Double-hole collaborative drainage system for water-rich tunnel and construction method

Abstract

The invention relates to a water-rich tunnel construction technology, in particular to a double-hole collaborative drainage system for a water-rich tunnel and a construction method. Hydrogeological comprehensive investigation is conducted on the crossing area of the water-rich tunnel, the plane position, the longitudinal slope and the section size of the through type drainage ditch are planned between the left hole and the right hole according to the investigation result, and the two ends of the through type drainage ditch are communicated with the middle drainage ditch of the left hole and the middle drainage ditch of the right hole respectively; excavating and reinforcing to obtain a through-type drainage ditch; and performing hydraulic connection and waterproof treatment on the through-type drainage ditch and the left and right holes, and arranging an intelligent monitoring device to obtain the double-hole collaborative drainage system. According to the method, through communication of drainage ditches in the left and right holes, double-hole common flood discharge is achieved, the drainage efficiency is greatly improved, a large amount of gushing water can be drained in time, and the risk of water pressure accumulation is reduced; wide applicability and practicability are realized; the construction process is simple and easy to operate and implement.

Description

Technical Field

[0001] This invention relates to water-rich tunnel construction technology, and more specifically, to a dual-tunnel coordinated drainage system and construction method for water-rich tunnels. Background Technology

[0002] As the construction of mountain highways extends into areas with complex geological conditions, the number of tunnels passing through high-pressure, water-rich strata is increasing, especially in Guizhou, which has a karst topography and frequently encounters karst water-rich tunnels during construction. The traditional "single-tunnel independent drainage" model has prominent problems such as insufficient instantaneous drainage capacity and structural damage caused by water pressure imbalance.

[0003] The Dejiang Tunnel on the Dejiang-Wuchuan Expressway in Guizhou Province has extremely complex hydrogeological conditions. The groundwater level is approximately 210 meters above the tunnel's designed top slab, posing a challenge of high-pressure water inrush (2.0 MPa). The catchment area covers 29 square kilometers, making it a high-pressure karst tunnel. The water-rich section of the tunnel contains numerous karst formations, fracture zones, and fissure zones, resulting in multiple sudden high-pressure water inrushes with large instantaneous volumes exceeding the drainage capacity of the central drainage ditch. To prevent large-scale instantaneous water inrushes from damaging the tunnel structure during operation, the insufficient drainage capacity of the central drainage ditch needs to be addressed. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a dual-tunnel coordinated drainage system and construction method for water-rich tunnels.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides a construction method for a dual-tunnel coordinated drainage system for a water-rich tunnel, the water-rich tunnel comprising a left tunnel and a right tunnel arranged side by side, with a central drainage ditch constructed on each of the left tunnel and the right tunnel; characterized in that the construction method includes the following steps: S1. Conduct a comprehensive hydrogeological survey of the area traversed by the water-rich tunnel and obtain the survey results; S2. Based on the survey results, plan the plan position, longitudinal slope and cross-sectional dimensions of the through-type drainage ditch between the left tunnel and the right tunnel, and the two ends of the through-type drainage ditch are respectively connected to the middle drainage ditch of the left tunnel and the right tunnel; S3. Based on the planning results of step S2, excavation and reinforcement are carried out to obtain the through-type drainage ditch; during the excavation process, the bearing capacity of the base is greater than or equal to 150 kPa; S4. Perform hydraulic connection and waterproofing treatment on the through-type drainage ditch and the left and right tunnels, and install an intelligent monitoring device to obtain the dual-tunnel coordinated drainage system.

[0006] Based on the above technical solution, the present invention can be further improved as follows.

[0007] Furthermore, in step S1, the survey results include the cross-sectional dimensions of the drainage ditch, the bottom elevation of the two drainage ditches, and the longitudinal slope.

[0008] Furthermore, the longitudinal slope is set to be consistent with the bottom elevation of the two drainage ditches of the left and right tunnels, the slope of the longitudinal slope is not less than 1‰, and the cross-sectional depth and area of ​​the through-type drainage ditch are both greater than the cross-sectional depth and area of ​​the drainage ditch.

[0009] Furthermore, the excavation and reinforcement process in step S3 is as follows: excavate a trench according to the planning results of step S2, tie a two-way steel reinforcement cage in the trench, install a fixed steel mold, pre-embed a corrugated steel pipe sleeve, and pour anti-seepage concrete on site to form a through drainage ditch with the same cross section as the drainage ditches in the left and right tunnels.

[0010] Furthermore, the steel bars in the bidirectional steel reinforcement cage are Φ12mm steel bars with a bidirectional spacing of 150mm.

[0011] Furthermore, in step S4, the hydraulic connection and waterproofing process involves using a 45° guide slope and an arc-shaped transition surface to hydraulically connect the through drainage ditch and the drainage ditches in the left and right holes, and setting a waterstop strip or a grouting waterproof layer around the interface.

[0012] Furthermore, after completing step S4, a water flow test is also included; the water flow test involves conducting a 72-hour water flow test on the dual-hole coordinated drainage system. The water flow test is considered qualified when the head difference between the two holes is less than or equal to 0.05 MPa and the drainage fluctuation rate is less than 5%.

[0013] Furthermore, the distance between the left and right tunnels of the water-rich tunnel is less than or equal to 30m.

[0014] Furthermore, the water-rich tunnel is a high-pressure, water-rich karst tunnel section with a hydrostatic pressure greater than or equal to 1 MPa and a predicted maximum instantaneous inflow greater than or equal to 0.5 m³ / s. 3 / s.

[0015] The present invention also provides a dual-tunnel coordinated drainage system for water-rich tunnels, which is obtained by the construction method described above.

[0016] The beneficial effects of this invention are as follows: (1) The construction method of the dual-tunnel coordinated drainage system for water-rich tunnels of the present invention realizes the joint flood discharge of the two tunnels by connecting the drainage ditches in the left and right tunnels, which greatly improves the drainage efficiency, can discharge a large amount of gushing water in time, and reduces the risk of water pressure accumulation. (2) The construction method of the dual-tunnel coordinated drainage system for water-rich tunnels of the present invention is applicable to tunnel engineering under various water-rich geological conditions, and is particularly effective in high-pressure water-rich sections, and has wide applicability and practicality. (3) The construction method of the dual-tunnel coordinated drainage system for water-rich tunnels of the present invention is based on the modification of the existing tunnel structure. The construction process is relatively simple, easy to operate and implement, and will not have a significant impact on the normal construction progress. (4) The dual-tunnel coordinated drainage system for water-rich tunnels of the present invention can effectively avoid damage to the main structure of the tunnel caused by water pressure due to untimely drainage, and improve the construction and operation safety of the tunnel in water-rich sections. Attached Figure Description

[0017] Figure 1 This is a construction method for a dual-tunnel coordinated drainage system for water-rich tunnels according to the present invention, and a construction diagram in the embodiment. Detailed Implementation

[0018] The principles and features of the present invention are described below. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0019] The present invention discloses a construction method for a dual-tunnel coordinated drainage system for a water-rich tunnel, wherein the water-rich tunnel comprises a left tunnel and a right tunnel arranged side by side, and a central drainage ditch is respectively opened on the left tunnel and the right tunnel; characterized in that the construction method includes the following steps: S1. Conduct a comprehensive hydrogeological survey of the water-rich tunnel crossing area and obtain the survey results; S2. Based on the survey results, plan the plan location, longitudinal slope and cross-sectional dimensions of the through-drainage ditch between the left and right tunnels, and connect the two ends of the through-drainage ditch to the middle drainage ditch of the left and right tunnels respectively. S3. Based on the planning results of step S2, excavate and reinforce to obtain a through-type drainage ditch; during the excavation process, the bearing capacity of the base is greater than or equal to 150 kPa; S4. Hydraulically connect the through-type drainage ditch with the left and right tunnels and waterproof it, and install intelligent monitoring devices to obtain a dual-tunnel coordinated drainage system.

[0020] This invention discloses a construction method for a dual-tunnel coordinated drainage system for water-rich tunnels. Based on the principle of interconnected pressure relief, a continuous drainage ditch is added between the central drainage ditches of the left and right tunnels, connecting the central drainage ditches of the two tunnels to form a unified drainage system. When a large-scale water inrush occurs on one side of the tunnel, the water can quickly flow into the central drainage ditch of the other tunnel through the added drainage ditch, achieving joint flood discharge from both tunnels, reducing water pressure, and preventing water pressure accumulation and structural damage caused by insufficient flood discharge capacity of a single-sided drainage ditch. Simultaneously, based on the principle of hydraulic balance, the connection of the central drainage ditches of the left and right tunnels allows for mutual adjustment and balance of water levels and pressures on both sides. When a water inrush occurs, the water automatically flows to the side with the lower water level, thereby achieving hydraulic balance and reducing the impact and damage of water pressure on the tunnel structure. This construction method solves the engineering problem of excessive instantaneous water inrush under high-pressure water inrush conditions in tunnel engineering, where a single-sided drainage pipe cannot discharge the floodwater in time. It prevents the tunnel from being damaged by excessive water inrush or from becoming unable to operate normally.

[0021] The construction method of this invention connects the central drainage ditch in the double tunnel with the transverse through-drainage ditch to form a three-dimensional drainage network, and establishes a water pressure balance equation using fluid mechanics principles: Q = K × (A1 + A2) × √(2gΔh) In the formula: Q is the total drainage volume of the system; K is the conductivity coefficient (0.6-0.9); A1 and A2 are the drainage cross sections of the left and right tunnels; Δh is the head difference between the two tunnels.

[0022] When the water pressure on one side increases, the cross channel diversion system automatically adjusts to keep the water pressure difference between the two tunnels less than 0.05 MPa.

[0023] In step S1 of the construction method of the present invention, the survey results include the cross-sectional dimensions of the central drainage ditch, the bottom elevation of the two central drainage ditches, and the longitudinal slope. By directly locking the survey results as the cross-sectional dimensions, bottom elevation, and longitudinal slope of the central drainage ditch, the subsequent through-drainage ditch can be accurately matched with the existing central drainage ditch in terms of plane, elevation, and slope, avoiding rework due to secondary measurements and water flow obstruction or backflow caused by elevation errors. This precise correspondence ensures instantaneous hydraulic balance between the two tunnels, with the head difference always less than 0.05 MPa. This eliminates scouring damage caused by sudden slope changes, saves the need for secondary lining and heightening / reinforcement of the transition section, directly reduces the risk of structural leakage, and shortens the construction cycle. During the operation period, there is no need for frequent adjustment of the ditch slope or dredging, maintaining efficient and coordinated flood discharge capacity in the long term.

[0024] The longitudinal slope is set to be consistent with the bottom elevation of the two drainage ditches of the left and right tunnels, and the slope of the longitudinal slope is not less than 1‰.

[0025] The cross-sectional area of ​​the through-type drainage ditch is larger than that of the intermediate drainage ditch, and the top of the through-type drainage ditch is equipped with a movable cover that can be opened and closed.

[0026] Preferably, in a specific embodiment, the cross-sectional dimensions of the drainage ditches in the left and right holes are 1.2m*0.6m, while the cross-sectional dimensions of the through drainage ditch are 2.0m*1.2m.

[0027] The aforementioned structure can drain underground water, which generally has a high sediment content. Enlarging and deepening the cross-section of the continuous drainage ditch acts as a sedimentation tank, performing initial sedimentation of the water and preventing large amounts of sediment from flowing into the central drainage ditches of the left and right tunnels. Because the tunnel is exceptionally long, this location is over 3000m from the tunnel entrance; excessive sediment in the central drainage ditch could potentially cause localized blockage.

[0028] The significance of the movable cover is twofold: firstly, the water inflow and drainage of the drainage ditch and tunnel can be observed in a timely manner through the inspection holes on the movable cover; secondly, during operation, the maintenance unit can open the movable cover (removable cover) to clean up the silt in the drainage ditch in a timely manner according to the silt deposition in the ditch.

[0029] By completely unifying the longitudinal slope, bottom elevation, and cross-sectional dimensions of the through-type drainage ditch with those of the central drainage ditch, the water flow in the left and right tunnels can be smoothly converged with zero elevation difference, avoiding localized drops or stagnation. Instantaneous water surges can be diverted in both directions without obstruction along the same slope.

[0030] It should be noted that, in the actual construction process, the survey results also include other parameters to determine whether the tunnel is suitable for establishing the dual-tunnel drainage system of the present invention.

[0031] The construction method of this invention targets a water-rich tunnel where the distance between the left and right tunnels is less than or equal to 30m. This distance minimizes the length of the drainage ditch, reducing excavation, concrete, and steel reinforcement, and shortening the construction period. The short-distance connection ensures that the head loss is close to zero, and instantaneous water inrush can be balanced and depressurized in both tunnels within seconds. The head difference is always less than or equal to 0.05MPa, avoiding the risks of scouring, siltation, and leakage caused by long-distance water transport. The maintenance-free period during operation is extended, and the overall economy and safety are significantly improved.

[0032] The water-rich tunnel of this invention is a high-pressure, water-rich karst tunnel section with a hydrostatic pressure greater than or equal to 1 MPa and a predicted maximum instantaneous inflow greater than or equal to 0.5 m³ / s. 3 / s; The above conditions can ensure the effective establishment and use of through-type drainage ditches.

[0033] The specific parameters of the aforementioned high-pressure, water-rich karst tunnel section can be obtained through comprehensive hydrogeological surveys before construction.

[0034] The excavation and reinforcement process in step S3 of the construction method of the present invention is as follows: Excavate the trench according to the planning result of step S2, tie a bidirectional steel bar framework in the trench, install a fixed-type steel mold, embed a steel corrugated pipe casing, and cast impermeable concrete on-site to form a through-drainage ditch with the same cross-section as the middle drainage ditches in the left and right tunnels; make the through-drainage ditch and the middle drainage ditches in the left and right tunnels form an integral structure with the same cross-section, the same material, and the same strength, synchronously improve the bearing capacity and impermeability grade, resist the impact of high-pressure water gushing without cracking or leakage, eliminate the later-stage reinforcement process, shorten the construction period, and maintain the efficient and stable coordinated flood discharge of the double tunnels.

[0035] Preferably, the steel bars in the bidirectional steel bar framework are Φ12mm steel bars, and the bidirectional spacing is 150mm.

[0036] In step S4 of the construction method of the present invention, the process of hydraulic connection and waterproof treatment is as follows: At the interface between the through-drainage ditch and the middle drainage ditches in the left and right tunnels, perform hydraulic connection with a 45° diversion slope and a circular arc transition surface, and set a water stop strip or a grouting waterproof layer around the interface; achieve smooth connection of the water flow through the 45° diversion slope and the circular arc transition surface, eliminate local eddy currents and head losses, ensure the rapid diversion of instantaneous large water gushing and the head difference is always less than 0.05MPa; the water stop strip or the grouting waterproof layer around the interface forms a secondary sealing barrier, completely blocks the high-pressure penetration channel, prevents joint leakage and concrete corrosion, and extends the structure life.

[0037] After completing step S4, it further includes the step of water passing test; the step of water passing test is to conduct a 72-hour water passing test on the double-tunnel coordinated drainage system. When the head difference between the double tunnels is less than or equal to 0.05MPa and the drainage volume fluctuation rate is less than 5%, the water passing test is qualified; verify the ultimate working condition bearing capacity of the double-tunnel coordinated drainage system through a 72-hour continuous water passing test at one time. When the head difference is less than or equal to 0.05MPa and the drainage volume fluctuation rate is less than 5%, it is determined to be qualified, ensure that the system has an instantaneous response, no leakage, and no structural deformation under actual high-pressure water gushing conditions, directly avoid the later-stage rework and sudden emergency rescue costs caused by hidden defects, shorten the acceptance period and improve the safety redundancy during the operation period.

[0038] In an embodiment of the present invention, the construction method of the double-tunnel coordinated drainage system for a water-rich tunnel of the present invention specifically includes the steps of construction preparation, geological advance prediction, lower excavation of the cross passage, drainage ditch construction, diversion system construction, drainage system connection, quality control and acceptance. The specific process is as follows: (1) Construction preparation: Through comprehensive geophysical exploration (TSP, geological radar, transient electromagnetic) and drilling verification, accurately obtain the data of high-pressure aquifers, tectonic fracture zones, karsts and water gushing volumes, provide a reliable basis for the connection plan; at the same time, complete the material preparation to ensure that the subsequent processes are in place at one time.

[0039] (2) Measurement and layout: The center line and excavation edge line of the drainage ditch were calibrated using a total station, and positioning stakes were set every 10m. Three-dimensional re-measurement ensured that the elevation error of the diversion pipe connection was ≤20mm, and that the position and slope of the ditch were completely consistent with the design.

[0040] (3) Through-type trench excavation: Excavate in layers under the bottom slab of the transverse channel, with each layer ≤0.5m, leaving 200mm for manual cleaning, controlling the bottom elevation deviation of the trench to ±10mm and the foundation bearing capacity ≥150kPa; in soft areas, replace with graded crushed stone ≥1m to ensure the foundation is stable.

[0041] (4) Foundation treatment and drainage structure construction: After compacting and leveling the foundation, tie a Φ12@150mm bidirectional steel reinforcement cage, erect a pre-formed steel mold and pre-embed a Φ600mm steel corrugated pipe sleeve, and pour C30P8 impermeable concrete in layers. Set expansion joints every 10m in the longitudinal direction to form a through drainage ditch with the same cross-section and slope as the central drainage ditch.

[0042] (5) Construction of the diversion system: The C30P8 concrete diversion channel is cast in place using a prefabricated steel mold. The inner surface of the mold is smooth and the joints are sealed. The 2m long 45° oblique section is equipped with a rounded transition. The adjustable steel support is ≤1m to ensure no deformation, reduce head loss and improve discharge efficiency.

[0043] (6) Drainage system connection: The two ends of the through ditch are seamlessly connected to the drainage ditches in the left and right tunnels with 45° guide slopes. Water-stop strips or grouting waterproof layers are installed around the interface, and a prefabricated top cover with a movable cover plate is installed to ensure smooth water flow and facilitate maintenance.

[0044] (7) Quality control and acceptance Throughout the construction process, the dimensions, slope, and concrete strength are strictly controlled. After completion, a 72-hour water flow test is conducted, requiring the drainage fluctuation rate to be <5% and the head difference between the two holes to be ≤5% of the design value. The system can only be put into use after a joint acceptance inspection is organized and approved.

[0045] The dual-tunnel coordinated drainage system for water-rich tunnels of the present invention is obtained using the construction method described above. This dual-tunnel coordinated drainage system is suitable for hydrostatic pressures greater than or equal to 1 MPa and instantaneous inflow rates greater than or equal to 0.5 m³ / s. 3 The extreme high-pressure, water-rich karst has a good synergistic drainage effect, which can effectively avoid the work stoppage and emergency rescue caused by sudden water inrush and the subsequent leakage plugging costs, directly reduce the maintenance cost during operation, and at the same time ensure the safety of the entire construction and operation process, significantly improving the durability and economy of high-pressure, water-rich karst tunnels.

[0046] The present invention will be illustrated by specific embodiments below.

[0047] Example The method of this invention was used to construct the water inrush treatment section of the Dejiang Tunnel in the DWTJ2 contract section of the Dewu Expressway.

[0048] like Figure 1 As shown, the Dejiang Tunnel is a key project of the Dewu Expressway. It is located on a slope transitioning from the Wuling Mountains to the Dalou Mountains in the northeastern part of the Guizhou Plateau. The left tunnel has chainages ZK6+760 and ZK12+265, a length of 5505m, and a maximum burial depth of approximately 534m. The right tunnel has chainages YK6+755 and YK12+180, a length of 5425m, and a maximum burial depth of approximately 537m. Sections ZK9+600.00 to ZK10+650.00 and YK9+600.00 to YK10+650.00 are located in the transition zone from the core to the flanks of the Shixiang Slope, where the hydrogeological conditions are extremely complex. The surrounding rock of the tunnel is mainly Permian Qixia Formation limestone interbedded with mudstone and calcareous mudstone, with weak karst development and low water content. The upper Maokou Formation is highly water-rich and has well-developed karst. Groundwater easily seeps down along the joints and fissures of the bedrock to the tunnel section, forming linear or gushing water. In addition, the stable groundwater level is located about 210m above the designed top plate of the tunnel, with high water head pressure and confined water, which makes it very easy to form water inrush and mudslide.

[0049] Actual measurements showed that the instantaneous water inflow reached 14,920 m³ / h, far exceeding the design prediction.

[0050] In June 2020, the Dejiang Tunnel began addressing high-pressure water inrush in its breakthrough section. This section had complex geological conditions, fractured surrounding rock, and high water pressure. During repeated high-pressure grouting reinforcement and sealing work, several large-scale water inrushes occurred. Observations revealed widespread dampness and seepage at the tunnel entrance, and the drainage ditch was overflowing, indicating that the drainage ditch was clearly inadequate for timely flood discharge. Subsequently, a simultaneous pressure relief measure was implemented by connecting the left and right tunnels in the vehicular cross passage near the breakthrough section. This technique effectively addressed the high-pressure water inrush section of the Dejiang Tunnel, allowing the project to proceed smoothly.

[0051] Based on the above effects, the construction method and system of the present invention were further applied to the Zimuyan Tunnel of Wudao Expressway and the Caijiapo Tunnel of Lu'an Expressway, and both achieved good results.

[0052] As can be seen from the specific applications of this embodiment in the aforementioned tunnels, the construction method and dual-tunnel coordinated drainage system of this invention effectively achieve coordinated drainage of the two tunnels in the construction of high-pressure, water-rich tunnels. Its technical level has reached the leading level in China, successfully solving the problem of instantaneous water inflow exceeding the design value and filling a gap in the industry.

[0053] This dual-tunnel coordinated drainage system directly reduces costs. By using an intelligent monitoring system to predict water inrush risks, it lowers the cost of emergency response to sudden water inrushes (reducing single emergency costs by 300,000 to 500,000 yuan). The coordinated construction of the dual-tunnel drainage system shortens the overall construction period by 10% to 15% (for a 1km water-rich tunnel, this can save 2 to 3 months). Modular construction technology reduces cross-process interference, improving construction efficiency by over 20%. The dynamic water pressure balance system reduces the risk of structural leakage, reducing maintenance and leak sealing costs during operation by over 60%. It also reduces the long-term energy consumption of mechanical drainage equipment, saving an average of 80,000 to 120,000 yuan per km in electricity costs annually.

[0054] The construction method and dual-tunnel coordinated drainage system of this invention form a dynamic drainage technology system for high-pressure, water-rich tunnels. After construction using this method, the original single-tunnel independent drainage was adjusted to dual-tunnel interconnected synchronous drainage. Since large-scale water inrushes generally do not occur simultaneously in the left and right tunnels, the drainage efficiency is greatly improved. To date, no safety or quality accidents have occurred in the high-pressure, water-rich sections of tunnels treated with this method due to excessive high-pressure water inrushes, achieving good social benefits.

[0055] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A construction method for a dual-tunnel coordinated drainage system for a water-rich tunnel, the water-rich tunnel comprising a left tunnel and a right tunnel arranged side by side, wherein a central drainage ditch is respectively constructed on the left tunnel and the right tunnel; characterized in that, The construction method includes the following steps: S1. Conduct a comprehensive hydrogeological survey of the water-rich tunnel and obtain the survey results; S2. Based on the survey results, plan the plan position, longitudinal slope and cross-sectional dimensions of the through-type drainage ditch between the left tunnel and the right tunnel, and the two ends of the through-type drainage ditch are respectively connected to the middle drainage ditch of the left tunnel and the right tunnel; S3. Based on the planning results of step S2, excavation and reinforcement are carried out to obtain the through-type drainage ditch; during the excavation process, the bearing capacity of the base is greater than or equal to 150 kPa; S4. The through-type drainage ditch is hydraulically connected to the left and right tunnels and waterproofed, and an intelligent monitoring device is installed to obtain the dual-tunnel coordinated drainage system.

2. The construction method of a dual-tunnel coordinated drainage system for water-rich tunnels according to claim 1, characterized in that, In step S1, the survey results include the cross-sectional dimensions of the drainage ditch, the bottom elevation of the two drainage ditches, and the longitudinal slope.

3. The construction method of a dual-tunnel coordinated drainage system for water-rich tunnels according to claim 2, characterized in that, The longitudinal slope is set to be consistent with the top elevation of the two drainage ditches of the left tunnel and the right tunnel, the slope of the longitudinal slope is not less than 1‰, and the cross-sectional depth and area of ​​the through drainage ditch are both greater than the cross-sectional depth and area of ​​the drainage ditch.

4. The construction method of a dual-tunnel coordinated drainage system for water-rich tunnels according to claim 1, characterized in that, The excavation and reinforcement process in step S3 is as follows: excavate a trench according to the planning results of step S2, tie a two-way steel reinforcement cage in the trench, install a fixed steel mold, pre-embed a corrugated steel pipe sleeve, and pour anti-seepage concrete on site to form a through drainage ditch with the same cross section as the drainage ditches in the left and right tunnels.

5. A construction method for a dual-tunnel coordinated drainage system for water-rich tunnels according to claim 4, characterized in that, The steel bars in the bidirectional steel reinforcement cage are Φ12mm steel bars with a bidirectional spacing of 150mm.

6. A construction method for a dual-tunnel coordinated drainage system for water-rich tunnels according to claim 1, characterized in that, In step S4, the hydraulic connection and waterproofing process is as follows: at the interface between the through drainage ditch and the drainage ditches in the left and right tunnels, a 45° guide slope and an arc-shaped transition surface are used for hydraulic connection, and a waterstop strip or grouting waterproof layer is set around the interface.

7. A construction method for a dual-tunnel coordinated drainage system for water-rich tunnels according to any one of claims 1-6, characterized in that, After completing step S4, the system also includes a water flow test step. The water flow test step involves conducting a 72-hour water flow test on the dual-hole coordinated drainage system. The water flow test is considered qualified when the head difference between the two holes is less than or equal to 0.05 MPa and the drainage fluctuation rate is less than 5%.

8. A construction method for a dual-tunnel coordinated drainage system for water-rich tunnels according to any one of claims 1-6, characterized in that, The distance between the left and right tunnels of the Fushui Tunnel is less than or equal to 30m.

9. A construction method for a dual-tunnel coordinated drainage system for water-rich tunnels according to claim 8, characterized in that, The water-rich tunnel is a high-pressure, water-rich karst tunnel section with a hydrostatic pressure greater than or equal to 1 MPa and a predicted maximum instantaneous inflow greater than or equal to 0.5 m³ / s. 3 / s.

10. A dual-tunnel coordinated drainage system for water-rich tunnels, characterized in that, Obtained by using the construction method described in any one of claims 1-9.

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