Dam seepage prevention structure with water permeable interlayer and construction method

Abstract

The application relates to a dam anti-seepage structure for a water-permeable interlayer, which comprises an anti-seepage wall arranged in a shallow water-permeable interlayer anti-seepage area, horizontal drilling arranged in a deep water-permeable interlayer anti-seepage area, horizontal grouting of the deep water-permeable interlayer anti-seepage area through the horizontal drilling to form a horizontal grouting area, one end of the anti-seepage wall close to the deep water-permeable interlayer extending into the deep water-permeable interlayer anti-seepage area, and an anti-seepage wall piercing wall arranged at the one end of the anti-seepage wall extending into the deep water-permeable interlayer anti-seepage area, and the connection part of the deep water-permeable interlayer and the shallow water-permeable interlayer being connected by the anti-seepage wall piercing wall extending into the horizontal grouting area. The application is designed in cooperation of the shallow anti-seepage area and the deep anti-seepage area, the shallow area adopts the anti-seepage wall, the deep area adopts the horizontal grouting through the directional drilling equipment, the sealing property of the connection part is enhanced by the anti-seepage wall piercing wall, the weak link of the anti-seepage caused by the non-close connection and the insufficient depth of the conventional anti-seepage wall is effectively avoided, and the geological conditions of the long deep water-permeable interlayer are adapted.

Description

Technical Field

[0001] This invention belongs to the field of dam seepage prevention technology in water conservancy projects, and relates to dam seepage prevention structures for permeable interlayers. This invention also relates to construction methods for dam seepage prevention structures for permeable interlayers. Background Technology

[0002] In the construction of water conservancy dams, deep and long permeable interlayers often lead to a large amount of seepage around the dam, and their seepage prevention performance directly affects the overall structural safety of the dam and the realization of the project benefits.

[0003] Existing seepage prevention technologies for permeable interlayers mainly include curtain grouting zones and conventional cutoff walls. However, conventional technologies have many shortcomings when dealing with the complex geological conditions of long and deep permeable interlayers: First, conventional cutoff walls are difficult to adapt to slope topography and have limited depth. Although they can partially penetrate the permeable interlayer, they are not tightly connected with the surrounding rock strata and the main dam structure, which can easily create weak links in seepage prevention. Second, the curtain grouting zone of long permeable interlayers on the bank slope requires the construction of a relatively long grouting zone tunnel, especially in cases where there is seepage around the dam in the valley, the tunnel needs to be even longer, resulting in large investments. Third, the construction process causes significant disturbance to other rock strata, which can easily damage the overall stability and increase construction safety risks.

[0004] Currently, there is still a technological gap in the development of specialized anti-seepage structures for long and deep permeable interlayers. There is an urgent need to develop an anti-seepage structure for deep permeable interlayer dams that is adaptable to the terrain of long and deep interlayers, has reliable anti-seepage effect, is easy to construct, and can work in synergy with the main dam body for anti-seepage, so as to solve the shortcomings of existing technologies. Summary of the Invention

[0005] The purpose of this invention is to provide a dam seepage prevention structure for permeable interlayers. It adopts a collaborative design of shallow and deep seepage prevention zones. The shallow layer uses a seepage prevention wall, while the deep layer is grouted horizontally using directional drilling equipment. Combined with the seepage prevention wall's reinforcement to enhance the sealing of the connection points, it effectively avoids the weak links in seepage prevention caused by the loose connection and insufficient depth of conventional seepage prevention walls, and is suitable for geological conditions of long and deep permeable interlayers.

[0006] The technical solution adopted in this invention is a dam seepage prevention structure for permeable interlayers, comprising setting a seepage barrier wall in the seepage prevention zone of the shallow permeable interlayer, setting horizontal boreholes in the seepage prevention zone of the deep permeable interlayer, and horizontally grouting the deep permeable interlayer seepage prevention zone through the horizontal boreholes to form a horizontal grouting zone. One end of the seepage barrier wall near the deep permeable interlayer extends into the deep permeable interlayer seepage prevention zone, and a seepage barrier spike is provided at the end of the seepage barrier wall extending into the deep permeable interlayer seepage prevention zone. The connection between the deep permeable interlayer and the shallow permeable interlayer is connected by the seepage barrier spike extending into the horizontal grouting zone.

[0007] Preferably, the horizontal boreholes are installed in the seepage prevention zone of the deep permeable interlayer as follows: The distribution of the deep permeable interlayer seepage prevention zone between the deep permeable interlayers is divided into upstream and downstream sections: downstream grouting zone, upstream grouting zone, and axial grouting zone. The downstream grouting zone and upstream grouting zone are located on the downstream side and upstream side, respectively, and the axial grouting zone is located between the downstream grouting zone and the upstream grouting zone. Horizontal drilling is performed in the downstream grouting zone to obtain downstream grouting sequence one holes and downstream grouting sequence two holes, specifically arranged as follows: In the downstream grouting zone, multiple downstream grouting sequence holes and downstream grouting sequence holes are arranged alternately from bottom to top along the thickness direction of the deep permeable interlayer. The cracks in the downstream grouting sequence holes and downstream grouting sequence holes spread outward to form the downstream grouting diffusion zone. The length direction of the downstream grouting sequence holes and downstream grouting sequence holes is the dam axis direction, that is, the horizontal direction. Horizontal boreholes were drilled in the upstream grouting zone to obtain upstream grouting sequence one boreholes and upstream grouting sequence two boreholes, specifically arranged as follows: In the upstream grouting zone, multiple upstream grouting sequence holes and upstream grouting sequence holes are arranged alternately from bottom to top along the thickness direction of the deep permeable interlayer. The cracks in the upstream grouting sequence holes and upstream grouting sequence holes spread outward to form the upstream grouting diffusion zone. The length direction of the upstream grouting sequence holes and upstream grouting sequence holes is horizontal. Horizontal drilling was performed in the axial grouting zone to obtain the first and second sequence axial grouting holes, arranged as follows: In the axial grouting zone, multiple axial grouting sequence holes and axial grouting sequence holes are arranged alternately from bottom to top in the thickness direction of the deep permeable interlayer, that is, vertically. The length direction of the axial grouting sequence holes and axial grouting sequence holes is horizontal. Furthermore, the downstream grouting sequence holes and the downstream grouting sequence holes are vertically aligned with the upstream grouting sequence holes and the upstream grouting sequence holes, and the axial grouting sequence holes or the axial grouting sequence holes are located between two adjacent downstream grouting sequence holes and downstream grouting sequence holes.

[0008] Preferably, the vertical spacing between the downstream grouting sequence holes and the downstream grouting sequence holes in the downstream grouting zone is not less than 1.0m, the distance between the top hole and the upper boundary of the permeable interlayer in the downstream grouting zone is not less than 10cm, and the distance between the bottom hole and the lower boundary of the permeable interlayer in the downstream grouting zone is not less than 10cm. The top hole and the bottom hole are either the downstream grouting sequence holes or the downstream grouting sequence holes. When arranged alternately in the upper and lower sections, the downstream grouting sequence holes and the downstream grouting sequence holes that are closest to the lower boundary of the permeable interlayer are the bottom holes in the downstream grouting zone, and the holes that are closest to the upper boundary of the permeable interlayer are the top holes in the downstream grouting zone. The diameter of the downstream grouting sequence holes and the downstream grouting sequence holes is 12cm to 15cm.

[0009] Preferably, the vertical spacing between the first and second grouting holes in the upstream grouting zone is not less than 1.0m, the distance between the top hole in the upstream grouting zone and the upper boundary of the permeable interlayer is not less than 10cm, the distance between the bottom hole in the upstream grouting zone and the lower boundary of the permeable interlayer is not less than 10cm, and the diameter of the first and second grouting holes in the upstream grouting zone is 8cm to 12cm. When arranged alternately in the upper and lower sections, the hole closest to the lower boundary of the permeable interlayer in the first and second grouting holes in the upstream grouting zone is the bottom hole in the upstream grouting zone, and the hole closest to the upper boundary of the permeable interlayer is the top hole in the upstream grouting zone.

[0010] Preferably, the vertical spacing between the first and second grouting holes in the axial grouting zone is not less than 1.0m, and the diameter of the first and second grouting holes is 12cm to 15cm.

[0011] Preferably, the seepage barrier includes a seepage barrier body with a thickness of not less than 0.6m, the bottom of the seepage barrier body is located 50cm below the lower boundary of the permeable interlayer, and the top of the seepage barrier body is connected to the dam body by reinforced concrete, and the reinforced concrete connection strength is not less than C25.

[0012] Preferably, the horizontal drilling line consists of an entry inclined section, a curved section, and a horizontal straight section, with a turning radius of approximately 1000 to 2000 times the horizontal drilling diameter; Inside the main body of the seepage barrier, there are reserved guide holes arranged through steel pipes. The diameter of the reserved guide holes is 15-20cm. The direction of the reserved guide holes is the curved section of the horizontal drilling line, and the turning radius is about 1000-3000 times the diameter of the horizontal drilling hole, which is 150m-600m.

[0013] The second technical solution adopted in this invention is a construction method for a dam seepage prevention structure using a permeable interlayer, which is implemented according to the following steps: Step 1: Determine the boundaries of the deep permeable interlayer seepage prevention zone and the shallow permeable interlayer seepage prevention zone; Step 2: Divide the dam into upper and lower sections according to the upper boundary of the permeable interlayer. First, construct the lower section of the dam as a construction platform for the seepage barrier layer, and place the directional drilling rig and grouting equipment on the construction platform for the seepage barrier layer. Step 3: Construct a seepage barrier wall in the shallow permeable interlayer seepage barrier zone; Step 4: Drill horizontal holes in the deep permeable interlayer seepage prevention zone, and then inject cement mortar to form the corresponding grouting diffusion zone. After completion, dismantle the directional drilling rig and grouting equipment. Step 5: Construct the upper part of the dam.

[0014] Preferably, in step 3, when constructing the anti-seepage wall in the shallow permeable interlayer anti-seepage zone, the two ends of the main body of the anti-seepage wall are extended to the corresponding side of the deep permeable interlayer anti-seepage zone, and anti-seepage wall spikes are constructed at the upper and lower ends of the main body of the anti-seepage wall corresponding to the thickness direction of the deep permeable interlayer. The anti-seepage wall spikes are connected to the deep permeable interlayer anti-seepage zone by grouting. Furthermore, during the construction of the main body of the anti-seepage wall, guide holes are reserved inside the main body of the anti-seepage wall through the construction of steel pipes.

[0015] Preferably, step 4 specifically involves: the drill rod of the directional drilling equipment extending into the deep permeable interlayer through the pre-reserved guide hole; sequentially constructing the upstream grouting sequence hole and the upstream grouting sequence hole of the downstream grouting zone 1, the axial grouting sequence hole and the axial grouting sequence hole of the axial grouting zone 3, and the upstream grouting sequence hole and the upstream grouting sequence hole of the upstream grouting zone; after drilling is completed, the area is first rinsed with clean water, and then cement mortar is injected to form the grouting diffusion zone; When flushing the upstream grouting sequence one hole, the upstream grouting sequence two hole, the axial grouting sequence one hole and the axial grouting sequence two hole, first use a water pump to inject clean water into the drill pipe, with a pressure not exceeding 0.8MPa, and flush until the return water is clear; When flushing the upstream grouting sequence one hole and the upstream grouting sequence two hole, use a water pump to inject clean water into the drill pipe at a pressure not exceeding 1MPa, and flush until the return water is clear. Step 5 specifically involves: after performing curtain grouting on the dam foundation, constructing the upper part of the dam to complete the overall seepage prevention system.

[0016] The beneficial effects of this invention are: (1) This invention has strong adaptability and can be adapted to complex terrain with long and deep permeable interlayers and seepage conditions near valleys and around dams, solving the adaptability shortcomings of conventional seepage prevention technologies, specifically: This invention employs a collaborative design of shallow and deep seepage prevention zones. The shallow seepage prevention wall adapts to the terrain of the dam foundation slope, with its bottom extending 50cm below the lower boundary of the permeable interlayer and its top tightly connected to the dam body. The deep layer utilizes directional drilling equipment for horizontal grouting, with the hole diameter, spacing, and arrangement of each grouting zone precisely matching the range of the permeable interlayer. Safety distances are reserved at both the top and bottom, and the seepage prevention wall's reinforcement enhances the sealing of the connection points. This effectively avoids weak seepage prevention links caused by loose connections and insufficient depth in conventional seepage prevention walls, making it suitable for various complex geological conditions involving long and deep permeable interlayers.

[0017] (2) The present invention has a reliable seepage prevention effect, achieving all-round and deep sealing of long and deep permeable interlayers, and significantly reducing the risk of seepage around the dam, specifically: This invention features a deep permeable interlayer with three grouting zones: downstream, upstream, and axial. These zones are arranged with alternating first-order and second-order holes. The grouting diffusion zone can fully fill the fissures in the permeable interlayer and the gaps between the grouting zones, forming a continuous and complete deep seepage barrier. The shallow seepage barrier wall serves both seepage prevention and guiding functions, working in conjunction with the deep grouting zone to form a dual seepage prevention system. This system can completely block the seepage channels of groundwater around the dam, significantly improving the reliability of the dam's seepage prevention and ensuring the long-term stable operation of the dam structure.

[0018] (3) The present invention is easy to construct and causes little disturbance to the surrounding rock strata, thus reducing construction safety risks, specifically: Compared to conventional curtain grouting, which requires the excavation of long tunnels, this invention uses directional drilling equipment to perform horizontal drilling grouting through pre-reserved guide holes, eliminating the need for large-scale excavation and significantly reducing investment costs. During construction, the borehole is first flushed with clean water before cement mortar is injected, minimizing disturbance to the surrounding rock strata and avoiding damage to the overall stability of the rock formation. The directional drilling equipment can be dismantled and reused after construction, further reducing construction costs, simplifying the construction process, reducing construction difficulty and safety risks, and improving construction efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the dam seepage prevention structure for permeable interlayers according to the present invention; Figure 2 yes Figure 1 Section 2-2; Figure 3 yes Figure 1 Section 3-3; Figure 4 yes Figure 1 Section 4-4; Figure 5 yes Figure 3 A magnified view of a section at point A in the middle; Figure 6 yes Figure 5 Section 5-5; Figure 7 This is a plan view of the connection between the seepage barrier wall and the grouting zone in the dam seepage prevention structure of the present invention used for permeable interlayer; Figure 8 This is a schematic diagram of the anti-seepage wall in the dam anti-seepage structure of the permeable interlayer of the present invention.

[0020] In the diagram: 1. Downstream grouting zone, 2. Upstream grouting zone, 3. Axis grouting zone, 4. Cutoff wall, 5. Reserved pilot hole, 6. Dam, 7. Directional drilling rig and grouting equipment, 8. Dam foundation curtain, 10. Original ground line, 11. Rock boundary line, 12. Upper boundary of permeable interlayer, 13. Lower boundary of permeable interlayer, 14. Boundary line of weakly weathered rock, 15. Original ground line, 16. Excavation line; 1-1. Downstream grouting sequence hole 1-2. Downstream grouting sequence hole 2-3. Downstream grouting diffusion zone; 2-1. Upstream grouting sequence hole 1-2. Upstream grouting sequence hole 2-3. Upstream grouting diffusion zone; 3-1. Axis grouting sequence hole 1-2. Axis grouting sequence hole 2-3. Axis grouting diffusion zone; 4-1. Main body of the seepage barrier wall; 4-2. Seepage barrier wall piercing wall. Detailed Implementation

[0021] The following detailed description is provided in conjunction with specific implementation methods.

[0022] Example 1 Based on the stratigraphic characteristics, the main stratigraphic feature lines are described as follows: from top to bottom, the elevation lines are: 10. Ground line, 11. Rock boundary line, 12. Upper boundary of permeable interlayer, 13. Lower boundary of permeable interlayer, 14. Boundary line of weakly weathered rock, 15. Original ground line, and 16. Excavation line. Based on this, the present invention is used for seepage prevention structures in dams with permeable interlayers, such as... Figure 1-4 As shown, this includes setting up a cutoff wall 4 in the shallow permeable interlayer seepage prevention zone, and setting up horizontal boreholes in the deep permeable interlayer seepage prevention zone. Horizontal grouting is then performed through these boreholes to form a horizontal grouting zone in the deep permeable interlayer seepage prevention zone. One end of the cutoff wall 4, closest to the deep permeable interlayer, extends into the deep permeable interlayer seepage prevention zone. Figure 7 and 8 As shown, the end of the seepage barrier wall 4 that extends into the seepage barrier zone of the deep permeable interlayer is provided with a seepage barrier wall spike 4-2, and the connection between the deep permeable interlayer and the shallow permeable interlayer is connected by the seepage barrier wall spike 4-2 extending into the horizontal grouting zone.

[0023] Example 2 Based on Example 1, the horizontal boreholes in the deep permeable interlayer seepage prevention zone are specifically designed as follows: like Figure 1 , 2 As shown in Figures 3, 5, and 6, Figure 1 for Figure 5 The 1-1 cross-sectional view shows the distribution of the deep permeable interlayer seepage prevention zone between the deep permeable interlayers, divided into upstream and downstream sections: downstream grouting zone 1, upstream grouting zone 2, and axial grouting zone 3. Downstream grouting zone 1 and upstream grouting zone 2 are located on the downstream and upstream sides, respectively, while axial grouting zone 3 is located between downstream grouting zone 1 and upstream grouting zone 2. Downstream grouting zone 1 is located on the downstream side and its main function is to provide support for the entire grouting zone. Upstream grouting zone 2 is located on the upstream side of axial grouting zone 3 and its main function is to improve seepage prevention capacity. Axis grouting zone 3 is located on the upstream side of downstream grouting zone 1 and its main function is to improve seepage prevention capacity and fill the gap between downstream grouting zone 1 and upstream grouting zone 2. Horizontal drilling was performed in downstream grouting zone 1 to obtain downstream grouting sequence hole 1-1 and downstream grouting sequence hole 1-2, specifically arranged as follows: In the downstream grouting zone 1, multiple downstream grouting sequence holes 1-1 and downstream grouting sequence holes 1-2 are arranged alternately from bottom to top in the thickness direction of the deep permeable interlayer. The cracks in the downstream grouting sequence holes 1-2 and downstream grouting sequence holes 1-1 diffuse outward to form the downstream grouting diffusion zone 1-3. The length direction of the downstream grouting sequence holes 1-2 and downstream grouting sequence holes 1-1 is the dam axis direction, that is, the horizontal direction. Horizontal drilling was performed in upstream grouting zone 2 to obtain upstream grouting sequence hole 2-1 and upstream grouting sequence hole 2-2, specifically arranged as follows: In the upstream grouting zone 2, multiple upstream grouting sequence holes 2-1 and upstream grouting sequence holes 2-2 are arranged alternately from bottom to top in the thickness direction of the deep permeable interlayer. The cracks in the upstream grouting sequence holes 2-1 and upstream grouting sequence holes 2-2 diffuse outward to form the upstream grouting diffusion zone 2-3. The length direction of the upstream grouting sequence holes 2-1 and upstream grouting sequence holes 2-2 is horizontal. Horizontal drilling was performed in axial grouting zone 3 to obtain axial grouting sequence hole 3-1 and axial grouting sequence hole 3-2, as follows: In the axial grouting zone 3, the thickness direction of the deep permeable interlayer is vertically arranged from bottom to top with multiple axial grouting sequence holes 3-1 and axial grouting sequence holes 3-2. The length direction of the axial grouting sequence holes 3-1 and axial grouting sequence holes 3-2 is horizontal. Furthermore, the downstream grouting sequence hole 1-1 and the downstream grouting sequence hole 1-2 are vertically corresponding to the upstream grouting sequence hole 2-1 and the upstream grouting sequence hole 2-2, and the axial grouting sequence hole 3-1 or the axial grouting sequence hole 3-2 is located between two adjacent downstream grouting sequence holes 1-1 and downstream grouting sequence holes 1-2.

[0024] Example 3 Based on Example 2, the vertical spacing between the downstream grouting sequence hole 1-1 and the downstream grouting sequence hole 1-2 in the downstream grouting zone 1 is not less than 1.0m. The distance between the top hole and the upper boundary 12 of the permeable interlayer in the downstream grouting zone 1 is not less than 10cm. The distance between the bottom hole and the lower boundary 13 of the permeable interlayer in the downstream grouting zone 1 is not less than 10cm. The top hole and the bottom hole are either the downstream grouting sequence hole 1-1 or the downstream grouting sequence hole 1-2. When arranged alternately, the downstream grouting sequence hole 1-1 and the downstream grouting sequence hole 1-2 that is closest to the lower boundary 13 of the permeable interlayer is the bottom hole in the downstream grouting zone 1, and the one that is closest to the upper boundary 12 of the permeable interlayer is the top hole in the downstream grouting zone 1. The diameter of the downstream grouting sequence hole 1-1 and the downstream grouting sequence hole 1-2 is 12cm to 15cm.

[0025] The vertical spacing between the upstream grouting sequence hole 2-1 and the upstream grouting sequence hole 2-2 in the upstream grouting zone 2 shall not be less than 1.0m. The distance between the top hole in the upstream grouting zone 2 and the upper boundary 12 of the permeable interlayer shall not be less than 10cm. The distance between the bottom hole in the upstream grouting zone 2 and the lower boundary 13 of the permeable interlayer shall not be less than 10cm. The diameter of the upstream grouting sequence hole 2-1 and the upstream grouting sequence hole 2-2 shall be 8cm to 12cm. When the holes are arranged alternately in the upper and lower sections, the hole closest to the lower boundary 13 of the permeable interlayer in the upstream grouting zone 2 is the bottom hole in the upstream grouting zone 2, and the hole closest to the upper boundary 12 of the permeable interlayer is the top hole in the upstream grouting zone 2.

[0026] The vertical spacing between the first grouting hole 3-1 and the second grouting hole 3-2 in the axial grouting zone 3 is not less than 1.0m, and the diameter of the first grouting hole 3-1 and the second grouting hole 3-2 is 12cm to 15cm.

[0027] Example 4 Based on Example 3, the seepage barrier 4 is arranged with a shallow permeable interlayer as the dam foundation. Its first function is to provide a reserved guide hole 5 for the directional drill rod, and its second function is to prevent seepage in the stratum where it is located. The seepage barrier 4 includes a seepage barrier body 4-1 with a thickness of not less than 0.6m. The bottom of the seepage barrier body 4-1 is located 50cm below the lower boundary of the permeable interlayer 13. The top of the seepage barrier body 4-1 is connected to the dam body by reinforced concrete, and the strength of the reinforced concrete connection is not less than C25.

[0028] The horizontal drilling route consists of an inclined entry section, a curved section, and a horizontal straight section, with a turning radius of approximately 1000 to 2000 times the horizontal borehole diameter. Inside the main body 4-1 of the seepage barrier wall, there are reserved guide holes 5 arranged through steel pipes. The diameter of the reserved guide holes 5 is 15-20cm. The direction of the reserved guide holes 5 is the curved section of the horizontal drilling line. The turning radius is about 1000-3000 times the diameter of the horizontal drilling hole, and is 150m-600m.

[0029] Example 5 Based on Example 4, this invention divides the dam 6 into upper and lower parts: the lower dam 6-1 and the upper dam 6-2. Taking a gravity dam as an example, the vertical segmentation of the dam 6 is slightly higher than the upper boundary 12 of the permeable interlayer. The lower dam 6-1 mainly provides a platform for constructing the seepage prevention layer. Subsequently, the upper dam 6-2 is constructed according to the original design. The directional drilling rig and grouting equipment 7 are temporary construction facilities, arranged above the lower dam 6-1. After the deep horizontal seepage prevention section is completed, the equipment is dismantled and reused later. The main parameters of the directional drilling rig are determined according to the seepage prevention depth, as shown in Table 1. Table 1

[0030] The present invention relates to a construction method for a dam seepage prevention structure with a permeable interlayer, which is implemented according to the following steps: Step 1: Determine the boundaries of the deep permeable interlayer seepage prevention zone and the shallow permeable interlayer seepage prevention zone; Step 2: According to the upper boundary 12 of the permeable interlayer, the dam 6 is divided into the upper part 6-2 and the lower part 6-1. The lower part 6-1 is constructed first as the construction platform for the seepage prevention layer. The directional drilling rig and grouting equipment 7 are arranged on the construction platform for the seepage prevention layer. Step 3: Construct the seepage barrier wall 4 in the shallow permeable interlayer seepage barrier zone; Step 4: Drill horizontal holes in the deep permeable interlayer seepage prevention zone, and then inject cement mortar to form the corresponding grouting diffusion zone. After completion, dismantle the directional drilling rig and grouting equipment 7. Step 5, construct the upper part of the dam 6-2.

[0031] Example 6 Based on Example 5, in step 3, when constructing the anti-seepage wall 4 in the shallow permeable interlayer anti-seepage zone, the two ends of the anti-seepage wall body 4-1 are extended to the corresponding side of the deep permeable interlayer anti-seepage zone, and the anti-seepage wall spikes 4-2 are constructed at the upper and lower ends of the anti-seepage wall body 4-1 corresponding to the thickness direction of the deep permeable interlayer. The anti-seepage wall spikes 4-2 are connected to the deep permeable interlayer anti-seepage zone through grouting liquid. Furthermore, during the construction of the main body 4-1 of the anti-seepage wall, a guide hole 5 is reserved inside the main body 4-1 of the anti-seepage wall by constructing a steel pipe.

[0032] Step 4 is as follows: The drill rod of the directional drilling equipment extends into the deep permeable interlayer through the reserved guide hole 5. In the seepage prevention zone, the upstream grouting sequence hole 2-1 and the upstream grouting sequence hole 2-2 of the downstream grouting zone 1, the axial grouting sequence hole 3-1 and the axial grouting sequence hole 3-2 of the axial grouting zone 3, and the upstream grouting sequence hole 2-1 and the upstream grouting sequence hole 2-2 of the upstream grouting zone 2 are constructed in sequence. After drilling is completed, the area is first rinsed with clean water and then cement mortar is injected to form the grouting diffusion zone. When flushing the upstream grouting sequence hole 2-1, the upstream grouting sequence hole 2-2, the axial grouting sequence hole 3-1 and the axial grouting sequence hole 3-2, first use a water pump to inject clean water into the drill rod, with a pressure not exceeding 0.8MPa, and flush until the return water is clear; When flushing upstream grouting sequence hole 2-1 and upstream grouting sequence hole 2-2, use a water pump to inject clean water into the drill pipe at a pressure not exceeding 1MPa, and flush until the return water is clear. Step 5 specifically involves: performing grouting of the dam foundation curtain to form the dam foundation curtain 8, followed by construction of the upper part of the dam 6-2, thus completing the overall seepage prevention system construction.

Claims

1. A dam seepage prevention structure for permeable interlayers, characterized in that, The method includes setting up a seepage barrier wall (4) in the seepage barrier zone of the shallow permeable interlayer, setting up horizontal boreholes in the seepage barrier zone of the deep permeable interlayer, and performing horizontal grouting in the seepage barrier zone of the deep permeable interlayer through the horizontal boreholes to form a horizontal grouting zone. The seepage barrier wall (4) extends into the seepage barrier zone of the deep permeable interlayer at one end near the deep permeable interlayer, and a seepage barrier spike wall (4-2) is set at the end of the seepage barrier wall (4) extending into the seepage barrier zone of the deep permeable interlayer. The connection between the deep permeable interlayer and the shallow permeable interlayer is connected by the seepage barrier spike wall (4-2) extending into the horizontal grouting zone.

2. The dam seepage prevention structure for permeable interlayers according to claim 1, characterized in that, The specific method for setting up horizontal boreholes in the deep permeable interlayer seepage prevention zone is as follows: The distribution of the deep permeable interlayer seepage prevention zone between the deep permeable interlayers is divided into the following categories according to upstream and downstream: downstream grouting zone (1), upstream grouting zone (2), and axial grouting zone (3). The downstream grouting zone (1) and upstream grouting zone (2) are located on the downstream side and upstream side, respectively, and the axial grouting zone (3) is located between the downstream grouting zone (1) and the upstream grouting zone (2). Horizontal drilling was performed in the downstream grouting zone (1) to obtain the downstream grouting sequence hole (1-1) and the downstream grouting sequence hole (1-2), which were specifically arranged as follows: The downstream grouting zone (1) has multiple downstream grouting sequence holes (1-1) and downstream grouting sequence holes (1-2) arranged alternately from bottom to top in the thickness direction of the deep permeable interlayer. The cracks in the downstream grouting sequence holes (1-2) and downstream grouting sequence holes (1-1) diffuse outward to form the downstream grouting diffusion zone (1-3). The length direction of the downstream grouting sequence holes (1-2) and downstream grouting sequence holes (1-1) is the dam axis direction, which is the horizontal direction. Horizontal drilling was carried out in the upstream grouting zone (2) to obtain the upstream grouting sequence hole (2-1) and the upstream grouting sequence hole (2-2), which were specifically arranged as follows: The thickness direction of the deep permeable interlayer in the upstream grouting zone (2) is that multiple upstream grouting sequence holes (2-1) and upstream grouting sequence holes (2-2) are arranged alternately from bottom to top in the vertical direction. The cracks of the upstream grouting sequence holes (2-1) and upstream grouting sequence holes (2-2) diffuse outward to form the upstream grouting diffusion zone (2-3). The length direction of the upstream grouting sequence holes (2-1) and upstream grouting sequence holes (2-2) is horizontal. Horizontal drilling is performed in the axial grouting zone (3) to obtain the first axial grouting sequence hole (3-1) and the second axial grouting sequence hole (3-2), which are specifically arranged as follows: The thickness direction of the deep permeable interlayer in the axial grouting zone (3) is that multiple axial grouting sequence holes (3-1) and axial grouting sequence holes (3-2) are arranged alternately from bottom to top in the vertical direction. The length direction of the axial grouting sequence holes (3-1) and axial grouting sequence holes (3-2) is horizontal. Furthermore, the downstream grouting sequence hole (1-1) and the downstream grouting sequence hole (1-2) are vertically corresponding to the upstream grouting sequence hole (2-1) and the upstream grouting sequence hole (2-2). The axial grouting sequence hole (3-1) or the axial grouting sequence hole (3-2) is located between two adjacent downstream grouting sequence holes (1-1) and downstream grouting sequence holes (1-2).

3. The dam seepage prevention structure for permeable interlayers according to claim 2, characterized in that, The vertical distance between the downstream grouting zone (1) and the downstream grouting sequence hole (1-1) and the downstream grouting sequence hole (1-2) is not less than 1.0m. The distance between the top hole and the upper boundary (12) of the permeable interlayer in the downstream grouting zone (1) is not less than 10cm. The distance between the bottom hole and the lower boundary (13) of the permeable interlayer in the downstream grouting zone (1) is not less than 10cm. The top hole and the bottom hole are either the downstream grouting sequence hole (1-1) or the downstream grouting sequence hole (1-2). When the downstream grouting sequence holes (1-2) are arranged alternately, the one closest to the lower boundary (13) of the permeable interlayer among the downstream grouting sequence holes (1-1) and the one closest to the upper boundary (12) of the permeable interlayer is the top hole in the downstream grouting zone (1). The diameter of the downstream grouting sequence holes (1-1) and the downstream grouting sequence holes (1-2) is 12cm to 15cm.

4. The dam seepage prevention structure for permeable interlayers according to claim 3, characterized in that, The vertical distance between the upstream grouting zone (2) and the upstream grouting first sequence hole (2-1) and the upstream grouting second sequence hole (2-2) is not less than 1.0m. The distance between the top hole in the upstream grouting zone (2) and the upper boundary (12) of the permeable interlayer is not less than 10cm. The distance between the bottom hole in the upstream grouting zone (2) and the lower boundary (13) of the permeable interlayer is not less than 10cm. The diameter of the upstream grouting first sequence hole (2-1) and the upstream grouting second sequence hole (2-2) is 8cm to 12cm. When the arrangement is alternating between the upper and lower parts, the upstream grouting first sequence hole (2-1) and the upstream grouting second sequence hole (2-2) that is closest to the lower boundary (13) of the permeable interlayer is the bottom hole in the upstream grouting zone (2), and the one that is closest to the upper boundary (12) of the permeable interlayer is the top hole in the upstream grouting zone (2).

5. The dam seepage prevention structure for permeable interlayers according to claim 4, characterized in that, The vertical spacing between the first grouting hole (3-1) and the second grouting hole (3-2) in the axial grouting zone (3) is not less than 1.0m, and the diameter of the first grouting hole (3-1) and the second grouting hole (3-2) is 12cm to 15cm.

6. The dam seepage prevention structure for permeable interlayers according to claim 5, characterized in that, The seepage barrier (4) includes a seepage barrier body (4-1), the thickness of the seepage barrier body (4-1) is not less than 0.6m, the bottom of the seepage barrier body (4-1) is located 50cm below the lower boundary (13) of the permeable interlayer, and the top of the seepage barrier body (4-1) is connected to the dam body by reinforced concrete, and the reinforced concrete connection strength is not less than C25.

7. The dam seepage prevention structure for permeable interlayers according to claim 6, characterized in that, The horizontal drilling route consists of an inclined entry section, a curved section, and a horizontal straight section, with a turning radius of approximately 1000 to 2000 times the horizontal borehole diameter. The main body (4-1) of the anti-seepage wall has a reserved guide hole (5) arranged in a steel pipe. The diameter of the reserved guide hole (5) is 15-20cm. The direction of the reserved guide hole (5) is the curved section of the horizontal drilling line, and the turning radius is about 1000-3000 times the diameter of the horizontal drilling hole.

8. A construction method for a dam seepage prevention structure using a permeable interlayer, characterized in that, The specific steps are as follows: Step 1: Determine the boundaries of the deep permeable interlayer seepage prevention zone and the shallow permeable interlayer seepage prevention zone; Step 2: According to the upper boundary (12) of the permeable interlayer, the dam (6) is divided into the upper part (6-2) and the lower part (6-1). The lower part (6-1) is constructed first as the construction platform for the seepage prevention layer. The directional drilling rig and grouting equipment (7) are arranged on the construction platform for the seepage prevention layer. Step 3, construct the seepage barrier wall in the shallow permeable interlayer seepage barrier zone (4); Step 4: Drill horizontal holes in the deep permeable interlayer seepage prevention zone, and then inject cement mortar to form the corresponding grouting diffusion zone. After completion, dismantle the directional drilling rig and grouting equipment (7). Step 5, construct the upper part of the dam (6-2).

9. The construction method for a dam seepage prevention structure using a permeable interlayer according to claim 8, characterized in that, In step 3, when constructing the anti-seepage wall (4) in the shallow permeable interlayer anti-seepage zone, the two ends of the anti-seepage wall body (4-1) are extended to the deep permeable interlayer anti-seepage zone on the corresponding side, and the anti-seepage wall spikes (4-2) are constructed at the upper and lower ends of the anti-seepage wall body (4-1) in the thickness direction of the deep permeable interlayer. The anti-seepage wall spikes (4-2) are connected to the deep permeable interlayer anti-seepage zone through grouting liquid. Furthermore, during the construction of the main body of the anti-seepage wall (4-1), a guide hole (5) is reserved inside the main body of the anti-seepage wall (4-1) through the construction of steel pipe.

10. The construction method for a dam seepage prevention structure using a permeable interlayer according to claim 9, characterized in that, Step 4 is as follows: The drill rod of the directional drilling equipment extends into the deep permeable interlayer through the reserved guide hole (5). In the seepage prevention zone, the upstream grouting sequence hole (2-1) and the upstream grouting sequence hole (2-2) of the downstream grouting zone 1, the axial grouting sequence hole (3-1) and the axial grouting sequence hole (3-2) of the axial grouting zone 3, and the upstream grouting sequence hole (2-1) and the upstream grouting sequence hole (2-2) of the upstream grouting zone (2) are constructed in sequence. After drilling is completed, the hole is first rinsed with clean water and then cement mortar is injected to form the grouting diffusion zone. When flushing the upstream grouting sequence hole (2-1), the upstream grouting sequence hole (2-2), the axial grouting sequence hole (3-1), and the axial grouting sequence hole (3-2), first use a water pump to inject clean water into the drill rod, with a pressure not exceeding 0.8MPa, and flush until the return water is clear; When flushing the upstream grouting sequence hole (2-1) and the upstream grouting sequence hole (2-2), use a water pump to inject clean water into the drill pipe at a pressure not exceeding 1MPa, and flush until the return water is clear. Step 5 specifically involves: after grouting the dam foundation curtain, constructing the upper part of the dam (6-2) to complete the construction of the overall seepage prevention system.

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