A layered rotary pile foundation and soft soil foundation reinforcement structure and construction method

Abstract

This invention discloses a layered rotating pile foundation and a soft soil foundation reinforcement structure and construction method, belonging to the field of soft soil foundation reinforcement technology. It includes rotatable piles and a superstructure layer. The rotating pile comprises layered pile bodies, pile ends, stone filling bodies, rotating grooves, a central rotating shaft, and rotating plates and filling plates arranged alternately along the axial direction. The rotating plates are inserted into the rotating plate holes of the central rotating shaft and rotate synchronously with it. The filling plates are placed in the rotating grooves of the layered pile bodies without rotating plates and remain in their original positions. The superstructure layer, from bottom to top, includes a crushed stone cushion layer, a waterproof layer, and a leveling layer. The crushed stone cushion layer extends to drainage ditches at both ends. Rotating the central rotating shaft causes the rotating plates to drive the corresponding layered pile bodies to rotate, forming an interlaced tooth-like embedded structure, increasing the pile side surface area and improving bearing capacity. The stone filling bodies of the pile bodies form vertical drainage channels, creating a three-dimensional drainage and consolidation system with the superstructure layer, accelerating soft soil consolidation. Construction is convenient and applicable to various types of soft soil foundation reinforcement.

Description

Technical Field

[0001] This invention belongs to the field of soft soil foundation reinforcement technology, specifically relating to a layered rotary pile foundation and a soft soil foundation reinforcement structure and construction method. Background Technology

[0002] As my country's infrastructure construction continues to expand into areas with soft soil distribution, such as coastal areas and alluvial plains, the quality of soft soil foundation reinforcement directly determines the overall stability and long-term operational safety of the structure. Soft soil foundations are mostly composed of soils such as silt, silty clay, and peat soil, and generally have characteristics such as high water content, high compressibility, weak soil cohesion, and slow consolidation. Soft soil foundations that have not been effectively reinforced are extremely prone to uneven settlement, soil slippage, and structural instability during the construction and operation stages, seriously restricting the quality of engineering construction.

[0003] Currently, pile foundations are the most mainstream treatment method for reinforcing soft soil foundations, with uniform cross-section cylindrical piles being the most widely used. However, traditional cylindrical piles have smooth, flat surfaces and small pile-soil contact areas, making it difficult to form an effective interlocking structure with the surrounding soft soil. Furthermore, the bearing capacity of pile foundations in soft soil foundations mainly relies on the side friction of the pile body. The limited contact area and smooth pile-soil interface result in insufficient pile-soil synergistic bearing capacity, limiting the overall bearing capacity of the pile foundation. Simultaneously, the drainage system design of existing conventional pile foundation structures is inadequate, relying solely on natural soil drainage and consolidation. The slow dissipation rate of pore water within the soft soil leads to a long consolidation period and insufficient consolidation, easily causing excessive post-construction settlement and uneven foundation deformation, making it difficult to meet the construction requirements of high-standard projects. In addition, traditional pile foundation construction has a low degree of prefabrication, complex construction procedures, and low work efficiency, making it poorly adaptable to complex soft soil foundations.

[0004] Existing conventional technologies cannot simultaneously meet the needs of improving the bearing capacity of pile foundations and rapidly consolidating and draining soft soil, resulting in limited overall treatment effectiveness. Summary of the Invention

[0005] The purpose of this invention is to provide a soft soil foundation treatment structure and construction method with higher bearing capacity, greater stability, and the ability to accelerate soft soil consolidation.

[0006] To achieve the above objectives, one technical solution of the present invention is: A layered rotating pile foundation and soft soil foundation reinforcement structure includes rotatable piles and an upper structural layer located on the soft soil foundation. The rotatable piles include: multiple layered pile bodies, stacked from bottom to top, each layered pile body having an internal cavity and a centrally located axially penetrating rotating groove; pile ends connected to the bottom of the lowest layered pile body; stone filler filling the internal cavities of the layered pile bodies; a central rotating shaft axially penetrating the rotating grooves of each layered pile body, its bottom end connected to the pile ends; multiple rotating plates and multiple filler plates, alternately arranged along the axial direction of the central rotating shaft, the rotating plates inserted into rotating plate holes on the central rotating shaft and capable of rotating synchronously with the central rotating shaft; the filler plates are located in the rotating grooves of the layered pile bodies without rotating plates and remain in place when the central rotating shaft rotates. The upper structural layer, from bottom to top, includes a crushed stone cushion layer, a waterproof layer, and a leveling layer, the two ends of the crushed stone cushion layer extending into pre-set drainage ditches on both sides of the foundation.

[0007] In this way, the rotating plate, driven by the rotating axis of the rotating center, rotates the corresponding layered piles, forming an interlocking toothed embedment structure. Compared with traditional cylindrical piles of equal volume, the side surface area of ​​the pile body can be effectively increased, thereby significantly increasing the pile-soil contact area and improving the pile side friction. At the same time, the interlocking toothed structure forms an embedded interlock with the surrounding soil, strengthening the pile-soil cooperative bearing capacity and effectively improving the overall vertical bearing capacity of the pile foundation. In addition, the stone filling material inside the pile body constitutes a vertical drainage channel, which, together with the upper crushed stone cushion layer and drainage ditch, forms a three-dimensional drainage and consolidation system. This system can quickly drain pore water from the soil, reduce the soil void ratio, increase the effective stress of the soil, accelerate the consolidation of soft soil, and reduce post-construction settlement. The impermeable layer can prevent surface water intrusion, comprehensively reducing post-construction settlement and deformation of soft soil foundations.

[0008] Furthermore, the horizontal cross-section of the layered pile is four-petal shaped, with a height of 300mm to 500mm, a central circle radius of 300mm to 500mm, and petal radii of 200mm to 300mm. The bottom plate of the layered pile has evenly distributed pores with a pore diameter of 2mm to 3mm. This four-petal shaped cross-section design effectively increases the side surface area of ​​the pile, and the pores in the bottom plate facilitate the entry of pore water into the internal drainage channels of the pile.

[0009] Furthermore, the cross-section of the rotating rod groove is a combination of a central circular shape and two symmetrical rectangular shapes. The diameter of the central circular shape is 52mm to 72mm, and the dimensions of the two rectangular shapes are: length 150mm to 200mm, width 40mm to 60mm, and height 300mm to 500mm. This combined cross-sectional structure ensures the smooth passage of the central rotating shaft while providing guidance and accommodating space for the rotating plate and the filling plate.

[0010] Furthermore, the pile end is a precast C30 concrete truncated cone with a slope height of 200mm to 300mm; the bottom end of the central rotating shaft is embedded in the top of the pile end to a depth of 80mm to 100mm. The truncated cone shape of the pile end facilitates pile driving, reduces end resistance, and ensures a reliable connection between the central rotating shaft and the pile end.

[0011] Furthermore, the stone filler is composed of crushed stone with a particle size of 10mm to 50mm and coarse sand with a particle size of 5mm to 10mm in a volume ratio of 7:3. This graded filler has both good permeability and drainage capacity, and can also provide a certain lateral stiffness for the pile body.

[0012] Furthermore, the diameter of the central rotating shaft is 50mm to 70mm; the dimensions of the rotating plate are: length 350mm to 470mm, width 40mm to 60mm, and height 300mm to 500mm; the filling plate consists of two symmetrical plates, each with dimensions of: length 150mm to 200mm, width 40mm to 60mm, and height 300mm to 500mm. These dimensions match the internal space of the layered pile body, ensuring that the rotating plate can smoothly drive the layered pile body to rotate, while the filling plate fills the hollow parts of the unrotated layers, ensuring the integrity of the pile body.

[0013] Furthermore, the layered rotary pile foundation is arranged in a quincunx pattern, with a pile spacing of 100cm to 180cm; the crushed stone cushion layer is made of crushed stone with a particle size of 1mm to 20mm, with a thickness of 50mm to 100mm and a flatness error of less than 5mm. The quincunx arrangement can fully utilize the group pile effect, and the crushed stone cushion layer acts as a horizontal drainage channel, working in conjunction with the vertical drainage channel of the pile body.

[0014] Furthermore, the waterproof layer is an SBS modified bitumen waterproof membrane with a thickness of 5mm and an overlap width of ≥100mm between adjacent membranes; the leveling layer is a modified cohesive soil incorporating plant fibers, containing 2%–3% geopolymer cementitious material, with a thickness of 150mm–200mm. The waterproof layer effectively prevents surface water infiltration, and the leveling layer provides a stable bearing layer for the superstructure.

[0015] The present invention also provides a construction method for the above-mentioned layered rotary pile foundation and soft soil foundation reinforcement structure, comprising the following steps: Step 1: Precast component preparation, precast pile end, embed the bottom end of the central rotating shaft into the pile end, and insert the rotating plate into the rotating plate hole on the central rotating shaft; Step 2: On-site assembly. Each layer of pile is sequentially inserted into the central rotating shaft through the rotating rod groove, and the lowest layer of pile is placed on the pile end. Stone filler is filled into each layer of pile. Filler plates are installed in the rotating rod grooves of each layer of pile without rotating plates to complete the overall assembly of the pile foundation. Step 3: Pile driving construction. The assembled pile foundation is hoisted and aligned with the pile position, and the pile is driven to the designed depth. Step 4: Pile body rotation and shaping. After the pile is driven to the design depth, the central rotation axis is rotated so that the rotating plate drives the corresponding layered pile body to rotate synchronously, while the filling plate and the corresponding layered pile body remain in place, forming an interlaced tooth-shaped pile body structure. Step 5: Foundation surface treatment, level the top surface of the soft soil foundation, lay a crushed stone cushion layer and compact it, extend both ends of the crushed stone cushion layer to the drainage ditch, lay a waterproof layer on top of the crushed stone cushion layer and seal it, and finally lay a leveling layer, compact it and cure it.

[0016] The above construction method has the advantages of high degree of component prefabrication, small amount of on-site work, convenient and efficient construction, and controllable quality.

[0017] Furthermore, in step three, the verticality deviation of the pile body is controlled to be ≤1%; in step four, the rotation angle of the central rotation axis is 45°. Verticality control ensures uniform stress on the pile foundation, and the 45° rotation angle can form an effective staggered tooth structure without generating excessive torsional stress.

[0018] To quantify the bearing capacity improvement effect of the pile foundation structure of this invention, the following calculation model is established by combining structural design parameters and geotechnical engineering theory: In soft soil foundations, the bearing capacity of pile foundations is mainly determined by the pile side skin friction, while the pile end resistance can be ignored. Therefore, the formula for calculating the standard value of the ultimate bearing capacity of pile foundations is: ; In the formula: This is the standard value of the ultimate bearing capacity of the pile foundation (kN). The standard value of the total limiting side resistance (kN); The standard value of the total limiting end resistance (kN); This is the correction factor for the pile side resistance, with a value ranging from 0.9 to 0.95; This is the correction factor for the pile end resistance, with a value ranging from 0.9 to 1.0; For the first Standard value of ultimate side friction resistance (kPa) of soft soil. For the first The standard value of the ultimate end resistance (kPa) of the soft soil layer is taken with reference to the "Technical Specification for Building Pile Foundations" (JGJ94-2008); For the first Thickness of the soil layer (mm); The perimeter of the cross section of the layered rotary pile foundation; This represents the area at the pile tip.

[0019] Let the radius of the center circle be... =300mm, petal radius If the diameter is 200mm, the calculation process for the increased bearing capacity of the pile body and pile tip is as follows: (1) Perimeter gain coefficient of pile body cross section The calculation formula is: ; ; ; In the formula: Perimeter (mm) of the cross section of the layered rotary pile foundation; The cross-sectional perimeter (mm) of a circular pile with equal area. The radius of the center circle of the cross section (mm); The radius of the four petals (mm) is where ≥ The gain coefficient can be obtained through calculation. = 0.71, meaning that the side surface area of ​​the pile body in this invention is increased by 71.0% compared to the side surface area of ​​a traditional circular pile of equal volume, considering the pile body side resistance correction coefficient. The increased pile bearing capacity is 0.71. times.

[0020] (2) Pile tip area gain coefficient k 2: The increased pile tip area at each layer is approximately half the area of ​​four petal circles. The number of layers in a layered rotary pile foundation is Since only half of the layers (interval rotation) were rotated, the total increase in pile end area is , ,when =300mm, When =200mm, =4 / 17, meaning that the end area of ​​the pile foundation of the present invention is increased by approximately 4% compared to the end area of ​​a traditional circular pile of equal volume. / 17 times, considering the pile end resistance correction factor The increased pile bearing capacity is 4 / 17 times.

[0021] Compared with the prior art, the technical advantages of this invention are as follows: (1) It can significantly improve the bearing capacity of the pile foundation: The iron cage of the pile body adopts a four-petal cross-section design, which increases the side surface area of ​​the pile body by more than 70% compared with the traditional circular pile of the same volume, effectively increasing the contact area between the pile and the soil and significantly improving the side friction resistance of the pile foundation. At the same time, the interlocking tooth structure formed by layered rotation can form a fixed interlocking effect with the surrounding soil, strengthen the pile-soil cooperative bearing capacity, constrain the relative displacement of the pile and the soil, and effectively improve the overall vertical bearing capacity of the pile foundation.

[0022] (2) Accelerate the consolidation of soft soil and reduce post-construction settlement: The vertical drainage channel is formed by the pile body crushed stone filling material, and a three-dimensional drainage consolidation system is formed by the upper crushed stone cushion layer and drainage ditch. This can quickly drain the pore water in the soil, reduce the void ratio of the soil, increase the effective stress of the soil, and complete the early consolidation settlement of the foundation in advance. At the same time, the water-proof layer can prevent the intrusion of surface water and reduce the post-construction settlement deformation of soft soil foundation in all aspects.

[0023] (3) Convenient and efficient construction with controllable quality: All components are prefabricated in the factory, and only assembly, pile driving, rotation and surface laying operations need to be completed on site, which greatly reduces the amount of on-site wet work and pouring work. The overall modular construction process effectively shortens the construction period, while facilitating standardized construction and quality control, and is suitable for rapid reinforcement construction of various soft soil foundations. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a schematic diagram of the initial three-dimensional structure of a layered rotating pile foundation and soft soil foundation reinforcement structure according to the present invention; Figure 2 This is a schematic diagram of the three-dimensional structure of a layered rotating pile foundation and soft soil foundation reinforcement structure after rotation according to the present invention; Figure 3 This is a schematic diagram of a layered rotating pile foundation and soft soil foundation reinforcement structure of the present invention before rotation; Figure 4 This is a schematic diagram of a layered rotating pile foundation and soft soil foundation reinforcement structure of the present invention during rotation; Figure 5 This is a schematic diagram of a layered rotating pile foundation and soft soil foundation reinforcement structure of the present invention after rotation; Figure 6 This is a schematic diagram of the central rotation axis structure of a layered rotating pile foundation and soft soil foundation reinforcement structure according to the present invention; Figure 7This is a schematic diagram of a layered rotary pile foundation and soft soil foundation reinforcement structure of the present invention, in which a rotating plate and a filling plate are placed on the central rotating axis; Figure 8 This is a schematic diagram showing the positions of the rotating plate and filling plate after the central rotating axis of the layered rotating pile foundation and soft soil foundation reinforcement structure of the present invention has been rotated. Figure 9 This is a schematic diagram of the rotating handle structure of a layered rotating pile foundation and soft soil foundation reinforcement structure according to the present invention; Figure 10 This is a schematic diagram of the layered rotating pile foundation and soft soil foundation reinforcement structure of the present invention before rotation; Figure 11 This is a schematic diagram of the structure of a layered rotating pile foundation and soft soil foundation reinforcement structure after rotation according to the present invention; Figure 12 This is a schematic diagram of the single-layer cross-sectional structure variation of a layered rotary pile foundation and soft soil foundation reinforcement structure according to the present invention; Figure 13 This is a schematic diagram of the bottom pore structure of a layered rotary pile foundation and soft soil foundation reinforcement structure according to the present invention; Figure 14 This is a schematic diagram of the horizontal projection of a layered rotating pile foundation and soft soil foundation reinforcement structure before rotation according to the present invention; Figure 15 This is a schematic diagram of the horizontal projection of a layered rotating pile foundation and soft soil foundation reinforcement structure of the present invention after rotation; Figure 16 This is a schematic diagram of a layered rotary pile foundation and soft soil foundation reinforcement structure according to the present invention, showing the staggered arrangement of the rotary pile foundation. Figure 17 This is a cross-sectional view of a layered rotating pile foundation and soft soil foundation reinforcement structure before rotation according to the present invention; Figure 18 This is a cross-sectional view of a layered rotating pile foundation and soft soil foundation reinforcement structure of the present invention after rotation; Figure 19 This is a Qs curve diagram of a layered rotary pile foundation and soft soil foundation reinforcement structure according to the present invention.

[0025] In the diagram: 1 is the layered pile body, 11 is the pore, 2 is the pile end, 3 is the stone filling body, 4 is the rotating rod groove, 5 is the central rotating shaft, 51 is the rotating plate, 52 is the filling plate, 53 is the rotating plate hole, 54 is the rotating handle, 6 is the crushed stone cushion layer, 7 is the waterproof layer, 8 is the leveling layer, 9 is the drainage ditch, and 10 is the soft soil foundation. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] Example 1 According to the present invention, a layered rotary pile foundation and soft soil foundation reinforcement structure are provided, such as... Figures 1 to 18 As shown, in this embodiment, the rotating pile includes a layered pile body 1, a pile end 2, a stone filling body 3, a rotating rod groove 4, a central rotating shaft 5, a rotating plate 51, a filling plate 52, a rotating plate hole 53, and a rotating handle 54; the upper structural layer includes a crushed stone cushion layer 6, a waterproof layer 7, a leveling layer 8, and a drainage ditch 9. The layered pile body 1 is formed by stacking layers from bottom to top; the stone filling body 3 is located in the cavity of the layered pile body 1; a rotating rod groove 4 is opened in the center of each layered pile body 1; the layered pile body 1 is axially sleeved on the central rotating shaft 5 through the rotating rod groove 4, and the bottom end of the central rotating shaft 5 is connected to the pile end 2; the upper structural layer is located on the upper part of the soft soil foundation 10, and is provided sequentially from bottom to top with a crushed stone cushion layer 6, a waterproof layer 7, and a leveling layer 8, and the two ends of the crushed stone cushion layer 6 extend into the drainage ditches 9 preset on both sides of the foundation. Figure 2 The diagram shows the interlaced tooth-like three-dimensional structure formed after rotation.

[0028] like Figure 6 As shown, a rotating plate hole 53 is provided on the central rotating shaft 5. Figure 7 As shown, the rotating plate 51 and the filling plate 52 are arranged alternately along the axial direction of the central rotating shaft 5. The rotating plate 51 is inserted into the rotating plate hole 53 on the central rotating shaft 5 and can rotate together with the central rotating shaft 5. The filling plate 52 is set in the rotating rod groove 4 of the layered pile body 1 without the rotating plate and remains in its original position when the central rotating shaft 5 rotates. Figure 8 The changes in position of the rotating plate and the filling plate are shown after the central rotating axis rotates. Figure 9 The structure of the rotating handle 54 is shown.

[0029] In this embodiment, the height of the layered pile 1 is 400mm, and the horizontal cross-section is a four-petal shape (e.g., Figure 12 As shown), the central circle has a radius of 300 mm, and the four petals have a radius of 200 mm. Compared with a circular cross-section of the same area, this four-petal cross-section significantly increases the side surface area of ​​the pile, with a calculated gain coefficient of 0.71, thereby greatly improving the pile side friction resistance. The bottom plate of the layered pile body 1 is provided with uniformly distributed pores 11 (such as... Figure 13 As shown in the figure, its aperture is 2mm, so that pore water in soft soil can enter the pile body to form a vertical drainage channel.

[0030] In this embodiment, the cross-section of the rotating rod groove 4 is a combination of a central circle and two symmetrical rectangles, wherein the diameter of the central circle is 60mm, and the dimensions of the two rectangles are 150mm in length × 60mm in width × 380mm in height. This structure provides guidance for the central rotating shaft and also accommodates the rotating plate and the filling plate.

[0031] In this embodiment, the pile end 2 is precast from C30 concrete and is truncated cone-shaped with a slope height of 300mm. The bottom end of the central rotating shaft 5 is embedded in the top of the pile end 2 to a depth of 100mm. The truncated cone shape of the pile end helps to reduce the pile driving resistance, and the embedded connection ensures the integrity of the rotating shaft and the pile end.

[0032] In this embodiment, the stone filler 3 is composed of crushed stone with a particle size of 10mm to 50mm and coarse sand with a particle size of 5mm to 10mm in a volume ratio of 7:3. This graded filler has good permeability, can form an efficient vertical drainage channel, and at the same time provides lateral stiffness for the pile body.

[0033] In this embodiment, the central rotating shaft 5 has a diameter of 60mm, and its surface is hot-dip galvanized for corrosion protection. The shaft length is consistent with the depth of the foundation pile. A threaded hole is provided on the upper part of the central rotating shaft 5. The rotating handle 54 is inserted into the threaded hole to rotate the central rotating shaft 5 by a rotation angle of 45°. This 45° rotation angle produces a significant interlaced tooth structure while avoiding excessive torsional stress.

[0034] In this embodiment, the rotating plate 51 has dimensions of 360mm (length) × 60mm (width) × 380mm (height), and the filling plate 52 consists of two symmetrical plates, each with dimensions of 150mm (length) × 60mm (width) × 380mm (height). These dimensions match the internal space of the layered pile body, ensuring that the rotating plate can effectively drive the pile body to rotate.

[0035] In this embodiment, the layered rotary pile foundation is arranged in a quincunx pattern (e.g., Figure 14 and Figure 15 As shown in the figure, the pile spacing is 150cm. The crushed stone cushion layer 6 is made of crushed stone with a particle size of 1mm to 20mm, with a thickness of 60mm and an overall flatness error of less than 5mm. The quincunx arrangement can give full play to the group pile effect. The crushed stone cushion layer, as a horizontal drainage channel, works in conjunction with the vertical drainage channel of the pile body to accelerate the drainage and consolidation of soft soil.

[0036] In this embodiment, the waterproof layer 7 is an SBS modified bitumen waterproof membrane with a thickness of 5mm and an overlap width of 120mm between adjacent membranes, sealed by hot-melt welding. This waterproof layer effectively prevents surface water infiltration and avoids secondary softening of the foundation. The leveling layer 8 is modified cohesive soil incorporating plant fibers. The modified cohesive soil is ordinary cohesive soil mixed with 2% geopolymer cementitious material, with a thickness of 150mm. The leveling layer provides a stable bearing layer for the superstructure, and the plant fibers enhance crack resistance.

[0037] The construction method in this embodiment is as follows: Step 1: Prefabrication of precast components. Prefabricate the pile end 2 in advance, embed the bottom end of the central rotating shaft 5 into the pile end 2, and insert the rotating plate 51 into the rotating plate hole 53 on the central rotating shaft 5.

[0038] Step 2: On-site assembly. Each layer of pile 1 is sequentially inserted into the central rotating shaft 5 through the rotating rod groove 4, and the lowest layer of pile is placed on the pile end 2. Stone filler 3 is filled into each layer of pile 1 and leveled. Filler plate 52 is installed in the rotating rod groove of each layer of pile without rotating plate, and the overall pile foundation assembly is completed.

[0039] Step 3: Pile driving construction. Locate the foundation piles according to the design drawings and mark the lines. Hoist the assembled pile foundations and align them with the pile positions. Start the vibratory pile driving equipment to gradually sink the pile foundations to the design depth. Monitor the verticality of the pile body in real time during the pile driving process and control its verticality deviation to ≤1%.

[0040] Step 4: Rotate and shape the pile body. Figures 3 to 5 The states before, during, and after rotation are shown respectively. Specifically, after the pile sinks to the design depth, a hydraulic rotating clamp is used to hold the top of the central rotating shaft 5, and the central rotating shaft 5 is rotated 45°. The fixed rotating plate 51 rotates with the central rotating shaft 5, which drives the corresponding layered pile body 1 to rotate synchronously with the central rotating shaft 5. The filling plate 52 and the corresponding layered pile body 1 remain in place, and finally form an interlaced tooth-shaped pile body structure. Figure 10 and Figure 11 The overall structure before and after rotation is shown in the comparison. Figure 12 The structural changes in a single-layer cross-section are shown. Figure 14 and Figure 15 The horizontal projections before and after rotation are shown respectively. Figure 17 The cross-sectional shape before rotation is shown. Figure 18 The cross-sectional shape after rotation is shown. This interlocking toothed structure enables the pile to mechanically interlock with the surrounding soil, significantly improving the pile's side friction and pull-out bearing capacity.

[0041] Step 5: Surface treatment of the foundation. Level the top surface of the soft soil foundation 10 to be treated, lay a crushed stone cushion layer 6 and compact it statically. Extend both ends of the cushion layer to the drainage ditch 9. Lay a waterproof layer 7 on top of the crushed stone cushion layer 6 and seal it. Finally, lay a leveling layer 8, compact it, and cure it for no less than 3 days. Heavy rolling is prohibited during the curing period. This three-dimensional drainage and consolidation system can quickly drain pore water from the soft soil, accelerate consolidation, and effectively control post-construction settlement.

[0042] To verify the improved bearing capacity of the soft soil foundation treatment structure of this invention, a comparative static load test was conducted at the construction site comparing layered rotating piles and traditional uniform-volume circular piles. The test piles were all 12m long with a central circle radius of... =300mm, petal radius =200mm, the soil within the pile foundation treatment area is homogeneous soft soil, the standard value of the ultimate side resistance of the pile. The standard value of the limiting end resistance is 22 kPa. 50 kPa The value is 0.95. The value is 0.90. =12 / 0.4=30. The detailed comparative analysis results are as follows: The results of the static load test on the vertical compressive strength of a single pile are as follows: Figure 19 As shown, the ultimate vertical compressive bearing capacity of a single pile of a traditional uniform-volume circular pile is 512.45 kN, while the ultimate vertical compressive bearing capacity of a single pile of the layered rotary pile foundation of this invention is 930.96 kN, an increase of 81.7% compared to the traditional pile type. Similarly, the pile type of this invention can significantly improve the uplift bearing capacity of the pile foundation, enabling it to withstand greater uplift loads. These measured results are consistent with the bearing capacity improvement trend predicted by the aforementioned theoretical calculation model of this invention.

[0043] Example 2 According to the present invention, a layered rotary pile foundation and soft soil foundation reinforcement structure is provided. In this embodiment, the basic structure is the same as that in embodiment 1, except that some parameter values ​​are different.

[0044] In this embodiment, the layered pile body 1 has a height of 300mm, a horizontal cross-section in the shape of four petals, a central circle radius of 300mm, a perimeter of 200mm, and a bottom plate pore diameter of 2mm.

[0045] The central circular groove 4 has a diameter of 60mm, and the rectangular dimensions on both sides are 150mm long × 60mm wide × 280mm high.

[0046] The pile end 2 has a cone-shaped slope height of 300mm, and the central rotating shaft 5 has an embedding depth of 100mm.

[0047] The stone filler 3 is the same as in Example 1.

[0048] The central rotating shaft 5 has a diameter of 60mm and a rotation angle of 45°.

[0049] The rotating plate 51 has dimensions of 360mm (length) × 60mm (width) × 280mm (height), and the filling plate 52 has dimensions of 150mm (length) × 60mm (width) × 280mm (height).

[0050] The layered rotary pile foundation is arranged in a quincunx pattern with a pile spacing of 160cm; the crushed stone cushion layer 6 is 60mm thick with a flatness error of <5mm.

[0051] The waterproof layer 7 is the same as in Example 1; the leveling layer 8 is mixed with 2% geopolymer cementitious material and laid with a thickness of 150mm.

[0052] The construction steps are the same as in Example 1. Related structures and changes can be found by referring to... Figures 1 to 18 .

[0053] To verify the improved bearing capacity of the soft soil foundation treatment structure of this invention, a comparative static load test was conducted at the construction site comparing layered rotating piles and traditional uniform-volume circular piles. The test piles were all 12m long with a central circle radius of... R =300mm, petal radius r =200mm, the pile foundation treatment area is layered soft soil: the first and second soil layers are both 6m thick, the standard value of the ultimate side resistance of the pile is... =20kPa, =30kPa, standard value of limiting end resistance =40kPa, The value is 0.90. The value is 0.95. =12 / 0.3=40. The detailed comparative analysis results are as follows: The results of the static load test on the vertical compressive strength of a single pile are as follows: Figure 19 As shown, the ultimate vertical compressive bearing capacity of a single pile of a traditional uniform-volume circular pile is 544.3 kN, while the ultimate vertical compressive bearing capacity of a single pile of the layered rotary pile foundation of this invention is 1110.84 kN, which is 104% higher than that of the traditional pile type. Similarly, the pile type of this invention can significantly improve the uplift bearing capacity of the pile foundation and can withstand greater uplift loads.

[0054] The layered rotary pile foundation of the present invention can significantly improve the compressive and tensile bearing capacity of the pile foundation without increasing the amount of pile material. The on-site measured bearing capacity improvement ratio is basically consistent with the theoretical calculation.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make various improvements and modifications without departing from the spirit and principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A layered rotary pile foundation and soft soil foundation reinforcement structure, characterized in that, Includes rotatable foundation piles and an upper structural layer located on the soft soil foundation (10); The rotatable foundation pile includes: Multiple layered pile bodies (1) are stacked from bottom to top. Each layered pile body (1) has an internal cavity and a rotating rod groove (4) that runs through the center along the axial direction. The pile end (2) is connected to the bottom of the lowest layered pile body (1); Stone filler (3) is filled into the internal cavity of the layered pile body (1); The central rotating shaft (5) is axially inserted into the rotating rod groove (4) of each layered pile body (1), and its bottom end is connected to the pile end (2). Multiple rotating plates (51) and multiple filling plates (52) are arranged alternately in layers along the axial direction of the central rotating shaft (5). The rotating plates (51) are inserted into the rotating plate holes (53) on the central rotating shaft (5) and can rotate synchronously with the central rotating shaft (5). The filling plates (52) are set in the rotating rod grooves (4) of the layered pile body (1) without rotating plates and remain in their original positions when the central rotating shaft (5) rotates. The upper structure layer includes, from bottom to top, a crushed stone cushion layer (6), a waterproof layer (7), and a leveling layer (8). The two ends of the crushed stone cushion layer (6) extend into the drainage ditches (9) pre-set on both sides of the foundation.

2. The layered rotary pile foundation and soft soil foundation reinforcement structure according to claim 1, characterized in that, The horizontal cross section of the layered pile body (1) is four-petal shaped. The height of the layered pile body (1) is 300mm to 500mm, the radius of the central circle is 300mm to 500mm, and the radius of the four petals is 200mm to 300mm. The bottom plate of the layered pile body (1) has uniformly distributed pores (11) with a pore diameter of 2mm to 3mm.

3. The layered rotary pile foundation and soft soil foundation reinforcement structure according to claim 1, characterized in that, The cross-section of the rotating rod groove (4) is a combination structure of a central circle and two symmetrical rectangles. The diameter of the central circle is 52mm to 72mm, and the dimensions of the two rectangles are: length 150mm to 200mm, width 40mm to 60mm, and height 300mm to 500mm.

4. The layered rotary pile foundation and soft soil foundation reinforcement structure according to claim 1, characterized in that, The pile end (2) is a precast cone made of C30 concrete with a slope height of 200mm to 300mm; the bottom end of the central rotating shaft (5) is embedded in the top of the pile end (2) with an embedding depth of 80mm to 100mm.

5. The layered rotary pile foundation and soft soil foundation reinforcement structure according to claim 1, characterized in that, The stone filler (3) is made by mixing crushed stone with a particle size of 10mm to 50mm and coarse sand with a particle size of 5mm to 10mm in a volume ratio of 7:

3.

6. The layered rotary pile foundation and soft soil foundation reinforcement structure according to claim 1, characterized in that, The diameter of the central rotating shaft (5) is 50mm to 70mm; the dimensions of the rotating plate (51) are: length 350mm to 470mm, width 40mm to 60mm, height 300mm to 500mm; the filling plate (52) is composed of two symmetrical plates, and the dimensions of a single plate are: length 150mm to 200mm, width 40mm to 60mm, height 300mm to 500mm.

7. A layered rotary pile foundation and soft soil foundation reinforcement structure according to claim 1, characterized in that, The layered rotary pile foundation is arranged in a plum blossom shape, with a pile spacing of 100cm to 180cm; the crushed stone cushion layer (6) is made of crushed stone with a particle size of 1mm to 20mm, with a thickness of 50mm to 100mm and a flatness error of less than 5mm.

8. A layered rotary pile foundation and soft soil foundation reinforcement structure according to claim 1, characterized in that, The waterproof layer (7) is an SBS modified bitumen waterproof membrane with a thickness of 5mm and an overlap width of ≥100mm between adjacent membranes; the leveling layer (8) is an improved clay soil mixed with plant fiber, which contains 2% to 3% geopolymer cementitious material and has a thickness of 150mm to 200mm.

9. A construction method for a layered rotary pile foundation and soft soil foundation reinforcement structure as described in any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Prefabrication of precast components, prefabrication of pile end (2), embedding the bottom end of the central rotating shaft (5) into the pile end (2), and inserting the rotating plate (51) into the rotating plate hole (53) on the central rotating shaft (5); Step 2: On-site assembly. Each layer of pile (1) is sequentially inserted into the central rotating shaft (5) through the rotating rod groove (4), and the lowest layer of pile is placed on the pile end (2). Stone filler (3) is filled into each layer of pile (1). Filler plate (52) is installed in the rotating rod groove of each layer of pile without rotating plate, and the overall assembly of the pile foundation is completed. Step 3: Pile driving construction. The assembled pile foundation is hoisted and aligned with the pile position, and the pile is driven to the designed depth. Step 4: Pile body rotation and shaping. After the pile is driven to the design depth, the rotation center rotation axis (5) is rotated so that the rotation plate (51) drives the corresponding layered pile body (1) to rotate synchronously, while the filling plate (52) and the corresponding layered pile body (1) remain in place, forming an interlaced toothed pile body structure. Step 5: Foundation surface treatment, level the top surface of the soft soil foundation (10), lay a crushed stone cushion layer (6) and compact it, extend both ends of the crushed stone cushion layer (6) to the drainage ditch (9), lay a waterproof layer (7) on top of the crushed stone cushion layer (6) and seal it, and finally lay a leveling layer (8), compact it and cure it.

10. The construction method according to claim 9, characterized in that, In step three, the verticality deviation of the pile body is controlled to be ≤1%; in step four, the rotation angle of the central rotation axis (5) is 45°.

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