WO2023193387A1

WO2023193387A1 - Composite pile foundation structure for steel pipe-concrete branch piles, and construction method therefor

Info

Publication number: WO2023193387A1
Application number: PCT/CN2022/113800
Authority: WO
Inventors: 沈道旭; 韩辉; 冯金; 吴万林; 刘灯明; 钟浪; 曹乾; 李剑锋; 陈清树
Original assignee: 中铁四局集团第五工程有限公司; 中铁四局集团有限公司
Priority date: 2022-04-08
Filing date: 2022-08-22
Publication date: 2023-10-12
Also published as: LU505665A1; CN114941318A; LU505665B1

Abstract

Disclosed in the present invention is a composite pile foundation structure for steel pipe-concrete branch piles, and a construction method therefor. The composite pile foundation structure comprises a concrete branch pile with a plurality of branches and an open steel pipe fixed inside the concrete branch pile with a plurality of branches, wherein the open steel pipe comprises a steel pipe body, and a plurality of squeezing and expansion openings are formed in the periphery of a side wall of the steel pipe body. The open steel pipe can reduce the impact of a soil squeezing effect on a hole wall and on an adjacent pile foundation, thereby reducing the collapsing of the hole wall, and improving the applicability of the pile foundation on soft ground; and the construction efficiency is significantly improved, the damage of the soil squeezing effect to a recently formed concrete pile body is reduced, and a hidden hazard of the pile foundation is thus avoided. By means of the composite pile foundation for steel pipe-concrete branch piles provided in the present invention, not only can the common bearing performance of the composite pile foundation and the pile forming quality of an internal rigid pile be greatly improved, so as to make the branch pile play a better role, but also an application range of the branch pile can be significantly extended, thereby providing a new technical method for the treatment of the soft ground.

Description

A steel pipe-concrete support pile composite pile foundation structure and its construction method

Technical field

The invention relates to the field of geotechnical engineering, and in particular to a steel pipe-concrete support plate pile composite pile foundation structure and a construction method thereof.

Background technique

Our country has a vast territory, the geological conditions are very complex, and weak foundations such as silt and loess are distributed over a wide range. With the rapid development of my country's economy, underground space has been greatly developed. In areas with developed economies and dense transportation networks, the bearing capacity of weak foundations has seriously affected the development of building structures and infrastructure. Weak foundations generally have high moisture content, high compressibility, low strength, and complex soil layer distribution. When building dense railways, highways, municipal and water conservancy projects on such foundations, necessary reinforcement must be carried out to increase the foundation. stability and reduce post-construction settlement. For example, the pile foundations of high-speed railway bridges are subject to loads from superstructures such as bridges, and the resulting settlement directly affects the stability and safe operation of high-speed railway lines.

At present, the main methods to improve the bearing capacity of weak foundations include cement cast-in-place piles, immersed tube cast-in-place piles, drilled cast-in-place piles, concrete prefabricated piles and extruded and expanded branch piles. However, these methods currently have the following shortcomings: the single pile bearing capacity of cement cast-in-place piles is low and the construction quality is difficult to control; sinking tube cast-in-place piles and bored cast-in-place piles are prone to pile failure due to the influence of grouting pressure, uneven grouting and hole walls. The body is necked, and mud treatment is also very inconvenient. The requirements for hole cleaning and concrete pouring are high, and the original soil cannot be fully utilized, causing greater environmental pollution. The site noise is loud during the construction of concrete prefabricated piles, and there is obvious soil squeezing. The effect may easily cause the pile foundation to float or affect the safety of surrounding buildings. As a new type of pile foundation technology, extruded and expanded support plate piles mainly use rotary drilling and then use a support plate drill to squeeze and expand the support plate cavity in the appropriate soil layer. Finally, concrete is poured to form a cast-in-place pile with a support plate. It can significantly improve the bearing capacity of a single pile and reduce the pile diameter and length. It has been widely used in many cities. However, due to the complex extrusion and expansion process and difficult construction technology, the construction efficiency is low and the construction cost is high. Secondly, due to the need for secondary extrusion and expansion after the hole is formed, it will have a greater impact on the hole wall, and because the secondary extrusion and expansion will inevitably have an impact on adjacent pile holes, the hole wall that lacks support will easily collapse, and the soil squeeze effect will cause the hole diameter to change. Changes lead to unsatisfactory pile quality. This phenomenon is more obvious in weak foundations. Therefore, currently due to technical limitations, extruded expanded branch piles are not suitable for most weak foundations.

In view of this, there is an urgent need for a composite pile foundation with reliable construction quality, high bearing capacity and excellent economic benefits.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a steel pipe-concrete support plate pile composite pile foundation structure and a construction method thereof.

In order to achieve the above objects, the technical solutions adopted by the present invention are:

A steel pipe-concrete support pile composite pile foundation structure, including a plurality of concrete support piles and an open steel pipe fixed inside the plurality of concrete support piles; the open steel pipe includes a steel pipe body, and the side of the steel pipe body A plurality of extruded and expanded openings are provided on the circumferential side of the wall; the plurality of concrete support plate piles include a pile body and a plurality of multiple support plates distributed around the pile body, and the multiple support plates are formed from the extruded and expanded openings of the open steel pipes. Mouth extends outward.

Preferably, the plurality of extruded and expanded openings are symmetrically distributed along the cross-section of the steel pipe body; the plurality of support plates are evenly spaced along the circumference of the pile body.

As a preferred technical solution, the plurality of concrete support and disk piles are obtained by constructing a continuous multi-branch extrusion and expansion device. The continuous multi-branch extrusion and expansion device includes a chassis, and a connecting plate is symmetrically provided above the chassis. The chassis and A telescopic rod is vertically fixed between the connecting plates; a plurality of extruding and expanding arms are installed between the connecting plate and the chassis, and the multiple extruding and expanding arms include at least two groups of mutually hinged extruding and expanding units, wherein: The top end of the extrusion and expansion unit of the connecting plate is hinged with the connecting plate, and the bottom end of the extrusion and expansion unit close to the chassis is hinged with the chassis; the extrusion and expansion unit includes a first extrusion and expansion arm and a second extrusion and expansion arm that are hinged to each other; the telescopic expansion unit A limited support steel ring is slidably connected to the rod, and the limited support steel ring is hingedly connected to the extrusion and expansion unit.

Further preferably, the limiting support steel ring includes an inner ring for slidingly fitting with the telescopic rod and an outer ring for hinged connection with the extrusion and expansion unit; the inner ring and the outer ring are fixedly connected through the limiting rod; A connecting lug is fixed on the outside of the outer ring, and a connecting hole is opened in the horizontal direction through the connecting lug. The extrusion and expansion unit is hingedly connected to the outer ring through a pin that is passed through the connecting hole.

More preferably, the first extrusion and expansion arm and the second extrusion and expansion arm are hinged through a rotation limiting device; the rotation limiting device includes a rotating shaft and a first connecting block and a second connecting block that are rotationally connected to the rotating shaft, so The first connecting block and the second connecting block are used to connect with the first extruding and expanding arm and the second extruding and expanding arm respectively; the middle part of one side of the first connecting block has a U-shaped clamping opening, and the first connecting block A pair of sleeves are symmetrically fixed on both sides of the U-shaped clamping opening, and the first connecting block is rotationally connected to the rotating shaft through the sleeves; a limiting clamping block is fixed on one side of the second connecting block, and the limiting clamp The block and the second connecting block are not in the same plane, and the obtuse angle formed by the limiting block and the second connecting block faces the first connecting block; a sleeve for rotational connection with the rotating shaft is fixed on one side of the limiting block. cylinder, the length of the limiting block is greater than the depth of the U-shaped blocking opening. When the first connecting block and the second connecting block rotate relative to each other, it can be ensured that the angle between the first connecting block and the second connecting block is always less than 180°, thereby limiting the relationship between the first extruding and expanding arm and the second extruding and expanding arm. The relative angle between them makes the extrusion and expansion unit always have a tendency to expand outward.

The present invention also provides the above-mentioned construction method of the steel pipe-concrete support pile composite pile foundation structure, which includes the following steps:

(1) After the hole is drilled to the specified depth, the open steel pipe is hoisted to the target depth in the hole to support the hole wall, and then the positions of each extrusion and expansion opening are marked to facilitate the subsequent work of multiple continuous extrusion and expansion devices. ;Compared with conventional full-section sealed steel pipes, intermittent openings can greatly save steel, reduce project costs, and have good hole wall support functions;

(2) Connect the continuous multiple extrusion and expansion devices to the external hydraulic device through the connecting plate, hoist the continuous multiple extrusion and expansion devices into the open steel pipe and align their multiple extrusion and expansion arms with the extrusion and expansion openings of the open steel pipe. ; When the hydraulic device is started to exert downward force on the continuous multi-branch extrusion and expansion device, it will be compressed. The multi-branch extrusion and expansion arms will extend outward to squeeze the foundation soil near the pile hole and expand the hole diameter. When the squeeze and expansion device is pressed, When the target aperture is reached, the continuous multi-branch extrusion and expansion device is stretched by the hydraulic device to reset the continuous multi-branch extrusion and expansion device, that is, the extrusion and expansion at this position is completed; when the open steel pipe has a multi-layer extrusion and expansion opening , change the position of the continuous multi-tube extrusion and expansion device to align it with the corresponding extrusion and expansion opening, repeat step (2) to complete the extrusion and expansion at the corresponding position; until all extrusion and expansion are completed, lift out the continuous multi-tube extrusion and expansion device; pass Using a continuous multi-branch extrusion and expansion device, during the extrusion and expansion process, multiple branches can be extruded and expanded simultaneously within the longitudinal length range of the pile foundation axis and the cross section, which can reduce the number of extrusion and expansion of conventional construction methods and avoid pile extrusion due to extrusion and expansion. The complexity of the expansion process leads to the problem that multiple expansions are needed to form a multi-branch pile foundation structure with high bearing capacity, which significantly improves the construction efficiency and reduces the project cost.

(3) Clean the slag accumulated in the hole due to squeeze and expansion, then hoist the steel cage into the hole and perform grouting. During grouting, the cement slurry can flow along the squeeze and expand opening in the open steel pipe to the space created by the squeeze and expansion. The support plate is finally formed inside, and after forming, a steel pipe-multiple concrete support plate pile composite pile foundation is obtained.

Compared with the prior art, the beneficial effects of the present invention are:

The steel pipe-concrete support-disc pile composite pile foundation structure provided by the invention includes a plurality of concrete support-disk piles and an open steel pipe fixed inside the multiple concrete support-disk piles. The open steel pipe can reduce the load of adjacent pile foundations during construction. The resulting soil squeezing effect affects the hole wall and adjacent pile foundations, reducing the collapse of hole walls lacking support and improving the applicability of pile foundations on weak foundations. Secondly, reduce the damage caused by the soil squeezing effect to the newly formed cement pile body and avoid hidden diseases of the pile foundation. It avoids a series of problems such as hole wall collapse caused by secondary expansion after conventional extrusion and expansion, and hole diameter changes due to soil squeezing effect, which affects pile quality. It also significantly improves the pile foundation bearing capacity and construction efficiency. In addition, compared with conventional full-section sealed steel pipe piles, interrupted openings can greatly save steel and reduce project costs.

The steel pipe-concrete supporting and disc pile composite pile foundation provided by the present invention can not only greatly improve the joint bearing performance of the composite pile foundation and the pile quality of the internal rigid piles, but also better exert the effect of supporting and disc piles, and can significantly improve the support and disc pile foundation. The applicable scope of piles provides new technical methods for the treatment of weak foundations, and has certain economic, technical and engineering benefits.

Description of the drawings

Figure 1 is a schematic diagram of the steel pipe-concrete support pile composite pile foundation structure;

Figure 2 is a schematic structural diagram of an open steel pipe;

Figure 3 is a schematic diagram of the construction of open steel pipes and continuous multi-branch extrusion and expansion devices;

Figure 4 is a schematic structural diagram of the continuous multi-branch extrusion and expansion device when it is not extruded and expanded;

Figure 5 is a schematic structural diagram of the continuous multi-branch extrusion and expansion device in the extrusion and expansion state;

Figure 6 is a schematic structural diagram of the limit support steel ring;

Figure 7 is a schematic structural diagram of the outer ring;

Figure 8 is a schematic structural diagram of the rotation limiting device;

Figure 9 is an exploded view of the rotation limiting device;

Reference signs: 1-Multiple concrete support disk piles, 11-Pile body, 12-Multiple support disks, 2-Open steel pipe, 21-Steel pipe body, 22-Extrusion expansion mouth, 3-Continuous multi-extrusion expansion device , 31-chassis, 32-connecting plate, 33-telescopic rod, 34-extrusion and expansion unit, 341-first extrusion and expansion arm, 342-second extrusion and expansion arm, 35-limiting support steel ring, 351-inner ring, 352-outer ring, 353-limiting rod, 354-connecting ear, 355-connecting hole, 356-pin, 361-rotating shaft, 362-first connecting block, 363-second connecting block, 364-U-shaped clamping position Mouth, 365-sleeve, 366-limiting block.

Detailed ways

The present utility model will be further described below with reference to the embodiments and drawings, so that those skilled in the art can better understand the present utility model and implement it, but the examples are not intended to limit the present utility model.

It should be noted that "fixed", "connected", "installed", "fixed connection", etc. in this utility model all mean that two components connected to each other are fixed together, usually by welding, screws, etc. Together. "Sliding connection", "hinged", etc. mean that two parts are connected together and can move relative to each other. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

It should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings and are only In order to facilitate the description of the present invention and simplify the description, it is not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. The "first" and "second" mentioned in the present invention do not represent the specific number and order, but are only used for the distinction of names.

Referring to Figure 1, a steel pipe-concrete support pile composite pile foundation structure includes a plurality of concrete support piles 1 and an open steel pipe 2 fixed inside the multiple concrete support piles; the open steel pipe 2 includes a steel pipe body 21, A plurality of extruded openings 22 are provided on the side wall of the steel pipe body; referring to Figure 2, the open steel pipe has two layers of extruded openings, and the extruded openings in each layer are distributed symmetrically along the cross section of the steel pipe body; multiple branches The concrete support plate pile 1 includes a pile body 11 and several multi-branch support plates 12 distributed around the pile body. The multi-branch support plates 12 extend outward from the extruded and expanded mouth 22 of the open steel pipe. In specific applications, according to the design requirements of multiple concrete support piles 1, the positions that need to be squeezed and expanded are determined in advance, and the side walls of the steel pipe body are positioned and opened. The squeezed and expanded openings are symmetrically distributed along the cross section of the steel pipe, and the number, length and The width can be factory-prefabricated according to the design requirements of the pile foundation.

The multiple concrete support piles 1 are constructed through the continuous multi-branch extrusion and expansion device 3. Referring to Figures 3 to 5, the continuous multi-branch extrusion and expansion device 3 includes a chassis 31. A connecting plate 32 is symmetrically provided above the chassis 31. The chassis 31 and A telescopic rod 33 is fixed vertically between the connecting plates 32; a plurality of extruding and expanding arms are installed between the connecting plate 32 and the chassis 31, and the multiple extruding and expanding arms are evenly spaced along the periphery of the chassis 31 and the connecting plate 32. Distribute it so that the multiple branches obtained by extrusion and expansion are evenly distributed around the pile foundation. During construction, the positions of the multiple extrusion and expansion arms correspond to the opening direction of the extrusion and expansion opening 22 in the open steel pipe. During the extrusion and expansion process, the expansion units in the multiple extrusion and expansion arms can extend from the extrusion expansion opening 22 and align with the hole wall. The surrounding soil is squeezed; the multiple squeezing and expansion arms include at least two groups of mutually hinged squeezing and expansion units 34, wherein: the top of the squeezing and expansion unit close to the connecting plate is hinged to the connecting plate, and the bottom end of the squeezing and expanding unit close to the chassis Hinged with the chassis; the extrusion and expansion unit 34 includes a first extrusion and expansion arm 341 and a second extrusion and expansion arm 342 that are hinged to each other; the telescopic rod 33 is slidably connected to a limited support steel ring 35, and the limit support steel ring 35 and the extrusion and expansion unit 34 Articulated. In Figure 4, the number of multi-branch extrusion and expansion arms is two groups, and each multi-branch expansion arm has three sets of extrusion and expansion units. It should be noted that the number of multi-branch extrusion and expansion arms and the number of extrusion and expansion units can be determined according to the opening. The number and size of the extrusion and expansion openings in the open steel pipe 2 are adjusted accordingly so that they match each other. During the extrusion and expansion process, it is only necessary to adjust the positions of the continuous multiple expansion devices at one time to make them match the extrusion expansion openings in the open steel pipe 2. Corresponding to the openings, a certain area can be squeezed and expanded to improve construction efficiency. Referring to Figures 6 and 7, the limit support steel ring 35 includes an inner ring 351 for slidingly fitting with the telescopic rod 33 and an outer ring 352 for hinged connection with the extrusion and expansion unit 34; the inner ring 351 and the outer ring 352 pass through the limit The rod 353 is fixedly connected; a connecting lug 354 is fixed on the outside of the outer ring 352, and the connecting lug 354 has a connecting hole 355 extending through the connecting lug in the horizontal direction; the extrusion and expansion unit 34 communicates with the outer ring through a pin 356 that is inserted in the connecting hole. 352 Articulated. Further preferably, the number of limiting rods 353 is four, and the four limiting rods are evenly distributed at 90° to each other between the inner ring 351 and the outer ring 352 . The limiting rod 353 serves as a connecting structure between the inner ring 351 and the outer ring 352, which can significantly improve the structural stability of the limiting support steel ring.

As a preferred embodiment, referring to Figures 8 and 9, the first extrusion and expansion arm 341 and the second extrusion and expansion arm 342 are hinged through a rotation limiting device; the rotation limiting device includes a rotating shaft 361 and a first connecting block that is rotationally connected to the rotating shaft. 362 and the second connecting block 363. The first connecting block 362 and the second connecting block 363 are used to connect with the first extruding and expanding arm 341 and the second extruding and expanding arm 342 respectively; the middle part of one side of the first connecting block 362 has a U shape. The first connecting block 364 is symmetrically fixed with a pair of sleeves 365 on both sides of the U-shaped clamping opening 364. The first connecting block 362 is rotationally connected to the rotating shaft 361 through the sleeves; one side of the second connecting block 363 is fixed with a limited number. The limiting blocking block 366 is not in the same plane as the second connecting block 363, and the obtuse angle formed by the limiting blocking block 366 and the second connecting block 363 faces the first connecting block 362; the limiting blocking block 366 A sleeve 365 for rotational connection with the rotating shaft is fixed on one side of the U-shaped stopper 366 . The length of the limiter block 366 is greater than the depth of the U-shaped stopper opening 64 .

(1) After the hole is drilled to the specified depth, the open steel pipe is hoisted to the target depth in the hole to support the hole wall, and then the positions of each extrusion and expansion opening are marked to facilitate the subsequent work of multiple continuous extrusion and expansion devices. ; The diameter of the open steel pipe is slightly smaller than the hole diameter, making it easy to hoist. Compared with conventional full-section sealed steel pipes, the intermittent opening can greatly save steel, reduce project costs, and has good hole wall support functions; in specific applications , according to the design requirements of the support plate pile foundation, the position that needs to be squeezed and expanded can be determined in advance, and the side wall of the steel pipe is positioned and opened. The squeezed and expanded openings are symmetrically distributed along the cross section of the steel pipe, and the number, length and width can be determined according to the pile foundation. The design requires factory prefabricated production.

(2) Connect the continuous multiple extrusion and expansion devices to the external hydraulic device through the connecting plate, hoist the continuous multiple extrusion and expansion devices into the open steel pipe and align their multiple extrusion and expansion arms with the extrusion and expansion openings of the open steel pipe. ; When the hydraulic device is started to exert downward force on the continuous multi-branch extrusion and expansion device, it will be compressed. The multi-branch extrusion and expansion arms will extend outward to squeeze the foundation soil near the pile hole and expand the hole diameter. When the squeeze and expansion device is pressed, When the target aperture is reached, the continuous multi-branch extrusion and expansion device is stretched by the hydraulic device to reset the continuous multi-branch extrusion and expansion device, that is, the extrusion and expansion at this position is completed; when the open steel pipe has a multi-layer extrusion and expansion opening , change the position of the continuous multi-tube extrusion and expansion device to align it with the corresponding extrusion and expansion opening, and repeat step (2) to complete the extrusion and expansion at the corresponding position; until all extrusion and expansion are completed, lift out the continuous multi-tube extrusion and expansion device.

(3) Clean the slag accumulated in the hole due to squeeze and expansion, then hoist the steel cage into the hole and perform grouting. During grouting, the cement slurry can flow along the squeeze and expand opening in the open steel pipe to the space created by the squeeze and expansion. A supporting plate is eventually formed inside to improve the bearing capacity of the weak foundation.

Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

Claims

A steel pipe-concrete support pile composite pile foundation structure, characterized by: including a plurality of concrete support piles and an open steel pipe fixed inside the plurality of concrete support piles; the open steel pipe includes a steel pipe body, and the A plurality of extruded and expanded openings are provided on the side wall of the steel pipe body; the plurality of concrete support-plate piles include a pile body and a plurality of multiple support plates distributed around the pile body, and the multiple support plates are formed from an open type The extrusion and expansion of the steel pipe extends outward.
The steel pipe-concrete support plate pile composite pile foundation structure according to claim 1, characterized in that: the plurality of extrusion and expansion openings are symmetrically distributed along the cross section of the steel pipe body; the plurality of support plates are evenly distributed along the circumference of the pile body. interval distribution.
The steel pipe-concrete support and disk pile composite pile foundation structure according to claim 1, characterized in that: the plurality of concrete support and disk piles are constructed through the construction of a continuous multi-branch extrusion and expansion device, and the continuous multi-branch extrusion and expansion device includes a chassis , a connecting plate is symmetrically provided above the chassis, and a telescopic rod is vertically fixed between the chassis and the connecting plate; a plurality of extruding expansion arms are installed between the connecting plate and the chassis, and the multiple extruding arms are The expansion arm includes at least two groups of mutually hinged extrusion and expansion units, wherein: the top of the extrusion and expansion unit close to the connecting plate is hinged to the connecting plate, and the bottom end of the extrusion and expansion unit close to the chassis is hinged to the chassis; the extrusion and expansion units include mutually hinged The first extrusion and expansion arm and the second extrusion and expansion arm; the telescopic rod is slidingly connected with a limited support steel ring, and the limit support steel ring is hingedly connected with the extrusion and expansion unit.
The steel pipe-concrete support pile composite pile foundation structure according to claim 3, characterized in that: the limiting support steel ring includes an inner ring for slidingly matching with the telescopic rod and an outer ring for hinged connection with the extrusion and expansion unit. ring; the inner ring and the outer ring are fixedly connected through a limiting rod; a connecting ear is fixed on the outside of the outer ring, and a connecting hole is opened in the horizontal direction through the connecting ear; the extrusion and expansion unit passes through The pin shaft located in the connecting hole is hinged with the outer ring.
The steel pipe-concrete support pile composite pile foundation structure according to claim 3, characterized in that: the first extrusion and expansion arm and the second extrusion and expansion arm are hinged through a rotation limiter; the rotation limiter includes a rotating shaft And a first connecting block and a second connecting block that are rotationally connected to the rotating shaft. The first connecting block and the second connecting block are used to connect with the first extruding and expanding arm and the second extruding and expanding arm respectively; the first connecting block There is a U-shaped clamping opening in the middle of one side, and a pair of sleeves are symmetrically fixed on both sides of the U-shaped clamping opening on the first connecting block. The first connecting block is rotationally connected to the rotating shaft through the sleeves; A limiting block is fixed on one side of the two connecting blocks, the limiting block and the second connecting block are not in the same plane, and the obtuse angle formed by the limiting block and the second connecting block faces the first connecting block; A sleeve for rotational connection with the rotating shaft is fixed on one side of the limiting block, and the length of the limiting block is greater than the depth of the U-shaped blocking opening.
The construction method of a steel pipe-concrete support pile composite pile foundation structure according to any one of claims 1 to 5, characterized in that it includes the following steps:

(1) After the hole is drilled to the specified depth, the open steel pipe is hoisted to the target depth in the hole to support the hole wall, and then the positions of each extrusion and expansion opening are marked to facilitate the subsequent work of multiple continuous extrusion and expansion devices. ;

(2) Connect the continuous multiple extrusion and expansion devices to the external hydraulic device through the connecting plate, hoist the continuous multiple extrusion and expansion devices into the open steel pipe and align their multiple extrusion and expansion arms with the extrusion and expansion openings of the open steel pipe. ; When the hydraulic device is started to exert downward force on the continuous multi-branch extrusion and expansion device, it will be compressed. The multi-branch extrusion and expansion arms will extend outward to squeeze the foundation soil near the pile hole and expand the hole diameter. When the squeeze and expansion device is pressed, When the target aperture is reached, the continuous multi-branch extrusion and expansion device is stretched by the hydraulic device to reset the continuous multi-branch extrusion and expansion device, that is, the extrusion and expansion at this position is completed; when the open steel pipe has a multi-layer extrusion and expansion opening , change the position of the continuous multi-tube extrusion and expansion device to align it with the corresponding extrusion and expansion opening, repeat step (2) to complete the extrusion and expansion at the corresponding position; until all extrusion and expansion are completed, lift out the continuous multi-tube extrusion and expansion device;

(3) Clean the slag accumulated in the hole due to squeeze and expansion, then hoist the steel cage into the hole and perform grouting. During grouting, the cement slurry can flow along the squeeze and expand opening in the open steel pipe to the space created by the squeeze and expansion. The support plate is finally formed inside, and after forming, a steel pipe-multiple concrete support plate pile composite pile foundation is obtained.