阅读说明：本技术 适于高填方湿陷性黄土场地的管桩复合地基及其施工方法 (Tubular pile composite foundation suitable for high-fill collapsible loess field and construction method thereof ) 是由 邱明明 黄加昊 王弘起 孙杰龙 杨红霞 李盛斌 于 2021-09-29 设计创作，主要内容包括：本发明公开了一种适于高填方湿陷性黄土场地的管桩复合地基及其施工方法,管桩复合地基包括多个伞状扩底管桩组件、加筋褥垫层和黄土地基层,伞状扩底管桩组件包括管桩、伞状扩底结构、注浆管和注浆体,伞状扩底结构包括连接套筒、固定环、中心钢管、外扩钢管、三通接头、第一撑杆、固定接头和注浆接头。本发明中伞状扩底结构在竖向压力作用下可张开一定角度,通过高压灌注水泥浆液包裹伞状扩底结构,形成扩大的水泥土桩底增强结构,伞状扩底结构与管桩连接形成组合桩结构,提升了桩体的竖向承载能力,进而增强伞状扩底管桩复合地基竖向承载性能；可适用于高填方的湿陷性黄土地基处理,具有较好的抗沉、抗不均匀沉降和变形协调能力。(The invention discloses a tubular pile composite foundation suitable for a high-fill collapsible loess field and a construction method thereof. The umbrella-shaped bottom expanding structure can be expanded by a certain angle under the action of vertical pressure, the umbrella-shaped bottom expanding structure is wrapped by high-pressure poured cement slurry to form an expanded cement soil pile bottom reinforcing structure, and the umbrella-shaped bottom expanding structure is connected with the tubular pile to form a combined pile structure, so that the vertical bearing capacity of the pile body is improved, and the vertical bearing performance of the umbrella-shaped bottom expanding tubular pile composite foundation is further enhanced; the method is suitable for treating the high-fill collapsible loess foundation, and has good anti-settling, anti-differential-settling and deformation coordination capabilities.)

1. The utility model provides a be suitable for tubular pile composite foundation in high fill collapsible loess place, its characterized in that, includes a plurality of umbelliform bottom extension tubular pile subassemblies, adds muscle mattress pad layer (6) and loess foundation bed layer (7), every umbelliform bottom extension tubular pile subassembly all includes tubular pile (1), umbelliform bottom extension structure (2), slip casting pipe (4) and slip casting body (5), the tubular pile sets up in the loess foundation bed, umbelliform bottom extension structure includes connecting sleeve (2.1), solid fixed ring (2.2), central steel pipe (2.3), slip casting joint (2.8) and a plurality of outer steel pipe (2.4) that expands, the connecting sleeve cover is established the bottom outside of tubular pile, gu fixed ring sets up the bottom of tubular pile and its outside with it is fixed to connect the sleeve, central steel pipe sets up in the tubular pile and its lower extreme stretches out to the lower extreme of tubular pile, a plurality of outer steel pipe use the central steel pipe is radial distribution as the center, every the upper end of expanding the steel pipe outward all with gu fixed ring links to each other, and every expand the steel pipe outward all through a first vaulting pole (2.6) with central steel pipe connects, slip casting articulate the grout outlet of slip casting pipe, the slip casting pipe sets up in the tubular pile, add muscle mattress layer and lay on the loess foundation bed layer.

2. The tubular pile composite foundation of claim 1, wherein the fixing ring is a polygonal structure made of steel tubes, and three-way joints (2.5) matched with the number of the outward-expanded steel tubes are arranged on the fixing ring; and the upper end of each outward-expanding steel pipe is connected with the fixing ring through one tee joint.

3. The tubular pile composite foundation of claim 1, wherein a fixing mechanism for fixing the central steel tube is further arranged in the fixing ring, and the fixing mechanism comprises a fixing sleeve (2.21) sleeved on the central steel tube and a plurality of second support rods (2.22) connecting the fixing sleeve and the fixing ring.

4. The tubular pile composite foundation of claim 1, wherein a plurality of positioning flanges (3) for fixing the central steel tube are arranged in the tubular pile, each positioning flange comprises an external steel ring (3.1), an internal steel tube sleeve (3.2) and a plurality of third support rods (3.3), the external steel ring is fixedly connected with the inner wall of the tubular pile, the internal steel tube sleeve is sleeved on the central steel tube, and the plurality of third support rods are uniformly arranged between the external steel ring and the internal steel tube sleeve.

5. The tubular pile composite foundation of claim 1, wherein the central steel tube is further sleeved with a fixed joint (2.7), the lower ends of the first supports are all hinged to the fixed joint, and the upper ends of the lower ends of the first supports are hinged to the outer expanding steel tube correspondingly.

6. The tubular pile composite foundation of claim 1, wherein the overlap length of the connecting sleeve and the tubular pile is 0.3-0.5 m.

7. The pipe pile composite foundation of claim 1, wherein each of the outwardly expanded steel pipes is arranged with a lower end inclined from the outside to the inside to an upper end; a plurality of slurry leaking holes are formed in the central steel pipe and the outer expanding steel pipe, and the diameter of each slurry leaking hole is 0.8-1.5 cm.

8. The pipe pile composite foundation according to claim 1, wherein the grout comprises a first grout formed of cement grout and a second grout formed of M30 grout, the first grout being disposed at the position of the umbrella-shaped bellout structure, the second grout being filled in the pipe pile; wherein the water-cement ratio of the cement slurry is 0.5-1: 1, grouting pressure is 0.5-1.0 MPa; the grouting pressure of the M30 grouting mortar is 0.3-0.5 MPa.

9. A construction method of a pipe pile composite foundation suitable for a high fill collapsible loess field, using the pipe pile composite foundation as set forth in any one of claims 1 to 8, the construction method comprising the steps of:

s1, prefabricating a tubular pile (1) and an umbrella-shaped bottom expanding structure (2);

s2, constructing a tubular pile hole on the loess foundation layer (7), wherein the diameter of the tubular pile hole is larger than that of the tubular pile;

s3, sequentially placing the umbrella-shaped bottom expanding structure and the tubular pile into the tubular pile hole, connecting the grouting pipe (4) with a grouting joint (2.8), and fixedly connecting the tubular pile with the umbrella-shaped bottom expanding structure to form a whole;

s4, applying a certain pressure on the top of the tubular pile to open the umbrella-shaped bottom expanding structure to a preset angle;

s5, connecting the grouting pipe (4) and the central steel pipe (2.3) with a grouting pump slurry conveying pipe respectively, grouting with cement slurry to form a first grouting body at the position of the umbrella-shaped bottom expanding structure, fully wrapping the umbrella-shaped bottom expanding structure with the first grouting body, filling the interior of the tubular pile with M30 grouting mortar, and forming a second grouting body; thereby forming an umbrella-shaped bottom expanding tubular pile component;

s6, after all umbrella-shaped bottom-expanding tubular pile components are constructed, constructing a reinforcement mattress layer (6) on the loess foundation layer, and finally completing the construction of the tubular pile composite foundation.

10. The construction method according to claim 9, wherein the thickness of the reinforcing mat layer is 0.3 to 1.0 m.

Technical Field

The invention relates to the technical field of high-fill loess engineering foundation treatment, in particular to a tubular pile composite foundation suitable for a high-fill collapsible loess field and a construction method thereof.

Background

The main problem of high fill loess field engineering is the uneven deformation caused by consolidation settlement, humidification settlement and the like after loess foundation construction, which causes disasters such as foundation instability, building structure cracking, large deformation and the like, and seriously affects the service safety of the engineering structure.

In the prior art, the invention patent with publication number CN101649613A discloses an enlarged head prestressed pipe pile and a construction method thereof, wherein the pipe pile comprises: the pipe pile comprises a pipe pile body and an enlarged head, wherein one end of the pipe pile body is connected with the enlarged head, and the enlarged head is provided with a steel bar expansion device; the construction method comprises the following steps: 1. drilling; 2. reaming; 3. placing a tubular pile inlet hole with a steel bar expansion device; 4. expanding the steel bar expanding device; 5. the filling material conveying pipe penetrates into the bottom of the formed hole from the inner hole of the pipe pile; 6. and filling filler between the hole wall and the pipe pile. The utility model discloses an application number is 202020449177.0's utility model discloses an umbelliform karst anti-floating pile, including the pile body, pull rod and the umbelliform self-expanding structure of pile tip, the pile body adopts cylindric steel-pipe pile body, the pull rod adopts the diameter to be equivalent to the steel pipe of pile body internal diameter, the umbelliform self-expanding structure of pile tip includes from the expander bar, bracing piece and pile head, the pile head is the taper shape, it is the front end to define pile head most advanced one side, the fixed front end that sets up at the pull rod of pile head, the pull rod nestification is in the cylindric pile body of pile body, pass through the bolt with the pull rod front end from the front end of expander bar and articulate, pass through the bolt with the bracing piece front end from the middle part of expander bar and articulate, the rear end and the pile body front end of bracing piece pass through the bolt and articulate. Although the pipe piles or anti-floating piles in the prior art can increase high bearing capacity or pile foundation anti-floating capacity to some extent, the pipe piles or anti-floating piles are still not suitable for high-fill collapsible loess fields.

Disclosure of Invention

The invention aims to provide a tubular pile composite foundation suitable for a high-fill collapsible loess field, which aims to improve and solve the problems of bearing capacity and deformation resistance of the high-fill loess foundation and improve the safety of a building in the high-fill loess field.

In order to achieve the above purpose, the invention provides a tubular pile composite foundation suitable for a high-fill collapsible loess field, which comprises a plurality of umbrella-shaped bottom-expanding tubular pile components, a reinforced mattress layer and a loess foundation layer, wherein each umbrella-shaped bottom-expanding tubular pile component comprises a tubular pile, an umbrella-shaped bottom-expanding structure, a grouting pipe and a grouting body, the tubular pile is arranged in the loess foundation layer, the umbrella-shaped bottom-expanding structure comprises a connecting sleeve, a fixing ring, a central steel pipe, a grouting joint and a plurality of outer-expanding steel pipes, the connecting sleeve is sleeved outside the bottom of the tubular pile, the fixing ring is arranged at the bottom of the tubular pile, the outer side of the fixing ring is fixed with the connecting sleeve, the central steel pipe is arranged in the tubular pile, the lower end of the central steel pipe extends out of the lower end surface of the tubular pile, the plurality of outer-expanding steel pipes are radially distributed by taking the central steel pipe as the center, and the upper end of each outer-expanding steel pipe is connected with the fixing ring, and every expand the steel pipe outward all through a first vaulting pole with central steel pipe connects, the slip casting articulate the grout outlet of slip casting pipe, the slip casting pipe sets up in the tubular pile, add muscle mattress layer and lay on the loess foundation bed layer.

Furthermore, the fixing ring is of a polygonal structure made of steel pipes, and three-way joints matched with the number of the outward-expanded steel pipes are arranged on the fixing ring; and the upper end of each outward-expanding steel pipe is connected with the fixing ring through one tee joint.

Further, still be provided with in the fixed ring and be used for fixing the fixed establishment of center steel pipe, fixed establishment establishes including the cover fixed cover on the center steel pipe with connect fixed cover with a plurality of second vaulting poles of solid fixed ring.

Further, be equipped with a plurality of being used for fixing in the tubular pile the flange of center steel pipe, flange includes external steel ring, inscription steel pipe sleeve and a plurality of third vaulting pole, external steel ring with the inner wall fixed connection of tubular pile, inscription steel pipe sleeve cover is established on the center steel pipe, it is a plurality of the third vaulting pole is evenly arranged external steel ring with between the inscription steel pipe sleeve.

Furthermore, a fixed joint is further sleeved on the central steel pipe, the lower ends of the first supports are hinged to the fixed joint, and the upper ends of the lower ends of the first supports are hinged to the corresponding outer expanding steel pipes.

Further, the length of the lap joint of the connecting sleeve and the tubular pile is 0.3-0.5 m.

Furthermore, each outward-expanding steel pipe is obliquely arranged from the lower end to the upper end from outside to inside; a plurality of slurry leaking holes are formed in the central steel pipe and the outer expanding steel pipe, and the diameter of each slurry leaking hole is 0.8-1.5 cm.

Further, the grout comprises a first grout formed by cement grout and a second grout formed by M30 grouting mortar, the first grout is arranged at the position of the umbrella-shaped bottom expanding structure, and the second grout is filled in the tubular pile; wherein the water-cement ratio of the cement slurry is 0.5-1: 1, grouting pressure is 0.5-1.0 MPa; the grouting pressure of the M30 grouting mortar is 0.3-0.5 MPa.

The invention also provides a construction method of the tubular pile composite foundation suitable for the high-fill collapsible loess field, which adopts the tubular pile composite foundation and comprises the following steps:

s1, prefabricating a tubular pile and an umbrella-shaped bottom expanding structure;

s2, constructing a tubular pile hole on the loess foundation layer, wherein the diameter of the tubular pile hole is larger than that of the tubular pile;

s3, sequentially placing the umbrella-shaped bottom expanding structure and the tubular pile into the tubular pile hole, connecting the grouting pipe with a grouting joint, and fixedly connecting the tubular pile with the umbrella-shaped bottom expanding structure to form a whole;

s4, applying a certain pressure on the top of the tubular pile to open the umbrella-shaped bottom expanding structure to a preset angle;

s5, connecting the grouting pipe and the central steel pipe with a grouting pump slurry conveying pipe respectively, grouting with cement slurry to form first grouting bodies at the positions of the umbrella-shaped bottom expanding structures, fully wrapping the umbrella-shaped bottom expanding structures with the first grouting bodies, filling the interiors of the tubular piles with M30 grouting mortar, and forming second grouting bodies; thereby forming an umbrella-shaped bottom expanding tubular pile component;

s6, after all umbrella-shaped bottom-expanding tubular pile components are constructed, constructing a reinforcement mattress layer on the loess foundation layer, and finally completing the construction of the tubular pile composite foundation.

Further, the thickness of the reinforced mattress layer is 0.3-1.0 m.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the tubular pile composite foundation, the umbrella-shaped bottom expanding structure can be expanded by a certain angle under the action of vertical pressure, cement grout is poured at high pressure to wrap the umbrella-shaped bottom expanding structure, so that an expanded cement soil pile bottom reinforcing structure is formed, the umbrella-shaped bottom expanding structure and the tubular pile are connected to form a combined pile structure, the vertical bearing capacity of a pile body is improved, and the vertical bearing performance of the umbrella-shaped bottom expanding tubular pile composite foundation is further enhanced; the method is suitable for treating the high-fill collapsible loess foundation, and has good anti-settling, anti-differential-settling and deformation coordination capabilities.

(2) The tubular pile composite foundation is mainly formed by assembling tubular piles, bottom umbrella-shaped structures and other prefabricated components, and has the advantages of simplicity and convenience in manufacturing, material saving, quickness in construction, economy, reliability and the like. The size of the tubular pile and the umbrella-shaped bottom expanding structure can be adjusted according to engineering requirements, the arrangement is flexible, and the strength and rigidity properties of the tubular pile and the umbrella-shaped bottom expanding structure are improved, so that the requirements of the bearing performance of the umbrella-shaped bottom expanding tubular pile composite foundation under different geological conditions are met.

(3) The construction method comprises the steps of arranging the umbrella-shaped bottom expanding tubular pile components in the loess foundation layer, constructing the reinforcement mattress layer on the umbrella-shaped bottom expanding tubular pile components to form the tubular pile composite foundation, opening the umbrella-shaped bottom expanding structure at a certain angle after prepressing, forming a reinforcement body for expanding the pile bottom structure with the surrounding soil body after high-pressure grouting, and effectively improving the vertical bearing capacity of the umbrella-shaped bottom expanding tubular pile.

In addition to the objects, features and advantages described above, other objects, features and advantages of the present invention are also provided. The present invention will be described in further detail below with reference to the drawings.

Drawings

The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the embodiments of the invention without limiting the embodiments of the invention. In the drawings:

fig. 1 is a schematic structural view of a pipe pile composite foundation according to a preferred embodiment of the present invention;

FIG. 2 is a perspective view of an umbrella-shaped bottom-expanding tubular pile assembly according to the present invention;

FIG. 3 is a plan view of the pile base of the pipe pile composite foundation of the present invention;

FIG. 4 is a schematic longitudinal sectional view of the umbrella-shaped under-reamed tubular pile assembly according to the present invention;

FIG. 5 is a schematic view of the structure of the fixing ring and the tubular pile of the present invention;

FIG. 6 is a plan view of a positioning flange structure according to a preferred embodiment of the present invention;

wherein, 1-tubular pile, 2-umbrella-shaped bottom expanding structure, 2.1-connecting sleeve, 2.2-fixing ring, 2.21-fixing sleeve, 2.22-second brace rod, 2.3-central steel pipe, 2.4-external expanding steel pipe, 2.5-three-way joint and 2.6-first brace rod; 2.7-fixed joint, 2.8-grouting joint, 3-positioning flange, 3.1-external steel ring, 3.2-internal steel pipe sleeve, 3.3-second support rod, 4-grouting pipe, 5-grouting body, 6-reinforced mattress layer and 7-loess foundation course.

Detailed Description

Embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways, which are defined and covered by the claims.

Referring to fig. 1 to 6, the present embodiment provides a tubular pile composite foundation suitable for a high fill collapsible loess field, including a plurality of umbrella-shaped bottom-expanding tubular pile components, a reinforcement mattress layer 6 and a loess foundation layer 7; the method specifically comprises the following steps: a plurality of umbrella-shaped bottom-expanding pipe pile components are arranged in the loess foundation layer, and a reinforced mattress layer is applied on the umbrella-shaped bottom-expanding pipe pile components to jointly form the composite foundation.

Each umbrella-shaped bottom-expanding tubular pile component comprises a tubular pile 1, an umbrella-shaped bottom-expanding structure 2, a grouting pipe 4 and grouting bodies 5. The tubular pile is preferably prefabricated by reinforced concrete or section steel materials, and taking a steel pipe tubular pile as an example, the tubular pile is preferably 10-30 cm in pipe diameter and 5-10 mm in wall thickness. The tubular piles are arranged in the loess foundation layer, the distance between the tubular piles can be 0.5-2.0 m, the pile length is 6-20 m, and the piles can be distributed according to an equilateral triangle or a square. The pipe pile is drilled into a pipe pile hole, and the diameter of the pipe pile hole is larger than that of the pipe pile; the inside of the pipe pile can also be provided with a reinforcement cage to enhance the bearing performance.

The umbrella-shaped bottom expanding structure comprises a connecting sleeve 2.1, a fixing ring 2.2, a central steel pipe 2.3, an outer expanding steel pipe 2.4, a three-way joint 2.5, a first support rod 2.6, a fixing joint 2.7 and a grouting joint 2.8, and all the components can be manufactured on site by adopting section steel materials. Specifically, the connecting sleeve is sleeved outside the bottom of the tubular pile, and the overlapping length of the connecting sleeve and the tubular pile is 0.3-0.5 m. The fixing ring is arranged at the bottom of the tubular pile, and the outer side of the fixing ring is fixed with the connecting sleeve; preferably, the fixing ring is of a regular hexagon structure formed by welding steel pipes, and the outer side of the preferable fixing ring is connected with the connecting sleeve in a welding mode; the fixing ring is provided with three-way joints 2.5 matched with the number of the outward-expanding steel pipes, the three-way joints are T-shaped three-way joints tightly sleeved on the fixing ring, and the upper ends of the outward-expanding steel pipes are inserted into downward side openings of the T-shaped three-way joints. The fixing ring can be further arranged into other regular polygon pipe rings or circular pipe rings according to design requirements.

The central steel pipe is arranged in the tubular pile, the lower end of the central steel pipe extends out of the lower end face of the tubular pile, and the length of the central steel pipe extending out of the tubular pile is larger than the length of the projection of the outward-expanding steel pipe in the vertical direction. A plurality of steel pipes that expand outward use central steel pipe to be radial distribution as the center, and every expands outward the upper end of steel pipe all through a three way connection with solid fixed ring and be connected with central steel pipe through a first vaulting pole 2.6. Slip casting connects fixed mounting on this hexagonal solid fixed ring to be connected with the grout outlet of slip casting pipe, the slip casting pipe sets up the one side in the tubular pile, adds muscle mattress pad layer and lays on loess foundation bed. In the structural arrangement, the number of the externally expanded steel pipes can be designed to be three or six, and the number of the steel pipes can also be properly adjusted according to the bearing requirements of the composite foundation design and the selection of pipe rings. The thickness of the reinforced mattress layer is 0.3-1.0 m.

In a preferred embodiment of the present invention, a fixing mechanism for fixing the central steel tube is further disposed in the fixing ring, and the fixing mechanism includes a fixing sleeve 2.21 sleeved on the central steel tube and a plurality of second support rods 2.22 connecting the fixing sleeve and the fixing ring. Still the cover is equipped with fixed joint 2.7 on the central steel pipe, and the lower extreme of a plurality of first supports all is connected with fixed joint is articulated, and the lower extreme upper end of a plurality of first supports is connected with corresponding outer expanding steel pipe is articulated respectively. The structure is convenient for the umbrella-shaped bottom expanding structure to be expanded to a preset angle after a certain pressure is applied to the top of the pipe pile.

In the preferred embodiment of the invention, a plurality of positioning flanges 3 for fixing the central steel pipe are arranged in the pipe pile, and the positioning flanges are arranged at intervals along the height direction of the pipe pile. The positioning flange is made of steel pipes and comprises an external steel ring 3.1, an internal steel pipe sleeve 3.2 and a plurality of third support rods 3.3, the external steel ring is fixedly connected with the inner wall of the pipe pile, the internal steel pipe sleeve is sleeved on the central steel pipe, the plurality of third support rods are uniformly arranged between the external steel ring and the internal steel pipe sleeve and mainly play a role in fixing,

in the preferred embodiment of the invention, each outward-expanding steel pipe is obliquely arranged from the lower end to the upper end from outside to inside. The central steel pipe and the outer expanding steel pipe are both made of section steel pipes, one slurry leakage hole is drilled in the pipe body of each steel pipe at intervals of 10cm, the aperture of each slurry leakage hole is 0.8-1.5 cm, the slurry leakage holes are arranged in a quincunx shape, and the whole length of each steel pipe can be divided into a non-drilling slurry stopping section, a drilling grouting section and a conical head section. The preferred pipe diameter of the central steel pipe is 5-10 cm; the preferable pipe diameter of the externally-expanding steel pipe is 3-8 cm. The specific specification of each component can be determined and adjusted according to the actual engineering.

In a preferred embodiment of the present invention, the grout comprises a first grout formed of cement grout and a second grout formed of M30 grouting mortar, the first grout is disposed at the position of the umbrella-shaped bottom-expanding structure, and the second grout is filled in the pipe pile; preferably, the cement slurry has a water cement ratio (WC) of 0.5-1: and 1, the grouting pressure is 0.5-1.0 MPa, and can also be determined according to field tests. The grouting pressure of the M30 grouting mortar is 0.3-0.5 MPa.

The invention relates to a construction method of a tubular pile composite foundation suitable for a high-fill collapsible loess field, which adopts the tubular pile composite foundation and comprises the following steps:

s1, prefabricating a tubular pile 1 and an umbrella-shaped bottom expanding structure 2;

s2, constructing pipe pile holes on the pre-treated loess foundation layer 7 by adopting a drilling method, wherein the aperture of each pipe pile hole is larger than the pile diameter of each pipe pile;

s3, sequentially placing the umbrella-shaped bottom expanding structure and the tubular pile into the tubular pile hole, connecting the grouting pipe 4 with the grouting joint 2.8, and firmly connecting the tubular pile with the umbrella-shaped bottom expanding structure to form a whole;

s4, applying a certain pressure on the top of the tubular pile to open the umbrella-shaped bottom expanding structure to a preset angle; namely the umbrella-shaped bottom expanding structure 2 can be opened after prepressing;

s5, connecting the grouting pipe 4 and the central steel pipe 2.3 with a grouting pump slurry conveying pipe respectively, grouting with cement slurry to form a first grouting body at the position of the umbrella-shaped bottom expanding structure, fully wrapping the umbrella-shaped bottom expanding structure with the first grouting body, filling the interior of the pipe pile with M30 grouting mortar, and forming a second grouting body; thereby forming an umbrella-shaped bottom expanding tubular pile component; after high-pressure grouting, the pile bottom structure is enlarged to form a reinforcement body with the surrounding soil body, and the vertical bearing capacity of the umbrella-shaped bottom-enlarging pipe pile is improved;

s6, after all the umbrella-shaped bottom-expanding tubular pile components are constructed, constructing a 0.3-1.0 m thick reinforced mattress layer 6 on the loess foundation layer, and finally completing the construction of the tubular pile composite foundation.

In the preferred embodiment of the invention, the tubular pile 1 and the umbrella-shaped bottom-expanding structure 2 are connected to form an integral structure, grouting bodies are injected into the umbrella-shaped bottom-expanding structure 2 and the tubular pile 1 through the grouting pipes 4 to realize the common bearing effect with the surrounding loess stratum, and the reinforced mattress layer 6 is laid on the top of the tubular pile to realize the uniform distribution bearing and the coordinated deformation effect.

The vertical bearing mechanism of the tubular pile composite foundation suitable for the high-fill collapsible loess field comprises the following steps: the upper building load is transmitted to the reinforced mattress layer 6, the load is transmitted to the umbrella-shaped bottom-expanding pipe pile component and the loess foundation 7 through the uniform load distribution effect of the reinforced mattress layer, and the upper load is borne through the cooperation of the pipe pile-umbrella-shaped bottom-expanding structure-soil among piles.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.