A combined drainage method for underground caverns in water-rich strata

Abstract

This invention discloses a combined drainage method for underground caverns in water-rich strata, comprising the following steps: S1, hydrogeological survey: dynamically monitoring the groundwater level in the underground cavern project area, analyzing the groundwater recharge, runoff, and discharge conditions; S2, inflow estimation and drainage system design: estimating the inflow into the cavern and determining the hydraulic gradient of the groundwater level; based on this, designing a combined drainage system including drainage tunnels and horizontal directional drainage holes; S3, pre-drainage construction: constructing the drainage tunnels and horizontal directional drainage holes before excavating the underground cavern. This invention has the advantages of strong spatial linkage, precise drainage without blind spots, outstanding anti-siltation capability, balanced hydraulic gradient, high dynamic drainage efficiency, low maintenance cost, and effective protection of surrounding rock stability and construction safety.

Description

Technical Field

[0001] This invention relates to the field of underground engineering seepage control technology, specifically a combined drainage method for underground caverns in water-rich strata. Background Technology

[0002] When constructing underground caverns in water-rich strata, effective control of groundwater is crucial to ensuring the stability of the surrounding rock and construction safety. Traditional drainage methods, such as blind drains, sump pits, and vertical drainage holes, have significant limitations.

[0003] Currently, blind drains and collection wells rely on gravity drainage, making them prone to siltation and blockage, resulting in high maintenance costs. Conventional vertical or radial drainage holes, limited by drilling precision, struggle to accurately intercept deep fissure water or dominant seepage channels, easily creating drainage blind spots, leading to localized water accumulation, and exacerbating the risk of surrounding rock softening. Furthermore, existing drainage structures lack systematic spatial coordination, resulting in redundant drainage paths and uneven hydraulic gradients, failing to meet the dynamic and efficient drainage needs under deep burial and complex hydrogeological conditions. While some studies have attempted improvements by optimizing drainage hole spacing or introducing monitoring technologies, none have fundamentally solved the bottlenecks of traditional drainage structures in terms of precise spatial water guidance and system synergy. Summary of the Invention

[0004] The purpose of this invention is to provide a combined drainage method for underground caverns in water-rich strata, which has the advantages of strong spatial linkage, precise drainage without blind spots, outstanding anti-siltation ability, balanced hydraulic gradient, high dynamic drainage efficiency, low maintenance cost, and can effectively ensure the stability of surrounding rock and construction safety, thus solving the problems in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A combined drainage method for underground caverns in water-rich strata includes the following steps: S1. Hydrogeological investigation: Conduct dynamic monitoring of groundwater level in the underground cavern project area, and analyze the groundwater recharge, runoff and discharge conditions; S2. Water Inflow Estimation and Drainage System Design: Estimate the water inflow into the cavern and determine the hydraulic gradient of the groundwater level; based on this, design a combined drainage system including drainage tunnels and horizontal directional drainage holes. S3. Pre-drainage construction: Before the excavation of the underground cavern, the drainage tunnel and horizontal directional drainage hole are constructed first; S4. Underground Cavern Excavation: Carry out the excavation of underground caverns; The horizontal directional drainage holes are drilled using a controllable trajectory to precisely penetrate deep, advantageous seepage channels or densely fractured zones, and are connected to the drainage holes to form a "branch-trunk" graded drainage system.

[0006] Preferably, in step S2, different drainage schemes are selected based on the water abundance of the groundwater: When the cave is located in a non-water-rich stratum with moderate or weak groundwater development, the "one cave, one hole" scheme is adopted, that is, a drainage cave is set up in the upper part of the cave, and directional drainage holes are used to divert the water accumulated in the cave to the outside of the mountain. When the cavern is located in a water-rich stratum with an abnormally high groundwater level, a "two-tunnel, one-hole, one-pit" scheme is adopted. That is, two layers of drainage tunnels, one high and one low, are set up around the cavern. The two layers of drainage tunnels are connected by a curved directional drainage hole, and a water collection pit is set up in the drainage tunnels for pumping out the water.

[0007] It is worth noting that the core advantage of this tiered scheme lies in its superior adaptability and systematic nature. For different hydrogeological conditions, the "one tunnel, one borehole" scheme achieves efficient drainage with a simple structure, saving engineering costs; while the "two tunnels, one borehole, one pit" scheme constructs a three-dimensional interception and tiered control system through the spatial layout of high- and low-level drainage tunnels. The high-level tunnel accurately captures shallow runoff, while the low-level tunnel effectively receives and discharges deep confined water. Combined with curved directional boreholes to achieve hydraulic interconnection, a collaborative drainage network is formed. This design significantly improves the system's ability to cope with different water-rich strata, effectively avoids the limitations of a single drainage structure, ensures the comprehensiveness and reliability of drainage effects, and fundamentally reduces engineering risks caused by errors in hydrological condition assessment.

[0008] Preferably, the method further includes an anti-clogging step: a variable diameter filter module is installed in the horizontal directional drainage hole, and a vortex separator is installed in the drainage hole to achieve dynamic interception and self-cleaning of sediment.

[0009] It is worth noting that the introduction of anti-clogging steps is a key innovation in this method to ensure long-term drainage efficiency. The variable-diameter filter module and the cyclone separator constitute a dual protection mechanism of "preliminary filtration inside the hole - fine separation inside the tunnel". The variable-diameter filter module performs primary filtration on the water flowing into the drainage hole through its tapering structure, effectively blocking larger particles; the cyclone separator uses the principle of fluid dynamics to perform secondary treatment on the water flowing into the drainage tunnel, efficiently separating fine particles of silt carried in the water through centrifugal force. This combination of measures significantly reduces the siltation rate of the drainage hole and drainage tunnel system, greatly extends the maintenance cycle, reduces the frequency and cost of manual dredging, and ensures the long-term stability and self-cleaning ability of the drainage system in a silt-rich groundwater environment.

[0010] Preferably, the variable diameter filter module is a filter tube whose pore size gradually changes along the water flow direction, with the inlet pore size being larger than the outlet pore size, forming a gradually narrowing filter channel.

[0011] It is worth noting that the design of this tapered filter channel embodies the advanced concept of gradient interception. Its larger inlet aperture ensures water flow capacity while prioritizing the interception of large-diameter particles, preventing them from instantly clogging the filter surface. As the water flows towards the outlet, the aperture gradually decreases, achieving step-by-step capture of medium and small-diameter particles. This structure not only effectively disperses sediment load and prevents the filter pores from being rapidly blocked at the inlet, maintaining a more stable flow cross-section, but also produces a more porous filter cake that is easily partially dispersed at a certain flow rate, possessing a certain degree of self-recovery capability. Compared to filter tubes with uniform pore size, this design significantly improves both anti-clogging capability and service life.

[0012] Preferably, in step S2, the cross-sectional dimensions of the drainage hole, the slope of the hole bottom, and the inclination and azimuth of the horizontal directional drainage hole are optimized by hydraulic calculation to improve the connectivity of the drainage path and the continuity of the hydraulic gradient.

[0013] It is worth noting that parameter optimization based on hydraulic calculations is the scientific basis for achieving "precise guidance and drainage" and "efficient drainage". Through precise hydraulic simulation, the optimal cross-sectional size and slope of the drainage hole can be determined to ensure that it has sufficient flow capacity and self-cleaning velocity, while avoiding unnecessary excavation. Optimization of the inclination and azimuth of the horizontal directional drainage hole can make it more accurately point to the dominant seepage channel and intersect with it at the best angle to maximize the capture of groundwater and form a smooth drainage path with low resistance. This ensures the smoothness of the hydraulic connection within the entire "branch-trunk" drainage system, eliminates local eddies or waterlogged areas, and thus improves the overall drainage efficiency and energy utilization of the system.

[0014] Preferably, in the "two tunnels, one hole, and one pit" scheme, the high-level drainage tunnel is arranged in the area where shallow fissure water is developed to intercept shallow water; the low-level drainage tunnel is arranged on the path of confined water or deep seepage; and the curved directional drainage hole is used to connect the hydraulic connection between the two drainage tunnels.

[0015] It is worth noting that this spatial layout strategy constructs a three-dimensional drainage and protection system with layered interception and coordinated pressure relief. The high-level drainage tunnels act as an "interception net," actively cutting off the supply path of shallow fissure water and preventing it from accumulating in the cavern area. The low-level drainage tunnels serve as "pressure release points," specifically diverting deep confined water and effectively reducing the uplift pressure acting on the surrounding rock of the cavern. The curved directional drainage holes act as "vertical connectors," cleverly connecting the high and low-level drainage tunnels. This not only guides the water collected in the high-level tunnels to the low-level tunnels for centralized discharge but, more importantly, strengthens the hydraulic connection between the two-layer drainage structure, forming a unified precipitation funnel. This achieves holistic and coordinated drainage of the aquifer from shallow to deep, greatly enhancing the overall efficiency and stability of the drainage system.

[0016] Preferably, in step S3, the construction of the drainage tunnel takes priority over the construction of the horizontal directional drainage hole. The entry point of the horizontal directional drainage hole is located inside the drainage tunnel, and its trajectory is dynamically adjusted according to real-time geological drilling data.

[0017] It is worth noting that this construction sequence and dynamic adjustment strategy are important guarantees for achieving "precise drilling" and "engineering risk avoidance". Prioritizing the construction of drainage tunnels provides a stable indoor working platform and accurate positioning benchmark for drilling horizontal directional drainage holes, avoiding trajectory deviations and increased costs caused by drilling long distances from the surface. Setting the entry point inside the tunnel greatly shortens the borehole length and improves drilling accuracy and control. More importantly, the dynamic adjustment of the borehole trajectory based on real-time geological drilling data (such as measurement while drilling) allows the drill bit to "avoid" unfavorable geological bodies in real time and accurately track and penetrate those advantageous seepage channels that were difficult to fully identify in the early exploration. This puts the concept of "targeted drainage" into practice and significantly improves the hit rate and effectiveness of drainage holes.

[0018] Preferably, after step S4, step S5 is further included: installing a removable protective grille or cover on the drainage opening and / or drainage hole.

[0019] It is worth noting that although this protective measure is simple in structure, it is crucial for ensuring the long-term safe operation of the drainage system. The detachable protective grille or cover plays a triple role: First, it effectively prevents large foreign objects such as rocks and debris from entering the drainage system, avoiding blockage or damage to drainage channels, filter modules, and even water pumps. Second, it provides safety protection to prevent people or animals from accidentally falling in. Third, its detachable design facilitates subsequent regular inspections, dredging, and maintenance, ensuring the convenience and operability of maintenance work. It is an indispensable auxiliary measure to maintain the proper functioning of the drainage system throughout its entire life cycle.

[0020] Preferably, the method further includes a monitoring and feedback step: installing water level sensors and flow meters at key nodes in the drainage tunnel and / or in directional drainage holes to monitor the drainage effect in real time, and dynamically adjusting the operating parameters of the drainage system based on the monitoring data.

[0021] It is worth noting that the introduction of monitoring and feedback steps marks a shift in this method from static drainage design to intelligent dynamic control. By deploying sensors at key nodes, the drawdown and drainage flow at different locations within the system can be monitored in real time, allowing for accurate assessment of whether the drainage effect meets expectations. More importantly, based on this real-time data, the operating status of the drainage system can be dynamically adjusted. For example, when the inflow increases, backup pumps can be activated or added in a timely manner, and when the water level drops below the safety line, operating strategies can be adjusted to save energy. This data-driven feedback control mechanism enables the drainage system to adapt to dynamic changes in groundwater, achieving an upgrade from "passive drainage" to "active control," ensuring the optimal balance between engineering safety and economic operation.

[0022] Preferably, the cyclone separator is installed on the bottom plate or side wall of the drainage hole, and uses the centrifugal force generated when the water flows in to separate the mud and sand particles from the water flow. The separated mud and sand are deposited in the matching mud collection hopper.

[0023] It is worth noting that the application of this cyclone separator has realized the physical and efficient treatment of silt in drainage tunnels. Its working principle is to use the strong centrifugal force field generated by tangential water intake to make the denser silt particles be thrown against the wall of the device and settle into the silt collection hopper under the action of gravity, while the clarified water is discharged from the central riser pipe. This separation method does not rely on the filter screen, completely avoiding the problem of filter screen clogging. It is particularly suitable for treating groundwater containing fine silt particles. The device is built into the bottom plate or side wall of the drainage tunnel, with a compact structure that does not occupy additional space. The silt collection hopper design facilitates centralized dredging, greatly reducing the complexity and intensity of maintenance work. It is an effective technical means to maintain the long-term unobstructed flow of the main drainage channel.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves spatially coordinated arrangement of drainage structures by constructing a branch-trunk hierarchical drainage system with drainage tunnels as the "main trunk" and horizontal directional drainage holes as "branches." The horizontal directional drainage holes employ controllable trajectory drilling technology, enabling them to actively track and precisely penetrate deep, dominant seepage channels or densely fractured zones, effectively collecting dispersed groundwater into the drainage tunnel as the main channel. This design fundamentally overcomes the shortcomings of traditional vertical drainage holes, such as unclear interception targets and the potential for creating drainage blind spots. It forms an active drainage mode rather than a passive waiting mode, significantly improving the interception efficiency of deep fracture water. 2. This invention innovatively proposes two differentiated drainage schemes for different hydrogeological conditions: "one tunnel and one borehole" and "two tunnels, one borehole, and one pit." The former is simple in structure and economically efficient; the latter constructs a three-dimensional interception network by deploying high and low-level drainage tunnels. The high-level drainage tunnel intercepts shallow fissure water, while the low-level drainage tunnel releases pressure for confined water and deep seepage. The two are hydraulically connected through curved directional drainage holes. This layered interception and coordinated pressure release layout effectively solves the problem that a single drainage structure cannot cope with complex and variable aquifers, achieving systematic drainage of groundwater from shallow to deep, with a more rational hydraulic gradient distribution. 3. This invention introduces a comprehensive anti-clogging mechanism. A variable-diameter filter module installed within the horizontally oriented drainage holes utilizes a gradually narrowing channel with a larger inlet and a smaller outlet to achieve gradient interception of sediment particles from coarse to fine, effectively preventing instantaneous blockage at the orifice. Simultaneously, a vortex separator installed within the drainage tunnel uses the centrifugal force generated by the tangential water inflow to separate sediment particles from the water flow and deposit them in the sediment collection hopper. This combination of "coarse filtration within the orifice - fine separation within the tunnel" significantly improves the system's anti-clogging capability, ensures long-term unobstructed drainage, and greatly reduces maintenance frequency and costs. 4. This invention integrates a monitoring and feedback mechanism into the entire operation of the drainage system. By arranging water level sensors and flow meters at key nodes within the drainage tunnels and outlets, the system's operating status and water pressure changes can be monitored in real time. Based on this monitoring data, the operating parameters of the drainage system (such as pump start / stop and frequency) can be dynamically adjusted, achieving an upgrade from static drainage design to intelligent dynamic control. This system can adapt to dynamic changes in groundwater levels, optimizing energy consumption while ensuring construction safety and surrounding rock stability, thus achieving a balance between safety and economy. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall layout of the "branch-trunk" graded drainage system in the combined drainage system of underground caverns and caverns in water-rich strata as described in this invention. Figure 2 This is a partial schematic diagram of the variable diameter filter module installed in the horizontal directional drainage hole and the cyclone separator installed in the drainage tunnel in the drainage system described in this invention. Figure 3 This is a schematic diagram of the "two holes, one hole, and one pit" drainage scheme of the present invention. Detailed Implementation

[0026] 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.

[0027] To address the shortcomings of existing technologies, such as gravity-dependent drainage structures leading to siltation and blockage, lack of spatial coordination in drainage holes resulting in significant blind spots, and the absence of a systematic and coordinated design, redundant drainage paths, and uneven hydraulic gradients, which make them unsuitable for dynamic and efficient drainage under deep burial and complex hydrogeological conditions, thus causing surrounding rock softening and increased construction safety risks, the following technical solution is proposed. Please refer to [link / reference]. Figures 1-3 ; A combined drainage method for underground caverns in water-rich strata includes the following steps: S1. Hydrogeological investigation: Conduct dynamic monitoring of groundwater level in the underground cavern project area, and analyze the groundwater recharge, runoff and discharge conditions; S2. Water Inflow Estimation and Drainage System Design: Estimate the water inflow into the cavern and determine the hydraulic gradient of the groundwater level; based on this, design a combined drainage system including drainage tunnels and horizontal directional drainage holes. S3. Pre-drainage construction: Before excavating the underground cavern, drainage tunnels and horizontal directional drainage holes are constructed first. S4. Underground Cavern Excavation: Carry out the excavation of underground caverns; Among them, the horizontal directional drainage holes adopt controlled trajectory drilling to accurately penetrate deep advantageous seepage channels or densely fractured zones, and connect with drainage holes to form a "branch-trunk" graded drainage system.

[0028] Preferably, in step S2, different drainage schemes are selected based on the water abundance of the groundwater: When the cave is located in a non-water-rich stratum with moderate or weak groundwater development, the "one cave, one hole" scheme is adopted, that is, a drainage cave is set up in the upper part of the cave, and directional drainage holes are used to divert the water accumulated in the cave to the outside of the mountain. When the cavern is located in a water-rich stratum with an exceptionally high groundwater level, a "two-tunnel, one-hole, one-pit" scheme is adopted. This involves setting up two layers of drainage tunnels, one high and one low, around the cavern. The two layers of drainage tunnels are connected by a curved directional drainage hole, and a sump is set up inside the drainage tunnels for pumping out the water.

[0029] Preferably, the method further includes an anti-clogging step: a variable diameter filter module is installed in the horizontal directional drainage hole, and a vortex separator is installed in the drainage hole to achieve dynamic interception and self-cleaning of sediment.

[0030] Preferably, the variable diameter filter module is a filter tube whose pore size gradually changes along the water flow direction, with the inlet pore size being larger than the outlet pore size, forming a gradually narrowing filter channel.

[0031] Preferably, in step S2, the cross-sectional dimensions of the drainage tunnel, the slope of the tunnel bottom, and the inclination and azimuth of the horizontal directional drainage holes are optimized through hydraulic calculations to improve the connectivity of the drainage path and the continuity of the hydraulic gradient.

[0032] Preferably, in the "two tunnels, one hole, and one pit" scheme, the high-level drainage tunnel is arranged in the area where shallow fissure water is developed to intercept shallow water; the low-level drainage tunnel is arranged on the path of confined water or deep seepage; and the curved directional drainage hole is used to connect the hydraulic connection between the two drainage tunnels.

[0033] Preferably, in step S3, the construction of the drainage tunnel takes priority over the horizontal directional drainage hole. The entry point of the horizontal directional drainage hole is located inside the drainage tunnel, and its trajectory is dynamically adjusted according to real-time geological drilling data.

[0034] Preferably, after step S4, step S5 is further included: installing a removable protective grille or cover on the drainage opening and / or drainage hole.

[0035] Preferably, the method further includes a monitoring and feedback step: installing water level sensors and flow meters at key nodes in the drainage tunnel and / or in directional drainage holes to monitor the drainage effect in real time, and dynamically adjusting the operating parameters of the drainage system based on the monitoring data.

[0036] Preferably, the cyclone separator is installed on the bottom plate or side wall of the drainage hole, and uses the centrifugal force generated when the water flows in to separate the mud and sand particles from the water flow. The separated mud and sand are deposited in the matching mud collection hopper.

[0037] Based on the above technical solutions, four specific implementation examples are provided below: Example 1: Drainage of underground powerhouse in pumped storage power station in moderately water-rich strata This embodiment is applied to the underground powerhouse project of a pumped storage power station. The regional hydrogeological conditions show that it is a medium-water-rich fractured rock mass.

[0038] First, step S1 was executed, where groundwater level dynamics were monitored through long-term observation wells to determine that the main recharge source was bedrock fissure water. In step S2, the maximum inflow during construction was estimated at approximately 350 m³ / d, with a hydraulic gradient of approximately 0.15. Based on this, a "one tunnel, one borehole" drainage scheme was designed: a 3m x 3m drainage tunnel was constructed 15 meters above the plant's arch, with a bottom slope of 0.8%. In step S3, this drainage tunnel was constructed first, and then, using it as a platform, six horizontal directional drainage holes were drilled into the potential dominant fissure zones around the plant. The drilling length was 80-120 meters, and the trajectory was dynamically adjusted using measurement-while-drilling technology to ensure precise penetration through densely fissure zones. Step S4 involved excavation of the plant, during which the area around the tunnel remained dry with no significant seepage. Step S5 involved installing a grating at the drainage tunnel opening. This scheme achieved precise drainage through a "branch-trunk" system, ensuring dry construction conditions for the large underground plant.

[0039] Example 2: Enhanced drainage in deep-buried long tunnels in highly water-rich strata This embodiment focuses on a deep-buried (deepness > 400m) water diversion tunnel project that traverses a high-pressure, water-rich fault fracture zone.

[0040] Steps S1 and S2: The survey revealed a high confined water head in this section, with a predicted inflow exceeding 2000 m³ / d. The design adopted a reinforced "two tunnels, one borehole, one pit" scheme: a high-level drainage tunnel (located 20m above the tunnel arch shoulder) and a low-level drainage tunnel (located 15m below the tunnel floor) were constructed on both sides of the tunnel. Step S3 prioritized the construction of the two drainage tunnels. The high-level tunnel primarily intercepted shallow weathered fissure water, while the low-level tunnel released deep confined water. The two were connected by a curved directional drainage hole, forming a vertical drainage link. A sump pit was installed every 200m within the low-level drainage tunnel, equipped with a high-power submersible pump. Step S4: By the time the tunnel was excavated, the groundwater level had significantly decreased, effectively reducing the risk of sudden water inrush at the tunnel face. This three-dimensional drainage system successfully coped with the extreme conditions of high water pressure and large inflow.

[0041] Example 3: Zoned Drainage of Underground Storage Groups in Urban Water-Rich Strata This embodiment is applied to an urban underground reservoir group project. The reservoir group is widely distributed and the aquifer is highly heterogeneous.

[0042] After executing steps S1-S2, different drainage schemes were adopted for each area of ​​the reservoir group based on the hydrogeological differences. For reservoirs #1 and #2, located in areas with weak water abundance, an economical "one tunnel, one opening" scheme was used. For reservoir #3, which is adjacent to the river and has strong water abundance, a "two tunnels, one opening, one pit" scheme was adopted, with increased drainage tunnel cross-section and pump configuration. In step S3, the drainage systems of each area were constructed simultaneously. All horizontal directional drainage holes were equipped with variable diameter filter modules (5mm inlet diameter, 1mm outlet diameter), and vortex separators were installed at key nodes in the main drainage tunnel. Step S4 saw the successful excavation of the reservoir group. This embodiment demonstrates the effectiveness of this method in flexible configuration and zoned treatment in complex engineering projects.

[0043] Example 4: Upgrading and Renovating the Existing Cavern Drainage System This embodiment describes the upgrading and renovation of the drainage system of an existing operational cavern with severe water seepage.

[0044] First, in step S1, monitoring instruments were added inside the tunnel to accurately pinpoint the main seepage points and recharge paths. Step S2, without compromising the structural safety of the tunnel, designed to add a new low-level drainage tunnel, and constructed horizontally directional drainage holes radiating outwards from the tunnel to target and penetrate the identified concentrated seepage channels. During step S3, drilling parameters were strictly controlled to avoid damage to the existing lining. A vortex separator, water level sensor, and flow meter were integrated and installed inside the new drainage tunnel. Step S5 involved installing removable protective covers at the new orifice. After the modification, the seepage volume inside the tunnel was reduced by more than 85%, effectively addressing the seepage problem of the existing project and demonstrating the significant value of this method during the operation and maintenance phase.

[0045] Working principle: The drainage system constructed based on this invention works as follows: After conducting detailed hydrogeological surveys and completing the drainage system design, the drainage tunnel, which serves as the main drainage channel, is constructed first. Subsequently, horizontal directional drainage holes with controllable trajectories are drilled from the drainage tunnel into the surrounding rock mass. These holes penetrate deep advantageous seepage channels or densely fractured zones through their precise spatial paths, actively guiding groundwater into the drainage tunnel, thereby forming a coordinated drainage network with the drainage tunnel as the "trunk" and multiple directional drainage holes as "branches". During this process, the variable diameter filter module installed in the directional drainage hole performs primary filtration of the incoming groundwater. Its larger inlet diameter intercepts coarse particles, while its smaller outlet diameter intercepts fine particles, effectively preventing clogging inside the hole. After the water carrying sediment enters the drainage tunnel, it flows through the vortex separator installed on the bottom plate or side wall of the tunnel. The water rotates in the device, and centrifugal force is used to separate the sediment particles and settle them in the sediment collection hopper, realizing dynamic interception of sediment and purification of water. For extremely water-rich strata using the "two tunnels, one hole, and one pit" scheme, the high-level drainage tunnel is responsible for intercepting shallow fissure water, while the low-level drainage tunnel is responsible for collecting deep seepage and water flow from the high-level drainage tunnel (which is drawn down through a curved directional drainage hole). Finally, the collected water is forcibly pumped out by a water pump through a sump located in the low-level drainage tunnel. During the entire system operation, water level sensors and flow meters deployed in drainage tunnels and key directional drainage holes monitor hydrological data in real time and feed the data back to the control system, thereby dynamically adjusting the operating status of the water pumps or providing decision-making basis for subsequent maintenance; ultimately achieving effective drainage of groundwater in the surrounding rock mass and lowering the water level before the excavation of the tunnel, ensuring construction safety and the stability of the surrounding rock.

[0046] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0047] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A combined drainage method for underground caverns in water-rich strata, characterized in that, Includes the following steps: S1. Hydrogeological investigation: Conduct dynamic monitoring of groundwater level in the underground cavern project area, and analyze the groundwater recharge, runoff and discharge conditions; S2. Water Inflow Estimation and Drainage System Design: Estimate the water inflow into the cavern and determine the hydraulic gradient of the groundwater level; based on this, design a combined drainage system including drainage tunnels and horizontal directional drainage holes. S3. Pre-drainage construction: Before the excavation of the underground cavern, the drainage tunnel and horizontal directional drainage hole are constructed first; S4. Underground Cavern Excavation: Carry out the excavation of underground caverns; The horizontal directional drainage holes are drilled using a controllable trajectory to precisely penetrate deep, advantageous seepage channels or densely fractured zones, and are connected to the drainage tunnels to form a "branch-trunk" graded drainage system.

2. The method according to claim 1, characterized in that, In step S2, different drainage schemes are selected based on the water abundance of the groundwater: When the cave is located in a non-water-rich stratum with moderate or weak groundwater development, the "one cave, one hole" scheme is adopted, that is, a drainage cave is set up in the upper part of the cave, and directional drainage holes are used to divert the water accumulated in the cave to the outside of the mountain. When the cavern is located in a water-rich stratum with an abnormally high groundwater level, a "two-tunnel, one-hole, one-pit" scheme is adopted. That is, two layers of drainage tunnels, one high and one low, are set up around the cavern. The two layers of drainage tunnels are connected by a curved directional drainage hole, and a water collection pit is set up in the drainage tunnels for pumping out the water.

3. The method according to claim 1, characterized in that, The method also includes an anti-clogging step: a variable diameter filter module is installed in the horizontal directional drainage hole, and a vortex separator is installed in the drainage hole to achieve dynamic interception and self-cleaning of sediment.

4. The method according to claim 3, characterized in that, The variable diameter filter module is a filter tube whose aperture gradually changes along the water flow direction. Its inlet aperture is larger than its outlet aperture, forming a gradually narrowing filter channel.

5. The method according to claim 1, characterized in that, In step S2, the cross-sectional dimensions of the drainage tunnel, the slope of the tunnel bottom, and the inclination and azimuth of the horizontal directional drainage hole are optimized through hydraulic calculations to improve the connectivity of the drainage path and the continuity of the hydraulic gradient.

6. The method according to claim 2, characterized in that, In the "two tunnels, one hole, and one pit" scheme, the high-level drainage tunnel is arranged in the shallow fissure water development area to intercept shallow water; the low-level drainage tunnel is arranged on the confined water or deep seepage path; the curved directional drainage hole is used to connect the hydraulic connection between the two drainage tunnels.

7. The method according to claim 1, characterized in that, In step S3, the construction of the drainage tunnel takes priority over the horizontal directional drainage hole. The entry point of the horizontal directional drainage hole is located inside the drainage tunnel, and its trajectory is dynamically adjusted according to real-time geological drilling data.

8. The method according to claim 1, characterized in that, After step S4, step S5 is also included: installing a removable protective grille or cover on the drainage opening and / or drainage hole.

9. The method according to claim 1, characterized in that, The method also includes a monitoring and feedback step: water level sensors and flow meters are installed at key nodes in the drainage tunnel and / or in the directional drainage holes to monitor the drainage effect in real time, and the operating parameters of the drainage system are dynamically adjusted based on the monitoring data.

10. The method according to claim 3, characterized in that, The cyclone separator is installed on the bottom plate or side wall of the drainage hole. It uses the centrifugal force generated when the water flows in to separate the mud and sand particles from the water flow. The separated mud and sand are deposited in the matching mud collection hopper.

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