Automatic water drainage and pressure reduction device and method for karst tunnel large cave under heavy rainfall condition

Abstract

The application provides a karst tunnel large cave automatic water discharge pressure reduction device and method under heavy rainfall conditions, which comprises a filtering mechanism, the top end of the filtering mechanism extends into the cave, the bottom end of the filtering mechanism is connected with a cylindrical mechanism, the end of the cylindrical mechanism away from the filtering mechanism is fixedly connected with the top end of a tunnel mechanism, the high end of the cylindrical mechanism is connected with the inlet of a fine drain pipe, the outlet of the fine drain pipe is connected with the tunnel mechanism, the low end of the cylindrical mechanism is connected with a coarse drain mechanism, and the other end of the coarse drain mechanism is connected with the tunnel mechanism. On the one hand, the hydrogeological environment of the tunnel is not damaged, the underground water balance is protected, the automatic grading discharge of the cave underground water is realized, the water pressure outside the tunnel structure is reduced, the tunnel structure performance is protected, and the unreasonable stress of the tunnel structure caused by excessive water pressure is avoided to prevent the structure damage. On the other hand, the integrity of the secondary lining structure of the tunnel is not damaged, and the structure performance reduction caused by local stress concentration is avoided.

Description

Automatic drainage and pressure reduction device and method for large karst caves under heavy rainfall conditions Technical Field

[0001] This invention belongs to the field of tunnel and underground engineering technology, and in particular relates to an automatic water discharge and pressure reduction device and method for large karst caves in karst tunnels under heavy rainfall conditions. Background Technology

[0002] With the implementation of the national strategy to build a strong transportation network, the focus of tunnel construction in my country is gradually shifting to the western and southwestern regions. Given the karst topography of Yunnan, Guizhou, and Hunan provinces, tunnel construction will inevitably encounter numerous water-rich karst geological conditions, such as caves, underground rivers, and fault fracture zones. When tunnel construction encounters or approaches large caves, during periods of heavy rainfall in the tunnel site area, the water level inside these caves rises sharply, inevitably leading to a surge in external water pressure. This poses significant safety hazards to tunnel construction and subsequent operation. Ensuring the safety of tunnel construction and operation is a critical issue that urgently needs to be addressed.

[0003] Chinese Patent Publication No. CN106761919A discloses an automatic pressure regulating and drainage control device for tunnels in high-pressure, water-rich areas. This device is installed at the bottom of cable troughs on both sides of the tunnel within the limited discharge zone at the toe of the tunnel wall in high-pressure, water-rich areas. The water inlet of the device is connected to a groundwater seepage pipe behind the lining, and the water outlet is connected to a transverse drainage pipe in the tunnel. Chinese Patent Publication No. CN208431437U discloses an automatic pressure relief device for reducing operational risks in karst tunnels. This device has a pressure relief valve installed on the tunnel lining, comprising a valve body, a valve plug, and a safety diaphragm. The pressure relief valve body penetrates the lining, and a pressure relief valve plug is installed inside the pressure relief valve body, which is in close contact with the pressure relief valve body; a safety diaphragm is fixed in the through space of the pressure relief valve plug; the paper "Construction and Countermeasures of Seasonal Karst Tunnel Structure Safety Early Warning System" (published in the journal Modern Tunnel Technology, Vol. 56, Supplement 2, 2019) discloses a device that can automatically release water and reduce pressure when the lining water pressure reaches the allowable water pressure of the lining structure, thereby avoiding the phenomenon of structural instability and failure of the lining structure due to excessive water pressure in a short period of time under rainfall conditions, and ultimately ensuring the safety of the karst tunnel structure.

[0004] However, the aforementioned patents or papers, on the one hand, compromise the integrity of the tunnel's secondary lining structure, causing localized stress concentration and further reducing its stability and safety. On the other hand, they neglect the characteristics of heavy rainfall, where water volume and pressure rise sharply in a short period, making it difficult for conventional drainage pipes to effectively remove the large amounts of rainfall generated during heavy downpours. Furthermore, the increased water volume and pressure may exacerbate stress concentration, potentially turning tunnel openings into accident trigger points and ultimately leading to tunnel water inrush accidents. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes an automatic water drainage and pressure reduction device and method for large karst caves under heavy rainfall conditions.

[0006] To achieve the above objectives, the present invention provides an automatic drainage and pressure reduction device for large karst caves under heavy rainfall conditions, comprising a filtration mechanism, the top end of which extends into the karst cave, the bottom end of which is connected to a cylindrical mechanism, the end of which, away from the filtration mechanism, is fixedly connected to the top end of a tunnel mechanism, the upper end of which is connected to the inlet of a fine drainage pipe, the outlet of which is connected to the tunnel mechanism, the lower end of which is connected to a coarse drainage mechanism, and the other end of which is connected to the tunnel mechanism.

[0007] Preferably, the tunnel mechanism includes a tunnel, a secondary tunnel lining structure is provided above the tunnel, an initial tunnel support structure is provided on the secondary tunnel lining structure, a drainage blind pipe is provided between the initial tunnel support structure and the secondary tunnel lining structure, the drainage blind pipe is connected to the outlet of the fine drainage pipe, and the bottom surrounding rock of the tunnel is connected to the coarse drainage mechanism.

[0008] Preferably, the filtration mechanism includes a primary filter, a secondary filter, and a tertiary filter that are sequentially connected to the cylindrical mechanism. The pore sizes of the primary filter, the secondary filter, and the tertiary filter increase sequentially, and the primary filter, the secondary filter, and the tertiary filter extend into the karst cave.

[0009] Preferably, the cylindrical mechanism includes a base fixed to the top of the initial support structure, a cylinder fixed to the base, the top of the cylinder communicating with the primary filter screen, a spring sealing assembly slidably connected inside the cylinder, one end of the spring sealing assembly being fixed to the end of the cylinder near the base, the high end of the cylinder communicating with the fine drain pipe, and the low end of the cylinder communicating with the coarse drain mechanism.

[0010] Preferably, the spring closure assembly includes a spring, on which an anti-slip rubber layer is applied, the anti-slip rubber layer being located between the cylinder and the spring, the spring being slidably connected to the side wall of the cylinder, and the spring being fixedly connected to one end of the cylinder near the base.

[0011] Preferably, the coarse drainage mechanism includes a coarse drainage pipe connected to the lower end of the cylinder, and a barrier filter is provided at the end of the coarse drainage pipe away from the cylinder, and the barrier filter is connected to the surrounding rock at the bottom of the tunnel.

[0012] A method for using an automatic drainage and pressure reduction device for large karst caves under heavy rainfall conditions includes the following steps:

[0013] Step 1: Investigate the geology of the karst caves and draw cross-sectional diagrams of the caves and tunnels;

[0014] Step 2: Excavate the tunnel and expose the karst cave;

[0015] Step 3: Pump out groundwater, remove backfill material, and locally reinforce surrounding rock;

[0016] Step 4: Set up the filtration system;

[0017] Step 5: Set up the cylindrical mechanism;

[0018] Step Six: Install the drain pipe on the cylindrical mechanism;

[0019] Step 7: Install the barrier filter screen on the coarse drainage pipe at the bottom of the tunnel arch;

[0020] Step 8: Fix the cylindrical mechanism;

[0021] Step 9: Install the spring-loaded closure assembly;

[0022] Step 10: Set up the base;

[0023] Step 11: Tunnel construction.

[0024] Preferably, in step three, after the tunnel connects with the karst cave, the groundwater inside the karst cave is pumped out, the filling material is cleaned, and the surrounding rock at the connection between the tunnel and the karst cave is locally reinforced. The reinforcement measures adopt the anchor bolt or anchor cable support method.

[0025] Preferably, in step eight, the cylindrical mechanism is fixed in position, and then the gap between the cylindrical mechanism and the surrounding rock is filled, wherein the filling material is cement grouting or chemical foam grouting.

[0026] Compared with the prior art, the present invention has the following advantages and technical effects:

[0027] Groundwater in the karst cave enters the cylindrical structure through a filtration mechanism. As the water volume and pressure increase, the groundwater will automatically drain into the tunnel structure when it is compressed to the fine drainage pipe. When the groundwater volume and pressure continue to increase until it is compressed to the coarse drainage mechanism, the groundwater will automatically drain into the tunnel structure from the coarse drainage mechanism.

[0028] This invention addresses two main issues. First, it preserves the hydrogeological environment surrounding the tunnel, maximizing the protection of groundwater balance. Simultaneously, it enables the automated, tiered drainage of groundwater within karst caves during heavy rainfall, minimizing external water pressure on the tunnel structure and thus protecting its structural performance. This prevents structural damage caused by excessive water pressure leading to unbalanced stress. Second, it preserves the integrity of the tunnel's secondary lining structure, thereby preventing structural performance degradation due to localized stress concentration. Attached Figure Description

[0029] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0030] Figure 1 is a schematic diagram of the structure of the present invention;

[0031] Figure 2 is a magnified view of part A in Figure 1;

[0032] Figure 3 is a schematic diagram of the implementation method of the present invention;

[0033] In the diagram: 1. Cave; 2. Tunnel; 3. Fine drainage pipe; 4. Primary filter screen; 5. Secondary filter screen; 6. Tertiary filter screen; 7. Base; 8. Cylinder; 9. Spring; 10. Anti-slip rubber layer; 11. Coarse drainage pipe; 12. Barrier filter screen; 13. Secondary tunnel lining structure; 14. Drainage blind pipe; 15. Initial tunnel support structure. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Referring to Figures 1-3, the present invention provides an automatic drainage and pressure reduction device for a large karst cave under heavy rainfall conditions, including a filtration mechanism. The top end of the filtration mechanism extends into the cave 1, and the bottom end of the filtration mechanism is connected to a cylindrical mechanism. The end of the cylindrical mechanism away from the filtration mechanism is fixedly connected to the top end of the tunnel mechanism. The upper end of the cylindrical mechanism is connected to the inlet of a thin drainage pipe 3, the outlet of the thin drainage pipe 3 is connected to the tunnel mechanism, the lower end of the cylindrical mechanism is connected to a coarse drainage mechanism, and the other end of the coarse drainage mechanism is connected to the tunnel mechanism.

[0037] Groundwater in cave 1 enters the cylindrical structure through the filtration mechanism. When the water volume and pressure increase, the groundwater will automatically be discharged from the thin drainage pipe 3 to the top of the tunnel structure when it is compressed to the coarse drainage mechanism. When the groundwater volume and pressure continue to increase until it is compressed to the coarse drainage mechanism, the groundwater will automatically be discharged from the coarse drainage mechanism into the tunnel structure.

[0038] Further optimization of the scheme: the tunnel structure includes tunnel 2, a secondary tunnel lining structure 13 is provided above tunnel 2, an initial tunnel support structure 15 is provided on the secondary tunnel lining structure 13, a drainage blind pipe 14 is provided between the initial tunnel support structure 15 and the secondary tunnel lining structure 13, the drainage blind pipe 14 is connected to the outlet of the thin drainage pipe 3, and the bottom surrounding rock of tunnel 2 is connected to the coarse drainage mechanism.

[0039] The fine drainage pipe 3 is directly connected to the drainage blind pipe 14, which can prevent the secondary lining structure 13 of the tunnel from being damaged and prevent the tunnel 2 from being damaged due to excessive water pressure and unreasonable stress. The groundwater runoff point of the surrounding rock at the bottom of the tunnel 2 is connected to the coarse drainage mechanism.

[0040] The scheme is further optimized. The filtration mechanism includes a primary filter screen 4, a secondary filter screen 5, and a tertiary filter screen 6 that are connected to the cylindrical mechanism in sequence. The pore sizes of the primary filter screen 4, the secondary filter screen 5, and the tertiary filter screen 6 increase in sequence. The primary filter screen 4, the secondary filter screen 5, and the tertiary filter screen 6 extend into the karst cave 1.

[0041] The primary filter (4), secondary filter (5), and tertiary filter (6) overlap. The tertiary filter (6) has the largest pore size, followed by the secondary filter (5), and the primary filter (4) has the smallest. The primary filter (4) is placed at the bottom, the secondary filter (5) is in the middle, and the tertiary filter (6) is placed at the top.

[0042] Further optimization of the scheme: the cylindrical mechanism includes a base 7 fixed to the top of the initial support structure 15, a cylinder 8 fixed to the base 7, the top of the cylinder 8 connected to the primary filter screen 4, a spring sealing assembly slidably connected inside the cylinder 8, one end of the spring sealing assembly being fixed to the end of the cylinder 8 near the base 7, a fine drain pipe 3 connected to the high end of the cylinder 8, and a coarse drain mechanism connected to the low end of the cylinder 8.

[0043] When the water volume and pressure inside the large karst cave 1 increase, the spring-loaded sealing assembly is compressed. When compressed to the narrow drainage pipe 3, the groundwater automatically drains from the narrow drainage pipe 3 into the blind drainage pipe 14. As the groundwater volume and pressure continue to increase, the spring-loaded sealing assembly is continuously compressed until it reaches the coarse drainage mechanism. At this point, the groundwater automatically drains from the coarse drainage mechanism into the groundwater runoff point at the bottom of the tunnel 2. The spring-loaded sealing assembly is used to withstand the impact force of the groundwater and allow it to flow into the cylinder 8 for some release. The main purpose of the base 7 is to support the automatic water discharge and pressure reduction device, preventing the weight of the device from being directly applied to the secondary lining structure of the tunnel, thereby increasing the external stress on the tunnel 2.

[0044] Further optimization of the design involves a spring-sealing assembly comprising a spring 9, on which an anti-slip rubber layer 10 is applied. The anti-slip rubber layer 10 is located between the cylinder 8 and the spring 9. The spring 9 is slidably connected to the side wall of the cylinder 8, and the spring 9 is fixedly connected to one end of the cylinder 8 near the base 7. An anti-slip rubber layer 10 is placed on the outside of the spring 9, and then the spring 9 with the anti-slip rubber layer 10 is installed inside the cylinder 8. The anti-slip rubber layer 10 is primarily used to prevent groundwater from inside the cave 1 from flowing to the bottom of the cylinder 8.

[0045] Further optimization of the scheme: the coarse drainage mechanism includes a coarse drainage pipe 11 connected to the lower end of the cylinder 8. A barrier filter 12 is installed at the end of the coarse drainage pipe 11 away from the cylinder 8, and the barrier filter 12 is connected to the surrounding rock at the bottom of the tunnel 2. The barrier filter 12 is a double-layer filter to prevent sludge, gravel, etc. from entering the coarse drainage pipe 11 and clogging it. The groundwater runoff point at the bottom of the surrounding rock of the tunnel 2 is connected to the coarse drainage pipe 11.

[0046] Furthermore, on one side of the cylindrical 8, a thin drainage pipe 3 is installed to connect the tunnel drainage pipe or blind pipe. The thin drainage pipe 3 needs to be inclined downward at 5 degrees to ensure that groundwater flows into the drainage pipe or blind pipe of the tunnel 2. On the other side, a thick drainage pipe 11 is installed to connect the bottom of the tunnel 2 arch. The thick drainage pipe 11 needs to be inclined downward at 10 degrees.

[0047] A method for using an automatic drainage and pressure reduction device for large karst caves under heavy rainfall conditions includes the following steps:

[0048] Step 1: Investigate the geology of Cave 1 and draw cross-sectional diagrams of Cave 1 and Tunnel 2;

[0049] The main technologies used include advanced geological drilling, ground-penetrating radar, borehole photography, and microseismic detection to obtain information on the scale, shape, elevation, type and form of filling material, and surrounding rock grade of the large karst cave 1, and then to draw a typical cross-sectional diagram between the large karst cave 1 and the tunnel 2.

[0050] Step 2: Excavate tunnel 2 and expose cave 1;

[0051] The excavation of Tunnel 2 will be carried out during the non-rainy season and non-precipitation period to avoid excessively high water levels inside Cave 1. The excavation methods for Tunnel 2 can include the bench method, CD method, and full-face method. When approaching the large cave 1, the large cave 1 will be actively exposed to connect Tunnel 2 and the large cave 1, which will facilitate subsequent groundwater drainage, backfill material removal, and equipment installation.

[0052] Step 3: Pump out groundwater, remove backfill material, and locally reinforce surrounding rock;

[0053] Step 4: Set up the filtration system;

[0054] At the interface between the large karst cave 1 and tunnel 2, a primary filter screen 4, a secondary filter screen 5, and a tertiary filter screen 6 are installed. The primary filter screen 4 mainly filters gravel, and its size is 10.0mm × 10.0mm. The secondary filter screen 5 mainly filters sand and fine gravel, and its size is 5.0mm × 5.0mm. The tertiary filter screen 6 mainly filters mud, fine sand, etc., and its size is 1.0mm × 1.0mm. From the primary filter screen 4 to the tertiary filter screen 6, the filter screen size gradually decreases, thereby ensuring that the filling material inside the large karst cave 1 does not flow into the drainage device and cause blockage of the drainage device.

[0055] Step 5: Set up the cylindrical mechanism;

[0056] A cylindrical mechanism for automatic water drainage and pressure reduction is installed between tunnel 2 and the large karst cave 1, and the upper part of the cylindrical mechanism is connected to the filtration mechanism.

[0057] Step Six: Install the drain pipe on the cylindrical mechanism;

[0058] On the side of the cylinder 8, a thin drainage pipe 3 is installed to connect the drainage pipe or blind pipe of the tunnel 2. The thin drainage pipe 3 needs to be inclined downward at 5 degrees to ensure that groundwater flows into the drainage pipe or blind pipe of the tunnel 2. On the other hand, a thick drainage pipe 11 is installed to connect the bottom of the tunnel 2 arch. The thick drainage pipe 11 needs to be inclined downward at 10 degrees.

[0059] Step 7: Install the barrier filter 12 on the coarse drainage pipe 11 at the bottom of tunnel 2;

[0060] Clean the outlet of the coarse drain pipe 11 and install a filter screen 12 to prevent sludge, gravel, etc. from entering the coarse drain pipe 11 and clogging it.

[0061] Step 8: Fix the cylindrical mechanism;

[0062] Step 9: Install the spring-loaded closure assembly;

[0063] A layer of anti-slip rubber 10 is arranged on the outside of the spring 9, and then the spring 9 with the anti-slip rubber layer 10 is installed inside the cylinder 8. The anti-slip rubber layer 10 is mainly to prevent groundwater inside the large karst cave from flowing to the bottom of the cylinder 8.

[0064] Step 10: Set up base 7;

[0065] After the spring 9 is installed inside the cylinder 8, the base 7 needs to be installed at the bottom of the cylinder 8. It can be constructed by cast-in-place concrete or precast concrete. The main purpose of the base 7 is to support the automatic water drainage and pressure reduction device, so as to avoid the self-weight of the automatic water drainage and pressure reduction device being directly applied to the tunnel 2 structure, thereby increasing the external stress on the tunnel 2 structure.

[0066] Step 11: Tunnel construction.

[0067] Tunnel construction includes initial tunnel support, steel arches, secondary lining, waterproofing membrane, and drainage pipes.

[0068] Further optimize the plan. In step three, after tunnel 2 connects with cave 1, the groundwater inside cave 1 is pumped out, the filling material is cleaned, and the surrounding rock at the connection between tunnel 2 and cave 1 is locally reinforced. The reinforcement measures adopt anchor bolt or anchor cable support.

[0069] To further optimize the scheme, in step eight, the position of the cylindrical structure is fixed, and then the gap between the cylindrical structure and the surrounding rock is filled with cement grouting or chemical foam grouting.

[0070] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0071] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. An automatic water drainage and pressure reduction device for large karst caves under heavy rainfall conditions, characterized in that: The system includes a filtration mechanism, the top of which extends into the karst cave (1), the bottom of which is connected to a cylindrical mechanism, the end of which, away from the filtration mechanism, is fixed to the top of the tunnel mechanism, the high end of which is connected to the inlet of a fine drainage pipe (3), the outlet of which is connected to the tunnel mechanism, the low end of which is connected to a coarse drainage mechanism, and the other end of which is connected to the tunnel mechanism; the tunnel mechanism includes a tunnel (2), a secondary tunnel lining structure (13) is provided above the tunnel (2), an initial tunnel support structure (15) is provided on the secondary tunnel lining structure (13), a blind drainage pipe (14) is provided between the initial tunnel support structure (15) and the secondary tunnel lining structure (13), the blind drainage pipe (14) is connected to the outlet of the fine drainage pipe (3), and the bottom of the tunnel (2) is connected to the coarse drainage pipe. The water mechanism is connected; the cylindrical mechanism includes a base (7) fixed to the top of the initial support structure (15), a cylinder (8) fixed to the base (7), a spring sealing assembly slidably connected inside the cylinder (8), one end of the spring sealing assembly being fixed to the end of the cylinder (8) near the base (7), the high end of the cylinder (8) being connected to the fine drainage pipe (3), and the low end of the cylinder (8) being connected to the coarse drainage mechanism; when the water volume and water pressure in the cave (1) increase, the spring sealing assembly will be compressed, and when it is compressed to the fine drainage pipe (3), the groundwater will automatically be discharged from the fine drainage pipe (3) into the drainage blind pipe (14); when the groundwater volume and water pressure continue to increase, the spring sealing assembly will be continuously compressed until it is compressed to the coarse drainage mechanism, at which time the groundwater will automatically be discharged from the coarse drainage mechanism into the groundwater runoff point of the bottom surrounding rock of the tunnel (2).

2. The automatic water drainage and pressure reduction device for large karst caves under heavy rainfall conditions as described in claim 1, characterized in that: The filtration mechanism includes a primary filter (4), a secondary filter (5), and a tertiary filter (6) that are sequentially connected to the cylindrical mechanism. The apertures of the primary filter (4), the secondary filter (5), and the tertiary filter (6) increase sequentially, and the primary filter (4), the secondary filter (5), and the tertiary filter (6) extend into the karst cave (1).

3. The automatic water drainage and pressure reduction device for large karst caves under heavy rainfall conditions as described in claim 2, characterized in that: The top of the cylinder (8) is connected to the primary filter screen (4).

4. The automatic drainage and pressure reduction device for large karst caves under heavy rainfall conditions as described in claim 3, characterized in that: The spring closure assembly includes a spring (9), on which an anti-slip rubber layer (10) is applied. The anti-slip rubber layer (10) is located between the cylinder (8) and the spring (9). The spring (9) is slidably connected to the side wall of the cylinder (8). The spring (9) is fixedly connected to one end of the cylinder (8) near the base (7).

5. The automatic drainage and pressure reduction device for large karst caves under heavy rainfall conditions as described in claim 1, characterized in that: The coarse drainage mechanism includes a coarse drainage pipe (11) connected to the lower end of the cylinder (8). A barrier filter (12) is provided at the end of the coarse drainage pipe (11) away from the cylinder (8). The barrier filter (12) is connected to the groundwater runoff point of the surrounding rock at the bottom of the tunnel (2).

6. A method for using an automatic drainage and pressure reduction device for large karst caves under heavy rainfall conditions, based on the automatic drainage and pressure reduction device for large karst caves under heavy rainfall conditions as described in any one of claims 1-5, characterized in that... Includes the following steps: Step Step 1: Investigate the geology of the karst cave (1) and draw a cross-sectional view of the karst cave (1) and the tunnel (2); Step 2: Excavate the tunnel (2) and expose the karst cave (1); Step 3: Pump out groundwater, clean up the filling material, and locally reinforce the surrounding rock; Step 4: Set up a filtration mechanism; Step 5: Set up a cylindrical mechanism; Step 6: Set up a drainage pipe on the cylindrical mechanism; Step 7: Set up a barrier filter (12) on the coarse drainage pipe (11) at the bottom of the tunnel (2); Step 8: Fix the cylindrical mechanism; Step 9: Set up a spring-sealed assembly; Step 10: Set up a base (7); Step 11: Construct the tunnel mechanism.

7. The method of using the automatic water drainage and pressure reduction device for large karst caves under heavy rainfall conditions as described in claim 6, characterized in that: In step three, after the tunnel (2) is connected to the karst cave (1), the groundwater inside the karst cave (1) is pumped out, the filling material is cleaned, and the surrounding rock at the connection between the tunnel (2) and the karst cave (1) is locally reinforced. The reinforcement measures adopt the anchor bolt or anchor cable support method.

8. The method of using the automatic water drainage and pressure reduction device for large karst caves under heavy rainfall conditions as described in claim 6, characterized in that: In step eight, the cylindrical mechanism is fixed in position, and then the gap between the cylindrical mechanism and the surrounding rock is filled with cement grout or chemical foam grout.

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