A compound soil-cement mixing pile with a diameter-expanding reinforcing device and a construction method

Abstract

The application discloses a compound soil-cement mixing pile and a construction method thereof, and relates to the technical field of construction machinery, in particular to a compound soil-cement mixing pile and a construction method thereof. The device comprises a steel pipe pile, a sliding sleeve ring, a plurality of reinforcing units, a traction rope and a traction guide pipe. The sliding sleeve ring is sleeved on the outer periphery of the steel pipe pile. The plurality of reinforcing units are arranged at intervals on the outer periphery of the pile end. The two ends of each reinforcing unit are connected with the sliding sleeve ring and the pile end respectively. The traction guide pipe is arranged on the inner wall of the steel pipe pile, and the traction rope is connected with the sliding sleeve ring. When the traction rope is pulled upwards, the sliding sleeve ring moves towards the pile end, the distance between the two ends of each reinforcing unit is reduced, the plurality of reinforcing units are driven to expand outward, and an expanding and reinforcing structure is formed on the outer periphery of the pile end. The device effectively solves the problem that large-size reinforcing members are difficult to be lowered in a limited construction passage. The construction method is not affected by later hardening by implanting and synchronously expanding and solidifying in a plastic state pile body, the forming quality is controllable, and the bearing capacity of the expanding head area of the compound soil-cement mixing pile is finally improved.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering and foundation treatment technology, specifically relating to an expandable diameter reinforcement device and construction method for composite cement-soil mixing piles. Background Technology

[0002] Cement-soil mixing piles are commonly used for soft soil foundation treatment. They utilize mixing equipment to forcibly mix a solidifying agent slurry with the in-situ soil, forming a cement-soil pile with a certain strength and integrity. To improve the bearing capacity of a single pile, reduce settlement, and enhance load transfer to deeper bearing layers, enlarged head structures are often installed at the pile tip to increase the end support area. However, existing enlarged head cement-soil mixing piles are mostly composed of pure cement-soil. While they have good compressive strength, their tensile, shear, and bending strengths are relatively weak. When the pile is subjected to large vertical, horizontal, or uplift loads, stress concentration easily occurs in the edge area of ​​the enlarged head and the transition area between the enlarged head and the pile body, leading to cracking or brittle shear failure, thus weakening the bearing capacity of the enlarged head. Existing technologies attempt to incorporate reinforcing components such as steel pipes and steel cages in the enlarged head area, but these still have the following shortcomings: First, most existing reinforcing components are axially uniform diameter structures (i.e., the top and bottom diameters are the same), which are usually arranged in the core area of ​​the pile body. It is difficult to form an external reinforcing skeleton that matches the geometric contour of the enlarged head outside the enlarged diameter area. As a result, the load in the outer area of ​​the enlarged head is still mainly borne by cement and soil, which cannot effectively improve the stress state of the outer edge and transition zone of the enlarged head.

[0003] Secondly, to meet the reinforcement requirements of the enlarged head, if a steel cage or steel component with a larger diameter is used, its external size and rigidity will be significantly increased; however, the size of the upper construction passage is limited, and the area around the pile end is a fluid plastic slurry-soil mixture. Large-sized components face great resistance and are difficult to control in terms of posture during the lowering, introduction, and positioning process, resulting in a construction contradiction of "narrow upper passage and wide bottom requirement". Summary of the Invention

[0004] This invention provides an expandable diameter reinforcement device and construction method for composite cement-soil mixing piles, solving the problems of existing reinforcement components being difficult to adapt to the geometry of the enlarged head, difficult to lower, and forming an externally expanded reinforcement skeleton in situ at the pile end. The device of this invention can be smoothly implanted along a limited construction channel in a retracted state and expands in situ at the pile end, achieving simultaneous consolidation and shaping of the enlarged head's peripheral reinforcement and cement-soil mixture. The construction method of this invention, by implanting and simultaneously expanding the diameter within the fluid-plastic pile body, avoids secondary disturbance, enabling the reinforcement structure, steel pipe pile, and cement-soil mixture to form an integral composite enlarged end, effectively improving the bearing capacity and deformation resistance of the enlarged head region.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: an expandable diameter reinforcement device for composite cement-soil mixing piles, comprising a steel pipe pile, a sliding collar, multiple reinforcement units, a traction rope, and a traction guide tube; The steel pipe pile is used to bear and drive the expandable diameter reinforcement device into the cement-soil mixing pile in the fluid plastic state or incompletely consolidated state during the implantation stage, and serves as the core rigid component of the composite pile after pile formation. The sliding collar is fitted around the outer periphery of the steel pipe pile and can move along the axial direction of the steel pipe pile. The plurality of reinforcing units are arranged at intervals along the circumference of the steel pipe pile on the outer periphery of the pile end, and the upper end and lower end of each reinforcing unit are respectively connected to the sliding collar and the pile end; The traction guide tube is disposed on the inner wall of the steel pipe pile and extends along the axial direction of the steel pipe pile. The traction rope passes through the traction guide tube from top to bottom and then goes around the bottom of the pile end to connect with the sliding collar. When the traction rope is pulled upward, the sliding collar moves toward the pile end, reducing the distance between the upper and lower ends of each reinforcing unit, driving the multiple reinforcing units to bulge outward along the radial direction of the steel pipe pile, forming an expanded diameter reinforcing structure around the pile end.

[0006] This invention relates to an expandable diameter reinforcement device that uses a steel pipe pile as the main load-bearing structure. A sliding collar is fitted around the outer circumference of the steel pipe pile and can move axially. Multiple reinforcement units are arranged at intervals around the pile end in a circumferential direction. Each reinforcement unit is connected to the sliding collar and the pile end at both ends, respectively. A traction rope passes through an inner traction guide and then around the bottom of the pile end to connect with the sliding collar. This structure allows the device to remain in a compact state during the implantation stage, enabling it to be directly driven into the pile body using the steel pipe pile. After reaching the predetermined position, the sliding collar is pulled upward by the traction rope, shortening the distance between the two ends of each reinforcement unit. Structurally, this forces the reinforcement units to bulge outward radially, forming an expanded diameter reinforcement structure around the pile end. This expanded diameter reinforcement structure is geometrically adapted to the enlarged head area and is rigidly connected to the steel pipe pile to form an integral whole. After cement-soil consolidation, it can directly bear the pile end load, increasing the end support area and improving the stress state of the edge and transition area of ​​the enlarged head. This effectively solves the problem of difficulty in lowering large-sized reinforcement components in limited construction channels.

[0007] Preferably, each reinforcing unit includes a flexible reinforcing sheet and a supporting skeleton, with the supporting skeleton attached to the flexible reinforcing sheet. The reinforcing unit employs a structure combining the flexible reinforcing sheet and the supporting skeleton. During the diameter expansion process, the supporting skeleton provides contour support to the flexible reinforcing sheet, ensuring the geometric stability of the multiple reinforcing units after unfolding into an outwardly bulging surface. The flexible reinforcing sheet and the gaps between it facilitate the entry of cement and soil into the unfolded outwardly bulging surface, and after the cement and soil solidify, they constrain the enlarged end, resulting in better overall integrity of the enlarged end.

[0008] As a further preferred embodiment, the support frame includes a plurality of longitudinal support ribs arranged along the length direction of the reinforcing unit and a plurality of transverse support ribs arranged along the width direction of the reinforcing unit. The plurality of longitudinal support ribs and the plurality of transverse support ribs are staggered and connected to form an integral frame structure. The upper end and lower end of each longitudinal support rib are respectively connected to the sliding collar and the pile end. The staggered connection of the longitudinal support ribs and the transverse support ribs forms an integral frame. When the two ends are compressed, the longitudinal support ribs bulge outwards, and the transverse support ribs maintain the relative positions between the longitudinal support ribs and limit and constrain the longitudinal support ribs during the diameter expansion process, so that the reinforcing unit forms a smooth and stable bulging surface during the diameter expansion process, which is beneficial to the forming quality of the enlarged end.

[0009] As a further preferred embodiment, the flexible reinforcing sheet is made of fiber cloth, and the supporting skeleton is sewn onto the flexible reinforcing sheet. The use of fiber cloth for the flexible reinforcing sheet and the attachment of the supporting skeleton to the fiber cloth via sewing simplifies the process. After unfolding, the fiber cloth forms a continuous convex surface, which improves the integrity of the enlarged end and the overall load-bearing performance after consolidation. The fiber cloth is preferably glass fiber cloth or carbon fiber cloth, with glass fiber cloth being more preferred.

[0010] As a further preferred embodiment, the number of traction ropes is multiple, and multiple fixing rings are fixed at intervals around the bottom circumference of the pile end. Multiple sliding rings are fixed at intervals around the circumference of the sliding collar. Each flexible reinforcing sheet has a pre-drilled hole at its bottom. Each traction rope passes through the traction guide from top to bottom, enters a fixing ring, then loops around the bottom of the pile end, folds upwards, passes through a pre-drilled hole, and enters the side of the flexible reinforcing sheet facing the steel pipe pile before being bound to a sliding ring. Using multiple traction ropes, each passing through the traction guide, fixing ring, and pre-drilled hole sequentially before connecting to the sliding ring, ensures that the traction ropes run along the side of the flexible reinforcing sheet closest to the steel pipe pile. When pulled, the force is directly transmitted to the sliding collar, and the fixing ring, pre-drilled hole, and sliding ring are used to position the traction ropes, ensuring uniform stress and stable unfolding shape for each reinforcing unit during the diameter expansion process.

[0011] As a further preferred embodiment, the upper and lower ends of each longitudinal support rib are connected to the sliding collar and the pile end respectively via connectors, and several sets of connectors are installed on the sliding collar and the pile end respectively. This connection method allows the longitudinal support ribs to rotate relative to each other during the diameter expansion process, reducing end stress concentration and improving the smoothness of the diameter expansion operation.

[0012] As a further preferred embodiment, each set of connectors includes a connecting lug and a pin, with the pin disposed on the connecting lug. The upper and lower ends of each longitudinal support rib are rotatably connected to one of the pins. The connector employs a connecting lug and pin structure, with the upper and lower ends of the longitudinal support ribs rotatably connected to the pins. This structure is simple, reliable, and allows for flexible rotation, which helps reduce frictional resistance and the risk of jamming during the diameter expansion process.

[0013] As a further preferred embodiment, the longitudinal support ribs of the plurality of reinforcing units are bound and constrained by metal cable ties on the side near the pile end, and each longitudinal support rib has a preset inward initial curvature. The binding and constraint with metal cable ties prevents the flexible reinforcing sheet from deforming or spreading out due to soil resistance during implantation; the preset inward initial curvature of the longitudinal support ribs makes it easier for the reinforcing unit to form an outward bulging surface during diameter expansion, ensuring the diameter expansion molding effect.

[0014] Preferably, there are two traction guides, symmetrically arranged on the inner wall of the steel pipe pile. The symmetrical arrangement of the two traction guides on the inner wall of the steel pipe pile provides a guiding channel for the traction rope, isolates the traction rope from the external slurry environment, reduces the adhesion and blockage of the traction rope by the slurry, lowers the frictional resistance during the traction process, and improves the reliability of the diameter expansion action.

[0015] A construction method for the above-mentioned composite cement-soil mixing pile with expandable diameter reinforcement device includes the following steps: S1. A deep mixing device is used to spray a curing agent slurry into the foundation soil and forcibly mix it with the in-situ foundation soil to form a cement-soil mixing pile in a fluid or incompletely consolidated state. S2. The plurality of reinforcing units are brought together and attached to the outer periphery of the steel pipe pile, and the traction rope is connected to the sliding collar through the traction guide tube; S3. Use a static pressure machine to press the steel pipe pile into the cement-soil mixing pile to the designed depth; S4. By pulling the traction rope with the traction device, the sliding collar moves towards the pile end along the axial direction of the steel pipe pile, driving the multiple reinforcing units to bulge outward along the radial direction of the steel pipe pile, forming an expanded diameter reinforcing structure around the pile end. Cement and soil enter the expanded diameter reinforcing structure through the gap between adjacent reinforcing units. S5. When the sliding collar reaches the preset stroke, the traction rope is tied to the top of the steel pipe pile to keep the multiple reinforcing units in the unfolded state until the surrounding cement soil is solidified, so that the diameter-enlarging reinforcing structure is formed synchronously with the steel pipe pile and the surrounding cement soil to form a composite enlarged end, and then the traction rope is cut off from the top of the steel pipe pile.

[0016] Compared with the prior art, the present invention has the following advantages: (1) The expansion-diameter reinforcement device of the present invention can be smoothly implanted along the limited construction channel and can be expanded in situ at the pile end. It can achieve the reinforcement of the outer periphery of the enlarged head under the condition of small disturbance and be simultaneously consolidated with the surrounding cement and soil. This effectively solves the problem of difficulty in lowering large-size reinforcement components in the limited construction channel. On the one hand, it ensures the contour forming and geometric stability during the expansion process. On the other hand, it forms a constraint on the enlarged end after the cement and soil are consolidated, improving the end bearing capacity, pull-out capacity, shear capacity and deformation resistance of the enlarged end area of ​​the composite cement and soil mixing pile. (2) The construction method of the present invention presses the device into the cement-soil mixing pile when it is in a fluid or incompletely solidified state, thus avoiding secondary disturbance caused by the implantation after the pile body has hardened; the reinforcing unit unfolds in situ at the pile end to form an enlarged diameter reinforcing structure, which is simultaneously solidified with the surrounding cement-soil, so that the enlarged diameter reinforcing structure, the steel pipe pile and the cement-soil form an integral composite enlarged end; the enlarged diameter reinforcing structure is unfolded before the cement-soil is solidified, and is not affected by the later hardening, so the forming quality is controllable, and ultimately improves the bearing capacity of the enlarged head area of ​​the composite cement-soil mixing pile. Attached Figure Description

[0017] Figure 1 This is a construction diagram of the expandable diameter reinforcement device being pressed into the cement-soil mixing pile in Example 1; Figure 2 This is an enlarged schematic diagram of the pile end in the retracted state of the expandable diameter reinforcement device in Example 1; Figure 3 This is a schematic cross-sectional view of the arrangement of the traction conduit and traction rope inside the steel pipe pile in Example 1. Figure 4 This is a construction diagram of the expandable diameter reinforcement device in Example 1, which is pulled and expanded at the pile end to form a composite enlarged end; Figures 1-4 The specific reference numerals in the attached figures are as follows: 1-Steel pipe pile, 11-Pile end, 12-Fixing ring, 13-Composite enlarged end, 2-Sliding collar, 21-Sliding ring, 3-Reinforcing unit, 31-Flexible reinforcing sheet, 32-Longitudinal support rib, 33-Transverse support rib, 34-Metal cable tie, 35-Reserved hole, 4-Traction rope, 5-Traction guide tube, 6-Cement-soil mixing pile, 7-Connector, 71-Connecting lug, 72-Pin, 8-Static press, 9-Traction equipment. Detailed Implementation

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0019] Example 1: An expandable diameter reinforcement device for composite cement-soil mixing piles, such as... Figures 1-4 As shown, the structure includes a steel pipe pile 1, a sliding collar 2, multiple reinforcing units 3, a traction rope 4, and two traction guides 5. The steel pipe pile 1 is used to support and drive the expandable diameter reinforcing device into the cement-soil mixing pile 6 in a fluid or incompletely consolidated state during the implantation stage, and serves as the core rigid component of the composite pile after pile formation. The sliding collar 2 is fitted around the outer periphery of the steel pipe pile 1 and can move along the axial direction of the steel pipe pile 1. Multiple reinforcing units 3 are arranged at intervals around the pile end 11 of the steel pipe pile 1 along the circumferential direction, so that they can form a near-continuous lantern-shaped expandable diameter reinforcing structure around the pile end 11 after unfolding. The two traction guides 5 are symmetrically arranged on the inner wall of the steel pipe pile 1, and each traction guide 5 extends along the axial direction of the steel pipe pile 1. The two traction guides 5 can be small-diameter guide steel pipes, welded to the inner wall of the steel pipe pile 1. The inlet and outlet of the traction guides 5 can be chamfered or ground to further reduce the frictional resistance during the traction process.

[0020] In Example 1, each reinforcing unit 3 includes a flexible reinforcing sheet 31 and a supporting skeleton. The supporting skeleton is attached to the flexible reinforcing sheet 31, which is made of fiberglass cloth. The supporting skeleton is sewn onto the flexible reinforcing sheet 31. Specifically, the supporting skeleton includes a plurality of longitudinal supporting ribs 32 arranged along the length of the reinforcing unit 3 and a plurality of transverse supporting ribs 33 arranged along the width of the reinforcing unit 3. The plurality of longitudinal supporting ribs 32 and the plurality of transverse supporting ribs 33 are interleaved to form an integral skeleton structure. The longitudinal supporting ribs 32 of the plurality of reinforcing units 3 are made of metal on the side near the pile end 11. The ties 34 are used for binding and restraint. Each longitudinal support rib 32 has an inwardly preset initial curvature. There are multiple traction ropes 4. Multiple fixing rings 12 are fixed at intervals in the circumferential direction at the bottom of the pile end 11. Multiple sliding rings 21 are fixed at intervals in the circumferential direction at the sliding collar 2. A reserved hole 35 is opened at the bottom of each flexible reinforcing sheet 31. Each traction rope 4 passes through the traction guide 5 from top to bottom, enters a fixing ring 12, then goes around the bottom of the pile end 11 and folds back upward. It passes through a reserved hole 35 and enters the side of the flexible reinforcing sheet 31 facing the steel pipe pile 1 and is then bound to the sliding ring 21.

[0021] In Example 1, the upper and lower ends of each longitudinal support rib 32 are connected to the sliding collar 2 and the pile end 11 respectively through connectors 7. Several sets of connectors 7 are installed on the sliding collar 2 and the pile end 11 respectively. Each set of connectors 7 includes a connecting lug 71 and a pin 72. The pin 72 is set on the connecting lug 71. The upper and lower ends of each longitudinal support rib 32 are rotatably connected to a pin 72 respectively.

[0022] In Example 1, to improve field applicability, the inner diameter of the sliding collar 2 is preferably 2-3 mm larger than the outer diameter of the steel pipe pile 1, and the height of the sliding collar 2 is preferably 40-50 mm; the width of the single flexible reinforcing sheet 31 is preferably 100-150 mm, and the length is preferably 1.5-1.8 times the height of the designed composite enlarged end 13; the diameter of each longitudinal support rib 32 is preferably 2-4 mm. The above parameters are preferred embodiments and do not constitute a limitation on the scope of protection of this invention.

[0023] During the construction of the expandable diameter reinforcement device in Example 1, when the traction rope 4 is pulled upward, the sliding collar 2 moves toward the pile end 11, reducing the distance between the upper and lower ends of each reinforcement unit 3. This causes the longitudinal support ribs 32 of multiple reinforcement units 3 to be compressed and bulge outward along the radial direction of the steel pipe pile 1, thereby driving multiple flexible reinforcement sheets 31 to unfold synchronously, thus forming an expanded diameter reinforcement structure around the pile end 11 of the steel pipe pile 1.

[0024] Example 2: Construction method of the expandable diameter reinforcement device based on Example 1, including the following steps: S1. A deep mixing device is used to spray a curing agent slurry into the foundation soil and forcibly mix it with the in-situ foundation soil to form a cement-soil mixing pile 6 in a fluid or incompletely consolidated state. S2. Gather and attach multiple reinforcing units 3 to the outer periphery of the steel pipe pile 1, and connect the traction rope 4 to the sliding collar 2 through the traction guide tube 5; S3. For example Figure 1 As shown, the assembled steel pipe pile 1 is pressed into the cement-soil mixing pile 6 to the designed depth using a static pressure press 8. S4. For example Figure 4 As shown, by pulling the traction rope 4 through the traction device 9, the sliding collar 2 moves along the axial direction of the steel pipe pile 1 toward the pile end 11, driving multiple reinforcing units 3 to bulge outward along the radial direction of the steel pipe pile 1, forming a lantern-shaped diameter expansion reinforcing structure around the pile end 11. Cement and soil enter the diameter expansion reinforcing structure through the gap between adjacent flexible reinforcing sheets 31. S5. When the sliding collar 2 reaches the preset stroke, the traction rope 4 is tied to the top of the steel pipe pile 1 to keep multiple reinforcing units 3 in the unfolded state until the surrounding cement soil is solidified, so that the diameter expansion reinforcing structure and the steel pipe pile 1 and the surrounding cement soil are formed synchronously to form the composite enlarged end 13, and then the traction rope 4 is cut off from the top of the steel pipe pile 1.

[0025] The above construction method involves pressing the device into the cement-soil mixing pile 6 while it is in a fluid or incompletely consolidated state, thus avoiding secondary disturbance caused by implantation after the pile body has hardened. The reinforcing unit 3 unfolds in situ at the pile end to form an enlarged diameter reinforcing structure, which is simultaneously consolidated with the surrounding cement-soil, so that the enlarged diameter reinforcing structure, the steel pipe pile 1, and the cement-soil form an integral composite enlarged end 13. The enlarged diameter reinforcing structure is unfolded before the cement-soil is consolidated, so it is not affected by the later hardening, the forming quality is controllable, and the bearing capacity of the enlarged head area of ​​the composite cement-soil mixing pile is ultimately improved.

Claims

1. A diameter-expandable reinforcement device for composite cement-soil mixing piles, characterized in that, Includes steel pipe piles, sliding collars, multiple reinforcing units, traction ropes, and traction guides; The steel pipe pile is used to bear and drive the expandable diameter reinforcement device into the cement-soil mixing pile in the fluid plastic state or incompletely consolidated state during the implantation stage, and serves as the core rigid component of the composite pile after pile formation. The sliding collar is fitted around the outer periphery of the steel pipe pile and can move along the axial direction of the steel pipe pile. The plurality of reinforcing units are arranged at intervals along the circumference of the steel pipe pile on the outer periphery of the pile end, and the upper end and lower end of each reinforcing unit are respectively connected to the sliding collar and the pile end; The traction guide tube is disposed on the inner wall of the steel pipe pile and extends along the axial direction of the steel pipe pile. The traction rope passes through the traction guide tube from top to bottom and then goes around the bottom of the pile end to connect with the sliding collar. When the traction rope is pulled upward, the sliding collar moves toward the pile end, reducing the distance between the upper and lower ends of each reinforcing unit, driving the multiple reinforcing units to bulge outward along the radial direction of the steel pipe pile, forming an expanded diameter reinforcing structure around the pile end.

2. The expandable diameter reinforcement device for composite cement-soil mixing piles according to claim 1, characterized in that, Each of the reinforcing units includes a flexible reinforcing sheet and a supporting skeleton, the supporting skeleton being attached to the flexible reinforcing sheet.

3. The expandable diameter reinforcement device for composite cement-soil mixing piles according to claim 2, characterized in that, The support frame includes several longitudinal support ribs arranged along the length of the reinforcing unit and several transverse support ribs arranged along the width of the reinforcing unit. The several longitudinal support ribs and the several transverse support ribs are interleaved to form an integral frame structure. The upper end and lower end of each of the longitudinal support ribs are respectively connected to the sliding collar and the pile end.

4. The expandable diameter reinforcement device for composite cement-soil mixing piles according to claim 3, characterized in that, The flexible reinforcing sheet is made of fiber cloth, and the supporting skeleton is sewn onto the flexible reinforcing sheet.

5. The expandable diameter reinforcement device for composite cement-soil mixing piles according to claim 3, characterized in that, The number of traction ropes is multiple. Multiple fixed rings are fixed at intervals around the bottom of the pile end. Multiple sliding rings are fixed at intervals around the circumference of the sliding collar. A reserved hole is opened at the bottom of each flexible reinforcing sheet. Each traction rope passes through the traction guide from top to bottom, enters a fixed ring, then goes around the bottom of the pile end, folds back upward, passes through a reserved hole, enters the side of the flexible reinforcing sheet facing the steel pipe pile, and is then bound to a sliding ring.

6. The expandable diameter reinforcement device for composite cement-soil mixing piles according to claim 3, characterized in that, The upper and lower ends of each of the longitudinal support ribs are connected to the sliding collar and the pile end respectively through connectors, and several sets of connectors are installed on the sliding collar and the pile end respectively.

7. The expandable diameter reinforcement device for composite cement-soil mixing piles according to claim 6, characterized in that, Each set of connectors includes a connecting lug and a pin, the pin being disposed on the connecting lug, and the upper and lower ends of each longitudinal support rib being rotatably connected to one of the pins respectively.

8. The expandable diameter reinforcement device for composite cement-soil mixing piles according to claim 3, characterized in that, The longitudinal support ribs of the plurality of reinforcing units are bound and constrained by metal cable ties on the side near the pile end, and each of the longitudinal support ribs has an inward preset initial curvature.

9. The expandable diameter reinforcement device for composite cement-soil mixing piles according to claim 1, characterized in that, The number of traction guide tubes is two, and the two traction guide tubes are symmetrically arranged on the inner wall of the steel pipe pile.

10. A construction method for an expandable diameter reinforcement device for composite cement-soil mixing piles according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. A deep mixing device is used to spray a curing agent slurry into the foundation soil and forcibly mix it with the in-situ foundation soil to form a cement-soil mixing pile in a fluid or incompletely consolidated state. S2. The plurality of reinforcing units are brought together and attached to the outer periphery of the steel pipe pile, and the traction rope is connected to the sliding collar through the traction guide tube. S3. Use a static pressure machine to press the steel pipe pile into the cement-soil mixing pile to the designed depth; S4. By pulling the traction rope with the traction device, the sliding collar moves towards the pile end along the axial direction of the steel pipe pile, driving the multiple reinforcing units to bulge outward along the radial direction of the steel pipe pile, forming an expanded diameter reinforcing structure around the pile end. Cement and soil enter the expanded diameter reinforcing structure through the gap between adjacent reinforcing units. S5. When the sliding collar reaches the preset stroke, the traction rope is tied to the top of the steel pipe pile to keep the multiple reinforcing units in the unfolded state until the surrounding cement soil is solidified, so that the diameter-enlarging reinforcing structure is formed synchronously with the steel pipe pile and the surrounding cement soil to form a composite enlarged end, and then the traction rope is cut off from the top of the steel pipe pile.

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