Deep permeable interlayer dam foundation anti-seepage structure and construction method

Abstract

The invention discloses a deep permeable interlayer dam foundation anti-seepage structure and a construction method. The anti-seepage structure is arranged along the axis of a dam foundation and comprises an in-situ cementing anti-seepage wall with the bottom embedded into a rock bottom plate, filling columns evenly distributed on the wall, glands covering the tops of the columns and combined with a dam body, and a curtain arranged at the bottom of the wall and continuously arranged in rock. During construction, a drill hole is drilled firstly, construction of the in-situ cementing diaphragm wall and the filling column is completed synchronously, and a gland is formed through backfilling; and then a grouting pipe is pre-buried for segmented curtain grouting. According to the invention, a multilayer anti-seepage system of'surface plugging-deep cutting-bottom seepage prevention 'is constructed, a deep permeable channel can be effectively cut off, and uplift pressure and seepage flow are reduced. And by dynamically adjusting the stirring and grouting process, disturbance to upper-layer soil rock is reduced, the continuity and reliability of an anti-seepage body and the overall stability of a dam foundation are improved, and good construction controllability and economical efficiency are achieved.

Description

Technical Field

[0001] This invention belongs to the field of dam foundation seepage prevention technology in water conservancy engineering, and relates to a deep permeable interlayer dam foundation seepage prevention structure, as well as a construction method for the deep permeable interlayer dam foundation seepage prevention structure. Background Technology

[0002] In the field of dam construction for water conservancy projects, the seepage prevention performance of the dam foundation is a core key indicator for ensuring the structural integrity of the dam and the long-term safe and stable operation of the project. During actual construction, some dam foundations contain deep permeable interlayers. These interlayers serve as the main channels for groundwater infiltration, easily leading to abnormal groundwater seepage and triggering a series of safety hazards to the dam foundation. These hazards can cause abnormal increases in uplift pressure and seepage exceeding design control standards, and may even induce serious seepage damage disasters such as piping and soil erosion, directly threatening the structural safety of the dam and even affecting the normal operation of the entire water conservancy project and the public safety of the surrounding area.

[0003] Currently, the mainstream technologies used for seepage prevention in water conservancy dam foundations are conventional curtain grouting and cutoff wall construction. However, these technologies still have significant shortcomings in complex geological conditions such as deep permeable interlayers. First, while conventional cutoff wall technology can penetrate deep permeable interlayers and reach the stable rock base, its construction depth is limited, the workload is large, and construction risks such as borehole collapse are prone to occur during drilling. In addition, it can damage the structure of the upper rock (soil) layers, potentially creating new anti-sliding stability hazards and affecting the overall stability of the dam foundation. Second, curtain grouting technology has poor adaptability to permeable interlayers such as gravel layers. The grout spreads unevenly in complex strata, easily leading to material waste, and the continuity and reliability of the formed cutoff curtain are difficult to guarantee, resulting in unstable seepage prevention effects.

[0004] In summary, there is currently a lack of dedicated and efficient anti-seepage structures and supporting construction methods for deep permeable interlayer dam foundations. Existing technologies cannot achieve a good balance between reliability, economy, and ease of construction, thus limiting the effectiveness of anti-seepage treatment for dam foundations under such geological conditions. Therefore, there is an urgent need to develop a new technical solution that is highly adaptable, has reliable anti-seepage performance, and is easy to construct, in order to fill the current technological gap and improve the overall quality and safety of dam foundation anti-seepage projects. Summary of the Invention

[0005] The purpose of this invention is to provide a deep permeable interlayer dam foundation seepage prevention structure, which solves the problems of easy collapse of holes, poor seepage prevention effect and low efficiency in the existing technology.

[0006] Another objective of this invention is to provide a construction method for a deep permeable interlayer dam foundation seepage prevention structure.

[0007] The technical solution adopted in this invention is a deep permeable interlayer dam foundation seepage prevention structure. This seepage prevention structure is arranged longitudinally along the dam foundation axis and includes an in-situ cemented seepage prevention wall. The bottom of the in-situ cemented seepage prevention wall is embedded in a rock base plate. Several filling columns are evenly distributed longitudinally on the top of the in-situ cemented seepage prevention wall. The top of the filling columns is covered with a cap. The top surface of the cap is tightly bonded to the bottom of the dam body. A curtain is also continuously arranged at the bottom of the in-situ cemented seepage prevention wall. The curtain is located in the rock base plate.

[0008] The features of this invention are:

[0009] The in-situ cemented cutoff wall is set inside the dam foundation. The top of the in-situ cemented cutoff wall is located in the upper weak permeable layer, and the bottom extends to and is located in the bottom fissured permeable layer. The main body of the in-situ cemented cutoff wall penetrates the deep permeable interlayer. The bottom of the curtain is embedded in the weakly permeable layer below the rock base, and the two ends of the curtain extend and are anchored in the impermeable rock layers on both sides of the dam foundation.

[0010] The top of the in-situ cemented seepage barrier wall shall be at least 1.0m higher than the bottom line of the upper weak permeable layer, and the bottom shall be embedded in the bottom fissure permeable layer to a depth of at least 1.0m.

[0011] Adjacent filling columns are isolated from each other, and the in-situ cemented seepage barrier wall, filling columns, curtain and cap are connected to each other to form a continuous seepage prevention structure system extending from the bottom of the dam body down to the deep part of the rock floor.

[0012] The in-situ cemented seepage barrier wall is formed into a continuous wall through an in-situ mixing and cementing process, using cement-bentonite-fly ash composite cement as the cementing material; the filling column is filled with bentonite slurry; the curtain is formed through a grouting process, using ultrafine cement slurry as the grouting material; the cap is cast with bentonite slurry, extending laterally to cover the filling column, and is cast integrally with the filling column and the bottom of the dam body.

[0013] In-situ cemented seepage prevention walls are divided into first-order walls, second-order walls, and third-order walls according to the construction sequence.

[0014] Another technical solution adopted in this invention is a construction method for a deep permeable interlayer dam foundation seepage prevention structure, comprising the following steps: Step 1: Conduct geological surveys along the dam foundation axis to determine the distribution of strata and the rock base, and level the site. Step 2: Drill holes on the dam foundation axis to carry out the separate construction of the in-situ cemented seepage barrier and the filling column. After the construction of the in-situ cemented seepage barrier is completed, while pulling out the construction equipment, backfill the filling column with bentonite slurry to the set elevation to form a pressure cap. Step 3: When the in-situ cemented seepage barrier wall is initially set, pre-embed curtain grouting pipes and inject ultrafine cement slurry through the curtain grouting pipes using a segmented process to form a curtain. Step 4: Conduct seepage prevention performance testing on the in-situ cemented seepage prevention wall and curtain.

[0015] The invention is further characterized by: Step 2 includes the following steps: Step 201: Mark the construction position of the in-situ cemented seepage barrier wall, fix the frame at the construction position of the cemented seepage barrier wall, adjust and start the drill bit, and use the casing to drill synchronously and in sections to the rock bottom line. At the same time, inject wall protection mud during the drilling process. Step 202: After reaching the predetermined depth, extend the mixing rod, inject the cement-bentonite-fly ash composite binder and mix it. During the mixing process, adjust the extension and retraction length of the mixing rod according to the thickness of the in-situ cemented seepage prevention wall. Step 203: First, construct multiple first-order walls distributed at intervals, then construct the second-order wall located between two adjacent first-order walls, and finally construct the third-order wall located between the first-order wall and the second-order wall. The interval between adjacent construction orders shall not be less than 72 hours, and the overlap width of adjacent walls shall not be less than 20 centimeters. Step 204: After the wall construction is completed, slowly lift the casing and drill bit, and simultaneously inject bentonite slurry into the borehole to form a filling column; Step 205: Backfill the filling column with bentonite slurry to the set elevation to form a cap.

[0016] Step 3 specifically includes the following steps: Step 301: Before the initial setting of the in-situ cemented seepage barrier wall, pre-embed the curtain grouting pipes at intervals into the boreholes and extend them into the bottom of the in-situ cemented seepage barrier wall. The spacing between the curtain grouting pipes is 1.5-3m. Step 302: Ultrafine cement slurry is injected into the borehole in sections through pre-embedded grouting pipes to form a curtain.

[0017] In step 4, a borehole water pressure test is used to check the seepage prevention performance. The test pressure is 1.5 times the design head, and the seepage flow rate is required to be less than 1×10⁻⁶. - The structural integrity of the seepage barrier wall was tested using ultrasonic waves at a speed of 6 cm / s.

[0018] The beneficial effects of this invention are: This invention relates to a deep permeable interlayer dam foundation seepage prevention structure. Through the synergistic action of in-situ cemented seepage prevention walls, filling columns, caps, and curtains, a multi-layered seepage prevention structure is constructed, consisting of "surface sealing - deep interception - bottom seepage prevention." This structure effectively penetrates the deep permeable interlayer and reaches the stable rock base, completely cutting off the main seepage channels of groundwater, significantly reducing uplift pressure and seepage flow in the dam foundation, and preventing seepage damage. This invention employs a coordinated operation of grouting pipes and drill bits, dynamically adjusting the mixing range according to the hydraulic gradient and geological characteristics of the permeable interlayer. This ensures uniform diffusion and full cementation of the cementing material in complex strata, resulting in a tight fit between the seepage prevention structure and the surrounding soil and rock mass, improving the continuity, reliability, and durability of the seepage prevention body. Furthermore, by setting small-diameter boreholes at intervals in the upper soil layer, precise seepage prevention treatment is directly applied to the deep permeable interlayer, minimizing disturbance and damage to the upper weakly permeable layer and the overall soil and rock structure, avoiding new anti-sliding stability risks, thereby ensuring and improving the overall stability of the dam foundation.

[0019] The present invention discloses a construction method for a deep permeable interlayer dam foundation seepage prevention structure. It adopts a phased construction process, such as three-phase in-situ cemented seepage prevention wall construction and three-phase curtain grouting construction. Combined with the coordinated operation of drill bit and grouting pipe, it optimizes the construction process in deep and complex strata, effectively reduces the risk of borehole collapse and construction difficulty, and improves construction efficiency, wall quality and overall project controllability. It achieves a good balance between reliability, economy and construction convenience. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the overall structure of the deep permeable interlayer dam foundation seepage prevention structure of the present invention; Figure 2 This is a schematic cross-sectional view of the deep permeable interlayer dam foundation seepage prevention structure of the present invention; Figure 3 This is a construction sequence diagram of the in-situ cemented seepage prevention wall of the deep permeable interlayer dam foundation seepage prevention structure of the present invention; Figure 4 This is a schematic diagram of the calculation of the in-situ cemented seepage barrier wall of the deep permeable interlayer dam foundation seepage barrier structure of the present invention; Figure 5 This is a top view of the deep permeable interlayer dam foundation seepage prevention structure of the present invention; Figure 6 This is a construction sequence diagram of the curtain grouting for the deep permeable interlayer dam foundation seepage prevention structure of the present invention.

[0021] In the diagram, 1. In-situ cemented seepage barrier wall; 1-1. First-order wall; 1-2. Second-order wall; 1-3. Third-order wall; 2. Filling column; 3. Curtain; 4. Overhead cap; 5. Upper weakly permeable layer; 6. Deep permeable interlayer; 7. Bottom fissure permeable layer; 8. Bottom weakly permeable layer; 9. Curtain grouting pipe; 9-1. First-order grouting pipe; 9-2. Second-order grouting pipe; 9-3. Third-order grouting pipe. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] Example 1 Deep permeable interlayer dam foundation seepage prevention structure, such as Figure 1 As shown, the seepage prevention structure is arranged longitudinally along the dam foundation axis, including an in-situ cemented seepage prevention wall 1. The bottom of the in-situ cemented seepage prevention wall 1 is embedded in the rock base plate. Several filling columns 2 are evenly distributed longitudinally on the top of the in-situ cemented seepage prevention wall 1. The top of the filling columns 2 is covered with a pressure cap 4. The top surface of the pressure cap 4 is tightly bonded to the bottom of the dam body. A curtain 3 is also continuously arranged at the bottom of the in-situ cemented seepage prevention wall 1. The curtain 3 is located in the rock base plate.

[0024] Example 2 Based on the deep permeable interlayer dam foundation seepage prevention structure provided in Example 1, the deep permeable interlayer dam foundation seepage prevention structure provided in this example is as follows: Figure 2 As shown, the in-situ cemented seepage barrier 1 is set inside the dam foundation. The top of the in-situ cemented seepage barrier 1 is located in the upper weakly permeable layer 5, and the bottom extends to and is located in the bottom fissured permeable layer 7. The main body of the in-situ cemented seepage barrier 1 penetrates the deep permeable interlayer 6. The bottom of the curtain 3 is embedded in the bottom weakly permeable layer 8 below the rock base. The two ends of the curtain 3 extend and are anchored in the impermeable rock layers on both sides of the dam foundation.

[0025] The top of the in-situ cemented cutoff wall 1 is at least 1.0m higher than the bottom line of the upper weakly permeable layer 5, and the bottom is embedded in the bottom fissured permeable layer 7 to a depth of at least 1.0m. Adjacent filling columns 2 are isolated from each other. The in-situ cemented cutoff wall 1, filling columns 2, curtain 3 and pressure cap 4 are interconnected to form a continuous seepage prevention structure system extending from the bottom of the dam body down to the deep part of the rock floor.

[0026] Example 3 Based on the deep permeable interlayer dam foundation seepage prevention structure provided in Example 2, the deep permeable interlayer dam foundation seepage prevention structure provided in this example uses an in-situ cemented seepage prevention wall 1, which forms a continuous wall through an in-situ mixing and cementing process, and the cementing material used is a cement-bentonite-fly ash composite cementitious material; the filling column 2 is filled with bentonite slurry; the curtain 3 is formed through a grouting process, and the grouting material used is ultrafine cement slurry; the cap 4 is cast using bentonite slurry, and the cap 4 extends laterally to cover the filling column 2, and is cast integrally with the filling column 2 and the bottom of the dam body. Figure 3 As shown, the in-situ cemented seepage barrier 1 is divided into three sections according to the construction sequence: the first section wall 1-1, the second section wall 1-2, and the third section wall 1-3.

[0027] Example 4 To ensure the continuity and reliability of the wall, the effective thickness of the wall is generally not less than 60cm, and the overlap width of adjacent walls is not less than 20cm. Based on the deep permeable interlayer dam foundation seepage prevention structure provided in Example 3, a specific explanation is given with a maximum design head of 25 meters for the dam and a dam foundation section length of 80 meters to be treated.

[0028] This seepage control structure uses an in-situ cemented cutoff wall as the core seepage barrier, which is arranged along the dam axis with a total length of 80 meters. The effective thickness of the wall is designed to be 0.6 meters to ensure sufficient seepage resistance and structural stability under a design water head of 25 meters. The wall is formed by overlapping cement-soil mixing piles, with each pile having a design diameter of 1.0 meter and a length of 0.8 meters. A 0.2-meter overlap width is set between adjacent piles to ensure the overall continuity and seepage control reliability of the wall. In this embodiment, a total of 100 pile holes are constructed within the 80-meter treatment area. The pile holes are arranged sequentially, and through the overlapping of the piles, a continuous, complete, and uniformly thick in-situ cemented cutoff wall is finally formed, thereby achieving the engineering objectives of sealing deep permeable interlayers, controlling seepage, and ensuring the stability of the dam foundation.

[0029] The seepage-proof structure provided in this embodiment has the following geometric relationship between the effective wall thickness T and the overlap width X: Figure 4 As shown, the specific value is determined by the following formula:

[0030]

[0031]

[0032]

[0033] In the formula, T is the effective thickness of the in-situ cemented seepage barrier wall, in meters; H 水 The maximum design head is m; J is the allowable permeability gradient of the cutoff wall, taken as 50; K is the safety factor, with a value of 1.1-1.3; D is the diameter of the mixing pile, m; L1 is the length of a single mixing pile, m; X is the overlap width of adjacent mixing piles, m.

[0034] Example 5 Based on the deep permeable interlayer dam foundation seepage prevention structure provided in any of Examples 1-4, the construction method of the deep permeable interlayer dam foundation seepage prevention structure provided in this example includes the following steps: Step 1: Conduct geological surveys along the dam foundation axis to determine the distribution of strata and the rock base, and level the site. Step 2: Drill holes on the dam foundation axis to carry out the separate construction of the in-situ cemented seepage barrier 1 and the filling column 2. After the construction of the in-situ cemented seepage barrier 1 is completed, while pulling out the construction equipment, backfill the filling column 2 with bentonite slurry to the set elevation to form the pressure cap 4. The pressure cap 4 and the filling column 2 are cast as one piece to increase the bonding surface with the dam body and eliminate the impact of settlement of bentonite slurry inside the filling column 2. Step 3: When the in-situ cemented seepage barrier wall 1 is initially set, pre-embed curtain grouting pipe 9, and inject ultrafine cement slurry through the curtain grouting pipe 9 using a segmented process to form curtain 3. Step 4: Conduct seepage prevention performance tests on the in-situ cemented seepage barrier wall 1 and curtain wall 3.

[0035] Example 6 Based on the construction method of the deep permeable interlayer dam foundation seepage prevention structure provided in Example 5, step 2 of the construction method of the deep permeable interlayer dam foundation seepage prevention structure provided in this example includes the following steps: Step 201: Mark the construction position of the in-situ cemented seepage barrier wall 1, fix the frame at the construction position of the cemented seepage barrier wall 1, adjust and start the drill bit, and use the casing to drill synchronously and in sections to the bottom of the rock plate. At the same time, inject wall protection mud during the drilling process. Step 202: After reaching the predetermined depth, extend the mixing rod, inject the cement-bentonite-fly ash composite binder and mix it. During the mixing process, adjust the extension and retraction length of the mixing rod according to the thickness of the in-situ cemented seepage prevention wall 1. Step 203, as follows Figure 2 As shown, first construct multiple first-order walls 1-1 with intervals, then construct second-order walls 1-2 located between two adjacent first-order walls 1-1, and finally construct third-order walls 1-3 located between first-order walls 1-1 and second-order walls 1-2. The interval between adjacent construction orders shall not be less than 72 hours, and the overlap width of adjacent walls shall not be less than 20 centimeters. Step 204: After the wall construction is completed, slowly raise the casing and drill bit, and simultaneously inject bentonite slurry into the borehole to form filling column 2, as shown. Figure 5 As shown, the filling columns 2 are spaced apart; Step 205: Backfill bentonite slurry into the filling column 2 to the set elevation to form the cap 4.

[0036] This embodiment employs the drill bit structure disclosed in the utility model patent application "Drilling and Mixing Device for Deep Permeable Interlayer Cutoff Wall" filed on the same day as this application. In this embodiment, the filling columns 2 are spaced apart, ensuring that the upper weakly permeable layer 5 retains its primary seepage-proof function. The filling columns 2 intersect the original soil of the upper weakly permeable layer 5, and by pre-setting structured permeable channels in the upper weakly permeable layer at intervals, rather than completely replacing or sealing it, the naturally distributed weakly permeable layer is utilized to the maximum extent as the main seepage barrier, significantly reducing the cost of complete replacement or laying of a fully enclosed artificial cutoff membrane; and avoiding damage to the engineering foundation or the cutoff layer itself caused by water pressure accumulation.

[0037] Example 7 Based on the construction method of the deep permeable interlayer dam foundation seepage prevention structure provided in Example 6, step 3 of the construction method of the deep permeable interlayer dam foundation seepage prevention structure provided in this example specifically includes the following steps: Step 301, as follows Figure 6 As shown, before the initial setting of the in-situ cemented cutoff wall 1, the curtain grouting pipes 9 are pre-embedded in the boreholes at intervals. The borehole diameter is 50-80cm, the depth is at least 5m into the bottom weakly permeable layer 8, and they extend into the bottom of the in-situ cemented cutoff wall 1. The spacing of the curtain grouting pipes 9 is 1.5-3m; Figure 6 As shown, for the in-situ cemented seepage barrier wall 1 with an effective thickness of 0.6m-1.0m, the curtain grouting pipe 9 is arranged in the third-order wall 1-3; Step 302: Ultrafine cement grout is injected into the borehole in sections through pre-embedded grouting pipes to form curtain 3; as Figure 6 As shown, the segmented arrangement of the curtain grouting pipes 9 must meet the interval requirements of the first sequence grouting pipe 9-1, the second sequence grouting pipe 9-2, and the third sequence grouting pipe 9-3. The grouting pressure range is 1.5-2.0 MPa. After each segment of grouting is completed, the grout should be allowed to set for at least 48 hours before the next segment is grouted to ensure that the grout fully diffuses and fills the cracks. After grouting is completed, the grouting holes are sealed with cement mortar to ensure the integrity of the curtain 3. In step 4, a borehole water pressure test is used to check the seepage prevention performance. The test pressure is 1.5 times the design head, and the seepage flow rate is required to be less than 1×10⁻⁶. - The structural integrity of the seepage barrier wall was tested using ultrasonic waves at a speed of 6 cm / s.

Claims

1. A deep permeable interlayer dam foundation seepage prevention structure, characterized in that, The seepage prevention structure is arranged longitudinally along the dam foundation axis, including an in-situ cemented seepage prevention wall (1). The bottom of the in-situ cemented seepage prevention wall (1) is embedded in the rock base plate. Several filling columns (2) are evenly distributed longitudinally on the top of the in-situ cemented seepage prevention wall (1). The top of the filling columns (2) is covered with a cap (4). The top surface of the cap (4) is tightly connected to the bottom of the dam body. A curtain (3) is also continuously arranged at the bottom of the in-situ cemented seepage prevention wall (1). The curtain (3) is located in the rock base plate.

2. The deep permeable interlayer dam foundation seepage prevention structure according to claim 1, characterized in that, The in-situ cemented seepage barrier (1) is set in the dam foundation. The top of the in-situ cemented seepage barrier (1) is located in the upper weak permeable layer (5), and the bottom extends to and is located in the bottom fissured permeable layer (7). The main body of the in-situ cemented seepage barrier (1) penetrates the deep permeable interlayer (6). The bottom of the curtain (3) is embedded in the bottom weakly permeable layer (8) below the rock base plate, and the two ends of the curtain (3) extend and are anchored in the impermeable rock layers on both sides of the dam foundation.

3. The deep permeable interlayer dam foundation seepage prevention structure according to claim 2, characterized in that, The top of the in-situ cemented seepage barrier (1) is not less than 1.0m above the bottom line of the upper weak permeable layer (5), and the bottom is embedded in the bottom fissure permeable layer (7) to a depth of not less than 1.0m.

4. The deep permeable interlayer dam foundation seepage prevention structure according to claim 1, characterized in that, The adjacent filling columns (2) are isolated from each other, and the in-situ cemented seepage barrier wall (1), filling columns (2), curtain (3) and cap (4) are connected to each other to form a continuous seepage barrier structure system extending from the bottom of the dam body down to the deep part of the rock base.

5. The deep permeable interlayer dam foundation seepage prevention structure according to claim 1, characterized in that, The in-situ cemented seepage barrier (1) is formed into a continuous wall through an in-situ mixing and cementing process, and the cementing material used is a cement-bentonite-fly ash composite cementitious material; the filling column (2) is filled with bentonite slurry; the curtain (3) is formed through a grouting process, and the grouting material used is ultrafine cement slurry; the cap (4) is cast with bentonite slurry, and the cap (4) extends horizontally to cover the filling column (2), and is cast as a whole with the filling column (2) and the bottom of the dam.

6. The deep permeable interlayer dam foundation seepage prevention structure according to claim 1, characterized in that, The in-situ cemented seepage barrier (1) is divided into a first-order wall (1-1), a second-order wall (1-2), and a third-order wall (1-3) according to the construction sequence.

7. A construction method for a deep permeable interlayer dam foundation seepage prevention structure, characterized in that, Includes the following steps: Step 1: Conduct geological surveys along the dam foundation axis to determine the distribution of strata and the rock base, and level the site. Step 2: Drill holes on the dam foundation axis and carry out separate construction of the in-situ cemented seepage barrier (1) and the filling column (2). After the construction of the in-situ cemented seepage barrier (1) is completed, bentonite slurry is backfilled into the filling column (2) to the set elevation while the construction equipment is pulled out to form a pressure cap (4). Step 3: When the in-situ cemented seepage barrier wall (1) is initially set, a curtain grouting pipe (9) is pre-embedded. Ultrafine cement grout is injected through the curtain grouting pipe (9) using a segmented process to form a curtain (3). Step 4: Conduct seepage prevention performance tests on the in-situ cemented seepage barrier wall (1) and curtain wall (3).

8. The construction method of the deep permeable interlayer dam foundation seepage prevention structure according to claim 7, characterized in that, Step 2 includes the following steps: Step 201: Mark the construction position of the in-situ cemented anti-seepage wall (1), fix the frame at the construction position of the cemented anti-seepage wall (1), adjust and start the drill bit, and use the casing to drill synchronously and in sections to the bottom of the rock plate. At the same time, inject the wall protection mud during the drilling process. Step 202: After reaching the predetermined depth, extend the stirring rod, inject the cement-bentonite-fly ash composite binder and stir. During the stirring process, adjust the extension and retraction length of the stirring rod according to the thickness of the in-situ cemented seepage prevention wall (1). Step 203: First, construct multiple first-order walls (1-1) spaced apart. Then, construct the second-order wall (1-2) located between two adjacent first-order walls (1-1). Finally, construct the third-order wall (1-3) located between the first-order wall (1-1) and the second-order wall (1-2). The interval between adjacent construction orders shall not be less than 72 hours, and the overlap width of adjacent walls shall not be less than 20 cm. Step 204: After the wall construction is completed, slowly lift the casing and drill bit, and simultaneously inject bentonite slurry into the borehole to form a filling column (2). Step 205: Backfill the filling column (2) with bentonite slurry to the set elevation to form a cap (4).

9. The construction method of the deep permeable interlayer dam foundation seepage prevention structure according to claim 7, characterized in that, Step 3 specifically includes the following steps: Step 301: Before the initial setting of the in-situ cemented seepage barrier wall (1), the curtain grouting pipes (9) are pre-embedded in the borehole at intervals and extended into the bottom of the in-situ cemented seepage barrier wall (1). The spacing of the curtain grouting pipes (9) is 1.5-3m. Step 302: Ultrafine cement slurry is injected into the borehole in sections through pre-embedded grouting pipes to form a curtain (3).

10. The construction method of the deep permeable interlayer dam foundation seepage prevention structure according to claim 7, characterized in that, In step 4, a borehole water pressure test is used to check the seepage prevention performance. The test pressure is 1.5 times the design head, and the seepage flow rate is required to be less than 1×10⁻⁶. -6 The structural integrity of the seepage barrier wall was tested using ultrasonic waves at a speed of cm / s.

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