A seepage cut-off structure of a tailings pond with a seepage cut-off wall and a precipitation well and a construction method thereof

Abstract

The present invention discloses a seepage interception structure of a tailings dam with a seepage interception wall and a precipitation well and a construction method thereof. The structure comprises a precipitation well and a vertical seepage interception wall, wherein the vertical seepage interception wall is arranged at the downstream position of the tailings dam, and a plurality of precipitation wells are arranged at the upstream of the vertical seepage interception wall. The upper part of the vertical seepage interception wall adopts a continuous wall, and the lower part of the vertical seepage interception wall adopts curtain grouting. The present invention arranges a plurality of precipitation wells upstream of the vertical seepage interception wall, and after the underground runoff part of the discharged wastewater is intercepted by the vertical seepage interception wall, the polluted groundwater is collected and returned for reuse in time through the precipitation well, effectively collecting the outflowing seepage water of the tailings dam and its surroundings, reducing the groundwater level of the vertical seepage interception wall, reducing the risk of seepage around the seepage dam shoulder or base leakage, and at the same time greatly improving the durability of the vertical seepage interception wall structure itself, and improving the service life, and the project investment is small, the application range is wide, the later maintenance is simple, the maintenance cost is low, and the environmental protection benefit, safety benefit and economic benefit are extremely significant.

Description

Technical Field

[0001] The invention relates to the application field of drainage engineering, and in particular to a tailings pond seepage cutoff structure of a seepage cutoff wall combined with a precipitation well and a construction method thereof. Background Art

[0002] A tailings pond refers to a place constructed by building a dam to block the valley mouth or enclosing land for storing tailings or other industrial waste. It is generally composed of several parts, such as the tailings storage system, the tailings dam drainage system, the tailings pond flood discharge system, and the tailings pond backwater system.

[0003] In the prior art, the anti-seepage of tailings ponds is usually prevented by setting a horizontal anti-seepage lining at the bottom of the tailings pond, which is generally made of artificial synthetic materials such as geomembranes or composite geomembranes. If the site engineering geological conditions permit, a concrete seepage cut-off wall or a grouting curtain can also be set up downstream of the tailings pond to cut off vertical seepage. The drainage of tailings pond dams generally adopts horizontal or vertical drainage forms such as slope drainage, drainage pipe drainage, well pipe drainage, and radial well drainage.

[0004] The horizontal anti-seepage of the tailings pond affects the consolidation and drainage effect of the tailings stored in the pond, and has a great adverse impact on the safety performance of the tailings dam body. It may also lead to a sharp increase in the investment in artificial drainage and precipitation measures of the tailings dam during operation, increasing the economic burden of the enterprise. For tailings ponds that have been built and put into use for many years and have not taken anti-seepage measures, a large amount of tailings water leakage and disorderly discharge during operation have caused serious pollution to the surrounding environment, especially the downstream environment. Later sewage treatment mostly adopts the method of setting large-diameter radiation wells in the accumulation dam body to collect and pump back the tailings seepage or adding vertical seepage walls such as seepage dams and anti-seepage curtain grouting at appropriate locations downstream of the tailings pond to intercept and recycle the tailings seepage.

[0005] A single vertical cut-off wall is subject to geological conditions at the dam site, making it prone to seepage around the dam shoulders or leakage at the base, and the cut-off effect is often less than ideal. In addition, since the cut-off wall is subject to long-term immersion erosion by highly corrosive groundwater at high levels, the durability of the structure is significantly reduced, and problems such as erosion or cracking may occur. After a period of operation, water seepage in the wall is difficult to avoid, making it difficult to meet the zero discharge requirements for tailings pond wastewater.

[0006] In view of this, it is necessary to propose a tailings pond seepage cutoff structure of a seepage cutoff wall combined with a precipitation well and a construction method thereof to solve the above-mentioned defects. Summary of the invention

[0007] The main purpose of the present invention is to provide a tailings pond seepage cutoff structure with a seepage cutoff wall and a drainage well and a construction method thereof, aiming to solve the shortcomings of the existing vertical seepage cutoff technology of tailings ponds, such as seepage around the dam shoulder or leakage at the base and low durability of the wall structure, which may lead to erosion or cracking of the seepage cutoff wall and water seepage. To achieve the above purpose, the present invention provides a tailings pond seepage cutoff structure with a seepage cutoff wall and a drainage well, comprising a drainage well and a vertical seepage cutoff wall, wherein the vertical seepage cutoff wall is arranged at the downstream position of the tailings pond, and a plurality of the drainage wells are arranged upstream of the vertical seepage cutoff wall, the upper part of the vertical seepage cutoff wall adopts a continuous wall, and the lower part of the vertical seepage cutoff wall adopts curtain grouting.

[0008] Preferably, the surface of the vertical cut-off wall is coated with an anti-corrosion coating, and / or an anti-seepage membrane is provided inside the continuous wall.

[0009] Preferably, an overflow dam section or a full dam section for drainage in emergency situations is provided on the top of the continuous wall.

[0010] Preferably, the bottom of the vertical cut-off wall and the shoulders on both sides thereof are grouted using either closed curtain grouting or suspended curtain grouting.

[0011] Preferably, the bottom of the vertical cut-off wall is embedded below the strongly weathered bedrock layer, wherein the closed curtain grouting extends below the slightly weathered bedrock layer to a depth of not less than 2 meters.

[0012] Preferably, a precipitation well seepage cutoff layer formed by an arrangement of a plurality of precipitation wells is arranged downstream of the tailings pond and upstream of the vertical seepage cutoff wall.

[0013] Preferably, the precipitation well is a large-diameter precipitation well that is excavated on a large scale. The upper part of the well wall of the large-diameter precipitation well is a water-impermeable structure, and the lower part of the well wall of the large-diameter precipitation well is a water-permeable structure with seepage holes. The outer wall of the lower part of the well wall of the large-diameter precipitation well is provided with an outer filter layer, and the wellhead of the large-diameter precipitation well is provided with an inspection cover plate. The interior of the large-diameter precipitation well is provided with pumping equipment, the inner diameter of the large-diameter precipitation well is greater than 1 meter, and the well body height of the large-diameter precipitation well is less than 6 meters. The outer part of the lower part of the well wall of the large-diameter precipitation well is radially provided with gravel filter material.

[0014] Preferably, the large-diameter precipitation well also includes a water filtering blind ditch radially arranged on the outside of the lower part of the well wall, and two adjacent large-diameter precipitation wells are connected through the water filtering blind ditch; the large-diameter precipitation well also includes a gravel water interception blind ditch arranged in a direction perpendicular to the direction of groundwater flow, and the gravel water interception blind ditch is used to connect the groundwater with the large-diameter precipitation wells adjacent to it, so as to cut off and drain the groundwater to the interior of the large-diameter precipitation well.

[0015] Preferably, the precipitation well is a small-diameter precipitation well drilled, the upper part of the well wall of the small-diameter precipitation well is a water-impermeable structure, the lower part of the well wall of the small-diameter precipitation well is a water-permeable structure with seepage holes, the outer wall of the lower part of the well wall of the small-diameter precipitation well is provided with an outer filter layer, the wellhead pores of the small-diameter precipitation well are filled with clay for sealing the wellhead, the wellhead of the small-diameter precipitation well is provided with a sealing cover plate, the interior of the small-diameter precipitation well is provided with pumping equipment, the inner diameter of the small-diameter precipitation well is less than 1 meter, and the outside of the lower part of the well wall of the small-diameter precipitation well is radially provided with gravel-filled filter material.

[0016] The present invention also provides a method for constructing a seepage-cutting structure of a tailings pond with a seepage-cutting wall and a precipitation well as described above, S1, obtaining information on the lithology, permeability characteristics and integrity of the stratum at the bottom of the tailings pond, obtaining information on the distribution, development, recharge source, runoff, discharge pathway, environmental category and corrosiveness of surface water and groundwater in the tailings pond, obtaining information on the integrity of the hydrogeological units of the tailings pond, obtaining information on the overall flow field of groundwater in the tailings pond, obtaining information on whether there is a relatively impermeable waterproof layer at the bottom of the tailings pond, and obtaining information on whether there is a deep or lateral leakage problem in the tailings pond area;

[0017] S2, provide a typical geological profile of the proposed vertical seepage wall, evaluate the groundwater resources in the tailings pond area, estimate the groundwater leakage and inflow, analyze the impact of tailings pond seepage on the groundwater recharge of the site, and evaluate and determine the main impact range of tailings pond seepage;

[0018] S3. Based on the survey results of the engineering geological conditions and hydrogeological conditions of the tailings pond site and the estimated maximum groundwater leakage value of the tailings pond, the location, number and depth of the precipitation wells are preliminarily determined, and the depth of the precipitation wells is determined according to the bedrock burial depth at different precipitation points;

[0019] S4, first build multiple precipitation wells upstream of the location where the vertical seepage cutoff wall is built to pump back the collected seepage water in time to lower the groundwater level, and then build a vertical seepage cutoff wall for seepage cutoff at a suitable location downstream of the tailings pond to form a tailings pond seepage cutoff structure.

[0020] Compared with the prior art, the tailings pond seepage cutoff structure of the seepage cutoff wall combined with the precipitation well and the construction method thereof provided by the present invention have the following beneficial effects:

[0021] The present invention provides a tailings dam seepage cutoff structure of a seepage cutoff wall combined with a precipitation well and a construction method thereof. The present invention arranges a plurality of precipitation wells upstream of a vertical seepage cutoff wall. After the underground runoff portion of the discharged wastewater is cut off by the vertical seepage cutoff wall, the contaminated groundwater is collected and returned for reuse in time through the precipitation wells, thereby effectively collecting the escaped seepage water from the tailings dam and its surroundings, lowering the groundwater level of the vertical seepage cutoff wall, and reducing the risk of seepage around the seepage dam shoulder. At the same time, the durability of the vertical seepage cutoff wall structure itself can be greatly improved, and the service life can be increased. The project investment is small, the adaptability is wide, the later maintenance is simple, the maintenance cost is low, and the environmental protection benefits, safety benefits and economic benefits are extremely significant. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0023] Figure 1 It is an overall layout diagram of the seepage interception structure of the tailings pond in one embodiment of the present invention;

[0024] Figure 2 for Figure 1 The enlarged view of point A in the middle;

[0025] Figure 3 It is a schematic diagram of the overall structure of the tailings pond seepage interception structure in one embodiment of the present invention;

[0026] Figure 4 for Figure 3 The enlarged view of point B in the middle;

[0027] Figure 5 It is a structural schematic diagram of a large-diameter precipitation well in one embodiment of the present invention;

[0028] Figure 6 A cross-sectional view of a large-diameter precipitation well in one embodiment of the present invention;

[0029] Figure 7 It is a structural schematic diagram of a small-diameter precipitation well in one embodiment of the present invention;

[0030] Description of Figure Numbers:

[0031] Tailings pond seepage interception structure 100; tailings pond 110; original ground line 111; slightly weathered bedrock layer 112; tailings dam 120; initial dam 130; tailings pond flood discharge structure 140; stilling pool and return pool 150; drainage well 160; drainage tunnel 161; drainage tunnel outlet 162; intercepting ditch 163; intercepting ditch outlet 164; return water structure 170; high-level water pool 171; return flow structure 180; return flow steel pipe 181 ; precipitation well 200; large-diameter precipitation well 210; seepage hole 211; outer filter layer 212; maintenance cover 213; pumping equipment 214; gravel filter material 215; water filtration blind ditch 216; small-diameter precipitation well 220; sealing cover 222; gravel-filled filter material 224; vertical cut-off wall 300; continuous wall 310; overflow dam section 311; left dam shoulder 312; right dam shoulder 313; concrete curtain grouting 320.

[0032] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0033] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0036] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0037] Please refer to the attached Figures 1 to 7The present invention provides a tailings pond seepage cutoff structure 100 with a seepage cutoff wall and a drainage well, comprising a drainage well 200 and a vertical seepage cutoff wall 300, wherein the vertical seepage cutoff wall 300 is arranged at a downstream position of the tailings pond 110, and a plurality of drainage wells 200 are arranged upstream of the vertical seepage cutoff wall 300, a continuous wall 310 is adopted at the upper part of the vertical seepage cutoff wall 300, and a curtain grouting 320 is adopted at the lower part of the vertical seepage cutoff wall 300.

[0038] Specifically, for a tailings pond site that is a relatively complete hydrogeological unit, the construction of the tailings pond 110 does not change the overall flow field of groundwater, and the stratum distribution at the tailings dam 120 site is relatively complex, a vertical seepage cutoff wall 300 is set at the downstream position of the tailings pond 110. Please refer to the attached Figure 1 The tailings pond 110 includes a tailings pond seepage interception structure 100, a tailings dam 120, an initial dam 130, a tailings pond flood discharge structure 140, a drainage system, a diversion ditch 163, a backwater structure 170 and a return flow structure 180, etc.; an energy dissipation pool and return water pool 150 is arranged in the tailings pond flood discharge structure 140, and the energy dissipation pool and return water pool 150 is arranged downstream of the tailings pond 110, and a vertical seepage interception wall 300 is arranged downstream of the energy dissipation pool and return water pool 150, and a plurality of precipitation wells 200 are arranged upstream of the vertical seepage interception wall 300, and the number and arrangement of the plurality of precipitation wells 200 can be set according to actual needs.

[0039] It should be understood that, in one embodiment, the drainage system includes a drainage well 160, a drainage tunnel 161 and a drainage tunnel outlet 162, and the intercepting ditch outlet 164 of the intercepting ditch 163 is connected to the energy dissipation pool and return pool 150. The surface wastewater discharged from the tailings pond 110 includes the external drainage of the drainage system in the reservoir and the seepage of the tailings pond 110. The drainage system and the intercepting ditch 163 are both used to discharge the surface wastewater discharged from the tailings pond 110. The external drainage of the drainage system in the reservoir and the seepage of the tailings pond 110 are both set at the energy dissipation pool and return pool 150 in the tailings pond flood discharge structure 140 on the downstream side of the tailings pond 110. The return water structure 170 returns the wastewater to the high-level water pool 171 for recycling. The underground runoff of the discharged wastewater is cut off by the vertical cut-off wall 300, and the polluted groundwater is collected in time by the precipitation well 200 arranged upstream of the vertical cut-off wall 300 and returned to the energy dissipation pool and return water pool 150 under the dam or the tailings pond 110 for reuse through the return flow structure 180, thereby forming a complete tailings pond anti-seepage system, completely cutting off the seepage discharge channel of the tailings pond 110, and achieving zero wastewater discharge.

[0040] In addition, the upper part of the vertical cut-off wall 300 adopts a continuous wall 310, and the lower part adopts a curtain grouting 320 type. The appropriate type of concrete or grouting slurry and admixture can be selected according to the actual situation such as the corrosiveness of the seepage water in the tailings pond 110. The curtain grouting 320 can effectively reduce the seepage volume and reduce the seepage pressure. The continuous wall 310 has high rigidity, good impermeability and durability, and high safety.

[0041] It is worth noting that the seepage cutoff effect of the tailings pond seepage cutoff structure 100 of the vertical seepage cutoff wall 300 and the precipitation well 200 is ideal. By setting a plurality of precipitation wells 200 upstream of the vertical seepage cutoff wall 300, the underground runoff of the discharged wastewater is cut off by the vertical seepage cutoff wall 300, and the contaminated groundwater is collected in time through the precipitation well 200 and returned for reuse through the reflux structure 180, thereby effectively collecting the seepage water from the dam body, foundation and bank slope of the tailings dam 120, reducing the groundwater level in front of the vertical seepage cutoff wall 300, and reducing the risk of seepage around the seepage dam shoulder or base leakage. At the same time, the durability of the vertical seepage cutoff wall 300 structure itself can be greatly improved, and the service life can be increased, thereby ensuring zero discharge of wastewater from the tailings pond 110 to the greatest extent possible. In addition, the project investment is small, the adaptability is wide, the later maintenance is simple, the maintenance cost is low, and the environmental protection benefits, safety benefits and economic benefits are extremely significant.

[0042] As a preferred embodiment of the present invention, the surface of the vertical cut-off wall 300 is coated with an anti-corrosion coating (not shown in the figure), and / or an anti-seepage membrane (not shown in the figure) is arranged inside the continuous wall 310. It should be understood that the anti-corrosion coating is applied on the surface of the vertical cut-off wall 300 to prevent the surface of the vertical cut-off wall 300 from being corroded, thereby causing problems such as cracking, peeling, and strength reduction, and the protective effect is good. The anti-seepage membrane is arranged inside the continuous wall 310, and the anti-seepage membrane has excellent anti-seepage performance and good heat resistance, good chemical stability, and relatively high deformation capacity, and can play the role of anti-seepage, anti-corrosion and moisture-proof.

[0043] As a preferred embodiment of the present invention, an overflow dam section 311 or a full dam section (not shown) for drainage in an emergency is provided on the top of the continuous wall 310. In detail, an overflow dam section 311 is provided on the top of the continuous wall 310, or a full dam section is provided as the overflow dam section 311, which is used for passing water in an emergency, and can both discharge water and block water, thereby protecting the continuous wall 310.

[0044] Further, the bottom of the vertical cut-off wall 300 and the shoulders on both sides thereof adopt one of closed curtain grouting or suspended curtain grouting. Specifically, the type of curtain grouting 320 can be selected according to actual needs, and closed curtain grouting or suspended curtain grouting can be selected, and single-row hole, double-row hole or multi-row hole curtain can be selected according to the actual engineering geological conditions and the anti-seepage requirements of the specific project, and the grouting parameters are determined through on-site grouting tests. In this embodiment, the curtain grouting 320 adopts closed curtain grouting, and the bottom of the vertical cut-off wall 300 and the shoulders on both sides thereof, that is, the left shoulder 312 and the right shoulder 313, also adopt closed curtain grouting to achieve a better anti-seepage effect.

[0045] As a preferred embodiment of the present invention, the bottom of the vertical cut-off wall 300 is embedded below the strongly weathered bedrock layer, and the depth of the closed curtain grouting 320 extending below the slightly weathered bedrock layer 112 is not less than 2 meters. It should be understood that by embedding the bottom of the vertical cut-off wall 300 below the strongly weathered bedrock layer and setting the depth of the closed curtain grouting 320 extending below the slightly weathered bedrock layer 112 to not less than 2 meters, a better anti-seepage effect can be achieved.

[0046] Furthermore, a plurality of precipitation wells 200 are arranged to form a precipitation well seepage cut-off layer, and the precipitation well seepage cut-off layer is arranged at the downstream position of the tailings pond 110 and upstream of the vertical seepage cut-off wall 300. Specifically, the number and arrangement of the precipitation wells 200 can be set according to actual conditions. In the present embodiment, a precipitation well seepage cut-off layer composed of a plurality of precipitation wells 200 is arranged, which can timely pump out underground seepage water, and timely return the cut-off tailings seepage water to the upstream stilling pool and return water pool 150 or the tailings pond 110 through the return steel pipe 181 of the return structure 180, thereby lowering the groundwater level in front of the vertical seepage cut-off wall 300, reducing the discharge of tailings seepage water, and preventing the vertical seepage cut-off wall 300 from being soaked in water for a long time to accelerate its corrosion, thereby affecting the environmental protection seepage cut-off effect.

[0047] As a preferred embodiment of the present invention, the precipitation well 200 is a large-diameter precipitation well 210 that is excavated on a large scale. The upper part of the well wall of the large-diameter precipitation well 210 is a water-impermeable structure, and the lower part of the well wall of the large-diameter precipitation well 210 is a water-permeable structure with seepage holes 211. The outer wall of the lower part of the well wall of the large-diameter precipitation well 210 is provided with an outer filter layer 212, and the wellhead of the large-diameter precipitation well 210 is provided with a maintenance cover 213. The interior of the large-diameter precipitation well 210 is provided with a pumping equipment 214. The inner diameter of the large-diameter precipitation well 210 is greater than 1 meter, and the well body height of the large-diameter precipitation well 210 is less than 6 meters. The outer part of the lower part of the well wall of the large-diameter precipitation well 210 is radially provided with gravel filter material 215.

[0048] In detail, the type of precipitation well 200 can be selected according to actual needs. A large-diameter precipitation well 210 formed by large excavation can be used, or a small-diameter precipitation well 220 formed by drilling can be used, or a combination of both pipe well point types can be used.

[0049] For details, please refer to the attached Figure 5-6 In this embodiment, the large-diameter precipitation well 210 adopts a large excavation method and a cast-in-place precipitation well, adopts a cast-in-place or prefabricated reinforced concrete structure, has an inner diameter greater than 1 meter, and a well body height less than 6 meters. The upper part of the well wall is a water-impermeable structure, and the lower part of the well wall is a permeable structure with a seepage hole 211. The upper part can be set as a solid pipe, and the lower part can be set as a filter pipe. The lower part of the well wall of the large-diameter precipitation well 210 is reserved with a plum blossom-shaped seepage hole 211. The outer part of the lower part of the well wall can be wrapped with geotextile or lead wire mesh or steel wire mesh according to the characteristics of the formation and tied firmly. The surrounding area of ​​the lower part of the well wall of the precipitation well 200 is filled with gravel filter material 215, and a maintenance cover 213 is set at the wellhead. When groundwater is collected and discharged into the large-diameter precipitation well 210, the seepage water is promptly refluxed through the pumping equipment 214 installed in the large-diameter precipitation well 210, thereby achieving the effect of reducing groundwater. The large-diameter precipitation well 210 has a strong seepage interception ability and a good precipitation effect.

[0050] Furthermore, the large-diameter precipitation well 210 also includes a water filtering blind ditch 216 radially arranged on the outer side of the lower part of the well wall, and two adjacent large-diameter precipitation wells 210 are connected through the water filtering blind ditch 216; the large-diameter precipitation well 210 also includes a gravel water interception blind ditch (not shown) arranged in a direction perpendicular to the direction of groundwater flow, and the gravel water interception blind ditch is used to connect the groundwater and the large-diameter precipitation well 210 adjacent thereto, so as to cut off and drain the groundwater to the interior of the large-diameter precipitation well 210.

[0051] It should be noted that the water filtering blind ditch 216 is arranged around the outside of the lower part of the well wall and is arranged radially. Two adjacent large-diameter precipitation wells 210 are connected through the water filtering blind ditch 216. The water filtering blind ditch 216 connects multiple large-diameter precipitation wells 210 one by one, which is more effective in cutting off the groundwater flow and recovering the seepage water; at the same time, the gravel interception blind ditch is arranged in a direction perpendicular to the groundwater flow direction. The gravel interception blind ditch connects the groundwater and the large-diameter precipitation well 210 adjacent to it to intercept and drain the groundwater to the inside of the large-diameter precipitation well 210, better collect the underground seepage water and recover it through the pumping equipment 214; at the same time, multiple layers of water filtering blind ditches 216 can be set, and the longitudinal slope inclined to the large-diameter precipitation well 210 is set to be not less than 2%, which can better cut off the groundwater and collect and recover the seepage water.

[0052] As a preferred embodiment of the present invention, the precipitation well 200 is a small-diameter precipitation well 220 drilled into a well, the upper part of the well wall of the small-diameter precipitation well 220 is a watertight structure, the lower part of the well wall of the small-diameter precipitation well 220 is a water-permeable structure with seepage holes, the outer wall of the lower part of the well wall of the small-diameter precipitation well 220 is provided with an outer filter layer, the wellhead pores of the small-diameter precipitation well 220 are filled with clay for sealing the wellhead, the wellhead of the small-diameter precipitation well 220 is provided with a sealing cover plate 222, the interior of the small-diameter precipitation well 220 is provided with a pumping equipment 214, the inner diameter of the small-diameter precipitation well 220 is less than 1 meter, and the outside of the lower part of the well wall of the small-diameter precipitation well 220 is radially provided with gravel-filled filter material 224.

[0053] It should be understood that the small-diameter drainage well 220 is drilled by a drilling rig and is not restricted by the depth of the well. The inner diameter is less than 1 meter, the construction speed is fast, the cost of a single well is low, the upper part of the well wall is a watertight structure, and the lower part of the well wall is a water-permeable structure with seepage holes. The upper part can be set as a solid pipe and the lower part as a filter pipe. The small-diameter drainage well 220 can use PE pipes or stainless steel pipes. Among them, the outside of the lower part of the well wall of the small-diameter drainage well 220 can be wrapped and tied firmly with geotextile, lead wire mesh, steel wire mesh or nylon mesh according to the characteristics of the formation, and the surrounding area of ​​the lower part of the well wall is filled with gravel-filled filter material 224, and the pores in the wellhead section are filled with a certain thickness of clay and compacted to seal the well, and a sealing cover plate 222 is provided at the wellhead for sealing.

[0054] The present invention also provides a method for constructing a tailings pond seepage cutoff structure 100 of the above-mentioned seepage cutoff wall combined with a precipitation well 200, S1, obtaining information on the lithology, permeability characteristics and integrity of the bottom stratum of the tailings pond 110, obtaining information on the distribution, development, recharge source, runoff, discharge path, environmental category and corrosiveness of the surface water and groundwater of the tailings pond 110, obtaining information on the integrity of the hydrogeological units of the tailings pond 110, obtaining information on the overall flow field of the groundwater of the tailings pond 110, obtaining information on whether there is a relatively impermeable waterproof layer at the bottom of the tailings pond 110, and obtaining information on whether there is a deep or lateral leakage problem in the tailings pond 110;

[0055] S2, provide a typical geological profile of the proposed vertical cut-off wall 300, evaluate the groundwater resources in the tailings pond area, estimate the groundwater leakage and water inflow, analyze the impact of the tailings pond 110 leakage on the groundwater recharge of the site, and evaluate and determine the main impact range of the tailings pond seepage;

[0056] S3. Based on the survey results of the engineering geological conditions and hydrogeological conditions of the tailings pond site and the estimated maximum groundwater leakage value of the tailings pond, the location, number and depth of the precipitation wells are preliminarily determined, and the depth of the precipitation wells is determined according to the bedrock burial depth at different precipitation points;

[0057] S4, first build a plurality of precipitation wells 200 upstream of the location where the vertical seepage cutoff wall 300 is built, so as to timely pump back the collected seepage water and thus lower the groundwater level, and then build a vertical seepage cutoff wall 300 for seepage cutoff at a suitable location downstream of the tailings pond 110, so as to form a tailings pond seepage cutoff structure 100.

[0058] Specifically, before construction, it is necessary to conduct a detailed survey of the engineering geology and hydrogeology of the tailings pond area to determine the data such as the layout position of the vertical cut-off wall 300. At the same time, the layout point location, number and depth of the precipitation well 200 may be determined based on the survey results. The precipitation well 200 effectively collects groundwater and timely discharges and recycles the seepage water in the precipitation well 200 through pumping equipment such as water pumping or vacuum air pressure difference, so as to achieve the purpose of lowering the groundwater level. The burial depth of the precipitation well 200 is determined according to the burial depth of the bedrock at different precipitation points. In this embodiment, the depth of the bottom end of the well pipe of the precipitation well 200 extending into the underlying relatively impermeable slightly weathered bedrock layer 112 is set to be not less than 0.5 meters, and the wellhead elevation of the precipitation well 200 is 0.5 meters higher than the original ground surface line 111 elevation;

[0059] At the same time, the construction design of the precipitation well 200 is carried out before the construction of the vertical cut-off wall 300, which is beneficial to improving the construction conditions of the continuous wall 310 and the curtain grouting 320 and ensuring construction safety, and can also improve the project quality, especially the effect of the curtain grouting 320, and can also effectively reduce the later settlement deformation of the structure and the resulting structural damage.

[0060] Specifically, when the tailings pond area is a complete hydrogeological unit and the permeability coefficient of the natural bedrock at the bottom of the pond is less than 1.0×10 -7 cm / s, the tailings pond area can use the bedrock aquiclude for horizontal seepage prevention, and use a vertical cutoff wall 300 that penetrates into the relative aquiclude at an appropriate downstream position to vertically cut off seepage. At the same time, a certain number of precipitation wells 200 are set upstream of the vertical cutoff wall 300 to timely pump back and collect seepage water to lower the groundwater level, thereby forming a complete tailings pond anti-seepage system, completely cutting off the seepage discharge channel of the tailings pond, and achieving zero wastewater discharge.

[0061] In addition, the seepage cutoff structure 100 of the tailings pond with a seepage cutoff wall and a precipitation well 200 makes full use of the anti-seepage characteristics of the tailings themselves. Although the amount of seepage in the early stage of the tailings pond operation is relatively large, which makes the sewage pumping cost of the precipitation well relatively high in the short term, the sewage pumping cost will gradually decrease in the middle and late stages of operation. Compared with engineering measures such as horizontal anti-seepage at the bottom of the reservoir that require an investment of tens of millions or even hundreds of millions of yuan, the engineering investment is greatly saved. At the same time, it will not have an adverse impact on the safety of the tailings dam 120, and the environmental protection benefits, safety benefits and economic benefits are extremely significant.

[0062] It should be understood that, compared with the existing tailings pond environmental protection and anti-seepage technology, the present invention has the following outstanding advantages:

[0063] (1) Good seepage control effect, green and environmentally friendly, and relatively small project investment

[0064] Compared with the seepage cutoff measures such as the horizontal anti-seepage lining at the bottom of the reservoir, the seepage cutoff technology of the vertical seepage cutoff wall 300 combined with the precipitation well 200 has ideal effect, is green and environmentally friendly, greatly reduces the project investment, and has a relatively fast construction speed. At the same time, the construction of the tailings pond seepage cutoff structure 100 does not interfere with or affect the construction of the tailings facilities.

[0065] (2) Wide range of applications and simple maintenance

[0066] The tailings pond seepage cutoff structure 100 of the vertical seepage cutoff wall 300 combined with the precipitation well 200 is suitable for both the environmental protection management of the existing old tailings pond project and the supporting anti-seepage measures of the new tailings pond project. The precipitation well 200 can increase the service life of the seepage cutoff wall, and the number of precipitation wells 200 can be appropriately increased according to the actual seepage cutoff effect during the later operation. It is also convenient to dredge the precipitation well 200 after it is blocked and fails after a period of use, and the maintenance cost is low.

[0067] (3) Make full use of the anti-seepage characteristics of the tailings sediment layer

[0068] Compared with other environmental protection and anti-seepage measures, the investment in the infrastructure project of the tailings pond seepage interception structure 100 in the present invention is greatly reduced. Although certain pumping and drainage operating costs are required for the later operation, including the costs of pumping equipment 214, pipelines and electricity, the tailings permeability coefficient is relatively small and the tailings pond 110 has the characteristics that the amount of tailings seepage gradually decreases and finally tends to be stable as the tailings deposition beach gradually forms. Therefore, the operating costs of the precipitation well 200 are controllable during most of the operation period of the tailings pond 110.

[0069] (4) Taking into account both environmental protection and anti-seepage of the tailings pond and the safety and stability of the dam

[0070] Environmental protection and anti-seepage measures such as horizontal anti-seepage often reduce the tailings drainage and consolidation speed, raise the burial depth of the infiltration line in the tailings dam 120, and affect the safety and stability of the tailings dam 120. A vertical seepage cutoff wall 300 and a precipitation well 200 are set at a certain distance downstream of the tailings pond 110 to achieve the purpose of environmental protection and cutoff seepage without affecting the drainage and consolidation of the tailings.

[0071] Please refer to the attached Figure 1-2 , which is a structural plan layout diagram of a vertical cut-off wall 300 and a precipitation well 200 added to the downstream side of the stilling pool and return pool 150 of the tailings pond 110 in a preferred embodiment of the present invention.

[0072] A seepage cutoff dam is set downstream of the stilling pool and return pool 150, and a continuous wall 310 and curtain grouting 320 anti-seepage type are set under the dam, so as to form a vertical seepage cutoff wall 300 in the direction perpendicular to the river ditch to cut off the seepage of groundwater along the ditch as much as possible. The seepage cutoff dam adopts a C25 modified concrete gravity dam structure. The dam body consists of an overflow dam section 311 and a non-overflow dam section. The concrete surface of the seepage cutoff dam is painted with a two-component water-based epoxy resin paint or other anti-corrosion coating.

[0073] The foundation of the cut-off dam at the upper part of the vertical cut-off wall 300 is located on the upper part of the original stratum not less than 2 meters below the strongly weathered bedrock layer. The lower part of the vertical cut-off wall 300 adopts closed curtain grouting. The depth of the anti-seepage curtain at the dam foundation and the shoulders on both sides is required to reach 5 meters below the slightly weathered bedrock, i.e., the slightly permeable layer. In this embodiment, according to the engineering geological and hydrogeological conditions of the tailings pond area, two rows of grouting holes are arranged longitudinally along the axis of the cut-off dam. The grouting hole spacing is 0.8 meters, the grouting hole spacing is 1.2 meters, and the plum blossom arrangement is adopted. The depth of the second row of grouting holes is not less than 2 / 3 of the depth of the first row of grouting holes on the upstream side. The standard permeability of the cut-off curtain wall is q<10Lu.

[0074] In order to effectively reduce the groundwater level in front of the cut-off dam and prevent the structure from being soaked in water for a long time, which will accelerate corrosion and affect the environmental protection and anti-seepage effect, 8 precipitation wells 200 are arranged in front of the cut-off dam to pump out groundwater. During the later operation period, the number of precipitation wells 200 can be appropriately increased according to the amount of groundwater. The burial depth of the precipitation well 200 is determined according to the burial depth of the bedrock at different precipitation points, ranging from 9.5 meters to 19 meters. The bottom of the precipitation well 200 well pipe extends into the underlying slightly weathered granite layer for not less than 0.5 meters, and the well pipe The pipe mouth elevation should be 0.5 meters higher than the original ground line 111 elevation; the precipitation well 200 is drilled by a drilling rig, and the well pipe is composed of a solid pipe and a filter pipe. The well pipe is made of PE63 material pipe; the lower end of the well pipe is equipped with a filter pipe, which is made of PE pipe with the same diameter as the well pipe. The outer surface of the filter pipe is drilled with plum blossom-shaped holes, with an opening rate of 15% to 20%. The outside of the filter pipe is wrapped with two layers of lead wire or 80 mesh steel wire mesh and tied firmly, and then wrapped with 400g / m 2 Two layers of corrosion-resistant non-woven geotextile; the pores between the solid pipe and the well wall below the wellhead of the precipitation well 200 are filled with clay and compacted to seal the well; gravel-filled filter material 224 is set between the filter pipe and the well wall; a submersible pump is installed in the precipitation well 200 to extract groundwater to the upstream energy dissipation pool and return water pool 150.

[0075] For tailings pond projects with complex engineering geological conditions downstream of the initial dam 130 of the tailings pond, the tailings pond seepage cut-off structure 100 of the present invention can achieve better management effects, effectively collect the escaped seepage water from the tailings dam 120 and its surroundings, lower the groundwater level of the vertical seepage cut-off wall, and reduce the risk of seepage around the seepage dam shoulder. At the same time, it can greatly improve the durability of the vertical seepage cut-off wall structure itself and increase its service life. In addition, the project investment is small, the later maintenance is simple, the maintenance cost is low, and the environmental protection benefits, safety benefits and economic benefits are extremely significant.

[0076] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A tailings pond seepage cut-off structure with a seepage cut-off wall and a precipitation well, characterized in that: It includes a precipitation well and a vertical seepage cutoff wall. The vertical seepage cutoff wall is arranged at the downstream of the tailings pond. The upper part of the vertical seepage cutoff wall adopts a continuous wall, and the lower part of the vertical seepage cutoff wall adopts curtain grouting. A precipitation well seepage cut-off layer composed of a plurality of precipitation wells arranged, the precipitation well seepage cut-off layer is arranged at the downstream position of the tailings pond and upstream of the vertical seepage cut-off wall, the precipitation well is a large-diameter precipitation well formed by large excavation or a small-diameter precipitation well formed by drilling, the upper part of the well wall of the precipitation well is a water-impermeable structure, and the lower part of the well wall of the precipitation well is a water-permeable structure with seepage holes, The tailings pond includes a tailings pond seepage interception structure, a tailings dam, an initial dam, a tailings pond flood discharge structure, a drainage system, a water interception ditch, a backwater structure and a return flow structure; an energy dissipation pool and a backwater pool are arranged in the tailings pond flood discharge structure, the energy dissipation pool and the backwater pool are arranged downstream of the tailings pond, a vertical seepage interception wall is arranged downstream of the energy dissipation pool and the backwater pool, and a plurality of precipitation wells are arranged upstream of the vertical seepage interception wall. The drainage system includes drainage wells, drainage tunnels and drainage tunnel outlets. The intercepting ditch outlet is connected to the energy dissipation pool and return pool. The surface wastewater discharged from the tailings pond includes the external drainage of the drainage system inside the reservoir and the seepage of the tailings pond. The drainage system and the intercepting ditch are used to discharge the surface wastewater discharged from the tailings pond. The external drainage of the drainage system inside the reservoir and the seepage of the tailings pond are returned to the high-level water pool for recycling through the return water structure set at the energy dissipation pool and return pool in the tailings pond flood discharge structure on the downstream side of the tailings pond. The underground runoff part of the discharged wastewater is cut off by the vertical seepage wall, and the contaminated groundwater is collected through the precipitation well set upstream of the vertical seepage wall and returned to the energy dissipation pool and return pool under the dam or the tailings pond through the return structure for reuse. The upper part of the vertical cut-off wall adopts a continuous wall, and the lower part adopts a curtain grouting type. The bottom of the vertical cut-off wall and the shoulders on both sides of the wall adopt one of closed curtain grouting or suspended curtain grouting. The bottom of the vertical cut-off wall is embedded below the strongly weathered bedrock layer, and the closed curtain grouting extends to a depth of not less than 2 meters below the slightly weathered bedrock layer.

2. The seepage cut-off structure of the tailings pond with a seepage cut-off wall and a precipitation well according to claim 1, characterized in that: The surface of the vertical cut-off wall is coated with an anti-corrosion coating, and / or an anti-seepage membrane is arranged inside the continuous wall.

3. The seepage cut-off structure of the tailings pond with a seepage cut-off wall and a precipitation well according to claim 1, characterized in that: The top of the continuous wall is provided with an overflow dam section or a full dam section for drainage in emergency situations.

4. The seepage cut-off structure of the tailings pond with a seepage cut-off wall and a precipitation well according to claim 1, characterized in that: The precipitation well is a large-diameter precipitation well that is excavated on a large scale. The upper part of the well wall of the large-diameter precipitation well is a water-impermeable structure, and the lower part of the well wall of the large-diameter precipitation well is a water-permeable structure with seepage holes. The outer wall of the lower part of the well wall of the large-diameter precipitation well is provided with an outer filter layer, and the wellhead of the large-diameter precipitation well is provided with an inspection cover. Pumping equipment is provided inside the large-diameter precipitation well. The inner diameter of the large-diameter precipitation well is greater than 1 meter, and the well body height of the large-diameter precipitation well is less than 6 meters. The outer part of the lower part of the well wall of the large-diameter precipitation well is radially provided with gravel filter material.

5. The seepage cut-off structure of the tailings pond with a seepage cut-off wall and a precipitation well according to claim 4, characterized in that: The large-diameter precipitation well also includes a water filtering blind ditch radially arranged on the outer side of the lower part of the well wall, and two adjacent large-diameter precipitation wells are connected through the water filtering blind ditch; the large-diameter precipitation well also includes a gravel water interception blind ditch arranged in a direction perpendicular to the direction of groundwater flow, and the gravel water interception blind ditch is used to connect the groundwater with the large-diameter precipitation wells adjacent to it, so as to cut off and drain the groundwater to the interior of the large-diameter precipitation well.

6. The seepage cut-off structure of the tailings pond with a seepage cut-off wall and a precipitation well according to claim 1, characterized in that: The precipitation well is a small-diameter precipitation well drilled, the upper part of the well wall of the small-diameter precipitation well is a water-impermeable structure, the lower part of the well wall of the small-diameter precipitation well is a water-permeable structure with seepage holes, the outer wall of the lower part of the well wall of the small-diameter precipitation well is provided with an outer filter layer, the wellhead pores of the small-diameter precipitation well are filled with clay for sealing the wellhead, the wellhead of the small-diameter precipitation well is provided with a sealing cover plate, the interior of the small-diameter precipitation well is provided with pumping equipment, the inner diameter of the small-diameter precipitation well is less than 1 meter, and the outer part of the lower part of the well wall of the small-diameter precipitation well is radially provided with gravel-filled filter material.

7. A method for constructing a tailings pond seepage cut-off structure of a seepage cut-off wall combined with a precipitation well as described in any one of claims 1 to 6, characterized in that: The method comprises the steps of, S1, obtain information on the lithology, permeability characteristics and integrity of the strata at the bottom of the tailings pond, obtain information on the distribution, development, recharge source, runoff, discharge pathway, environmental category and corrosiveness of the surface water and groundwater of the tailings pond, obtain information on the integrity of the hydrogeological units of the tailings pond, obtain information on the overall flow field of the groundwater of the tailings pond, obtain information on whether there is a relatively impermeable aquiclude at the bottom of the tailings pond, and obtain information on whether there are deep or lateral leakage problems in the tailings pond area; S2, provide a typical geological profile of the proposed vertical seepage wall, evaluate the groundwater resources in the tailings pond area, estimate the groundwater leakage and inflow, analyze the impact of tailings pond seepage on the groundwater recharge of the site, and evaluate and determine the main impact range of tailings pond seepage; S3. Based on the survey results of the engineering geological conditions and hydrogeological conditions of the tailings pond site and the estimated maximum groundwater leakage value of the tailings pond, the location, number and depth of the precipitation wells are preliminarily determined, and the depth of the precipitation wells is determined according to the bedrock burial depth at different precipitation points; S4, first build multiple precipitation wells upstream of the location where the vertical seepage cutoff wall is built to pump back the collected seepage water in time to lower the groundwater level, and then build a vertical seepage cutoff wall for seepage cutoff at a suitable location downstream of the tailings pond to form a tailings pond seepage cutoff structure.

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