain and the water level within the cave. The tunnel crosses the water-rich karst cave in a straight line from the middle, and its location is above the highest water level within the cave. The escape passage is positioned above the tunnel on the horizontal plane at an angle of 45° to 60° with the tunnel axis, intersecting the tunnel on the outer wall of the water-rich karst cave. The escape passage's angle with the tunnel axis on the vertical plane is 15° to 20°. The water diversion tunnel is positioned below the tunnel on the vertical plane at an angle of 10° to 15° with the tunnel axis. Its angle on the horizontal plane is determined based on the shortest distance from the water-rich karst cave to the surface of the surrounding rock of the mountain. The entrance of the water diversion tunnel where it intersects with the water-rich karst cave is located directly below the point where the escape passage intersects with the tunnel.

[0013] As a preferred option, in step two, the escape passage is excavated and supported up to the outer wall of the water-rich karst cave. Multiple sets of orthogonal anchors are installed on the upper part of the escape passage section near the water-rich karst cave to stabilize the top of the escape passage. The rubble generated from the excavation of the escape passage is transported to the outside of the surrounding rock of the mountain. Hanging rods are installed on the top of the escape passage, and then the drainage pipe connected to the water pump is fixed along the hanging rods to the upper part of the escape passage. The water pump is hoisted to the bottom of the intersection of the load-bearing double-row frame and the water-rich karst cave.

[0014] Preferably, in step three, a scaffold is installed on the side wall of the water-rich karst cave using the escape passage. The scaffold includes a load-bearing double-row scaffold and a vertical construction scaffold. The lower part of the load-bearing double-row scaffold is embedded in the bedrock of the outer wall of the water-rich karst cave. The top height of the load-bearing double-row scaffold is set between the bottom of the tunnel passing through the water-rich karst cave and the entrance of the water diversion tunnel. A connecting platform is provided at the top of the load-bearing double-row scaffold. A lower platform extending to the water diversion tunnel is constructed on the load-bearing double-row scaffold below the entrance of the water diversion tunnel for the construction work of the water diversion tunnel. One end of the lower platform is fixed to the load-bearing double-row scaffold. On the double-row scaffold, the other end of the lower platform is fixed to the side wall of the water-rich karst cave; a vertical construction scaffold is installed on the connecting platform of the load-bearing double-row scaffold near the escape passage. An elevator is installed on the vertical construction scaffold, and an upper platform is installed on the vertical construction scaffold. The upper platform has the same structure as the lower platform, and the height of the upper platform is located at the exit of the escape passage in the water-rich karst cave; first, the water level in the water-rich karst cave is lowered to the bottom of the lower platform by a water pump, and then the lower platform is used as a construction platform to install a water-permeable protective head at the exit of the water diversion tunnel in the water-rich karst cave.

[0015] As a preferred option, step four is as follows: First, dismantle the lower platform; then, use the drainage pipe connected to the water pump to backfill the water body in reverse, so that the water level in the water-rich cave rises to meet the requirements for pontoon assembly; then, assemble the pontoons on the water body of the water-rich cave, with the height of the pontoons being greater than the static distance between the permeable protective head and the steel trestle; the assembled pontoons are fixed to the load-bearing double-row frames on both sides using steel cables; finally, use the connecting platform at the top of the pontoons and the load-bearing double-row frames to assemble the steel trestle, and continue to use the water pump to control the changes in the water level in the water-rich cave according to the height fluctuations of the pontoons during the assembly of the steel trestle; after the steel trestle is assembled, remove the drainage pipe connected to the water pump.

[0016] As a preferred option, in step five, the exhaust pipe connected to the exhaust fan is fixed along the suspender to the upper part of the escape passage, with the inner side of the exhaust pipe extending into the water-rich karst cave to form an exhaust system; using a steel trestle bridge as a construction platform, the tunnel is excavated and supported by blasting from the inside out in the water-rich karst cave, and the crushed stone produced by the tunnel excavation is loaded into gabions; finally, the gabions are hoisted down to the lower part of the water-rich karst cave using the steel trestle bridge, and when the height of the gabions in the water-rich karst cave reaches the connecting platform at the top of the load-bearing double-row frame, the tunnel construction is stopped, and the tunnel faces on both sides are sealed with sprayed concrete.

[0017] As a preferred option, in step five, the steel trestle bridge is dismantled; then a sealing and leveling layer is laid on top of the gabion; then the piers are constructed on the sealing and leveling layer, and the piers are fixed on the connecting platform at the top of the load-bearing double-row frame. Then the supports are installed on the piers, and finally the prestressed panels are constructed. The height of the prestressed panels is consistent with the bottom of the tunnel, and the two ends of the prestressed panels are fixed to the bottom of the two tunnels that have been constructed.

[0018] As a preferred option, in step six, firstly, based on the spatial location of the tunnel, and drawing on the drill-and-blast method or shield tunneling method, the excavation and support construction of one side of the tunnel is carried out from the outside to the inside on one side of the surrounding rock of the mountain until it is connected with the tunnel that has been completed in the water-rich karst cave; then, the ventilation system in the escape passage and the upper platform and vertical construction frame in the water-rich karst cave are dismantled in sequence.

[0019] As a preferred option, in step six, the sidewalls and arch of the tunnel within the water-rich karst cave section are first constructed using cast-in-place or precast methods on the prestressed panels. The prestressed panels serve as the tunnel's invert arch, thus completing the construction of the tunnel section within the water-rich karst cave section. Then, holes are drilled in the arch of the tunnel, and a transition passage is used to connect to the entrance and exit of the escape passage in the water-rich karst cave, enabling the escape passage to connect with the tunnel. An escape ladder is installed at the bottom of the transition passage to lead to the tunnel, thereby completing the construction of the large-span water-rich karst cave tunnel.

[0020] The tunnel traversing a large-span, water-rich karst cave is obtained by any of the methods described above.

[0021] The beneficial effects of this invention are:

[0022] 1) This invention adopts a technical solution in which the escape passage and tunnel intersect in the water-rich karst cave, which is conducive to the entry and exit of construction equipment, materials and personnel, thereby realizing the excavation and support construction of the two-way tunnel inside the water-rich karst cave, and orderly filling the bottom of the water-rich karst cave with the gravel generated by the two-way tunnel excavation. This not only improves the construction efficiency of tunnel crossing the water-rich karst cave, but also solves the problem of efficient treatment of gravel generated by tunnel excavation. It not only reduces the cost and time of gravel treatment, but also improves the load-bearing capacity of the load-bearing double-row frame and the stability of the water-rich karst cave to a certain extent.

[0023] 2) This invention solves the technical problem of water level control during the construction and operation of tunnels passing through water-rich karst caves by laying out escape passages and water diversion tunnels, thus ensuring the safety of tunnels passing through water-rich karst caves.

[0024] 3) This invention directly uses prestressed panels as the invert arch of the tunnel passing through water-rich karst caves, which not only avoids the repeated construction of the invert arch, but also provides a better load-bearing foundation for the tunnel section through the piers and load-bearing double-row frames.

[0025] 4) This invention achieves adjustable water level in water-rich karst caves during tunnel construction through a drainage system and water diversion tunnel, ensuring that the water level is at a reasonable position at different times. In turn, water diversion is used to make the pontoon float, and the technical problem of the difficulty in erecting steel trestle bridges inside large-span water-rich karst caves is solved in conjunction with the load-bearing double-row frame. This is conducive to ensuring the smooth implementation of tunnel construction through water-rich karst caves, and also helps to ensure that the danger caused by excessive water loss in the later stages of water-rich karst caves does not increase. In addition, during the later tunnel operation, the water level in the water-rich karst caves will always be lower than the tunnel invert surface, which also ensures the safe operation of the tunnel. Attached Figure Description

[0026] Figure 1 It is a construction process flowchart for tunneling through a large-span water-rich karst cave;

[0027] Figure 2 It is a plan view of the tunnels, escape routes, and water diversion tunnels to be constructed;

[0028] Figure 3 It is a cross-sectional view of the tunnel, escape route, and water diversion tunnel to be constructed;

[0029] Figure 4 This is a schematic diagram of the excavation and support construction of the escape route;

[0030] Figure 5 This is a schematic diagram of drainage construction inside a water-rich karst cave;

[0031] Figure 6 This is a schematic diagram of the installation of the load-bearing double-row scaffold, upper and lower platforms, and vertical construction scaffold;

[0032] Figure 7 This is a schematic diagram of the water diversion tunnel construction;

[0033] Figure 8 This is a schematic diagram of the steel trestle bridge construction.

[0034] Figure 9 This is a schematic diagram of two-way tunnel construction from the inside out in a water-rich karst cave.

[0035] Figure 10 It involves the construction of piers and prestressed panels;

[0036] Figure 11 This is a schematic diagram of the tunnel breakthrough construction within the surrounding rock of the mountain;

[0037] Figure 12 This is a schematic diagram illustrating the completion of a large-span tunnel crossing a water-rich karst cave.

[0038] In the diagram: 1-Tunnel crossing section; 2-Tunnel; 3-Prestressed panel; 4-Escape ladder; 5-Transition passage; 6-Water-rich karst cave; 7-Pier column; 8-Sealing leveling layer; 9-Support; 10-Load-bearing double-row scaffold; 11-Water body; 12-Gabion; 13-Water diversion tunnel; 14-Permeable protective head; 15-Escape passage; 16-Orthogonal anchor bolt; 17-Surrounding rock of the mountain; 18-Ventilation system; 19-Hanging rod; 20-Vertical construction scaffold; 21-Upper platform; 22-Connecting platform; 23-Steel trestle bridge; 24-Floating box; 25-Steel cable; 26-Drainage pipe; 27-Water pump; 28-Lower platform. Detailed Implementation

[0039] The present invention will be further described below with reference to embodiments. The description of the embodiments below is only for the purpose of helping to understand the present invention. It should be noted that those skilled in the art can make several modifications to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0040] Example 1

[0041] As one example, such as Figure 1 As shown, this construction method for tunneling through a large-span, water-rich karst cave includes the following construction steps:

[0042] Step 1: Determine the spatial locations of Tunnel 2, Escape Passage 15, and Water Diversion Tunnel 13:

[0043] like Figure 2 and Figure 3 As shown, based on the determined tunnel 2 crossing path, the escape passage 15 is positioned above the tunnel 2 at an angle of 45° to 60° with the tunnel 2 axis in the plane, intersecting with the tunnel 2 on the outer wall of the water-rich karst cave 6. The escape passage 15 is positioned at an angle of 15° to 20° with the tunnel 2 axis in the vertical section, thus determining the spatial position of the escape passage 15. Finally, based on the determined tunnel 2 crossing path and the spatial position of the escape passage 15, the water diversion tunnel 13 is positioned below the tunnel 2 at an angle of 10° to 15° with the tunnel 2 axis in the vertical section. Its angle in the plane is determined based on the shortest distance of the water diversion tunnel 13. The opening of the water diversion tunnel 13 intersecting with the water-rich karst cave 6 is located directly below the point where the escape passage 15 intersects with the tunnel 2, thus determining the spatial position of the water diversion tunnel 13.

[0044] Step 2: Excavation and support construction of escape route 15:

[0045] Based on the predetermined angle and spatial location of the escape passage 15, and drawing on the drilling and blasting method or shield tunneling method, the escape passage 15 is rapidly excavated and supported until it reaches the outer wall of the water-rich karst cave 6.

[0046] Drainage within the water-rich karst cave 6:

[0047] like Figure 4 and Figure 5 As shown, a hanging rod 19 is installed at the top of the completed escape passage 15. Then, a drain pipe 26 connected to a water pump 27 is fixed along the hanging rod 19 to the upper part of the escape passage 15. The water pump 27 is then lowered into the water body 11 in the water-rich cave 6 to drain the water-rich cave 6.

[0048] Step 3: Installation of the load-bearing double-row scaffolding 10, upper and lower platforms 28, and vertical construction scaffolding 20:

[0049] like Figure 6 As shown, after the water level in the water-rich karst cave 6 drops to a safe position, the escape passage 15 is used as the entrance and exit for construction equipment, materials, and workers. First, the load-bearing double-row scaffolding 10 is installed. The load-bearing double-row scaffolding 10 is symmetrically arranged around the two side walls of the water-rich karst cave 6. The top height of the load-bearing double-row scaffolding 10 is set between the bottom of the tunnel 2 passing through the water-rich karst cave 6 and the entrance of the water diversion tunnel 13. Then, a lower platform is assembled on the load-bearing double-row scaffolding 10 below the entrance of the water diversion tunnel 13 using Bailey beam components. Platform 28 facilitates the construction of the water diversion tunnel 13. One end of the lower platform 28 is fixed to the load-bearing double-row frame 10, and the other end of the lower platform 28 is fixed to the side wall of the water-rich karst cave 6. Then, a vertical construction frame 20 is installed on the connecting platform 22 of the load-bearing double-row frame 10 near the escape passage 15. Finally, an upper platform 21 is installed on the vertical construction frame 20. The structure of the upper platform 21 is the same as that of the lower platform 28. The height of the upper platform 21 is located at the exit of the escape passage 15 in the water-rich karst cave 6.

[0050] Construction of Water Diversion Tunnel 13:

[0051] like Figure 7 As shown, firstly, the water pump 27 is raised to the bottom of the lower platform 28 to ensure that the highest water level in the water-rich cave 6 does not exceed the bottom of the lower platform 28; then, according to the determined angle and spatial position of the water diversion tunnel 13, the drilling is carried out from the outside of the mountain towards the water-rich cave 6, and the resulting gravel is transported outside the mountain of the water diversion tunnel 13; finally, using the lower platform 28 as a construction platform, a permeable protective head 14 is installed at the outlet of the water diversion tunnel 13 in the water-rich cave 6 to improve the protective capability of the water diversion tunnel 13.

[0052] Step 4: Erection of steel trestle bridge 23:

[0053] Figure 8As shown, firstly, the lower platform 28 is removed; then, the water body 11 is recharged using the drainage system to raise the water level in the water-rich cave 6 to meet the requirements for assembling the pontoon 24. After that, the pontoon 24 is assembled on the water body 11 of the water-rich cave 6. The height of the pontoon 24 is greater than the static distance between the permeable protective head 14 and the steel trestle bridge 23. The assembled pontoon 24 is fixed to the load-bearing double-row frame 10 on both sides using steel cables 25. Finally, the steel trestle bridge 23 is assembled by connecting the pontoon 24 and the top of the load-bearing double-row frame 10. Each unit of the steel trestle bridge 23 adopts Bailey beam components.

[0054] Step 5: Construct Tunnel 2 from the inside out in the water-rich karst cave 6:

[0055] like Figure 9 As shown, first, the floating box 24 is removed; then, drawing on the drill-and-blast method, the steel trestle bridge 23 is used as a construction platform to carry out the two-way blasting excavation and support construction of the tunnel 2 from the inside to the outside in the water-rich karst cave 6; finally, the gabion 12 is hoisted to the lower part of the water-rich karst cave 6 using the steel trestle bridge 23.

[0056] Construction of pier 7 and prestressed panel 3:

[0057] like Figure 10 As shown, firstly, the steel trestle bridge 23 is dismantled; then, a sealing and leveling layer 8 is laid on top of the piled gabion 12; then, the piers 7 and prestressed panels 3 are constructed on the sealing and leveling layer 8. The piers 7 on both sides are made of reinforced concrete and fixed on the connecting platform 22 at the top of the load-bearing double-row frame 10. Then, the supports 9 are installed on the piers 7. Finally, the prestressed panels 3 are constructed using the cast-in-place prestressing tensioning method. The height of the prestressed panels 3 is consistent with the bottom of the constructed tunnel 2, and the two ends of the prestressed panels 3 are fixed to the bottom of the constructed tunnels 2 on both sides.

[0058] Step Six: Tunnel 2 within the 17th section of the surrounding rock of the mountain is completed.

[0059] like Figure 11 As shown, based on the determined spatial location of Tunnel 2, and drawing on the drill-and-blast method or shield tunneling method, the excavation and support construction of one side of Tunnel 2 is carried out from the outside to the inside on one side of the mountain until it is connected to the completed Tunnel 2 in the water-rich karst cave 6.

[0060] Example 2

[0061] As another embodiment, this embodiment two proposes a more specific construction method for tunneling through a large-span water-rich karst cave based on embodiment one.

[0062] In step one, based on the spatial location of the water-rich karst cave 6 in the surrounding rock 17 and the water level inside the water-rich karst cave 6, the tunnel 2 crossing path is first determined. The tunnel 2 crosses the water-rich karst cave 6 in a straight line from the middle of the water-rich karst cave 6, and the location of the tunnel 2 should be above the highest water level in the water-rich karst cave 6.

[0063] In step two, while the escape passage 15 is being rapidly excavated and supported, multiple sets of orthogonal anchor rods 16 are installed on the upper part of the section of escape passage 15 near the water-rich karst cave 6 to stabilize the top of escape passage 15. The rubble generated from the excavation of escape passage 15 is transported to the outside of the mountain where escape passage 15 is located.

[0064] When draining water from the water-rich karst cave 6, the water pump 27 is initially placed below the intersection of the load-bearing double-row frame 10 and the water-rich karst cave 6 to lower the water level, which facilitates the subsequent construction work of the load-bearing double-row frame 10.

[0065] In step three, the load-bearing double-row scaffold 10 is a statically indeterminate permanent load-bearing component formed by bolting together rust-proofed steel sections. Its lower part is embedded in the bedrock of the outer wall of the water-rich karst cave 6. If necessary, the embedded section can be enlarged to enhance its load-bearing capacity. The upper part of the load-bearing double-row scaffold 10 is a connecting platform 22 made of steel components. The vertical construction scaffold 20 is also a temporary structure assembled from steel components. An elevator is installed on the vertical construction scaffold 20 to facilitate the transportation of equipment, materials, and workers.

[0066] In step four, based on the height fluctuations of the pontoon 24 during the assembly of the steel trestle bridge 23, the drainage system is used to control the water level changes in the water-rich cave 6 to adapt to them. After the pontoon 24 is used, the drainage system is removed.

[0067] In step five, the exhaust pipe connected to the exhaust fan is fixed along the hanger 19 to the upper part of the escape passage 15, and the inner side of the exhaust pipe extends into the water-rich karst cave 6 to form an exhaust system 18; the gravel produced by the bidirectional excavation of tunnel 2 is orderly loaded into the gabion 12; when the gabion 12 reaches the top of the load-bearing double-row frame 10 at the connecting platform 22, the bidirectional construction of tunnel 2 is stopped, and the working faces of tunnel 2 on both sides are sprayed and sealed.

[0068] It should be noted that the parts in this embodiment that are the same as or similar to those in Embodiment 1 can be referred to each other, and will not be repeated in this application.

[0069] Example 3

[0070] As another embodiment, based on embodiments one and two, this embodiment three proposes a construction method for tunneling through a large-span water-rich karst cave, which further includes:

[0071] After step six is ​​completed, the ventilation system 18 in the escape passage 15 and the upper platform 21 and vertical construction frame 20 in the water-rich karst cave 6 are dismantled in sequence.

[0072] Completed the construction of Tunnel 2, which traverses a large-span, water-rich karst cave:

[0073] like Figure 12 As shown, firstly, the sidewalls and arch of the tunnel 2 within the water-rich karst cave 6 section are constructed on the prestressed panel 3 using either cast-in-place or prefabrication methods. The prestressed panel 3 serves as the invert arch of the tunnel 2, thus completing the construction of the tunnel section 1 within the water-rich karst cave 6 section. Then, an opening is made in the arch of the tunnel 2 corresponding to the space of the upper platform 21 to construct the transition passage 5. The transition passage 5 is then connected to the entrance and exit of the escape passage 15 in the water-rich karst cave 6, enabling the escape passage 15 to connect with the tunnel 2. An escape ladder 4 is being installed at the bottom of the transition passage 5 to reach the tunnel 2, thereby completing the tunnel 2 construction of the large-span water-rich karst cave 6.

[0074] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

Claims

1. A construction method for tunneling through a large-span water-rich karst cave, characterized in that, The construction steps include the following: Step 1: Determine the tunnel route through the water-rich karst cave; then design the escape route and the water diversion tunnel route. Step 2: Construct an escape tunnel. The escape tunnel uses a boom to lower a drainage pipe connected to a water pump into the water body in the water-rich cave to drain the water from the cave. Step 3: Construct scaffolding along the sidewall of the water-rich karst cave, and set up lower and upper platforms; construct the water diversion tunnel from the outside into the water-rich karst cave, installing a permeable protective head at the water-rich karst cave end of the water diversion tunnel; utilize the escape passage to construct scaffolding along the sidewall of the water-rich karst cave, including load-bearing double-row scaffolding and vertical construction scaffolding. The lower part of the load-bearing double-row scaffolding is embedded in the bedrock of the outer wall of the water-rich karst cave, and the top height of the load-bearing double-row scaffolding is set between the bottom of the tunnel passing through the water-rich karst cave and the entrance of the water diversion tunnel. A connecting platform is provided at the top of the load-bearing double-row scaffolding; an extension to the water diversion tunnel is constructed on the load-bearing double-row scaffolding below the entrance of the water diversion tunnel. The lower platform is used for the construction of the water diversion tunnel. One end of the lower platform is fixed to the load-bearing double-row scaffold, and the other end is fixed to the side wall of the water-rich karst cave. A vertical construction scaffold is installed on the connecting platform of the load-bearing double-row scaffold near the escape passage. An elevator is installed on the vertical construction scaffold. An upper platform is installed on the vertical construction scaffold. The upper platform has the same structure as the lower platform. The height of the upper platform is located at the exit of the escape passage in the water-rich karst cave. First, the water level in the water-rich karst cave is lowered to the bottom of the lower platform by a water pump. Then, the lower platform is used as a construction platform to install a water-permeable protective head at the exit of the water diversion tunnel in the water-rich karst cave. Step 4: Dismantle the lower platform, set up floating boxes in the water-rich karst cave, use drainage pipes to recharge the water, assemble the steel trestle bridge using the floating boxes, and then dismantle the floating boxes and drainage pipes. Step 5: Using the steel trestle bridge as a construction platform, the tunnel is constructed from the inside out in both directions. The generated gravel is loaded into gabions and hoisted to the bottom of the water-rich karst cave; the steel trestle bridge is dismantled; and then prestressed panels are constructed at the bottom of the tunnel. Step Six: The tunnel within the surrounding rock of the mountain is completed. The tunnel section is then constructed on the prestressed panel, and the escape passage and tunnel are connected.

2. The construction method of tunneling through large-span water-rich karst cave according to claim 1, characterized in that, In step one, based on the spatial location of the water-rich karst cave within the surrounding rock and the water level within the cave, the tunnel crossing route is first determined. The tunnel crosses the middle of the water-rich karst cave in a straight line, and its location is above the highest water level within the cave. The escape passage is positioned above the tunnel on the horizontal plane at an angle of 45° to 60° to the tunnel axis, intersecting with the tunnel on the outer wall of the water-rich karst cave. The escape passage's vertical angle with the tunnel axis is 15° to 20°. The water diversion tunnel is positioned below the tunnel on the vertical plane at an angle of 10° to 15° to the tunnel axis. Its horizontal angle is determined based on the shortest distance from the water-rich karst cave to the surface of the surrounding rock. The entrance of the water diversion tunnel where it intersects with the water-rich karst cave is located directly below the point where the escape passage intersects with the tunnel.

3. The construction method of tunneling through large-span water-rich karst cave according to claim 1, characterized in that, In step two, the escape passage is excavated and supported up to the outer wall of the water-rich karst cave. Multiple sets of orthogonal anchors are installed on the upper part of the escape passage section near the water-rich karst cave to stabilize the top of the escape passage. The rubble generated from the excavation of the escape passage is transported outside the surrounding rock of the mountain. Hanging rods are installed on the top of the escape passage, and then the drainage pipe connected to the water pump is fixed along the hanging rods to the upper part of the escape passage. The water pump is hoisted to the lower part of the intersection between the load-bearing double-row frame and the water-rich karst cave.

4. The construction method of tunneling through large-span water-rich karst cave according to claim 1, characterized in that, Step four is as follows: First, dismantle the lower platform; then, use the drainage pipe connected to the water pump to backfill the water, raising the water level in the rich karst cave to meet the requirements for pontoon assembly. Next, assemble the pontoons on the water in the rich karst cave, ensuring the pontoons are taller than the static distance between the permeable protective head and the steel trestle. Secure the assembled pontoons to the double-row load-bearing frames on both sides using steel cables. Finally, use the connecting platform at the top of the pontoons and the double-row load-bearing frames to assemble the steel trestle. Continue to use the water pump to control the water level in the rich karst cave according to the height fluctuations of the pontoons during assembly. Once the steel trestle is assembled, remove the drainage pipe connected to the water pump.

5. The construction method of tunneling through large-span water-rich karst cave according to claim 1, characterized in that, In step five, the exhaust pipe connected to the exhaust fan is fixed along the suspender to the upper part of the escape passage, and the inner side of the exhaust pipe extends into the water-rich karst cave to form an exhaust system. Using a steel trestle bridge as a construction platform, the tunnel is excavated and supported by blasting from the inside out in the water-rich karst cave. The crushed stone produced by the tunnel excavation is loaded into gabions. Finally, the gabions are hoisted to the lower part of the water-rich karst cave using the steel trestle bridge. When the gabions are piled up to the top of the load-bearing double-row frame at the top of the water-rich karst cave, the tunnel construction is stopped, and the tunnel faces on both sides are sealed with sprayed concrete.

6. The construction method for tunneling through a large-span water-rich karst cave according to claim 1, characterized in that, In step five, the steel trestle bridge is dismantled; then a sealing and leveling layer is laid on top of the gabion; then the piers are constructed on the sealing and leveling layer, and the piers are fixed on the connecting platform at the top of the load-bearing double-row frame. Then the supports are installed on the piers, and finally the prestressed panels are constructed. The height of the prestressed panels is consistent with the bottom of the tunnel, and the two ends of the prestressed panels are fixed to the bottom of the two tunnels that have been constructed.

7. The construction method for tunneling through a large-span water-rich karst cave according to claim 5, characterized in that, In step six, firstly, based on the spatial location of the tunnel, and drawing on the drill-and-blast method or shield tunneling method, the excavation and support construction of one side of the tunnel is carried out from the outside to the inside on one side of the surrounding rock of the mountain until it is connected with the tunnel that has been completed in the water-rich karst cave; then, the ventilation system in the escape passage and the upper platform and vertical construction frame in the water-rich karst cave are dismantled in sequence.

8. The construction method for tunneling through a large-span water-rich karst cave according to claim 5, characterized in that, In step six, the sidewalls and arch of the tunnel within the water-rich karst cave section are constructed first using cast-in-place or precast methods on the prestressed panels. The prestressed panels serve as the tunnel's invert arch, thus completing the construction of the tunnel section within the water-rich karst cave section. Then, holes are drilled in the arch of the tunnel, connecting to the entrance and exit of the escape passage in the water-rich karst cave via a transition passage, thus connecting the escape passage with the tunnel. An escape ladder is installed at the bottom of the transition passage to lead into the tunnel, thereby completing the construction of the large-span water-rich karst cave tunnel.

9. A tunnel traversing a large-span, water-rich karst cave, characterized in that: It is obtained by any of the methods described in claims 1 to 8.

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