Drainage and exhaust structure of dynamic high groundwater anti-seepage reservoir basin and design method of drainage and exhaust structure

Abstract

The invention provides a drainage and exhaust structure of a dynamic high groundwater anti-seepage reservoir basin and a design method of the drainage and exhaust structure. The drainage and exhaust structure comprises a full reservoir basin anti-seepage structure, a foundation drainage system, a reservoir bank water interception system, a reservoir bottom exhaust-pumping system and a flow distribution system. The foundation drainage system efficiently intercepts and discharges high underground water around the reservoir, the water intercepting system is adopted at the top of the reservoir bank to directly intercept suddenly rising underground water in a mountain around the reservoir, collection of the dynamic high underground water around the reservoir to the bottom of the reservoir basin is effectively coped, and the reservoir bottom geomembrane liquid expansion risk is remarkably reduced; longitudinally and transversely distributed exhaust and drainage pipes are arranged below the geomembrane so as to play an under-membrane exhaust and pressure reduction role when risks such as local failure of a foundation drainage system occur, meanwhile, the effect of discharging potential geomembrane defect leakage water is taken into consideration, and the safety of a reservoir basin anti-seepage system is further improved; and on the basis of water-gas two-phase seepage coupling calculation of the geomembrane anti-seepage reservoir basin under the dynamic high underground water level condition, the arrangement distance between exhaust and drainage pipes under the membrane is optimized, and the geomembrane is effectively prevented from being inflated and damaged.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering, specifically to the drainage and venting structure and design method of a seepage-proof reservoir basin with dynamic high groundwater. Background Technology

[0002] In water conservancy projects, reservoir seepage prevention methods are divided into vertical seepage prevention and surface seepage prevention. When faced with scarce water supply and unsealed hydrogeological conditions, reservoir seepage prevention design usually adopts surface seepage prevention methods such as full-basin geomembrane seepage prevention to ensure the reservoir's water storage capacity. When constructing reservoirs in special engineering geological areas such as karst development zones with abundant groundwater resources, although the high groundwater around the reservoir has a direct water supply effect, the widespread distribution of unfavorable geological structures such as karst development zones and the difficulty in probing complex geological conditions in reservoir areas lead to problems such as insufficient grouting depth, high difficulty in grouting construction, and unclear curtain range for vertical seepage prevention methods. Therefore, surface seepage prevention methods such as full-basin geomembrane seepage prevention become the better choice.

[0003] When constructing geomembrane-lined reservoir basins in areas with high and frequently active groundwater levels, controlling groundwater seepage and mitigating the risks of geomembrane gas / liquid swelling are crucial for the safe operation of the geomembrane seepage control system. This is especially true under conditions such as heavy rainfall, when groundwater levels in the surrounding mountains rise sharply, significantly increasing the tendency for the geomembrane to converge towards the bottom of the reservoir basin. Under seepage pressure, dynamic high groundwater seeps into the foundation of the reservoir basin along the dam foundation or around the reservoir, easily causing the geomembrane at the bottom to bear significant seepage pressure, potentially leading to membrane uplift, localized liquid swelling damage, and other engineering hazards. Simultaneously, if the gas accumulated under the membrane is not promptly released, it will cause gas swelling, severely affecting the structural stability of the seepage control system. In existing technologies, traditional reservoir basin seepage control structures only employ geomembrane seepage barriers and a single drainage and venting structure beneath the membrane. Faced with high and frequently changing groundwater conditions around the reservoir, these methods are insufficient to meet the large-scale foundation drainage needs and cannot effectively address the risks of liquid / gas swelling damage to the geomembrane caused by complex water-gas coupling under high groundwater levels. In addition, existing drainage facilities are inefficient in utilizing groundwater, and usually adopt a direct discharge treatment mode, which fails to form a linkage mechanism with the needs of ecological water replenishment and irrigation water, resulting in inefficient use of water resources. Summary of the Invention

[0004] The main objective of this invention is to provide a drainage and venting structure and its design method for a seepage-proof reservoir basin with dynamic high groundwater levels, thereby solving the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention includes: a whole reservoir basin seepage prevention structure, a foundation drainage system, a reservoir bank water interception system, a reservoir bottom ventilation and drainage system, and a flow distribution system; The entire reservoir basin seepage prevention structure includes a geomembrane laid on the bottom and banks of the reservoir. The geomembrane is fixed to the top anchoring trench of the bank by cast-in-place concrete, and a precast concrete wave wall is used to weigh it down. The foundation drainage system includes a foundation drainage gallery located in the foundation below the junction of the reservoir bottom and the reservoir bank. It is arranged in a ring around the reservoir. Vertical drainage pipes and inclined drainage pipes are installed directly above and below the outer side of the reservoir, respectively, to intercept and discharge groundwater flowing from the surrounding mountains to the foundation at the bottom of the reservoir basin under dynamic high groundwater level conditions. The reservoir bank interception system includes an interception ditch located outside the precast concrete wave wall at the top of the reservoir bank. The geomembrane at the anchorage at the top of the reservoir bank extends outward to the surface of the interception ditch, and its end is weighed down by permeable concrete. The reservoir bottom ventilation and drainage system includes ventilation and drainage pipes A and B arranged longitudinally and transversely under the geomembrane at the bottom of the reservoir. Ventilation and drainage pipes A and B are connected to the ventilation outlet at the top of the reservoir bank through ventilation pipes, and are also connected to the intercepting ditch through pumping pipes. The flow distribution system includes a collection pool located downstream of the reservoir dam, which is equipped with pump A. The collection pool is connected to a discharge pipe, a bidirectional water conveyance pipe, and a water conveyance tunnel. Water in the collection pool is transported to the downstream of the reservoir through the discharge pipe. Water in the collection pool is then transported to the intercepting ditch through pump A and the bidirectional water conveyance pipe. Pump B is installed in the intercepting ditch, and pump B collects the water in the intercepting ditch into the reservoir through the top water conveyance pipe.

[0006] Preferably, the outer walls of exhaust and drainage pipes A and B are covered with geotextile and surrounded by a protective covering material, which is a certain graded permeable and permeable gravel.

[0007] The design method for the drainage and venting structure of a geomembrane-lined seepage-proof reservoir basin with dynamic high groundwater is characterized by the following steps: the spacing between venting and drainage pipes A and B is determined by a water-air two-phase seepage coupling calculation model of the geomembrane-lined seepage-proof reservoir basin. S1, Assuming the initial spacing of exhaust and drain pipe arrangement (l) 0A , l 0B ); S2. Using finite element calculation software based on nonlinear Richards equations, a coupled finite element model of water-air two-phase seepage in the geomembrane seepage-proof reservoir basin is constructed, including the dam, reservoir basin, geomembrane, surrounding mountains, geological stratification of the reservoir area, foundation drainage system, exhaust and drainage pipe A, and exhaust and drainage pipe B. The model is meshed using 8-node isoparametric elements. The geomembrane (1) uses an adaptively refined boundary mesh. A radially gradient mesh is set around the exhaust and drainage pipes. The exhaust and drainage pipes are meshed with (l 0A , l 0B Spacing arrangement; S3. Input dam body zone material and stratum parameters: Based on the test results of reservoir structure materials and stratum soil mechanics, input the material and stratum calculation parameters for each zone of the dam body; S4. Set multi-mode coupling boundary conditions, including: Dynamic groundwater boundary: Based on the groundwater distribution data of the reservoir area, the boundary is applied around the model and on the surface through lateral recharge and rainfall infiltration. Exhaust boundary: Applied to the inner walls of exhaust drain pipe A and exhaust drain pipe B by setting the air pressure-related flux through the exhaust pipe grid nodes; Drainage boundary: A free-flowing design established through the grid nodes of the drainage facility, applied within the foundation drainage system; Reservoir basin head boundary: The surface of the reservoir basin below the reservoir water level, applied according to the reservoir operating conditions; Impermeable and airtight boundary: applied to the bottom of the model; S5. Multi-condition reservoir basin water-air two-phase seepage coupling calculation: The water-air two-phase seepage coupling calculation module is invoked, and the built-in VG model is used to describe the relationship between the air and water phases. By solving the water-air two-phase seepage coupling control equations, the air pressure distribution under the geomembrane in the reservoir basin under different coupling boundary conditions is calculated, and the extreme air pressure value Q is obtained. max ; S6. Determine the risk of geomembrane air expansion in Kupen using the following formula: (1) Among them: Q a Q represents atmospheric pressure. w is the reservoir water pressure value corresponding to the moment when the air pressure under the membrane reaches its extreme value; k is the geomembrane air expansion safety factor.

[0008] 4. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 3, characterized in that: the specific method steps of step S6 are as follows: S601. If equation (1) is satisfied, proceed to step S602; if equation (1) is not satisfied, proceed to step S603. S602. Optimize and determine the spacing of exhaust and drain pipes: Let l nA =l 0A +△l,l mB =l 0B (n=1, 2, 3, ...), or let l nA =l 0A , l mB =l 0B +△l (m=1, 2, 3, ...), adjust the spacing of the exhaust and drainage pipes in the model to (l nA , l mB Repeat steps S3 to S6 until equation (1) is no longer satisfied; if the last spacing adjustment object is lA Then the spacing of the exhaust and drainage pipes is determined to be (l nA -△l,l mB If the last spacing adjustment object is l B Then the spacing of the exhaust and drainage pipes is determined to be (l nA , l mB -△l); S603. Optimize and determine the spacing of exhaust and drain pipes: Let l nA =l 0A -△l,l mB =l 0B (n=1, 2, 3, ...), or let l nA =l 0A , l mB = l0B -△l (m=1, 2, 3, ...), adjust the spacing of the exhaust and drainage pipes in the model to (l nA , l mB Repeat steps S3 to S6 until equation (1) is satisfied, and determine the spacing of the exhaust and drainage pipes (l). nA , l mB ).

[0009] Preferably, the flow distribution system is used to collect water discharged from the foundation drainage system and the reservoir bank interception system into a collection tank, and distribute it in the following manner: Distribution to downstream of the reservoir: Water in the collection pool is transported to the downstream of the reservoir through the flow pipe to meet the needs of ecological flow and irrigation water; Replenishing the reservoir: First, water from the collection pool is pumped into the intercepting ditch via pump A and a two-way water conveyance pipe. Then, water is pumped into the reservoir via pump B and a bank-top water conveyance pipe. Alternatively, groundwater collected in the intercepting ditch can be directly pumped into the reservoir to increase the water consumption for power generation.

[0010] Preferably, a piezometer is installed at the connection between the pumping pipe and the exhaust / drainage pipes A and B, with k being the number of pumping pipes and piezometers, and the corresponding piezometer pressure value being H. i (i=1, 2, 3, ..., k), when the seepage pressure value meets the following condition, the pumping pipe is opened to pump water from the venting and draining pipe to the intercepting ditch: (2) Wherein: H imax Let be the extreme values ​​of the k piezometers; h be the water head above the geomembrane; and α be the safety factor for piezometer pressure, ranging from 0.2 to 0.4.

[0011] Preferably, the dynamic groundwater boundary conditions in step S4 include normal groundwater level and groundwater levels with different degrees of dynamic rise, which are used to simulate the complex dynamic groundwater distribution in the reservoir area.

[0012] Preferably, in step S4, the drainage boundary of the foundation drainage system includes the foundation drainage corridor, vertical drainage pipe, and inclined drainage pipe operating normally and in the case of partial drainage failure, which is used to determine the venting effect of the reservoir bottom venting facility when there is pore water pressure in the reservoir bottom foundation.

[0013] Preferably, the water head boundary conditions inside the reservoir basin in step S4 include constant characteristic water level conditions at normal storage level, design flood level, check flood level and dead water level, as well as dynamic water level changes between normal storage level and dead water level during reservoir operation.

[0014] Preferably, the calculation parameters for materials and strata in each section of the dam body in step S3 include porosity, density, saturated permeability coefficient, hydraulic conductivity coefficient, matrix suction, and soil-water characteristic curves.

[0015] This invention provides a drainage and venting structure and its design method for a seepage-proof reservoir basin with dynamic high groundwater levels, with the following beneficial effects: 1. This invention addresses the dynamic high groundwater level conditions around the reservoir by employing a multi-system collaborative design structure consisting of a foundation drainage system, a reservoir bank interception system, and a reservoir bottom venting-pumping system. Through drainage facilities arranged in a ring around the reservoir foundation and interception facilities at the top of the reservoir bank, the groundwater level in the reservoir basin foundation is significantly reduced. This effectively addresses the risk of geomembrane gas / liquid swelling caused by the convergence of dynamic high groundwater around the reservoir to the reservoir bottom. Furthermore, the use of longitudinally and transversely distributed venting and drainage pipes under the membrane further mitigates the risk of geomembrane rupture under pressure in cases of partial failure of the foundation drainage system. This improves the safety of the reservoir basin seepage prevention system and ensures the long-term safe operation of the reservoir basin seepage prevention body under dynamic high groundwater levels.

[0016] 2. This invention innovatively proposes an optimized design method for the spacing of venting and drainage pipes in a geomembrane-based reservoir basin, based on dynamic water-air two-phase seepage coupling. It establishes a complex calculation system for multiple combinations of working conditions, including dynamic high groundwater levels, reservoir operating water level fluctuations, and localized failures of foundation drainage facilities. Based on an iterative optimization method, the spacing of the longitudinally and transversely arranged venting and drainage pipes at the reservoir bottom is determined. Through verification using geomembrane air expansion safety criteria, it ensures that the air pressure under the membrane remains within a safe threshold range under both normal reservoir operation and adverse conditions. This improves the venting efficiency at the reservoir bottom and effectively prevents geomembrane air expansion damage, thus guaranteeing the safety of the geomembrane seepage prevention in the reservoir basin.

[0017] 3. This invention employs a flow distribution system to collaboratively collect and multi-directionally allocate groundwater and surface water discharged from the foundation drainage system and the reservoir bank interception system. It can replenish ecological flow and irrigation water to the surrounding area of ​​the reservoir, and also replenish water within the reservoir to increase power generation water demand. It flexibly adapts to water demand in various scenarios, breaks through the traditional one-way drainage mode, and realizes integrated management of groundwater drainage-collection-utilization in the reservoir area, significantly improving the utilization efficiency of groundwater resources in the reservoir area.

[0018] 4. This invention extends the geomembrane to the top of the reservoir bank and fixes it with anchoring trenches and cast-in-place concrete, which enhances the stability of the geomembrane on the reservoir bank and extends the geomembrane to the surface of the intercepting ditch on the top of the bank, forming a continuous seepage barrier. This effectively avoids the risk of leakage of groundwater discharged into the intercepting ditch and maximizes the seepage prevention advantages of the geomembrane. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a partial cross-sectional view of the overall structure of the present invention; Figure 2 This is a schematic cross-sectional view of the vent pipe of the present invention; Figure 3 This is a partial schematic diagram of the air-pumped water system of the present invention; Figure 4 This is a schematic diagram of the reservoir bank interception system of the present invention; Figure 5 This is a schematic diagram of the overall structural layout of the present invention; Figure 6 This is a schematic diagram of the calculation results for the air venting of the geomembrane seepage prevention reservoir basin of the present invention; In the diagram: 1. Geomembrane; 2. Ventilation and drainage pipe A201; 3. Ventilation and drainage pipe B202; 4. Covering and protective material; 5. Ventilation pipe; 6. Ventilation outlet; 7. Anchoring trench; 8. Cast-in-place concrete; 9. Precast concrete wave wall; 10. Pumping pipe; 11. Foundation drainage corridor; 1201. Vertical drainage pipe; 1202. Inclined drainage pipe; 13. Water conveyance tunnel; 14. Intercepting ditch; 15. Permeable concrete; 16. Excavated slope of reservoir bank; 17. Collection pool; 18. Flow pipe; 19. Two-way water conveyance pipe; 20. Water conveyance pipe on the bank top; 2101. Water pump; 2102. Water pump; 22. Piezometer; 23. Dam; 24. Surrounding mountain of reservoir. Detailed Implementation

[0020] Example 1 like Figures 1-5 As shown, the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater includes a full reservoir basin seepage-proof structure, a foundation drainage system, a reservoir bank interception system, a reservoir bottom venting and drainage system, and a flow distribution system. The full reservoir basin seepage-proof structure includes a geomembrane 1 laid on the reservoir bottom and reservoir bank. The geomembrane 1 is fixed to the top anchoring trench 7 of the reservoir bank by cast-in-place concrete 8, and is weighed down by a precast concrete wave wall 9.

[0021] like Figure 1As shown, the foundation drainage system includes a foundation drainage gallery 11 located in the foundation below the junction of the reservoir bottom and the reservoir bank. It is arranged in a ring around the reservoir. Vertical drainage pipes 1201 and inclined drainage pipes 1202 are respectively installed above and below the reservoir outside the gallery. These are used to intercept and discharge groundwater flowing from the surrounding mountains to the foundation at the bottom of the reservoir basin under dynamic high groundwater level conditions. The efficient drainage of groundwater at the bottom of the reservoir is achieved through a ring-shaped three-dimensional drainage network.

[0022] like Figure 1 As shown, the reservoir bank interception system includes an interception ditch 14 located outside the precast concrete wave wall 9 at the top of the reservoir bank. The geomembrane 1 anchored at the top of the reservoir bank extends outward to the surface of the interception ditch 14, and its end is weighed down by permeable concrete 15. It is used to intercept and collect surface water and shallow groundwater flowing from the reservoir perimeter to the vicinity of the top of the reservoir bank when the groundwater level rises suddenly under special conditions such as heavy rainfall. It effectively prevents water infiltration by intercepting surface flow.

[0023] The combined action of the ground drainage system and the reservoir bank interception system complements each other in terms of spatial layout and function, effectively intercepting dynamic high groundwater that accumulates in the reservoir area from the periphery under both normal and extreme conditions.

[0024] like Figures 1-2 As shown, the reservoir bottom venting and drainage system includes venting and drainage pipes A201 and B202 arranged longitudinally and transversely below the geomembrane 1 at the reservoir bottom. These pipes serve to vent when pore water pressure exists in the reservoir bottom foundation due to adverse conditions such as partial failure of the foundation drainage facilities, and also serve to drain potential seepage water from geomembrane defects. Venting and drainage pipes A201 and B202 are connected to the vent outlet 6 at the top of the reservoir bank via vent pipe 5, and also connected to the intercepting ditch 14 via pumping pipe 10. The outer walls of venting and drainage pipes A201 and B202 are covered with geotextile 3, and surrounded by a protective covering material 4, which is a permeable and breathable gravel material with a specific gradation.

[0025] The flow distribution system includes a collection pool 17 located downstream of the reservoir dam, which is equipped with a water pump A2101. The collection pool 17 is connected to a discharge pipe 18, a bidirectional water conveyance pipe 19, and a water conveyance tunnel 13. Water in the collection pool 17 is transported to the downstream of the reservoir through the discharge pipe 18. Water in the collection pool 17 is transported to the intercepting ditch 14 through the water pump A2101 and the bidirectional water conveyance pipe 19. A water pump B2102 is installed in the intercepting ditch 14. The water pump B2102 collects the water in the intercepting ditch 14 into the reservoir through the bank-top water conveyance pipe 20.

[0026] Example 2 like Figures 1-6As shown in Example 1, the design method for the drainage and venting structure of a geomembrane seepage-proof reservoir basin with dynamic high groundwater is characterized by the following: the spacing between the venting and drainage pipes A201 and B202 is determined by a water-air two-phase seepage coupling calculation model for the geomembrane seepage-proof reservoir basin. The determination method includes the following steps: S1, Assuming the initial spacing of exhaust and drain pipes (l) 0A , l 0B ); S2. Using finite element calculation software based on nonlinear Richards equations, a coupled finite element model of water-air two-phase seepage in the geomembrane seepage prevention reservoir basin is constructed, including the dam 23, reservoir basin, geomembrane 1, reservoir surrounding mountains 24, reservoir geological stratification, foundation drainage system, exhaust and drainage pipe A201, and exhaust and drainage pipe B202. The model is meshed using 8-node isoparametric elements. The geomembrane 1 uses an adaptively refined boundary mesh, and the ventilation and drainage pipes are surrounded by a radially gradient mesh. The ventilation and drainage pipes are designed with (l) 0A , l 0B Spacing arrangement; S3. Input dam body zone material and stratum parameters: Based on the test results of reservoir structure materials and stratum soil mechanics, input the material and stratum calculation parameters for each zone of the dam body; The calculation parameters for materials and strata in each section of the dam body include porosity, density, saturated permeability coefficient, hydraulic conductivity coefficient, matrix suction, and soil-water characteristic curves.

[0027] S4. Set multi-mode coupling boundary conditions, including: Dynamic groundwater boundary: Based on the groundwater distribution data of the reservoir area, the boundary is applied around the model and on the surface through lateral recharge and rainfall infiltration. The dynamic groundwater boundary conditions include normal groundwater level and groundwater level with different degrees of dynamic rise, which are used to simulate the complex dynamic groundwater distribution in the reservoir area.

[0028] Exhaust boundary: Applied to the inner walls of exhaust drain pipe A201 and exhaust drain pipe B202 by setting the air pressure related flux through the exhaust pipe grid node; Drainage boundary: It is applied to the foundation drainage system through the free seepage setting of the drainage facility grid nodes; the drainage boundary of the foundation drainage system includes the normal operation of the foundation drainage gallery 11, vertical drainage pipe 1201, and inclined drainage pipe 1202 and the local drainage failure condition, which is used to judge the venting effect of the reservoir bottom venting facility when there is pore water pressure in the reservoir bottom foundation.

[0029] Reservoir head boundary: The water level applied to the surface of the reservoir basin below the reservoir water level, based on the reservoir operating conditions; The water head boundary conditions inside the reservoir basin include the constant characteristic water level conditions at normal storage level, design flood level, check flood level and dead water level, as well as the dynamic water level change conditions between normal storage level and dead water level during reservoir operation.

[0030] Impermeable and airtight boundary: applied to the bottom of the model; S5. Multi-condition reservoir basin water-air two-phase seepage coupling calculation: The water-air two-phase seepage coupling calculation module is invoked, and the built-in VG model is used to describe the relationship between the air and water phases. By solving the water-air two-phase seepage coupling control equations, the air pressure distribution under the geomembrane in the reservoir basin under different coupling boundary conditions is calculated, and the extreme air pressure value Q is obtained. max The calculation results of the geomembrane seepage prevention reservoir venting in this embodiment are shown in the figure. Figure 6 ; S6. Determine the risk of geomembrane air expansion in Kupen using the following formula: (1) Among them: Q a Q represents atmospheric pressure. w is the reservoir water pressure value corresponding to the moment when the air pressure under the membrane reaches its extreme value; k is the geomembrane air expansion safety factor.

[0031] Preferably, the specific method steps for step S6 are as follows: S601. If equation (1) is satisfied, proceed to step S602; if equation (1) is not satisfied, proceed to step S603. S602. Optimize and determine the spacing of exhaust and drain pipes: Let l nA =l 0A +△l,l mB =l 0B (n=1, 2, 3, ...), or let l nA =l 0A , l mB =l 0B +△l (m=1, 2, 3, ...), adjust the spacing of the exhaust and drainage pipes in the model to (l nA , l mB Repeat steps S3 to S6 until equation (1) is no longer satisfied; if the last spacing adjustment object is l A Then the spacing of the exhaust and drainage pipes is determined to be (l nA -△l,l mB If the last spacing adjustment object is l B Then the spacing of the exhaust and drainage pipes is determined to be (l nA , l mB -△l); S603. Optimize and determine the spacing of exhaust and drain pipes: Let lnA =l 0A -△l,l mB =l 0B (n=1, 2, 3, ...), or let l nA =l 0A , l mB = l0B -△l (m=1, 2, 3, ...), adjust the spacing of the exhaust and drainage pipes in the model to (l nA , l mB Repeat steps S3 to S6 until equation (1) is satisfied, and determine the spacing of the exhaust and drainage pipes (l). nA , l mB ).

[0032] Preferably, the flow distribution system is used to collect water discharged from the foundation drainage system and the reservoir bank interception system into the collection tank 17, and distribute it in the following manner: Distribution to downstream of the reservoir: Water in the collection pool 17 is transported to the downstream of the reservoir through the flow pipe 18 to meet the needs of ecological flow and irrigation water. Replenishing the reservoir: First, water in the collection pool 17 is pumped into the intercepting ditch 14 by water pump A2101 and bidirectional water transmission pipe 19. Then, water is pumped into the reservoir by water pump B2102 and the bank-top water transmission pipe 20. Alternatively, groundwater collected in the intercepting ditch 14 can be directly pumped into the reservoir to increase the water consumption for power generation.

[0033] Preferably, a piezometer 22 is installed at the connection between the pumping pipe 10 and the exhaust / drainage pipes A201 and B202. The number of pumping pipes 10 and piezometers 22 is k, and the osmotic pressure value of the corresponding piezometer is H. i (i=1, 2, 3, ..., k), when the seepage pressure value meets the following condition, the pumping pipe 10 is opened to pump water from the venting and draining pipe to the intercepting ditch 14: (2) Wherein: H imax Let be the extreme values ​​of the k piezometers; h be the water head above the geomembrane; and α be the safety factor for piezometer pressure, ranging from 0.2 to 0.4. In this embodiment, α = 0.2 is preferred.

[0034] The above embodiments are merely preferred technical solutions of the present invention and should not be considered as limitations on the present invention. The scope of protection of the present invention should be limited to the technical solutions described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. The drainage and venting structure of a seepage-proof reservoir basin with dynamic high groundwater levels, characterized by: It includes a full reservoir basin seepage prevention structure, a foundation drainage system, a reservoir bank interception system, a reservoir bottom ventilation and drainage system, and a flow distribution system; The entire reservoir basin seepage prevention structure includes a geomembrane (1) laid on the bottom and bank of the reservoir. The geomembrane (1) is fixed to the top anchoring groove (7) of the bank by cast-in-place concrete (8) and weighed down by a precast concrete wave wall (9). The foundation drainage system includes a foundation drainage gallery (11) located in the foundation below the junction of the reservoir bottom and the reservoir bank. It is arranged in a ring around the reservoir. Vertical drainage pipes (1201) and inclined drainage pipes (1202) are respectively provided above and below the outside of the reservoir to intercept and discharge groundwater flowing from the surrounding mountains to the foundation at the bottom of the reservoir basin under dynamic high groundwater level conditions. The reservoir bank interception system includes an interception ditch (14) located outside the precast concrete wave wall (9) at the top of the reservoir bank. The geomembrane (1) at the anchorage at the top of the reservoir bank extends outward to the surface of the interception ditch (14), and its end is weighed by permeable concrete (15). The reservoir bottom ventilation and drainage system includes ventilation and drainage pipes A (201) and B (202) arranged longitudinally and transversely below the geomembrane (1) at the bottom of the reservoir. Ventilation and drainage pipes A (201) and B (202) are connected to the ventilation outlet (6) at the top of the reservoir bank through ventilation pipe (5) and are also connected to the intercepting ditch (14) through pumping pipe (10). The flow distribution system includes a collection pool (17) located downstream of the reservoir dam, which is equipped with a water pump A (2101). The collection pool (17) is connected to a discharge pipe (18), a bidirectional water conveyance pipe (19), and a water conveyance tunnel (13). Water in the collection pool (17) is transported to the downstream of the reservoir through the discharge pipe (18). Water in the collection pool (17) is transported to the intercepting ditch (14) through the water pump A (2101) and the bidirectional water conveyance pipe (19). Water pump B (2102) is installed in the intercepting ditch (14). Water pump B (2102) collects water in the intercepting ditch (14) into the reservoir through the bank-top water conveyance pipe (20).

2. The drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 1, characterized in that: The outer walls of exhaust and drainage pipes A (201) and B (202) are covered with geotextile (3) and surrounded by protective covering material (4), which is a certain grade of permeable and permeable sand and gravel.

3. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in any one of claims 1 to 2, characterized in that: The spacing between exhaust and drainage pipes A (201) and B (202) was determined using a geomembrane seepage prevention reservoir basin water-air two-phase seepage coupling calculation model. The determination method included the following steps: S1, Assuming the initial spacing of exhaust and drain pipe arrangement (l) 0A , l 0B ); S2. Using finite element calculation software based on nonlinear Richards equations, a geomembrane seepage prevention reservoir basin water-air two-phase seepage coupling finite element model is constructed, including dam (23), reservoir basin, geomembrane (1), reservoir surrounding mountains, reservoir geological stratification, foundation drainage system, exhaust drainage pipe A (201), and exhaust drainage pipe B (202). The model is meshed using 8-node isoparametric elements. The geomembrane (1) uses an adaptively refined boundary mesh. A radially gradient mesh is set around the exhaust and drainage pipes. The exhaust and drainage pipes are meshed with (l 0A , l 0B Spacing arrangement; S3. Input dam body zone material and stratum parameters: Based on the test results of reservoir structure materials and stratum soil mechanics, input the material and stratum calculation parameters for each zone of the dam body; S4. Set multi-mode coupling boundary conditions, including: Dynamic groundwater boundary: Based on the groundwater distribution data of the reservoir area, the boundary is applied around the model and on the surface through lateral recharge and rainfall infiltration. Exhaust boundary: Applied to the inner walls of exhaust drain pipe A (201) and exhaust drain pipe B (202) by setting the gas pressure related flux through the exhaust pipe grid node; Drainage boundary: A free-flowing design established through the grid nodes of the drainage facility, applied within the foundation drainage system; Reservoir basin head boundary: The surface of the reservoir basin below the reservoir water level, applied according to the reservoir operating conditions; Impermeable and airtight boundary: applied to the bottom of the model; S5. Multi-condition reservoir basin water-air two-phase seepage coupling calculation: The water-air two-phase seepage coupling calculation module is invoked, and the built-in VG model is used to describe the relationship between the air and water phases. By solving the water-air two-phase seepage coupling control equations, the air pressure distribution under the geomembrane in the reservoir basin under different coupling boundary conditions is calculated, and the extreme air pressure value Q is obtained. max ; S6. Determine the risk of geomembrane air expansion in Kupen using the following formula: （1） Among them: Q a Q represents atmospheric pressure. w is the reservoir water pressure value corresponding to the moment when the air pressure under the membrane reaches its extreme value; k is the geomembrane air expansion safety factor.

4. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 3, characterized in that: The specific steps for step S6 are as follows: S601. If equation (1) is satisfied, proceed to step S602; if equation (1) is not satisfied, proceed to step S603. S602. Optimize and determine the spacing of exhaust and drain pipes: Let l nA =l 0A +△l,l mB =l 0B (n=1, 2, 3, ...), or let l nA =l 0A , l mB =l 0B +△l (m=1, 2, 3, ...), adjust the spacing of the exhaust and drainage pipes in the model to (l nA , l mB Repeat steps S3 to S6 until equation (1) is no longer satisfied; if the last spacing adjustment object is l A Then the spacing of the exhaust and drainage pipes is determined to be (l nA -△l,l mB If the last spacing adjustment object is l B Then the spacing of the exhaust and drainage pipes is determined to be (l nA , l mB -△l); S603. Optimize and determine the spacing of exhaust and drain pipes: Let l nA =l 0A -△l,l mB =l 0B (n=1, 2, 3, ...), or let l nA =l 0A , l mB = l0B -△l (m=1, 2, 3, ...), adjust the spacing of the exhaust and drainage pipes in the model to (l nA , l mB Repeat steps S3 to S6 until equation (1) is satisfied, and determine the spacing of the exhaust and drainage pipes (l). nA , l mB ).

5. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 3, characterized in that: The flow distribution system is used to collect water discharged from the foundation drainage system and the reservoir bank interception system into the collection tank (17) and distribute it in the following ways: Distribution to downstream of the reservoir: Water in the collection pool (17) is transported to the downstream of the reservoir through the flow pipe (18) to meet the needs of ecological flow and irrigation water. Replenishing the reservoir: First, water in the collection pool (17) is collected into the intercepting ditch (14) by water pump A (2101) and bidirectional water transmission pipe (19), and then water is collected into the reservoir by water pump B (2102) and the bank top water transmission pipe (20), or groundwater collected in the intercepting ditch (14) is directly collected into the reservoir to increase the water consumption for power generation in the reservoir.

6. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 3, characterized in that: A piezometer (22) is installed at the connection between the pumping pipe (10) and the exhaust / drainage pipe A (201) and the exhaust / drainage pipe B (202). The number of pumping pipes (10) and piezometers (22) is k, and the osmotic pressure value of the corresponding piezometer is H. i (i=1, 2, 3, ..., k), when the seepage pressure value meets the following condition, open the pumping pipe (10) to pump the water in the venting and draining pipe to the intercepting ditch (14): （2） Wherein: H imax Let be the extreme values ​​of the k piezometers; h be the water head above the geomembrane; and α be the safety factor for piezometer pressure, ranging from 0.2 to 0.

4.

7. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 3, characterized in that: In step S4, the dynamic groundwater boundary conditions include normal groundwater levels and groundwater levels that rise dynamically to varying degrees, which are used to simulate the complex dynamic groundwater distribution in the reservoir area.

8. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 3, characterized in that: In step S4, the drainage boundary of the foundation drainage system includes the foundation drainage corridor (11), vertical drainage pipe (1201), and inclined drainage pipe (1202) under normal operating conditions and local drainage failure conditions, which are used to determine the venting effect of the reservoir bottom venting facility when there is pore water pressure in the reservoir bottom foundation.

9. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 3, characterized in that: The water head boundary conditions inside the reservoir basin in step S4 include constant characteristic water level conditions at normal storage level, design flood level, check flood level and dead water level, as well as dynamic water level changes between normal storage level and dead water level during reservoir operation.

10. The design method for the drainage and venting structure of the seepage-proof reservoir basin with dynamic high groundwater as described in claim 3, characterized in that: In step S3, the calculation parameters for materials and strata in each section of the dam body include porosity, density, saturated permeability coefficient, hydraulic conductivity coefficient, matrix suction, and soil-water characteristic curves.

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