CN110886291B

CN110886291B - Pile structure in coral sand environment and construction method

Info

Publication number: CN110886291B
Application number: CN201911066402.0A
Authority: CN
Inventors: 刘杰; 石谦; 魏子璇; 程怡君; 王天龙; 李运舟; 杨浩宇; 杜卓兴; 黎照; 唐洪宇; 李政; 高素芳; 孙涛; 谢晓康; 李洪亚
Original assignee: China Three Gorges University CTGU
Current assignee: China Three Gorges University CTGU
Priority date: 2019-11-04
Filing date: 2019-11-04
Publication date: 2021-05-14
Anticipated expiration: 2039-11-04
Also published as: CN110886291A

Abstract

The invention provides a pile structure and a construction method in a coral sand environment, wherein a plurality of shells are fixed at the top of a steel casing; the processing of the different altitude positions of a steel casing has the multiunit hole, the steel casing inside of hole position has a plurality of expanded head structures that can overturn open through fan page buckle connecting device is articulated, the bottom that the steel casing was fixed with a bottom baffle, the bottom terminal surface of bottom baffle is fixed with many support claws, be provided with the base under the bottom baffle, the inside of base is provided with the arc track, support claw and arc track and cooperate to can open along the arc track is crooked under the pressure, make the bottom baffle support on the base. The problem that pile side frictional resistance, pile end resistance, bearing capacity of the pile in the process of piling in the coral sand are reduced or even disappear is solved, the stability of the pile body in the coral sand environment can be effectively guaranteed, and the method has the characteristics of simplicity and convenience in operation, high piling efficiency, simple structure, good quality and low cost.

Description

Pile structure in coral sand environment and construction method

Technical Field

The invention relates to the technical field of treatment of sea coral sand foundations, in particular to a pile structure in a coral sand environment, namely, a pile is treated so as to be more suitable for the special environment.

Background

For the special geology of the coral reef, a large number of experiments and engineering examples show that the coral reef pile has the characteristics of easiness in crushing, multiple gaps, high compression, low strength, small bearing capacity, large foundation settlement and the like, the structure of the coral reef pile is not easy to recover after being damaged, the pile side friction resistance and the pile end resistance of the pile in the piling process on the coral reef are reduced or even disappear due to the influence of a seawater medium, the bearing capacity can be lost, and the pile driving on the coral reef is difficult to multiple times. In current coral sand pile driving technique, because the characteristic of coral sand environment, bury down behind the steel casing the steady state of steel casing itself in the coral sand environment and can't effectively guarantee, the pile body is firm and keep the position not slope and hardly compromise, the hole that collapses sinks, the steel casing that buries in advance falls into and can't take place for phenomenon such as extracting in the stake hole, this causes and can't normally be under construction in former stake position, have to carry out the stake hole and backfill after change rig type or pile foundation position and carry out the construction again, waste time and energy, bring very big puzzlement for constructor.

At present, the gravity type punching hammer hole-forming cast-in-place pile construction process adopted by the red sea shoreside engineering of the multi-coral sand cannot effectively ensure that the steel casing and the surrounding environment keep a vertical stable relation after the steel casing is buried, and the subsequent construction steps are greatly influenced. For the common steel casing, the adaptation condition under the coral sand environment is not ideal, and some spaces for improving the design are provided. The applicant has referred to relevant documents in patent searches, such as application numbers: CN201610903940.0 discloses a pile-forming method for a cast-in-place pile in coral sand foundation, which forms a reinforced area completely isolated from the surrounding seawater for construction by injecting high polymer or expansive mortar, but this state is difficult to be continuously ensured under the condition that there are many factors affecting the vertical stable state of the pile body and uncertain factors of coral sand, and the long-term state of the pile body maintaining vertical stability in coral sand environment cannot be effectively solved.

Disclosure of Invention

Aiming at the development trends of national sea side and island construction and the problem that the steel pile casing and the pile body cannot be effectively stabilized during pile driving due to the natural characteristics of coral sand at present, the invention designs and processes the cast-in-place pile, overcomes the problems of reduction or even disappearance of pile side friction, pile end resistance and bearing capacity of the pile in the coral sand driving process, can effectively ensure the stability of the pile body in the coral sand environment, and has the characteristics of simple and convenient operation, high pile driving efficiency, simple structure, good quality and low cost.

In order to achieve the technical features, the invention is realized as follows: a pile structure in a coral sand environment comprises a steel pile casing, wherein a plurality of shells are fixed at the top of the steel pile casing; the processing of the different altitude positions of a steel casing has the multiunit hole, the steel casing inside of hole position has a plurality of expanded head structures that can overturn open through fan page buckle connecting device is articulated, the bottom that the steel casing was fixed with a bottom baffle, the bottom terminal surface of bottom baffle is fixed with many support claws, be provided with the base under the bottom baffle, the inside of base is provided with the arc track, support claw and arc track and cooperate to can open along the arc track is crooked under the pressure, make the bottom baffle support on the base.

The shell is made of high-strength steel and is a hyperbolic shell, the hyperbolic shells are fixedly connected in a multi-layer overlapping mode, and the overlapping mode is thick in the middle and thin in two sides or equal in thickness.

The shape of the expanding head structure is matched with that of the hole; the structure of expanding head is the confined state when initial, and when the grout, the slurry can be with its extrusion, outwards expands and expands the structure of expanding head.

The fan blade buckle connecting devices are arranged on the periphery inside the steel protective cylinder, the contact area of the expansion head structure and the protective cylinder wall is connected through the fan blade buckle connecting devices, and each fan blade buckle connecting device consists of a fan blade buckle; a hole for passing is reserved in the wall of the protective cylinder of the steel protective cylinder, when the expansion head extends out of the limit, the expansion head on the hole and a fan blade buckle connecting device of the wall of the protective cylinder can clamp the expansion head, and the expansion head can prevent coral sand from entering through a hole, so that the concentration of slurry is in a normal value.

A one-way plate connecting device for limiting the coral sand is arranged between the adjacent expanded head structures at the same height, and the coral sand is prevented from being extruded by the pressure of the coral sand when the steel casing is placed by the one-way plate, so that the coral sand enters the pile body; when grouting, the unidirectional plate is pressed to expand outwards together with the expansion head.

The base adopts a double-layer structure, the upper layer adopts a conical table structure, the lower layer adopts a circular table structure, and the base supports the whole pile structure; and a layer of circular ring is reinforced at the periphery of the bottom baffle, and the thickness of the circular ring is greater than that of the baffle.

The supporting claw adopts a hollow pipe structure, the top end of the supporting claw penetrates through the bottom baffle and is communicated with the inside of the steel casing, and the bottom end of the supporting claw is inserted into the base along the arc-shaped track and is bent in the grouting process until penetrating out of the base.

The inner wall of the arc-shaped track is embedded with balls, and the balls and the supporting claws form rolling fit and smoothly pass through the arc-shaped track.

The tail end of the bottom of the supporting claw is provided with a round hole for slurry to flow out, and a small hole for penetrating through the supporting claw is formed in the base and positioned at the tail end of the arc-shaped track; the position of the small hole is sealed and blocked by a plastic film before grouting, and the plastic film is pierced by the acting force of the supporting claw in the grouting process.

The construction method of the special pile structure in the coral sand environment comprises the following steps:

step1, manufacturing a top pile cap structure: after the steel casing is knocked down, fixing the high-strength shell at the top end of the steel casing, and fixing the shell in a multi-layer overlapping mode to form a pile cap structure;

step2, prefabricating a pile body expanding structure: processing holes at different height positions of the upper part of the pile body, installing an expanding head structure on the inner wall of the steel casing at the position of the hole through a fan-shaped buckle connecting device, enabling the expanding head structure to be in an initial closed state, when grouting is carried out to the position in the steel casing, slurry can extrude the expanding head structure to expand the expanding head outwards, and a stable relation is established with an external coral sand system, so that the friction force of the whole pile body is increased, and the stability of the pile is increased;

step3, pouring into the steel casing: when the expanded head structure is grouted, the expanded head structure is pushed to extend outwards, when the expanded head structure extends to the limit, the expanded head structure can be clamped by a connecting device of the hole and the inner wall, the expanded head structure can rotate to the outside through the hole, coral sand outside cannot enter, and the concentration of the grout is also kept at a normal value;

step4, fixing of base structure: when the grouting slurry just reaches the bottom baffle, a small amount of slurry firstly enters the hollow pipe of the support claw through the bottom baffle;

step5, when enough paddles are present on the bottom baffle plate, the bottom baffle plate stably moves downwards under the guarantee of the circular ring of the bottom baffle plate until the support claws on the lower end surface of the bottom baffle plate are pressed out of the arc-shaped tracks of the base to establish a stable relation with an external coral sand system;

step6, at the same time, the slurry passes through the rigid hollow pipe of the supporting claw, a certain amount of slurry is discharged out of the steel casing, the discharged slurry is contacted with coral sand and seawater at the tail end of the supporting claw, and after diffusion, the slurry is solidified into a spherical-like structure with strength, so that the stability and upward supporting force of the whole cast-in-place pile are increased.

The invention has the following beneficial effects:

1. the device provided by the invention has the advantages of easily available materials, strong operability, simple structure and low cost, effectively solves the problems of easy breakage, multiple gaps, high compression and low strength of the coral reef, designs a brand new pile body structure, provides a new solution for piling on complex terrains such as coral sand and the like, has advanced technology, is economic and reasonable, and has wide engineering practice significance and application prospect.

2. Through the hyperbolic flat shell body that adopts high strength steel preparation, the different shapes of flat shell, the stack of the different number of piles can improve the easy problem that sinks of pile under the different conditions, and the casing makes the ascending buoyancy of coral sand pile body to make the pile body keep vertical stable and increase the difficult sinking of buoyancy.

3. Through the prefabricated head expanding structure, the friction force of the whole pile body is increased after grouting is expanded, the stability of the pile body is increased, and the pile body is not easy to incline or sink.

4. The special clamping groove-shaped structure of the hole expanding head and the wall of the protective cylinder can clamp the expanding head when the expanding head extends out of the limit, the expanding head can prevent coral sand from entering through a hole, and meanwhile, the slurry is further stabilized after being solidified, so that the concentration of the slurry is in a normal value, and the strength of the formed pile body is prevented from being weakened.

5. The designed one-way through-plate structure is used for preventing the coral sand from entering the pile body through the reserved holes due to the pressure generated outside when the coral sand is pressed downwards into the wall of the protective cylinder; when grouting, the unidirectional plate is pressed from the inside, so that the unidirectional plate and the expansion head are expanded outwards.

6. Through the base of above-mentioned structure, a solid round platform is added more to its below, improves the bearing capacity of bottom, ensures the overall structure stability of pile body.

7. Through design bottom baffle, consolidate one deck circle ring below the baffle, the thickness of circle ring is greater than the thickness of baffle, and baffle atress is uneven when preventing to be in milk, leads to the baffle slope, guarantees its steady decurrent motion.

8. After grouting, the bottom of the supporting claw with strength extends outwards, the tail end of the supporting claw is contacted with coral sand and seawater, and after diffusion, the supporting claw is solidified into a spherical-like structure with strength, so that the stability and the upward supporting force of the whole pile body are increased.

9. When the expanding head is hollow, the reserved holes can enable cement to form a tree root-shaped structure, the cement injected by grouting can enable the baffle, the expanding head and the side surface of the pile body to form a whole body to be more stable, the weight of the pile body is lighter, the weight can be reduced when the column is installed, and the operation is convenient; when the head is solid, the rigidity is stronger, coral sand can be better pressed in, and the solid head-expanding part is firmer and more stable and is not easy to damage.

10. Inlay at arc track internal surface through the design ball inside the track, add a class of material of lubricating oil simultaneously, make claw-shaped structure can be better pass through the arc track, and can not make outside sea water of pile body and coral sand get into between the two, make pile body internal environment stable.

11. The sliding contact surface of the spherical bearing with the free movement of the fan blade buckle connecting device of the expansion head structure and the protective cylinder wall is an inner ball and an outer spherical surface, the spherical bearing can rotate and swing at any angle during movement, and the spherical bearing has the characteristics of large load capacity, impact resistance, corrosion resistance, self-aligning, good lubrication and the like, so that the expansion head and the protective cylinder wall can move better, and the spherical bearing can be smoothly pushed to move when grouting is performed.

12. Through set up the round hole at the end that has the support claw to seal through the film that has certain rigidity, during the grout, the slurry flows to the claw and breaks through the film, and partly slurry flows out from the round hole, solidifies to the spheroidic structure that has intensity after using the round hole device as centre of a circle slurry diffusion, increases the stability and the ascending holding power of whole pile body.

13. Through the terminal aperture of arc track, make it seal by the sealed plastic film that can resist compression, prevent that external material from getting into, after the grout, along with the claw column structure that has intensity reserves track structure motion at the bottom base, the claw is pricked and is got into external environment by broken plastic film, hugs closely claw pipe after the plastic film is broken, prevents that external environment material from getting into and protects a section of thick bamboo.

14. The arch support column at the head of the pile body is enlarged by supporting the claws in the pile body and pressing the claws out of the pile body through grouting pressure, and the expansion shape of the arch support column and the stress diagram of the pile body are combined under deformation settlement, different levels of loads and different depths, the corresponding relation between the compression settlement and the load value in different time, and the conditions of stress transmission in rock soil along with the change of time and space, so that a structure which is efficient and enables dispersed pressure to be uniform and stable is formed.

Drawings

The invention is further illustrated by the following figures and examples.

Fig. 1 is a schematic view of the overall structure of the invention before placement.

Fig. 2 is a top view of the unidirectional plate connection apparatus of the present invention.

Fig. 3 is a side view of the one-way plate connection device of the present invention.

Fig. 4 is a schematic view of the structure of the arc track of the present invention.

FIG. 5 is a schematic top view of a bottom baffle of the present invention.

Fig. 6 is a clamping groove structure connected with the steel casing after the expanding head structure of the invention extends out.

Fig. 7 is a schematic view of the overall structure of the grouting apparatus of the present invention.

Fig. 8 is a schematic view of the base structure of the present invention.

Fig. 9 shows a rigid double-curved flat shell structure according to the present invention.

Fig. 10 is a schematic view of the overall structure of the completed body of the present invention.

In the figure: the coral sand cleaning device comprises a steel protective cylinder 1, a shell 2, a flaring structure 3, a hole 4, a one-way plate connecting device 5, a leaf buckle connecting device 6, a base 7, an arc-shaped track 8, a bottom baffle 9, a supporting claw 10, a coral sand area 11, a ball 12, a water area 13, a round hole 14 and a small hole 16.

Detailed Description

Embodiments of the present invention will be further described with reference to the accompanying drawings.

Example 1:

referring to fig. 1-10, a pile structure in coral sand environment comprises a steel casing 1, wherein a plurality of shells 2 are fixed on the top of the steel casing 1; the processing of the different altitude positions of a steel protective cylinder 1 has multiunit hole 4, 1 inside of a steel protective cylinder of hole 4 position has a plurality of expanded head structures 3 that can overturn open through the articulated fan page buckle connecting device 6, the bottom that the steel protected a 1 is fixed with bottom baffle 9, the bottom end face of bottom baffle 9 is fixed with many support claws 10, be provided with base 7 under bottom baffle 9, the inside of base 7 is provided with arc track 8, support claw 10 and arc track 8 with cooperate to can be under the pressure effect open along arc track 8 is crooked outward, make bottom baffle 9 support on base 7. Through the pile structure of above-mentioned structure, utilize the casing, built-in expanding first structure 3, bottom sprag claw 10 reequips traditional pile technique, makes it can adapt to more environment to guarantee that it is safer and more stable, can effectively guarantee the steadiness of pile body under the sand environment of coral, have the simple and convenient of operability, pile efficiently, simple structure, of high quality, characteristics with low costs.

Further, the shell 2 is made of high-strength steel and is a double-curved shell, multiple double-curved shells are fixedly connected in a multi-layer overlapping mode, and the overlapping mode is a overlapping mode with thick middle and thin sides or equal thickness. The acting force of the shell 2 on the coral sand enables the flat shell to have upward force, so that the pile body can keep vertical and stable, and buoyancy is increased to prevent the flat shell from sinking easily.

Further, the shape of the expanding head structure 3 is matched with that of the hole 4; the structure 3 of expanding is the confined state when initial, and when the grout, the slurry can be with its extrusion, outwards expands and expands the structure of expanding. And further the friction force of the whole pile body is increased, the stability of the pile is increased, and the pile is not easy to incline or sink.

Furthermore, a plurality of fan blade buckle connecting devices 6 are arranged on the periphery inside the steel casing 1, the contact area of the expansion head structure 3 and the casing wall is connected through the fan blade buckle connecting devices 6, and each fan blade buckle connecting device 6 consists of a fan blade buckle; a hole for passing is reserved in the wall of the protective cylinder of the steel protective cylinder 1, when the expansion head extends out of the limit, the expansion head on the hole and the fan blade buckle connecting device 6 of the wall of the protective cylinder clamp the expansion head, and the expansion head can prevent coral sand from entering through the hole, so that the concentration of slurry is in a normal value. And the strength of the formed pile body is prevented from weakening.

Furthermore, a one-way plate connecting device 5 for limiting the coral sand is arranged between the adjacent flaring head structures 3 at the same height, and the coral sand is prevented from being extruded by the pressure of the coral sand when the steel casing 1 is placed by the one-way plate, so that the coral sand enters the pile body; when grouting, the unidirectional plate is pressed to expand outwards together with the expansion head.

Further, the base 7 is of a double-layer structure, the upper layer of the base adopts a conical table structure, the lower layer of the base adopts a circular table structure, and the base supports the whole pile structure; huge impact force when preventing to be in milk through toper platform structure improves the bearing capacity of bottom through the round platform structure, ensures the overall structure of pile body.

Furthermore, a layer of circular ring is reinforced at the periphery of the bottom baffle 9, and the thickness of the circular ring is larger than that of the baffle. The baffle is prevented from being stressed unevenly when grouting, so that the baffle is inclined, and the stable downward movement of the baffle is ensured.

Further, the supporting claw 10 is of a hollow pipe structure, the top end of the supporting claw penetrates through the bottom baffle 9 and is communicated with the inside of the steel casing 1, and the bottom end of the supporting claw is inserted into the base 7 along the arc-shaped rail 8 and is bent until penetrating out of the base 7 in the grouting process. In the concrete use process, the supporting claw 10 connects the upper part of the claw-shaped tough and strong hollow pipe with the hole on the bottom baffle plate, so that the claw-shaped tough and strong hollow pipe can penetrate through the baffle plate, the lower end of the claw is just connected into the arc-shaped track 8 before grouting, the lower end of the claw moves along the arc-shaped track 8 along with the movement of the baffle plate after grouting until reaching the expected position, the supporting claw 10 with the strength is pressed out of the wall of the protecting cylinder when the arc-shaped track 8 is under pressure, so as to provide stability for the pile body, when grouting, the slurry is discharged out of the pile body through the tough and rigid hollow pipe in the supporting claw 10, a certain amount of slurry is contacted with coral sand and seawater at the tail end of the supporting claw 10 with the strength, and is solidified into a spherical-like structure with the strength after diffusion, so that the.

Furthermore, the inner wall of the arc-shaped track 8 is embedded with a ball 12, and the ball 12 and the support claw 10 form rolling fit and smoothly pass through the arc-shaped track 8. And seawater and coral sand outside the pile body cannot enter between the two, so that the internal environment of the pile body is stable.

Further, a circular hole 14 for flowing out slurry is arranged at the bottom tail end of the supporting claw 10, and a small hole 16 for penetrating through the supporting claw 10 is arranged on the base 7 and positioned at the tail end of the arc-shaped track 8; the position of the small hole 16 is sealed and sealed by a plastic film before grouting, and the plastic film is pierced by the acting force of the supporting claw 10 in the grouting process.

The column body is convenient to install initially, light in weight and easy to fix, the weight can be reduced when the column body is installed, the operation is convenient, and the hollow expanding head is filled and extruded out during grouting, so that the stability of the column body is improved; the solid head expanding part is an expansion object after forming, is easy to extrude out because of having certain quality by self when grouting, and is firmer and more stable in the solid head expanding part and not easy to damage.

Furthermore, the fan buckle connecting device 6 comprises a freely movable spherical bearing, the expansion head is hinged with the wall of the protective cylinder, the sliding contact surface of the expansion head is an inner ball and an outer spherical surface, the expansion head can rotate and swing at any angle during movement, and the fan buckle connecting device has the characteristics of large load capacity, impact resistance, corrosion resistance, self-aligning, good lubrication and the like, so that the expansion head and the wall of the protective cylinder can move better, and the fan buckle connecting device can smoothly push the expansion head to move when grouting.

Furthermore, the small holes 16 are plugged by adopting a high-strength one-way plate structure, and a device which can only pass through one way on the one-way plate connecting device 5 between the expansion heads is adopted and consists of a plurality of same parts, wherein the single part is a plate, and a long rod, a long rod and other parts are arranged under the plate to act, so that the one-way through function is realized.

Example 2:

step1, manufacturing a top pile cap structure: after the steel casing 1 is knocked down, fixing the high-strength shell 2 at the top end of the steel casing 1, and fixing the shell 2 in a multi-layer overlapping mode to form a pile cap structure;

step2, prefabricating a pile body expanding structure: processing holes 4 at different height positions of the upper part of a pile body, installing expanding head structures 3 on the inner walls of a steel casing 1 at the positions of the holes 4 through fan-shaped buckle connecting devices 6, enabling the expanding head structures 3 to be in an initial closed state, when grouting is carried out in the steel casing 1 to the positions, grout can extrude the expanding heads to expand the expanding heads outwards, and a stable relation is established between the expanding heads and an external coral sand system, so that the friction force of the whole pile body is increased, and the stability of the pile is increased;

step3, pouring the steel casing 1: when grouting to the enlarged head structure 3, the enlarged head structure 3 is pushed to extend outwards, when the enlarged head structure 3 extends to the limit, the connection device of the hole and the inner wall can clamp the enlarged head structure 3, the hole enables the enlarged head structure 3 to rotate to the outside, and coral sand outside cannot enter, so that the concentration of the slurry is in a normal value;

step4, fixing of base structure: when the grouting slurry just reaches the bottom baffle 9, a small amount of slurry firstly enters the hollow pipe of the support claw 10 through the bottom baffle 9;

step5, when enough paddles are present on the bottom baffle 9, namely enough pressure is applied, the bottom baffle 9 can stably move downwards under the guarantee of the self-circular ring until the supporting claws 10 on the lower end surface of the bottom baffle 9 are pressed out of the arc-shaped tracks 8 of the base 7 to establish a stable relation with an external coral sand system;

step6, at the same time, the slurry passes through the rigid hollow pipe of the supporting claw 10, a certain amount of slurry is discharged out of the steel casing 1, the discharged slurry is contacted with coral sand and seawater at the tail end of the supporting claw 10, and after diffusion, the slurry is solidified into a spherical-like structure with strength, so that the stability and the upward supporting force of the whole cast-in-place pile are increased.

Claims

1. The utility model provides a stake structure under coral sand environment which characterized in that: the steel casing comprises a steel casing (1), wherein a plurality of shells (2) are fixed at the top of the steel casing (1); a plurality of groups of holes (4) are processed at different height positions of the steel casing (1), a plurality of expanding structures (3) capable of being opened in a turnover mode are hinged inside the steel casing (1) at the positions of the holes (4) through fan-shaped buckle connecting devices (6), a bottom baffle (9) is fixed at the bottom of the steel casing (1), a plurality of supporting claws (10) are fixed on the bottom end face of the bottom baffle (9), a base (7) is arranged right below the bottom baffle (9), an arc-shaped track (8) is arranged inside the base (7), the supporting claws (10) are matched with the arc-shaped track (8) and can be bent and stretched out along the arc-shaped track (8) under the action of pressure, and the bottom baffle (9) is supported on the base (7);

the shape of the expanding head structure (3) is matched with that of the hole (4); the structure (3) is in a closed state initially, and when grouting is performed, slurry can extrude the structure to expand the structure outwards;

a plurality of fan blade buckle connecting devices (6) are arranged on the periphery inside the steel protective cylinder (1), the contact area of the expanding head structure (3) and the protective cylinder wall is connected through the fan blade buckle connecting devices (6), and each fan blade buckle connecting device (6) consists of a fan blade buckle; a hole for passing is reserved in the wall of the protective cylinder of the steel protective cylinder (1), when the expansion head extends out of the limit, the expansion head on the hole and a fan blade buckle connecting device (6) on the wall of the protective cylinder clamp the expansion head, and the expansion head can prevent coral sand from entering through the hole, so that the concentration of slurry is at a normal value.

2. The pile structure in coral sand environment of claim 1, wherein: the shell (2) is made of high-strength steel and is a hyperbolic shell, the hyperbolic shells are fixedly connected in a multi-layer overlapping mode, and the overlapping mode is thick in the middle and thin in two sides or equal in thickness.

3. The pile structure in coral sand environment of claim 1, wherein: a one-way plate connecting device (5) for limiting the coral sand is arranged between the adjacent expanding head structures (3) at the same height, and the coral sand is prevented from being extruded by the pressure of the coral sand when the steel casing (1) is placed by arranging the one-way plate, so that the coral sand enters the pile body; when grouting, the unidirectional plate is pressed to expand outwards together with the expansion head.

4. The pile structure in coral sand environment of claim 1, wherein: the base (7) adopts a double-layer structure, the upper layer adopts a conical table structure, the lower layer adopts a circular table structure, and the whole pile structure is supported; and a layer of circular ring is reinforced at the periphery of the bottom baffle (9), and the thickness of the circular ring is greater than that of the baffle.

5. The pile structure in coral sand environment of claim 1, wherein: the supporting claw (10) is of a hollow pipe structure, the top end of the supporting claw penetrates through the bottom baffle (9) and is communicated with the inside of the steel casing (1), and the bottom end of the supporting claw is inserted into the base (7) and bent along the arc-shaped rail (8) in the grouting process until penetrating out of the base (7).

6. The pile structure in coral sand environment of claim 1, wherein: the inner wall of the arc-shaped track (8) is embedded with balls (12), and the balls (12) and the support claws (10) form rolling fit and smoothly pass through the arc-shaped track (8).

7. The pile structure in coral sand environment of claim 1, wherein: a circular hole (14) for slurry to flow out is formed in the tail end of the bottom of the supporting claw (10), and a small hole (16) for penetrating through the supporting claw (10) is formed in the base (7) and located at the tail end of the arc-shaped track (8); the position of the small hole (16) is sealed and plugged by a plastic film before grouting, and the plastic film is pierced by the acting force of the supporting claw (10) in the grouting process.

8. A construction method of a pile structure in coral sand environment as set forth in any one of claims 1 to 7, comprising the steps of:

step1, manufacturing a top pile cap structure: after the steel casing (1) is knocked down, fixing the high-strength shell (2) at the top end of the steel casing (1), and fixing the shell (2) in a multi-layer overlapping mode to form a pile cap structure;

step2, prefabricating a pile body expanding structure: processing holes (4) at different height positions of the upper part of a pile body, installing an expanding head structure (3) on the inner wall of a steel casing (1) at the position of the hole (4) through a fan buckle connecting device (6), enabling the expanding head structure (3) to be in an initial closed state, and when grouting is carried out to the position in the steel casing (1), slurry can extrude the steel casing to expand the expanding head outwards to establish a stable relation with an external coral sand system, so that the friction force of the whole pile body is increased, and the stability of the pile is increased;

step3, pouring the steel casing (1) with the following steps: when grouting to the enlarged head structure (3), the enlarged head structure (3) is pushed to extend outwards, when the enlarged head structure (3) extends to the limit, the connection device of the hole and the inner wall can clamp the enlarged head structure (3), the hole enables the enlarged head structure (3) to rotate to the outside, and the coral sand outside cannot enter, so that the concentration of the slurry is in a normal value;

step4, fixing of base structure: when the grouting slurry just reaches the bottom baffle (9), a small amount of slurry enters the hollow pipe of the support claw (10) through the bottom baffle (9);

step5, when enough paddles are generated on the bottom baffle (9), namely enough pressure is applied, the bottom baffle (9) can stably move downwards under the guarantee of a self circular ring until the supporting claws (10) on the lower end surface of the bottom baffle (9) are pressed out of the arc-shaped tracks (8) of the base (7) to establish a stable relation with an external coral sand system;

step6, at the same time, the slurry passes through the rigid hollow pipe of the supporting claw (10), a certain amount of slurry is discharged out of the steel casing (1), the discharged slurry is contacted with coral sand and seawater at the tail end of the supporting claw (10), and after diffusion, the slurry is solidified into a spherical-like structure with strength, so that the stability and upward supporting force of the whole cast-in-place pile are increased.