Binary geological dike deep mixing pile composite anti-seepage system and construction method thereof

Abstract

The application provides a binary geological embankment deep mixing pile composite anti-seepage system and a construction method thereof, and relates to the technical field of dam anti-seepage. The upper layer of the binary geology is silty clay or silt, and the lower layer is medium-coarse sand or gravel. The composite anti-seepage system is continuously arranged along the extension direction of the embankment, and sequentially comprises an embankment body anti-seepage layer, a vertical anti-seepage curtain layer, an embankment foundation reinforcement layer and a filter drainage layer from the water side to the backwater side. The embankment body anti-seepage layer comprises a composite geomembrane laid on the surface of the embankment body on the water side of the embankment and a clay inclined wall laid outside the composite geomembrane. The application has the beneficial effect that the deep mixing pile of the combined pile type of the biaxial wet method and the uniaxial dry method is adopted according to the layered characteristics of the binary geology, that is, the upper soft soil layer is uniformly mixed and has good anti-seepage effect, and the lower hard soil layer has strong penetrability and can effectively intercept the seepage of the strong water-permeable layer; meanwhile, the double-layer deformation is coordinated through the cushion layer to avoid uneven embankment foundation settlement.

Description

Technical Field

[0001] This invention relates to the field of dam seepage prevention technology, and in particular to a composite seepage prevention system for deep mixing piles in binary geological dams and its construction method. Background Technology

[0002] The binary geological structure is a common type of embankment foundation in embankment engineering. Its typical characteristics are that the upper layer is silty clay and silt from the floodplain facies, which has low permeability but is easy to soften and has poor resistance to deformation; the lower layer is medium-coarse sand and gravel from the riverbed facies, which has high permeability and bearing capacity but is prone to forming concentrated seepage channels. The interface between the two layers is prone to horizontal seepage, which can lead to seepage damage such as piping, soil erosion, and embankment slope sliding, seriously threatening the safety of embankment engineering.

[0003] Currently, for seepage prevention treatment of embankments with dual geological structures, existing technologies mostly adopt single seepage prevention measures or simple combinations, such as setting up only deep mixing pile vertical seepage prevention curtains, laying composite geomembranes alone, or using clay inclined walls. These technologies have many drawbacks: First, a single deep mixing pile curtain is difficult to adapt to the differences in soil properties between the two layers. The soft soil layer is unevenly mixed and has poor seepage prevention effect, while the hard soil layer has insufficient penetration and cannot effectively cut off the seepage of the lower highly permeable layer. Second, using only seepage prevention on the embankment body (such as clay inclined walls or geomembranes) without reinforcing the embankment foundation and coordinating with drainage can easily lead to uneven settlement of the embankment foundation, causing cracking of the embankment body and failure of the seepage prevention structure.

[0004] In existing technologies, some solutions combine clay inclined walls with high-pressure jet grouting walls to address seepage issues in double-layered embankment foundations. However, high-pressure jet grouting walls have high construction costs and poor forming quality in soft soil layers, easily leading to uneven wall structure and loose overlaps. Other solutions employ deep-mixing composite walls, but these do not optimize parameters such as pile type and cement content based on the layered characteristics of binary geology, nor do they incorporate a coordinated reverse-filtration drainage structure, failing to completely resolve the risk of piping and the coordination of double-layer deformation. Therefore, there is an urgent need for a composite seepage prevention system and its construction method that can adapt to the characteristics of binary geological structures, achieve integrated seepage prevention and reinforcement, have tight connections, be easy to construct, and have controllable costs, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0005] In view of this, embodiments of the present invention provide a deep mixing pile composite seepage prevention system for binary geological embankments and its construction method, which is used to solve the technical problem of poor adaptability of deep mixing composite walls to binary geology in the prior art.

[0006] Embodiments of the present invention provide a composite seepage prevention system for deep mixing piles in a binary geological embankment. The upper layer of the binary geological embankment is silty clay or silt, and the lower layer is medium-coarse sand or gravel. The composite seepage prevention system is continuously arranged along the extension direction of the embankment, and sequentially includes, from the water-facing side to the backwater side, the following components: The dike body has a seepage-proof layer, a vertical seepage-proof curtain layer, a dike foundation reinforcement layer, and a reverse filter drainage layer; The seepage-proof layer of the embankment includes a composite geomembrane laid on the surface of the embankment on the water-facing side and a clay inclined wall laid on the outside of the composite geomembrane, with the bottom of the clay inclined wall extending to the top of the vertical seepage-proof curtain layer. The vertical seepage-proof curtain layer includes multiple deep mixing piles continuously arranged along the embankment axis. The multiple deep mixing piles are continuously overlapped to form a seepage-proof wall. Each deep mixing pile penetrates the upper layer and is embedded in the bottom impermeable layer of the lower layer. The deep mixing piles adopt a biaxial wet mixing method in the upper layer and a uniaxial dry mixing method in the lower layer. The embankment reinforcement layer is arranged inside the embankment on the backwater side of the vertical seepage prevention curtain layer, and includes a reinforced mixing pile foundation and a mattress layer laid on top of the reinforced mixing pile foundation. The reverse filter drainage layer is arranged on the backwater side of the dike foundation reinforcement layer and at the backwater slope toe of the dike, and includes a reverse filter pressure platform and a drainage pressure relief well.

[0007] Furthermore, the composite geomembrane is an HDPE geomembrane, which is continuously laid from top to bottom along the slope of the embankment, and the overlap is welded by hot melt welding; the clay sloping wall is made of silty clay laid in layers and compacted, and the bottom of the clay sloping wall is connected to the top of the vertical seepage prevention curtain layer through clay grooves, and the joint is filled with sealing mortar.

[0008] Furthermore, the cement grout is used as the solidification material for the deep mixing pile. The cement content is different between the upper soft soil layer and the lower sandy soil layer. After multiple cement grouts solidify, a seepage barrier is formed.

[0009] Furthermore, HDPE membrane units are installed between adjacent deep mixing piles of the vertical seepage-proof curtain layer. A counterweight is installed at the bottom of the HDPE membrane unit. The HDPE membrane units are connected by a coupling lock with a water-stop strip and embedded in the deep mixing pile.

[0010] Furthermore, a geomembrane groove is provided at the junction of the composite geomembrane of the embankment seepage prevention layer and the vertical seepage prevention curtain layer, and one end of the composite geomembrane is embedded in the geomembrane groove and fixed.

[0011] Furthermore, the foundation of the reinforced mixing piles of the embankment reinforcement layer is constructed simultaneously with the deep mixing piles of the vertical seepage prevention curtain layer. The pile type is consistent with the pile type of the corresponding soil layer of the vertical seepage prevention curtain layer. The cushion layer is laid with crushed stone and compacted.

[0012] Furthermore, the reverse filter pressure infiltration platform is divided into multiple layers of reverse filter material from top to bottom, and a permeable pipe is installed inside the drainage pressure relief well, with the permeable pipe wrapped with a geotextile reverse filter layer.

[0013] Furthermore, the toe of the clay sloping wall is protected by a masonry toe block.

[0014] The construction method for deep mixing pile composite seepage prevention in binary geological embankments includes the following steps: S1. Construction preparation; S2. Vertical seepage prevention curtain layer construction: Locate pile positions along the embankment axis. For the upper silty clay or silt layer, use a twin-axis wet mixing pile machine for construction. For the lower medium-coarse sand or gravel layer, use a single-axis dry mixing pile machine for construction to form a continuously overlapping seepage prevention wall and ensure that the deep mixing piles penetrate the upper layer and embed into the bottom impermeable layer of the lower layer. S3. Construction of the embankment foundation reinforcement layer: reinforcement mixing pile foundation is arranged on the backwater side of the vertical seepage prevention curtain layer. The pile type is consistent with the soil layer corresponding to the vertical seepage prevention curtain layer. After the construction is completed, a cushion layer is laid on the top of the pile. S4. Construction of reverse filter drainage layer: Lay reverse filter pressure platform and arrange drainage pressure well on the back water side of the dike foundation reinforcement layer and at the back water slope toe of the dike. S5. Construction of the seepage prevention layer of the dike: A composite geomembrane is laid on the slope of the dike on the water-facing side of the dike. A clay inclined wall is laid on the outside of the composite geomembrane, and the bottom of the clay inclined wall is extended to the top of the vertical seepage prevention curtain layer to achieve connection. S6. Quality inspection and finalization.

[0015] Furthermore, in step S2, during the construction of biaxial wet mixing piles, clean water is injected during the drilling process, and after reaching the designed pile bottom elevation, the drill rod is lifted and cement slurry is injected; during the construction of uniaxial dry mixing piles, dry cement powder is added during the drilling process, and the pile is stirred again during the lifting process; before the initial setting of the mixing pile curing material, the prefabricated HDPE film unit is vertically lowered into the mixing pile.

[0016] 1. The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: The deep mixing pile composite seepage prevention system and its construction method for binary geological embankments of the present invention, which is designed for the layered characteristics of binary geology with soft upper layer and hard lower layer, and weak upper layer and strong lower layer, adopts a deep mixing pile with a combination of biaxial wet method and uniaxial dry method. The upper soft soil layer is uniformly mixed and has a good seepage prevention effect, while the lower hard soil layer has strong penetration and can effectively cut off the seepage of the strong permeable layer; at the same time, the double-layer deformation is coordinated by the cushion layer to avoid uneven settlement of the embankment foundation, thus solving the problem of poor adaptability of the existing technology.

[0017] 2. This invention achieves a tight connection between various seepage prevention layers and reinforcement layers through structures such as clay grooves, sealing mortar, and geomembrane grooves; the combination of HDPE membrane units and deep mixing piles further improves the seepage prevention performance and durability of the vertical seepage prevention curtain, avoids seepage leaks at the joints, and solves the defects of unreasonable connection in the existing technology.

[0018] 3. The deep mixing pile solidification material of the present invention is suitable for layered soil properties, has high strength and strong impermeability. The composite structure of HDPE membrane and mixing pile improves the chemical erosion resistance of the seepage prevention curtain. The reverse filter drainage layer can maintain smooth drainage for a long time, effectively extending the service life of the dike seepage prevention system. Compared with the existing solutions, the service life is extended. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the binary geological embankment deep mixing pile composite seepage prevention system and its construction method of the present invention; Figure 2 This is the present invention. Figure 1 Enlarged view of the structure at point A in the middle; Figure 3 This is a schematic diagram of the HDPE membrane unit of the present invention.

[0020] 1. Dike body seepage prevention layer; 101. Composite geomembrane; 102. Clay inclined wall; 103. Geomembrane groove; 104. Sealing mortar; 105. Clay groove; 106. Masonry toe; 2. Vertical seepage prevention curtain layer; 201. Biaxial wet mixing pile; 202. Uniaxial dry mixing pile; 203. Waterstop; 204. HDPE membrane unit; 205. Counterweight block; 3. Dike foundation reinforcement layer; 301. Cushion layer; 302. Reinforced mixing pile foundation; 4. Reverse filter drainage layer; 401. Reverse filter pressure platform; 4011. Medium sand layer; 4012. Coarse sand layer; 4013. Gravel layer; 402. Drainage pressure relief well; 5. Upper layer; 6. Lower layer. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described below with reference to the accompanying drawings. The following description presents a preferred embodiment of the various possible embodiments of the present invention, intended to provide a basic understanding of the invention, but not intended to identify key or decisive elements of the invention or to limit the scope of protection sought.

[0022] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0023] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0024] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures. Also, it should be understood that, for ease of description, the dimensions of the various parts shown in the figures are not drawn to actual scale.

[0025] In the description of this invention, it should be noted that the circuits, electronic components and modules involved in this invention are all prior art, which can be fully implemented by those skilled in the art, and need not be elaborated upon. The content protected by this invention does not involve improvements to the internal structure and method.

[0026] It should be further noted that, unless otherwise explicitly specified and limited, the terms "installation" and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0027] like Figure 1-3 As shown, this embodiment provides a deep mixing pile composite seepage prevention system suitable for dikes with binary geological structures. The dike foundation has a typical binary geological structure. The upper layer 5 is silty clay of the floodplain facies, about 8m thick, with low permeability but easy softening; the lower layer 6 is medium-coarse sand and gravel of the riverbed facies, about 12m thick, with high permeability. The composite seepage prevention system is continuously arranged along the extension direction of the dike, and from the water-facing side to the back water-facing side, it includes a dike body seepage prevention layer 1, a vertical seepage prevention curtain layer 2, a dike foundation reinforcement layer 3, and a reverse filter drainage layer 4.

[0028] The seepage-proof layer 1 is laid on the water-facing side of the dike and includes a composite geomembrane 101 and a clay inclined wall 102. The composite geomembrane 101 is made of HDPE geomembrane, with a thickness of 0.5 mm and a permeability coefficient of 1×10⁻⁶. -7 cm / s, continuously laid from top to bottom along the slope of the embankment, with an overlap width of 10cm, and the overlap is hot-melt welded.

[0029] The clay inclined wall 102 is laid on the outside of the composite geomembrane 101, with a thickness of 1.5m. It is constructed by layering and compacting silty clay with a compaction degree of 95%. The bottom of the clay inclined wall 102 extends to the top of the vertical seepage prevention curtain layer 2 and is connected by clay grooves 105. The joint is filled with sealing mortar 104.

[0030] like Figure 1 As shown, the vertical seepage-proof curtain layer 2 is continuously arranged along the embankment axis and includes multiple deep mixing piles continuously overlapping to form a seepage-proof wall. Each deep mixing pile includes a biaxial wet mixing pile 201 and a uniaxial dry mixing pile 202.

[0031] Among them, in the upper layer 5 silty clay, biaxial wet mixing piles 201 are used, with a pile diameter of Φ600mm, a pile spacing of 1.2m, an overlap width of 200mm between adjacent piles, a cement content of 18%, and a water-cement ratio of 0.5; in the lower layer 6 medium-coarse sand and gravel, uniaxial dry mixing piles 202 are used, with a pile diameter of Φ600mm, a cement content of 14%, and a water-cement ratio of 0.5.

[0032] Furthermore, the deep mixing pile penetrates the upper layer 5 and embeds itself 1.2m into the impermeable layer at the bottom of the lower layer 6. After 28 days of curing, the unconfined compressive strength is 1.0MPa, and the permeability coefficient is 5×10⁻⁶. -7 cm / s.

[0033] like Figure 3 As shown, HDPE membrane units 204 are installed between adjacent deep mixing piles in the vertical seepage prevention curtain layer 2. The width of the HDPE membrane unit 204 is 600mm, matching the pile diameter. A reinforced concrete counterweight 205 is installed at the bottom. The counterweight is arranged with V-shaped steel bars, and the top cross-section is an inverted triangle. The HDPE membrane units 204 are connected by coupling locks with slow-expansion waterstops 203 and embedded in the curing material of the mixing pile.

[0034] At the junction of the seepage-proof layer 1 and the vertical seepage-proof curtain layer 2, such as Figure 1 As shown, geomembrane grooves 103 are provided. The geomembrane grooves 103 are spaced 0.5m apart vertically, 0.2m wide at the bottom, have a slope ratio of 1:0.75 on both sides, and are 0.2m deep.

[0035] The foundation reinforcement layer 3 is located inside the foundation and includes a reinforced soil mixing pile foundation 302 and a cushion layer 301 laid on top of the piles. The reinforced soil mixing pile foundation 302 is constructed simultaneously with the vertical seepage prevention curtain layer 2. The pile type and parameters correspond to the soil layers, with a pile spacing of 1.4m and a replacement rate of 20%. The cushion layer 301 is 0.4m thick, made of graded crushed stone with a particle size of 5~20mm and a compaction degree of 93%, and is used to coordinate the deformation difference between the upper soft soil and the lower hard soil.

[0036] The reverse filter drainage layer 4 is arranged on the backwater side of the dike foundation and at the toe of the backwater slope of the dike, including a reverse filter pressure infiltration platform 401 and a drainage pressure relief well 402. For example... Figure 2 As shown, the reverse filter press 401 is 6m wide and 1.2m high, and is divided into three layers of filter material from top to bottom, including a medium sand layer 4011, a coarse sand layer 4012, and a gravel layer 4013: the medium sand layer 4011 uses medium sand with a particle size of 0.5~2.0mm and a thickness of 0.3m; the coarse sand layer 4012 uses coarse sand with a particle size of 2.0~5.0mm and a thickness of 0.4m; and the gravel layer 4013 uses gravel with a particle size of 5~20mm and a thickness of 0.3m.

[0037] Furthermore, drainage and pressure relief wells 402 are arranged at 6m intervals along the extension direction of the embankment, with a well diameter of Φ350mm and a well depth penetrating the lower layer of 6m. A permeable pipe is installed inside the well, and the permeable pipe is wrapped with a geotextile filter layer. Gravel is used to fill the space between the well wall and the permeable pipe.

[0038] like Figure 1 As shown, the slope toe of the clay inclined wall 102 is protected by a masonry toe 106. The top elevation of the masonry toe 106 is higher than the ground line of the backfill at the toe of the embankment. The masonry toe 106 adopts a pentagonal structure to prevent water erosion.

[0039] Construction method: This embodiment provides a construction method for the above-mentioned composite seepage prevention system, specifically including the following steps: Step S1: Construction Preparation. Clear debris and vegetation from the construction area, level the site, and construct temporary drainage facilities. Conduct a geological survey of the embankment foundation to determine the layer boundaries, thickness, permeability coefficient, and location of the impermeable layer between the upper 5 silty clay and the lower 6 medium-coarse sand, and determine the pile length, diameter, spacing, and cement content of the deep mixing piles. Prepare a biaxial wet mixing pile machine, a uniaxial dry mixing pile machine, a geomembrane welding machine, compaction machinery, and drainage and pressure relief well drilling equipment. Simulate the deep mixing material in the laboratory to obtain the initial setting time, viscosity development curve, and solid permeability index under the action of a retarder, providing parameter basis for the laying time window of HDPE membrane unit 11.

[0040] Step S2: Construction of the vertical seepage-proof curtain layer. Lay out the control lines for the mixing pile construction along the embankment axis, and use a total station to locate the pile positions. For the upper layer 5 silty clay, use a biaxial wet mixing pile machine. Adjust the verticality of the drilling rig to ensure the vertical deviation of the pile body is ≤1%. Inject clean water during drilling. After reaching the designed pile bottom elevation (embedded in the impermeable layer 19 ≥ 1.0m), raise the drill rod and inject cement slurry. The mixing speed is 1.0m / min, and the lifting speed is 0.6m / min. For the lower layer 6 medium-coarse sand and gravel, replace with a single-axis dry mixing pile machine. Add dry cement powder during drilling and mix again during lifting. The overlap width between adjacent piles is 200mm, and the construction interval is controlled within 24 hours.

[0041] Before the initial setting of the curing material in the mixing pile, the prefabricated HDPE membrane unit 204 is vertically lowered into the mixing pile using an installation frame consisting of a guide frame and a tensioner. The HDPE membrane unit 204 is manufactured by welding HDPE membranes using a hot-melt method. A reinforced concrete counterweight is installed at the bottom, with pre-reserved clamping positions for the HDPE membranes on the counterweight. The membrane units are connected by coupling locks, and the bottom counterweight ensures proper positioning. After lowering, they are fixed using a suspension frame until the mixing pile has cured to the predetermined strength, at which point they are removed. If a prolonged interruption occurs during construction, a joint protection plate is installed at the end of the HDPE membrane unit 204 and raised out of the installation frame. During subsequent construction, the protection plate is removed, and the connection can continue.

[0042] Step S3: Construction of the embankment foundation reinforcement layer. During the simultaneous construction of the vertical seepage-proof curtain layer 2, reinforced mixing pile foundations 302 are arranged on its backwater side according to the designed pile positions. The pile type and parameters of the reinforced mixing pile foundations 302 are consistent with the corresponding soil layer of the vertical seepage-proof curtain layer 2. After construction, a cushion layer 301 is laid on top of the reinforced mixing pile foundations 302, using crushed stone laid in layers with a layer thickness of 0.2m. Each layer is compacted after laying, achieving a compaction degree of 93%.

[0043] Step S4: Construction of the reverse filter drainage layer. On the backwater side of the embankment foundation reinforcement layer 3 and at the toe of the embankment's backwater slope, excavate the reverse filter pressure platform 401 foundation pit according to the design dimensions. The excavation slope of the foundation pit is 1:1.5, and slope protection is implemented. Three layers of reverse filter material are laid from top to bottom and compacted to a compaction degree of 93%. Drainage and pressure relief wells 402 are arranged at 6m intervals along the extension direction of the embankment. After drilling, the well walls are cleaned, and permeable pipes wrapped with geotextile reverse filter layers are inserted. The gaps are filled with gravel.

[0044] Step S5: Construction of the seepage prevention layer of the dike. Clean the water-facing slope of the dike and adjust the slope. Lay an 8cm thick layer of fine sand on the slope, then lay the composite geomembrane 101 continuously from top to bottom along the slope with an overlap of 10cm, and heat-melt weld it. Lay a clay inclined wall 102 on the outside of the composite geomembrane 101, using silty clay laid in layers, each layer 0.4m thick, with each layer compacted to ≥95%. Excavate clay grooves 102 at the bottom of the clay inclined wall 102 and fill them with sealing mortar 104 to achieve a tight connection with the vertical seepage prevention curtain layer 2. Lay a masonry toe block 106 at the toe of the slope.

[0045] Step S6: Quality Inspection and Finishing. The deep mixing piles are tested for 28-day unconfined compressive strength and permeability coefficient; the composite geomembrane 101 is tested for welding quality and seepage prevention performance; the reverse filter drainage layer 4 is tested for filter material gradation and drainage smoothness; the embankment seepage prevention layer 1 is tested for compaction degree and connection quality. Any non-compliant parts are rectified, the site is cleaned, and vegetation and topography are restored.

[0046] In this document, the directional terms such as front, back, top, and bottom are defined based on the location of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that these are relative concepts and can vary depending on the method of use and placement; the use of directional terms should not limit the scope of protection claimed in this application.

[0047] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0048] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite seepage prevention system using deep mixing piles in a binary geological embankment, wherein the upper layer (5) of the binary geological embankment is silty clay or silt, and the lower layer (6) is medium-coarse sand or gravel, characterized in that, The composite seepage prevention system is continuously arranged along the extension direction of the dike, and sequentially includes, from the water-facing side to the backwater side, the following components: The dike body seepage prevention layer (1), vertical seepage prevention curtain layer (2), dike foundation reinforcement layer (3) and reverse filter drainage layer (4); The seepage-proof layer (1) of the dike body includes a composite geomembrane (101) laid on the surface of the dike body on the water-facing side of the dike and a clay inclined wall (102) laid on the outside of the composite geomembrane. The bottom of the clay inclined wall (102) extends to the top of the vertical seepage-proof curtain layer (2). The vertical seepage-proof curtain layer (2) includes multiple deep mixing piles arranged continuously along the embankment axis. The multiple deep mixing piles are continuously overlapped to form a seepage-proof wall. Each deep mixing pile penetrates the upper layer and is embedded in the bottom impermeable layer of the lower layer. The deep mixing piles in the upper layer (5) adopt biaxial wet mixing piles (201) and in the lower layer (6) adopt uniaxial dry mixing piles (202). The embankment reinforcement layer (3) is arranged inside the embankment on the backwater side of the vertical seepage prevention curtain layer (2), including a reinforced mixing pile foundation (302) and a mattress layer (301) laid on top of the reinforced mixing pile foundation (302). The reverse filter drainage layer (4) is arranged on the backwater side of the dike foundation reinforcement layer (3) and at the backwater slope toe of the dike, including the reverse filter pressure seepage platform (401) and the drainage pressure relief well (402).

2. The composite seepage prevention system according to claim 1, characterized in that, The composite geomembrane (101) is an HDPE geomembrane, which is laid continuously from top to bottom along the slope of the embankment, and the overlap is welded by hot melt welding; the clay sloping wall (102) is made of silty clay, which is laid in layers and compacted. The bottom of the clay sloping wall (102) is connected to the top of the vertical anti-seepage curtain layer (2) through clay grooves (103), and the joint is filled with sealing mortar (104).

3. The composite seepage prevention system according to claim 1, characterized in that, The solidification material for the deep mixing piles is cement grout. The cement content is different between the upper soft soil layer and the lower sandy soil layer. After multiple cement grouts solidify, they form a seepage barrier wall.

4. The composite seepage prevention system according to claim 1, characterized in that, HDPE membrane units (204) are provided between adjacent deep mixing piles of the vertical anti-seepage curtain layer (2). A counterweight (205) is installed at the bottom of the HDPE membrane unit (204). The HDPE membrane unit (204) is connected by a coupling connection lock with a waterstop (203) and embedded in the deep mixing pile.

5. The composite seepage prevention system according to claim 2, characterized in that, The composite geomembrane (101) of the embankment seepage prevention layer (1) and the vertical seepage prevention curtain layer (2) are provided with geomembrane grooves (103), and one end of the composite geomembrane (101) is embedded in the geomembrane grooves (103) and fixed.

6. The composite seepage prevention system according to claim 1, characterized in that, The reinforced mixing pile foundation (302) of the embankment reinforcement layer (3) is constructed simultaneously with the deep mixing pile of the vertical anti-seepage curtain layer (2). The pile type is consistent with the pile type of the corresponding soil layer of the vertical anti-seepage curtain layer (2). The cushion layer (301) is laid with crushed stone and compacted.

7. The composite seepage prevention system according to claim 1, characterized in that, The reverse filter pressure infiltration platform (401) is divided into multiple layers of reverse filter material from top to bottom. The drainage pressure relief well (402) is equipped with a permeable pipe, and the permeable pipe is wrapped with a geotextile reverse filter layer.

8. The composite seepage prevention system according to claim 2, characterized in that, The slope toe of the clay inclined wall (102) is protected by a masonry toe block.

9. A method for constructing a composite seepage prevention system using deep mixing piles in binary geological embankments, employing the composite seepage prevention system described in any one of claims 1 to 8, characterized in that... Includes the following steps: S1. Construction preparation; S2. Construction of vertical anti-seepage curtain layer (2): Locate the pile position along the embankment axis. For the upper layer (5) silty clay or silt layer, use a double-axis wet mixing pile machine for construction. For the lower layer (6) medium and coarse sand or gravel layer, use a single-axis dry mixing pile machine for construction to form a continuous overlapping anti-seepage wall and ensure that the deep mixing pile penetrates the upper layer (5) and is embedded in the bottom impermeable layer of the lower layer (6). S3. Construction of the foundation reinforcement layer (3): Reinforced mixing pile foundation (302) is arranged on the back side of the vertical seepage prevention curtain layer (2). The pile type is consistent with the soil layer corresponding to the vertical seepage prevention curtain layer. After the construction is completed, a cushion layer (301) is laid on the top of the pile. S4. Construction of reverse filter drainage layer (4): On the back side of the dike foundation reinforcement layer (3) and at the back slope toe of the dike, a reverse filter pressure platform (401) is laid and a drainage pressure relief well (402) is arranged. S5. Construction of the seepage prevention layer (1) of the dike body: a composite geomembrane (101) is laid on the slope of the dike body on the water-facing side of the dike. A clay inclined wall (102) is laid on the outside of the composite geomembrane (101), and the bottom of the clay inclined wall (102) is extended to the top of the vertical seepage prevention curtain layer (2) to achieve connection. S6. Quality inspection and finalization.

10. The construction method according to claim 9, characterized in that, In step S2, during the construction of biaxial wet mixing piles, clean water is injected during the drilling process, and after reaching the designed pile bottom elevation, the drill rod is lifted and cement slurry is injected; during the construction of uniaxial dry mixing piles, dry cement powder is added during the drilling process, and the mixture is stirred again during the lifting process; before the initial setting of the mixing pile curing material, the prefabricated HDPE film unit is vertically lowered into the mixing pile.

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