Composite foundation embankment system for liquefiable site and construction method

Abstract

The invention provides a composite foundation embankment system for a liquefiable site and a construction method, and relates to the field of foundation reinforcement. The composite foundation embankment system comprises a plurality of rigid plastic drainage plate combined piles, a plurality of vertical plastic drainage plates and a sheet pile wall; a plurality of rigid plastic drainage plate combined piles and a plurality of vertical plastic drainage plates are longitudinally arranged in a foundation at equal intervals in a square mode, sheet pile walls are arranged in the foundation on the two sides of an embankment, and a geotechnical cloth cushion layer and a geogrid reinforced broken stone cushion layer are sequentially laid on the top of the foundation to form a horizontal drainage channel. And an embankment bottom covering reinforcement layer and embankment filling soil are sequentially arranged above the horizontal drainage channel. The method has the effect of enhancing the liquefaction resistance of the foundation.

Description

Technical Field

[0001] The present application relates to the technical field of foundation reinforcement, and in particular to a composite foundation embankment system and construction method for liquefiable sites. Background Art

[0002] Frequent crustal activity and earthquakes in recent years have led to widespread ground liquefaction, severely damaging transportation infrastructure and causing significant economic losses. Under the influence of earthquakes, excess pore water pressure in liquefiable foundation soils (such as loose sand and silt) rises rapidly, significantly reducing effective stress to near zero, leading to a loss of soil strength and liquefaction, which in turn causes instability and even destruction of the superstructure. Pile-supported embankments are widely used in engineering due to their ease of construction and high bearing capacity. However, in liquefiable foundation conditions, they still face structural instability caused by the difficulty in dissipating pore water pressure.

[0003] Currently, three main approaches are used to treat liquefiable foundations: stiffness enhancement, enhanced drainage, and vibration compaction. Existing technologies often employ only one or two of these approaches, resulting in limited effectiveness and failing to meet the higher demands for seismic performance and sustainability of embankment structures. Summary of the Invention

[0004] In order to overcome the technical problems described in the above-mentioned prior art, the present application provides a composite foundation embankment system and a construction method for liquefiable sites.

[0005] In a first aspect, the present application provides a composite foundation embankment system for liquefiable sites, which adopts the following technical solutions: A composite foundation embankment system for liquefiable sites includes a plurality of rigid plastic drainage board combination piles, a plurality of vertical plastic drainage boards, and a sheet pile wall. The plurality of rigid plastic drainage board combination piles and the plurality of vertical plastic drainage boards are longitudinally arranged in a square manner at equal intervals in the foundation. The sheet pile walls are arranged in the foundation on both sides of the embankment. A geotextile cushion layer and a geogrid reinforced gravel cushion layer are laid in sequence on the top of the foundation to form a horizontal drainage channel. A roadbed bottom reinforcement layer and roadbed fill are arranged in sequence above the horizontal drainage channel.

[0006] Furthermore, the rigid plastic drainage board combination pile includes a pile body, a rigid tube fixedly wrapped around the outer periphery of the pile body, a plurality of steel plates distributed on the outer periphery of the rigid tube, and a PVD drainage board fixed on the steel plate. The steel plate is V-shaped, and the V-shaped opening side of the steel plate faces the rigid tube and is fixedly connected to the rigid tube. The PVD drainage board is fixed on the outer wall of the steel plate.

[0007] Furthermore, a fixing screw distributed along its radial direction is fixed in the pile body, and both ends of the fixing screw pass through the rigid tube wall and abut against the inner side of the steel plate. Both ends of the fixing screw are threaded with fixing nuts, and the two fixing nuts are respectively tightened on the side walls on both sides of the rigid tube.

[0008] Furthermore, the sheet pile wall includes a plurality of steel sheet piles, a connecting member for connecting two adjacent steel sheet piles together, and a supporting member arranged on the steel sheet piles and used to stably support the steel sheet piles in the foundation, wherein the supporting member is retracted and extended on the steel sheet piles.

[0009] Furthermore, the connecting component includes a connecting screw vertically fixed to the end of the steel sheet pile, a gasket connected between two adjacent steel sheet piles, and a connecting nut threadedly sleeved on the connecting screw, two through holes are penetrated through the gasket, and the connecting screws on the two adjacent steel sheet piles are respectively passed through the two through holes on the gasket, and the connecting nut is threadedly sleeved on the connecting screw and presses the gasket against the end of the steel sheet pile.

[0010] Furthermore, a slide groove is provided through the steel sheet pile, and the length direction of the slide groove is consistent with the height direction of the steel sheet pile. The supporting member includes a fixed seat fixed on the steel sheet pile, two support rods hinged at one end to the fixed seat, a sliding rod fixed in the slide groove, a slider slidingly sleeved on the sliding rod, and a connecting rod connected between the slider and the support rod. The fixed seat is located above the slide groove, the two support rods are respectively located on both sides of the steel sheet pile, and the two ends of the connecting rod are respectively hinged to the slider and the support rod.

[0011] Furthermore, one end of the support rod away from the fixing seat is configured as a spike head.

[0012] Furthermore, a drainage structure is provided in the embankment.

[0013] Furthermore, drainage ditches are arranged on both sides of the embankment on the foundation.

[0014] In a second aspect, the present application provides a construction method for a composite foundation embankment system for a liquefiable site, based on the above-mentioned composite foundation embankment system for a liquefiable site, comprising the following steps: S1, site preparation: clear debris in the construction area and level the site to provide conditions for the subsequent construction of rigid plastic drainage board combination piles, vertical plastic drainage boards and sheet pile walls; S2, pile position and drainage board positioning: Arrange the layout points of rigid plastic drainage board combination piles, vertical plastic drainage boards and sheet pile walls according to the design drawings; S3, vibration compaction and pile construction: Perform vibration compaction treatment, using the vibro-impact method to drill holes at the positioning points and then pour concrete to form piles, thereby improving the density and rigidity of the foundation and thus its anti-liquefaction performance; S4, inserting drainage boards: using a board inserting machine to insert vertical plastic drainage boards according to the designed points to form a vertical drainage channel; S5, Sheet Pile Wall Construction: Use a pile driver to drive the sheet pile wall vertically into the foundation to form a sheet pile wall system with lateral resistance and drainage functions; S6, horizontal drainage system construction: laying geotextile cushion layer and multi-layer reinforced crushed stone cushion layer on top of rigid plastic drainage board composite piles in sequence; S7, drainage ditch construction: excavate drainage ditches in the foundation on both sides of the bottom of the embankment; S8, embankment construction: laying the embankment bottom backfill reinforcement layer on top of the geogrid reinforced gravel cushion layer and carrying out embankment layer filling to complete the embankment structure construction; S9, embankment drainage system: PVD drainage system will be installed in the embankment fill to further improve the safety performance and seismic resilience of the embankment structure in liquefiable sites. After the embankment construction is completed, the overall height and structural stability will be inspected to ensure that they meet the design requirements.

[0015] In summary, this application includes at least one of the following beneficial technical effects: 1. Compared with conventional rigid piles, rigid plastic drainage board composite piles have higher shear resistance and drainage function. They not only effectively improve the rigidity and bearing capacity of the foundation, but also can quickly dissipate pore water pressure under earthquakes or strong disturbances, thereby significantly enhancing the foundation's anti-liquefaction performance; 2. Sheet pile walls, with additional permeable holes and retractable support members, enhance the embankment's overall stability by suppressing lateral deformation of the foundation soil under normal conditions. They also assist with lateral drainage and lateral restraint under liquefaction conditions, significantly improving their lateral displacement resistance compared to conventional sheet pile systems. 3. The geogrid-reinforced crushed stone cushion is made up of multiple layers of crushed stone and geogrid bodies laid alternately. The tensioning force is applied by fastening nuts and tensioning screws installed on both sides, forming a stable tensioning structure. This can fully utilize the tensile membrane effect of the reinforcement material, significantly improving the stiffness, strength and shear resistance of the cushion, and is superior to conventional reinforced crushed stone cushions. 4. A drainage structure is set up inside the embankment. The drainage structure is composed of an embedded vertical plastic drainage board system, which can form an efficient vertical drainage network inside the embankment. Under earthquake or heavy rainfall conditions, it can quickly drain the accumulated water, reduce pore pressure accumulation, significantly reduce the liquefaction risk of the embankment structure, and improve its service safety and seismic toughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present application.

[0018] Figure 2 This is a distribution diagram of the combined piles of vertical plastic drainage boards and rigid plastic drainage boards in the embodiment of the present application.

[0019] Figure 3 It is a structural diagram of the rigid plastic drainage board combination pile in the embodiment of the present application.

[0020] Figure 4 It is a structural schematic diagram of the sheet pile wall in an embodiment of the present application.

[0021] Figure 5 It is a schematic cross-sectional view of the steel sheet pile, fixed seat, support rod, sliding rod, slider and connecting rod in the embodiment of the present application.

[0022] Figure 6 It is a structural diagram of the geogrid reinforced gravel cushion layer in the embodiment of the present application.

[0023] Figure numerals: 1. Vertical plastic drainage board; 2. Geotextile cushion layer; 3. Geogrid reinforced gravel cushion layer; 31. Gravel; 32. Geogrid body; 33. Fastening nut; 34. Tensioning screw; 4. Back-wrapped reinforcement layer at the bottom of the embankment; 5. Embankment fill; 6. Rigid plastic drainage board combination pile; 61. Pile body; 62. Rigid cylinder; 63. Steel plate; 64. PVD drainage board; 7. Sheet pile wall; 71. Steel sheet pile; 72. Connecting screw; 73. Gasket; 74. Connecting nut; 75. Fixing seat; 76. Support rod; 77. Sliding rod; 78. Sliding block; 79. Connecting rod; 8. Fixing screw; 9. Fixing nut; 10. Chute; 11. Spike head; 12. Drainage structure; 13. Drainage ditch; 14. Water-permeable hole. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0025] The present application discloses a composite foundation embankment system and construction method for liquefiable sites. Figure 1 and Figure 2 A composite foundation embankment system for liquefiable sites includes a plurality of rigid plastic drain board combination piles 6, a plurality of vertical plastic drain boards 1, and a sheet pile wall 7. The plurality of rigid plastic drain board combination piles 6 and the plurality of vertical plastic drain boards 1 are longitudinally arranged in a square pattern at equal intervals in the foundation, and the sheet pile walls 7 are arranged in the foundation on both sides of the embankment. The arrangement of the plurality of rigid plastic drain board combination piles 6 and the plurality of vertical plastic drain boards 1 in the roadbed not only effectively improves the rigidity and bearing capacity of the foundation, but also rapidly dissipates pore water pressure under earthquakes or strong disturbances, thereby significantly enhancing the foundation's resistance to liquefaction. The sheet pile wall 7 can suppress lateral deformation of the foundation soil and improve the overall stability of the embankment.

[0026] Reference Figure 1 and Figure 6 A geotextile mat 2 and a geogrid-reinforced gravel mat 3 are sequentially laid on top of the foundation to form a horizontal drainage channel. The tensile strength of the geotextile mat 2 is no less than 20 kN / m, and the tensile strength of the geogrid-reinforced gravel mat 3 is no less than 30 kN / m. The geogrid-reinforced gravel mat 3 is composed of alternating layers of gravel 31 and geogrid bodies 32. Simultaneously, two tensioning screws 34 are passed through the geogrid-reinforced gravel mat 3, and fastening nuts 33 are threaded onto each end of the tensioning screws 34, so that the fastening nuts 33 on each end of the tensioning screws 34 are respectively pressed against the upper and lower sides of the geogrid-reinforced gravel mat 3. The geogrid-reinforced gravel cushion 3, fastening nuts 33, and tensioning screws 34 form a stable tensioned structure. The tensioning screws 34 at both ends horizontally tension and secure the geogrid-reinforced gravel cushion 3. The tensioning force of the geogrid-reinforced gravel cushion 3 can be adjusted, thereby improving the overall stiffness and load-bearing capacity of the geogrid-reinforced gravel cushion 3. The geogrid-reinforced gravel cushion 3 serves as a horizontal drainage channel, effectively draining vertical water seepage from the foundation and embankment. It also acts as a structural reinforcement layer, effectively suppressing settlement and lateral deformation of the upper embankment structure.

[0027] Reference Figure 1The embankment bottom backfill reinforcement layer 4 and the embankment fill 5 are arranged in sequence above the geogrid reinforced gravel cushion layer 3. The embankment bottom backfill reinforcement layer 4 is located at the bottom of the embankment and is arranged in contact with the geogrid reinforced gravel cushion layer 3. The reinforcement material used is geogrid with a tensile strength of not less than 30kN / m. The two ends are backfilled to suppress the lateral deformation of the embankment bottom and equalize the force. The embankment bottom backfill reinforcement layer 4 can enhance the stability of the overall structure of the embankment. A drainage structure 12 is provided in the embankment. The drainage structure 12 is composed of a plurality of embedded vertical PVD plastic drainage boards. The plurality of embedded vertical PVD plastic drainage boards form an efficient vertical drainage network in the embankment. Under earthquake or heavy rainfall conditions, it can quickly drain the accumulated water, reduce pore pressure accumulation, significantly reduce the liquefaction risk of the embankment structure, and improve its service safety and seismic toughness. In addition, drainage ditches 13 are set on both sides of the embankment on the foundation. The depth of the drainage ditch 13 is 0.5-1m, and the cross-sectional width of the drainage ditch 13 is 1-1.5m.

[0028] For the setting of rigid plastic drainage board combination pile 6, refer to Figure 3 The rigid plastic drainage board combination pile 6 includes a pile body 61, a rigid tube 62 fixedly wrapped around the outer periphery of the pile body 61, a plurality of steel plates 63 distributed around the outer periphery of the rigid tube 62, and a PVD drainage board 64 fixed on the steel plate 63. The pile body 61 is cylindrical, with a pile diameter of 0.8–1.5m, a pile spacing of 2–6m, and a pile length of not less than 5m. The rigid tube 62, steel plate 63, and PVD drainage board 64 are the same length as the pile body 61. There are four steel plates 63, which are evenly distributed around the outer periphery of the rigid tube 62. The steel plates 63 are V-shaped, and the V-shaped opening side of the steel plates 63 faces the rigid tube 62 and is welded to the rigid tube 62. The PVD drainage board 64 is bonded and fixed to the outer wall of the steel plate 63. The steel plates 63 can support and fix the PVD drainage board 64 to ensure that the PVD drainage board 64 can drain water smoothly. To prevent deformation of the steel plate 63, a plurality of fixed screws 8 distributed along its radial direction are fixed in the pile body 61. The two ends of the fixed screws 8 pass through the wall of the rigid tube 62 and abut against the inner side of the steel plate 63. The two ends of the fixed screws 8 are threaded with fixed nuts 9, and the two fixed nuts 9 are respectively pressed against the side walls of the rigid tube 62. The pile body 61 adopts the vibration method to form a hole and pour concrete. Before pouring, the rigid tube 62 with fixed screws 8, fixed nuts 9, steel plate 63 and PVD drainage board 64 is inserted into the hole. Then concrete is poured into the rigid tube 62. After the concrete solidifies, a rigid plastic drainage board composite pile 6 is formed. During the process of being inserted into the hole, the rigid tube 62 can produce a vibration compaction reinforcement effect on the foundation, forming the three core mechanisms in the anti-liquefaction design: enhanced rigidity, accelerated drainage, and vibration compaction consolidation.

[0029] For the installation of the sheet pile wall 7, refer to Figure 4 and Figure 5The sheet pile wall 7 includes a plurality of steel sheet piles 71, connecting members for connecting two adjacent steel sheet piles 71 together, and supporting members disposed on the steel sheet piles 71 to stably support the steel sheet piles 71 in the foundation. The cross-section of the steel sheet piles 71 is U-shaped to enhance the stability of the placement of the steel sheet piles 71. A plurality of water-permeable holes 14 are provided through the vertical side walls of the steel sheet piles 71 to achieve lateral drainage of the foundation during earthquake liquefaction, thereby alleviating lateral deformation caused by liquefaction. The supporting members are retractable and arranged on the steel sheet piles 71. During transportation, the supporting members are folded to improve the convenience of transporting the steel sheet piles 71. When the steel sheet piles 71 are inserted into the foundation, the supporting members are unfolded to further improve the stability of the steel sheet piles 71 installed in the foundation.

[0030] Reference Figure 4 The connecting components include connecting screws 72 vertically fixed to the ends of both sides of the steel sheet piles 71, gaskets 73 connected between two adjacent steel sheet piles 71, and connecting nuts 74 threadedly sleeved on the connecting screws 72. Two through holes are penetrated on the gasket 73, and the connecting screws 72 on the two adjacent steel sheet piles 71 are respectively penetrated by the two through holes on the gasket 73. The connecting nuts 74 are threadedly sleeved on the connecting screws 72 and press the gasket 73 against the end of the steel sheet pile 71, thereby stably connecting the two adjacent steel sheet piles 71 together, so that multiple steel sheet piles 71 can form an integral wall structure with permeability and lateral restraint capability, which can not only restrain the lateral displacement of the foundation and improve stability under normal load, but also enhance the overall stiffness under earthquake action and inhibit the lateral displacement damage of liquefied soil.

[0031] Reference Figure 4 and Figure 5The vertical side wall of the steel sheet pile 71 is provided with a slide groove 10, and the length direction of the slide groove 10 is consistent with the height direction of the steel sheet pile 71. The supporting member includes a fixed seat 75 welded and fixed on the steel sheet pile 71, two support rods 76 at one end hinged on the fixed seat 75, a sliding rod 77 fixed in the slide groove 10, a slider 78 slidingly sleeved on the sliding rod 77 and a connecting rod 79 connected between the slider 78 and the support rod 76. The slider 78 is arranged through the slide groove 10, the fixed seat 75 is located above the slide groove 10, and the two support rods 76 are respectively located on both sides of the steel sheet pile 71. The length of the support rod 76 is greater than the height of the steel sheet pile 71, and the end of the support rod 76 away from the fixed seat 75 is set as a spike head 11, and the two ends of the connecting rod 79 are respectively hinged to the slider 78 and the support rod 76. In the process of inserting the steel sheet pile 71 into the foundation, the spike head 11 on the support rod 76 is first inserted into the soil. As the steel sheet pile 71 is continuously inserted, the support rods 76 on both sides of the steel sheet pile 71 are pushed to the open state. At this time, the support rod 76 drives the connecting rod 79 to rotate, and the connecting rod 79 drives the slider 78 to slide up and down on the slide rod 77, so that the steel sheet pile 71 can be stably erected in the foundation under the support of the support rods 76 opened on both sides, realizing the stable lateral support effect of the sheet pile wall 7, thereby improving the sheet pile structure's ability to resist lateral displacement during earthquakes.

[0032] This application provides a construction method for a composite foundation embankment system for liquefiable sites, which adopts the following technical solutions: S1, site preparation: clear the debris in the construction area and level the site to provide conditions for the subsequent construction of rigid plastic drainage board combination piles 6, vertical plastic drainage board 1 and sheet pile wall 7; S2, pile position and drainage board positioning: According to the design drawings and layout plan, accurately locate the positions of the rigid plastic drainage board combination piles 6, vertical plastic drainage board 1 and sheet pile wall 7 on the site, and lay out the rigid plastic drainage board combination piles 6 and vertical plastic drainage board 1 in a square grid with equal spacing; S3, vibration compaction and pile body 61 construction: The site is subjected to overall vibration compaction treatment, and then the rigid plastic drainage board combination pile 6 positioning point is vibrated and drilled by vibro-fluxing method. Then, the rigid tube 62 with fixed screw 8, fixed nut 9, steel plate 63 and PVD drainage board 64 is inserted into the hole, and concrete is poured into the rigid tube 62. After the concrete solidifies, the rigid plastic drainage board combination pile 6 is formed. The vibration compaction treatment before construction and the vibration-fluxing method of drilling can both improve the density of the foundation soil. At the same time, the rigid plastic drainage board combination pile 6 after pile formation can effectively enhance the bearing capacity and overall rigidity of the foundation, thereby improving its anti-liquefaction performance. S4, inserting drainage boards: Use a board inserting machine to insert vertical plastic drainage boards 1 at the predetermined position. After the insertion is completed, a quality inspection is carried out to ensure that the design requirements are met. All vertical plastic drainage boards 1 form a vertical drainage channel that penetrates the foundation. At the same time, the insertion construction also produces a vibration compaction effect on the foundation, further improving the foundation condition; S5, sheet pile wall 7 construction: The sheet pile wall 7 is driven vertically into the foundation according to the designed position using a pile driver. During the driving process, the support rods 76 on both sides are automatically opened by connecting rods 79 and sliders 78, and the steel sheet piles 71 are connected to form a whole through connecting components, forming a sheet pile wall 7 system with anti-lateral displacement and drainage functions; S6, construction of horizontal drainage system: first lay a geotextile cushion layer 2 on the top of the rigid plastic drainage board combination pile 6 to play the role of backfiltration and horizontal drainage; then fill and compact gravel 31 in layers, and lay geogrid bodies 32 with a tensile strength of not less than 30kN / m in layers in the gravel 31 layer to form a geogrid reinforced gravel cushion layer 3 to enhance the bearing capacity and overall rigidity of the cushion layer; at the same time, two tensioning screws 34 are passed through the geogrid reinforced gravel cushion layer 3 and fastening nuts 33 are threadedly sleeved on both ends of the tensioning screws 34, so that the fastening nuts 33 on both ends of the tensioning screws 34 are respectively pressed against the upper and lower sides of the geogrid reinforced gravel cushion layer 3, and the geogrid reinforced gravel cushion layer 3 is horizontally tensioned and fixed by the tensioning screws 34 at both ends, and the tensioning force of the geogrid reinforced gravel cushion layer 3 can be adjusted, thereby improving the structural stability and performance of the geogrid reinforced gravel cushion layer 3; S7, construction of drainage ditches 13: excavate drainage ditches 13 in the foundations on both sides of the embankment bottom to collect and guide drainage from the foundation and cushion system, further accelerating the dissipation of pore pressure; S8, embankment construction: a reinforced layer 4 is laid on top of the geogrid reinforced gravel cushion 3, and embankment fill 5 is layered thereon. Both ends of the reinforced layer 4 are subjected to a backfill treatment to suppress lateral deformation of the embankment bottom and enhance the overall structural stability; S9, laying out a drainage structure 12 system in the embankment: A PVD drainage structure 12 system is laid out in the embankment fill 5. This system, combined with an underground vertical plastic drainage board 1, can quickly dissipate pore water pressure under excitations such as earthquakes, reduce liquefaction risks, and further enhance the safety performance and seismic resilience of the embankment structure in liquefiable sites. After the embankment construction is completed, the overall height and structural stability are inspected and accepted to ensure that they meet the design requirements.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A composite foundation embankment system for liquefiable sites, characterized in that: It includes multiple rigid plastic drainage board combination piles, multiple vertical plastic drainage boards and sheet pile walls. Multiple rigid plastic drainage board combination piles and multiple vertical plastic drainage boards are longitudinally arranged in the foundation at equal intervals in a square manner. The sheet pile walls are arranged in the foundation on both sides of the embankment. The top of the foundation is laid with a geotextile cushion layer and a geogrid reinforced gravel cushion layer in sequence to form a horizontal drainage channel. Above the horizontal drainage channel, the embankment bottom back-wrapped reinforcement layer and the embankment fill are arranged in sequence.

2. A composite foundation embankment system for liquefiable sites according to claim 1, characterized in that: The rigid plastic drainage board combination pile includes a pile body, a rigid tube fixedly wrapped around the outer periphery of the pile body, a plurality of steel plates distributed on the outer periphery of the rigid tube, and a PVD drainage board fixed on the steel plate. The steel plate is V-shaped, and the V-shaped opening side of the steel plate faces the rigid tube and is fixedly connected to the rigid tube. The PVD drainage board is fixed on the outer side wall of the steel plate.

3. A composite foundation embankment system for liquefiable sites according to claim 2, characterized in that: A fixing screw distributed along its radial direction is fixed in the pile body, and both ends of the fixing screw pass through the rigid tube wall and abut against the inner side of the steel plate. Both ends of the fixing screw are threadedly sleeved with fixing nuts, and the two fixing nuts are respectively tightly pressed against the side walls on both sides of the rigid tube.

4. A composite foundation embankment system for liquefiable sites according to claim 1, characterized in that: The sheet pile wall includes a plurality of steel sheet piles, a connecting member for connecting two adjacent steel sheet piles together, and a supporting member arranged on the steel sheet piles and used for stably supporting the steel sheet piles in the foundation, wherein the supporting member is retracted and extended on the steel sheet piles.

5. A composite foundation embankment system for liquefiable sites according to claim 4, characterized in that: The connecting component includes a connecting screw vertically fixed to the end of the steel sheet pile, a gasket connected between two adjacent steel sheet piles, and a connecting nut threadedly sleeved on the connecting screw. Two through holes are penetrated through the gasket, and the connecting screws on the two adjacent steel sheet piles are respectively passed through the two through holes on the gasket. The connecting nut is threadedly sleeved on the connecting screw and presses the gasket against the end of the steel sheet pile.

6. A composite foundation embankment system for liquefiable sites according to claim 4, characterized in that: The steel sheet pile is provided with a slide groove, the length direction of the slide groove is consistent with the height direction of the steel sheet pile, the supporting member includes a fixed seat fixed on the steel sheet pile, two support rods hinged at one end to the fixed seat, a sliding rod fixed in the slide groove, a slider slidingly sleeved on the sliding rod, and a connecting rod connected between the slider and the support rod. The fixed seat is located above the slide groove, the two support rods are respectively located on both sides of the steel sheet pile, and the two ends of the connecting rod are respectively hinged to the slider and the support rod.

7. A composite foundation embankment system for liquefiable sites according to claim 6, characterized in that: One end of the support rod away from the fixing seat is arranged as a spike head.

8. A composite foundation embankment system for liquefiable sites according to claim 2, characterized in that: A drainage structure is provided in the embankment.

9. A composite foundation embankment system for liquefiable sites according to claim 8, characterized in that: Drainage ditches are arranged on both sides of the embankment on the foundation.

10. A construction method for a composite foundation embankment system for a liquefiable site, based on the composite foundation embankment system for a liquefiable site according to any one of claims 2 to 9, characterized in that: The following steps are included: S1, site preparation: clear debris in the construction area and level the site to provide conditions for the subsequent construction of rigid plastic drainage board combination piles, vertical plastic drainage boards and sheet pile walls; S2, pile position and drainage board positioning: Arrange the layout points of rigid plastic drainage board combination piles, vertical plastic drainage boards and sheet pile walls according to the design drawings; S3, vibration compaction and pile construction: Perform vibration compaction treatment, using the vibro-impact method to drill holes at the positioning points and then pour concrete to form piles, thereby improving the density and rigidity of the foundation and thus its anti-liquefaction performance; S4, inserting drainage boards: using a board inserting machine to insert vertical plastic drainage boards according to the designed points to form a vertical drainage channel; S5, Sheet Pile Wall Construction: Use a pile driver to drive the sheet pile wall vertically into the foundation to form a sheet pile wall system with lateral resistance and drainage functions; S6, horizontal drainage system construction: laying geotextile cushion layer and multi-layer reinforced crushed stone cushion layer on top of rigid plastic drainage board composite piles; S7, drainage ditch construction: excavate drainage ditches in the foundation on both sides of the bottom of the embankment; S8, embankment construction: laying the embankment bottom reinforcement layer on top of the geogrid reinforced gravel cushion layer and filling the embankment in layers to complete the embankment structure construction; S9, embankment drainage system: PVD drainage system will be installed in the embankment fill to further improve the safety performance and seismic resilience of the embankment structure in liquefiable sites. After the embankment construction is completed, the overall height and structural stability will be inspected to ensure that they meet the design requirements.

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