CN114687671A - Lifting type variable-diameter self-retaining wall hole-forming cast-in-place pile drill bit and drilling method - Google Patents

Abstract

The invention relates to the technical field of constructional engineering, in particular to a lifting type variable-diameter self-retaining wall hole-forming cast-in-place pile drill bit and a drilling method. The drill bit is arranged at the lower end of the main drilling component, and a wall protection outer cylinder is sleeved on the outer wall of the main drilling component; the main drill part is provided with a lifting oil cylinder connected with a wall protection outer cylinder; notches are distributed on the outer wall protection barrel, and blades are arranged in the notches; the main drill part is provided with a pushing piece for controlling the opening and closing of the blades; one side of each blade is provided with a knife edge, and the other side of each blade is provided with a slurry outlet for outputting concrete slurry and a liquid outlet for outputting an accelerating agent; the lower end of the main drilling component is provided with a mud inlet, and a mud suction pipe is arranged in the main drilling component and communicated with the mud inlet. The invention can realize the cement-mixed soil self-retaining wall, and can realize that cement paste and an accelerating agent are injected into the wall-protecting layer and stirred to quickly form the cement-mixed soil self-retaining wall while forming holes.

Description

Lifting type variable-diameter self-retaining wall hole-forming cast-in-place pile drill bit and drilling method

Technical Field

The invention relates to the technical field of constructional engineering, in particular to a lifting type variable-diameter self-retaining wall hole-forming cast-in-place pile drill bit and a drilling method.

Background

The cast-in-place pile system is a pile formed by forming a pile hole in foundation soil through mechanical drilling, steel pipe soil extrusion or manual excavation and the like on an engineering site, placing a reinforcement cage and cast-in-place concrete in the pile hole, and the cast-in-place pile can be divided into a immersed tube cast-in-place pile, a cast-in-place pile and a cast-in-place pile according to different hole forming methods.

The existing pore-forming cast-in-place pile has two types of artificial pore-forming and mechanical pore-forming:

the manual hole-forming cast-in-place pile adopts manual excavation, and the reinforced concrete retaining wall has less required equipment, can be simultaneously cast at one time after large-area hole forming is finished, reduces field cross operation and reduces the cost of casting equipment; the pile bottom is thoroughly cleaned, the pile forming quality is high and stable, the cost is high but controllable, and the bearing capacity of a single pile with the same section is high;

however, the artificial pile is being eliminated at present due to the defects that the labor intensity of workers is high, the safety risk of underground operators is high, the pile forming depth generally cannot exceed 16 meters, simultaneously more workers are needed, the progress is slow, the workers are difficult to organize, the cost of the wall protection material is high, and the like.

Secondly, most of the existing mechanical pore-forming cast-in-place piles adopt the modes of rotary drilling pore-forming and mechanical impact pore-forming

The rotary digging bored concrete pile has the advantages that the rotary digging bored concrete pile adopts the rotary digging steel pile casing retaining wall or the slurry retaining wall, so that the required operation personnel are few, the labor intensity of the personnel is low, the single stratum progress is fast, the operation cost is lower than that of the manual pile, the underground operation risk is avoided, and the pile forming depth is not limited; the disadvantages are that: the rotary drilling hole-forming method has the advantages that the rotary drilling hole-forming method is high in cost due to the fact that a plurality of devices are needed by the retaining wall, the pile bottom cannot be thoroughly cleaned, sediment exists, the hole-forming quality is unstable, the bearing capacity of a single pile with the same cross section is lower than that of an artificial pile, the waste of concrete in the complex stratum is large, the cost is uncontrollable, and sometimes the cost is far beyond that of the artificial pile.

The impact hole-forming cast-in-place pile adopts the impact hole-forming and mud wall protection, is suitable for complex strata, has low labor intensity of workers, but has slow progress of impacting the pile, high cost, large field damage and general pile-forming quality.

Disclosure of Invention

Aiming at the problems, the invention provides a lifting type variable-diameter self-retaining wall pore-forming cast-in-place pile drill bit which can realize the self-retaining wall of cement-mixed soil, and can realize the rapid formation of the cement-mixed soil retaining wall by injecting cement paste and an accelerating agent into the wall-protecting layer and stirring while pore-forming.

In order to achieve the purpose, the invention adopts the technical scheme that: a lifting type variable-diameter self-retaining wall hole-forming cast-in-place pile drill bit comprises a main drill part, wherein a drill bit is arranged at the lower end of the main drill part, and a retaining wall outer cylinder is sleeved on the outer wall of the main drill part; the main drill part is provided with a lifting oil cylinder connected with a wall protection outer cylinder; notches are distributed on the outer protective wall cylinder, and blades capable of being vertically turned are arranged in the notches; the main drill part is provided with a pushing piece for controlling the opening and closing of the blades; one side of each blade is provided with a knife edge, and the other side of each blade is provided with a slurry outlet for outputting concrete slurry and a liquid outlet for outputting an accelerating agent; the lower end of the main drilling component is provided with a mud inlet, and a mud suction pipe is arranged in the main drilling component and communicated with the mud inlet.

The beneficial effects of the above technical scheme are: the dado urceolus is rotatory with main drilling component synchronous, realizes when drilling, can utilize the dado urceolus to carry out the operation of being in a milk in hole inner wall, and concrete thick liquid forms the concrete inner wall with accelerator and earth flash mixed, and the blade of dado urceolus can also be with the earth of reaming production simultaneously with concrete mixing stirring when realizing reaming, realizes the synchronous completion of concrete dado.

As a further improvement of the technical scheme, the blades are spirally distributed on the wall protection outer cylinder.

The beneficial effect of the improvement is as follows: the spiral blade distributes and to have the automatic function of boring down at rotatory in-process for the dado urceolus, still makes simultaneously to be produced the motion that rises along with the motion of spiral blade by the broken earth of blade, prevents that earth whereabouts from piling up, makes the earth can be even simultaneously mix with the concrete thick liquid, ensures the dado quality.

As a further improvement of the technical scheme, the other end of the grout outlet is communicated with the grouting pipe; the other end of the liquid outlet hole is communicated with the liquid injection pipe.

The beneficial effect of the improvement is as follows: through slip casting pipe and concrete thick liquid delivery source being connected, through annotating the liquid pipe and being connected with the accelerator delivery source, slip casting pipe and notes liquid pipe adopt flexible bendable structure, are convenient for opening of blade and fold.

As a further improvement of the above technical scheme, a chute is arranged in the blade; the inner wall of each blade is provided with a clamping groove; the clamping groove is communicated with the sliding groove; the end of the pushing piece is provided with a pushing head; the push head is arranged in the sliding groove in a sliding manner.

The beneficial effect of the improvement is as follows: when the pushing piece rises, the pushing head pushes the blades to open, and when the pushing piece falls, the pushing head pulls the blades to close; the pushing piece can be used for controlling the opening and closing of the blades, and can scrape soil on the inner walls of the blades in the process of controlling the closing of the blades by moving up and down, so that the situation that the blades cannot be closed due to the soil accumulated on the inner walls of the blades is prevented.

As a further improvement of the technical scheme, the main drill component is of a hollow structure, and a cavity is formed inside the main drill component.

The beneficial effect of the improvement is as follows: the cavity inside the main drilling component can collect soil generated by drilling the main drilling component through the soil inlet hole, and then the soil is conveniently sucked and discharged through the sludge suction pipe.

As a further improvement of the technical scheme, vertical grooves are distributed on the side wall of the main drilling component; convex parts are distributed on the inner wall of the wall protection outer cylinder; the protrusions are slidably disposed within the corresponding grooves.

The beneficial effect of the improvement is as follows: the convex part slides up and down in the groove, so that the wall protection outer cylinder can move up and down, the wall protection outer cylinder can synchronously rotate with the main drill component, and the movable connection stability of the wall protection outer cylinder and the main drill component is improved.

As a further improvement of the technical scheme, a rotary joint is arranged at the upper end of the main drilling component; the mud suction pipe and the grouting pipe are connected with a rotary joint.

As a further improvement of the above technical scheme, the drill bit is provided with a water outlet hole; the other end of the water outlet hole is connected with a water inlet pipe in the main drilling component.

The beneficial effect of the improvement is as follows: the inlet tube comes out from the apopore in pouring into the drill bit with water, can carry out the cooling action to the drill bit, can moisten earth simultaneously again, improves drilling efficiency, makes the broken earth of drilling contain the moisture of capacity moreover, is convenient for the suction dredge suction discharge.

As a further improvement of the technical scheme, the blades are distributed at the lower end of the outer cylinder of the protecting wall; the outer wall of the upper end of the wall protection outer barrel is a smooth surface.

The beneficial effect of the improvement is as follows: the blades are distributed at the lower end of the outer protection wall cylinder, so that hole expansion and protection wall forming can be performed through the blades, meanwhile, the smooth wall face at the upper end can also be used for scraping the concrete inner wall which is just formed, and the formation quality of the protection wall is improved.

A method for drilling by a lifting type variable-diameter self-retaining wall-forming cast-in-place pile drill bit comprises the following steps:

reducing operation: controlling the lifting oil cylinder to lift according to the diameter of the cast-in-place pile hole, so that the outer wall protection barrel descends, and driving the blades to open according to a set angle;

drilling operation: driving the main drill part and the outer protective wall cylinder to synchronously rotate and drill downwards, wherein the main drill part sucks away soil generated by drilling through a mud suction pipe in the drilling process; the opened blades scrape and crush soil on the wall of the hole, and simultaneously the main slurry pipe inputs concrete slurry into the blades, the concrete slurry is sprayed out of the slurry outlet hole, is uniformly mixed with the crushed soil and is then solidified to form a concrete retaining wall;

hole withdrawing operation: after drilling is finished, stopping injecting concrete slurry and an accelerator, and controlling the outer cylinder of the protective wall to ascend by the oil cylinder so as to enable the blades to be folded; then the drill bit integrally rises to exit the pouring hole to form a pouring pile hole with a concrete protecting wall.

As a preferred mode of the method, the method for drilling the hole by the lifting type variable-diameter self-retaining wall-forming cast-in-place pile drill bit comprises the following steps:

reducing operation: controlling a lifting oil cylinder to lift according to the diameter of a cast-in-place pile hole, so that a wall protection outer cylinder descends to drive blades to open according to a set angle;

drilling operation: driving the main drill part and the outer protective wall cylinder to synchronously rotate and drill downwards, wherein the main drill part sucks away soil generated by drilling through a mud suction pipe in the drilling process; the opened blades scrape and crush soil on the wall of the hole, simultaneously the main slurry pipe inputs concrete slurry into the blades and sprays out from the slurry outlet, the liquid injection pipe inputs an accelerator into the blades and sprays out from the liquid outlet, the concrete slurry and the accelerator are uniformly mixed with the crushed soil and then are solidified to form the concrete retaining wall;

hole withdrawing operation: after drilling is finished, stopping injecting concrete slurry and an accelerator, and controlling the outer cylinder of the protective wall to ascend by the oil cylinder so as to close the blades; then the drill bit integrally rises to exit the pouring hole to form a pouring pile hole with a concrete protecting wall.

Drawings

FIG. 1 is a schematic view of the exterior of the drill bit of the present invention;

FIG. 2 is a schematic cross-sectional view of the flaring blades of the drill bit of the present invention;

FIG. 3 is a schematic cross-sectional view of a gathering blade of the drill bit of the present invention;

FIG. 4 is a schematic view of a closed blade configuration;

FIG. 5 is a schematic view of the opened blade configuration;

FIG. 6 is a schematic view of a blade back structure;

FIG. 7 is a schematic view of the inner wall structure of the blade;

fig. 8 is a top view of the internal structure of the rotary joint.

In the figure: 1. a main drill component; 2. a drill bit; 3. a mud inlet hole; 4. a main shaft; 5. a wall protection outer cylinder; 6. a convex portion; 7. a groove; 8. A lift cylinder; 9. a blade; 10. a notch; 11. a water inlet pipe; 12. a mud suction pipe; 13. a grouting pipe; 14. a liquid injection pipe; 15. an oil pipe; 16. a rotary joint; 17. pushing the workpiece; 18. pushing the head; 19. a cavity; 91. a chute; 92. a card slot; 93. a knife edge; 94. a slurry outlet; 95. a liquid outlet hole; 96. a grouting port; 97. and a liquid injection port.

Detailed Description

The following detailed description of the present invention is given for the purpose of better understanding technical solutions of the present invention by those skilled in the art, and the present description is only exemplary and explanatory and should not be construed as limiting the scope of the present invention in any way.

Referring to fig. 1 to 8, in a specific embodiment, a lifting type variable-diameter self-retaining wall-forming bored pile drill bit comprises a main drill part 1, a drill bit 2 is arranged at the lower end of the main drill part 1, and a retaining wall outer cylinder 5 is sleeved on the outer wall of the main drill part 1; the main drill part 1 is provided with a lifting oil cylinder 8 connected with a wall protection outer cylinder 5; notches 10 are distributed on the wall protecting outer cylinder 5, and blades 9 which can be vertically turned over are arranged in the notches 10; the main drill part 1 is provided with a pushing piece 17 for controlling the blades 9 to open and close; a knife edge 93 is arranged on one side of the blade 9, and a slurry outlet 94 for outputting concrete slurry and a slurry outlet 95 for outputting an accelerating agent are arranged on the other side of the blade; the lower end of the main drilling component 1 is provided with a mud inlet hole 3, and a mud suction pipe 12 communicated with the mud inlet hole 3 is arranged inside the main drilling component.

The main drilling component 1 is a hollow cylinder, a main shaft 4 is arranged at the center of the top end of the main drilling component, a mud inlet hole 3 is formed in the bottom of the main drilling component, various conveying pipelines such as a mud suction pipe 12 are arranged inside the main drilling component, the conveying pipelines are attached to the inner wall of the main drilling component 1 and installed, in order to prevent soil from extruding and damaging the pipelines, the side wall of the main drilling component 1 can be arranged into a double-layer wall structure, so that the various conveying pipelines are located in an interlayer cavity of the double-layer wall and isolated from the inner cavity of the main drilling component 1.

The upper end of the main drilling part 1 is provided with a rotary joint 16, and the mud suction pipe 12 is connected with the rotary joint 16; the mud suction pipe 12 moves synchronously along with the rotation of the main drilling component 1, and the rotary joint 16 is connected with an external pipeline; the external pipes do not move with the rotation of the main drill part 1.

The accelerator is a special accelerator for concrete, cement paste and the accelerator are sprayed from the blades 9 and then mixed with soil, so that initial setting can be completed within 10 seconds, and certain strength can be achieved within 45 seconds; initial setting is formed in a period of time by the cement paste which originally takes 45 minutes to form initial setting.

The knife edge 93 is sharp and used for scraping and cutting the inner wall of the bored concrete pile hole, scraping off soil and crushing the soil.

The slurry outlet 94, the slurry outlet 95 and the knife edge 93 are respectively arranged on different side edges of the blade, so that the slurry outlet 94 and the slurry outlet 95 can be prevented from being blocked by mud.

The suction pipe 12 can be directly communicated with the mud inlet hole 3, so that the mud can be conveniently sucked, and can also be indirectly communicated, the mud inlet hole 3 guides the mud into the cavity of the main drill part 1, and then the suction pipe 12 sucks the mud in the cavity again.

As shown in fig. 1, further optimization is performed on the basis of the above embodiment: the blades 9 are spirally distributed on the wall protection outer cylinder 5. The notches 10 are spirally distributed on the wall protection outer cylinder 5, and then the blades 9 are arranged in the notches 10; when the drill bit rotates, the spiral line rotating direction of the blades is the same as the rotating direction of the drill bit.

As shown in fig. 2, further optimization is performed on the basis of the above embodiment: the other end of the grout outlet 94 is communicated with the grouting pipe 13; the other end of the liquid outlet hole 95 is communicated with the liquid injection pipe 14. The upper end of the injection pipe 13 and the upper end of the injection pipe 14 are connected with a rotary joint 16, and the other end of the rotary joint 16 is connected with a corresponding conveying pipeline.

As shown in fig. 4-5, further optimization is performed on the basis of the above-mentioned embodiments: a chute 91 is arranged in the blade 9; the inner wall of the blade 9 is provided with a clamping groove 92; the clamping groove 92 is communicated with the sliding groove 91; the end of the pushing piece 17 is provided with a pushing head 18; the pusher head 18 is slidably disposed within the chute 91. Wherein the width of the locking groove 92 is smaller than the width of the sliding groove 91; the pushing head 18 can be a ball-shaped body and is clamped in the sliding groove 91 to slide; the pushing head 18 can also be a roller which rolls in the chute 91; the pushing element 17 is a rod-shaped structure, and the diameter of the pushing element is smaller than the width of the pushing head 18 and smaller than the width of the clamping groove 92. The locking groove 92 and the sliding groove 91 can penetrate through the upper end face and the lower end face of the blade 9.

As shown in fig. 2, further optimization is performed on the basis of the above embodiment: the main drill component 1 is of a hollow structure, and a cavity 19 is formed inside the main drill component. The bottom of the main drilling component 1 is provided with a bottom plate, the drill bits 2 are arranged on the bottom plate side by side, and the upper opening of the bottom plate forms a mud inlet hole 3; the cavity 19 can be used both to reduce the weight of the main drill part 1 and to collect crushed earth.

As shown in fig. 2-3, further optimization is performed on the basis of the above-mentioned embodiments: vertical grooves 7 are distributed on the side wall of the main drill part 1 and are uniformly distributed in an annular shape; the inner wall of the wall protection outer cylinder 5 is distributed with convex parts 6; said protrusions 6 are slidably arranged in corresponding recesses 7. The groove 7 is positioned on the side wall of the upper end of the main drilling component 1; the convex part 6 is a convex strip structure and is positioned at the upper end part of the inner wall of the protective wall outer cylinder 5.

As shown in fig. 2 and 8, the optimization is further performed on the basis of the above embodiment: the upper end of the main drill part 1 is provided with a rotary joint 16; FIG. 8 shows a top view of the internal structure of the upper or lower disk; the rotary joint 16 is disc-shaped and comprises an upper disc and a lower disc, the upper disc and the lower disc are folded, a plurality of layers of mutually isolated cavities are annularly distributed in the upper part, and the bottom of each cavity is provided with a connector which is respectively connected with each corresponding pipeline; the upper disc and the lower disc can rotate mutually; the lower disc is fixedly connected with the main drilling component 1 and rotates along with the rotation of the main drilling component 1, and the interface on the upper disc is connected with each corresponding pipeline and keeps fixed; a conduit connected to the upper disk conveys material into the annular cavity and then out of a conduit at the interface of the lower disk.

Further optimization is carried out on the basis of the embodiment: a water outlet hole is formed in the drill bit 2; the other end of the water outlet hole is connected with a water inlet pipe 11 in the main drilling component 1. As the arrangement of the water outlet hole on the drill bit 2 belongs to the mature technology, the detailed description is omitted here.

As shown in fig. 1, further optimization is performed on the basis of the above embodiment: the blades 9 are distributed at the lower end of the wall protection outer cylinder 5; the outer wall of the upper end of the wall protection outer cylinder 5 is a smooth surface. The blades 9 are distributed at the lower end part of the outer protecting wall cylinder 5, the upper end part of the outer protecting wall cylinder 5 is still smooth and whole, and the outer wall of the upper end can play a role in ironing the formed concrete protecting wall.

A method for radially drilling a drill bit of a lifting type variable-diameter self-retaining wall-forming cast-in-place pile comprises the following steps of:

reducing operation: controlling the lifting oil cylinder 8 to lift according to the diameter of the cast-in-place pile hole, so that the outer wall protection barrel 5 descends, and driving the blades 9 to open according to a set angle;

drilling operation: the main drill part 1 and the outer protecting wall cylinder 5 are driven to synchronously rotate and drill downwards, and soil generated by drilling is sucked away by the main drill part 1 through a mud suction pipe 12 in the drilling process; the opened blades 9 scrape and crush the soil on the wall of the hole, meanwhile, the main slurry pipe 13 inputs concrete slurry into the blades 9, the concrete slurry is sprayed out from the slurry outlet 94, is uniformly mixed with the crushed soil and is solidified to form a concrete retaining wall;

hole withdrawing operation: after drilling is finished, stopping injecting concrete slurry and an accelerator, and controlling the outer cylinder of the protective wall to ascend by the oil cylinder so as to fold the blades 9; then the drill bit integrally rises to exit the pouring hole to form a pouring pile hole with a concrete protecting wall.

A method for radially drilling a drill bit of a lifting type variable-diameter self-retaining wall-forming cast-in-place pile comprises the following steps of:

reducing operation: controlling the lifting oil cylinder 8 to lift according to the diameter of the cast-in-place pile hole, so that the outer protective wall cylinder 5 descends, and driving the blades 9 to open according to a set angle;

drilling operation: the main drill part 1 and the outer protecting wall cylinder 5 are driven to synchronously rotate and drill downwards, and soil generated by drilling is sucked away by the main drill part 1 through a mud suction pipe 12 in the drilling process; the opened blades 9 scrape and crush hole wall soil, meanwhile, the main slurry pipe 13 inputs concrete slurry into the blades 9 and sprays out of the slurry outlet 94, the liquid injection pipe 14 inputs an accelerator into the blades 9 and sprays out of the liquid outlet 95, the concrete slurry and the accelerator are uniformly mixed with the crushed soil and then are solidified to form a concrete retaining wall;

hole withdrawing operation: after drilling is finished, stopping injecting concrete slurry and an accelerator, and controlling the outer cylinder of the protective wall to ascend by the oil cylinder so as to fold the blades 9; then the drill bit integrally rises to exit the pouring hole, and a pouring pile hole with a concrete retaining wall is formed.

The invention has the specific working principle that:

the invention uses the main drilling component 1 to complete the main drilling work of the cast-in-place pile hole, uses the blade 9 of the outer cylinder 5 of the retaining wall to perform reaming operation on the drilled hole, then synchronously pours concrete slurry and accelerating agent into the inner wall of the cast-in-place pile hole, uses the blade 9 to synchronously mix the soil generated by reaming with the concrete slurry and the accelerating agent to form the retaining wall of the cast-in-place pile hole, and uses the outer wall of the outer cylinder 5 of the retaining wall to perform scraping operation on the retaining wall.

The technical scheme of the invention is compared with the manual hole-forming cast-in-place pile and the traditional rotary-digging hole-forming cast-in-place pile as follows:

item	Artificial hole-forming cast-in-place pile	Rotary digging hole-forming filling pile	Reducing self-protecting wall pore-forming pile
				Required operating personnel	Many workers and difficult organization	Chinese character shao (a Chinese character of 'shao')	Chinese character shao (a Chinese character of 'shao')
Progress of excavation	Slow	Is quicker	Is quicker
				Cost of excavation	Height of	In general	In general
Excavation depth limitation	Generally no more than 16 m	30 to 72 meters	30 to 72
				Risk of operating personnel	Extreme high	Is low in	Is low in
Loss of concrete	Low loss	Height of	Is low in
				Wall protection mode	Reinforced concrete	Steel casing	Self-protecting wall for stirring soil
Wall protection equipment	Artificial operation	Vibration hammer with steel protective cylinder	One-step forming non-increasing equipment
				Comprehensive cost of wall protection	Height of	Super high	Is low in
Working equipment	Chinese character shao (a Chinese character of 'shao')	Multiple purpose	Much more
				Pouring properties	Large area continuous casting	Intermittent pouring	Large area ofContinuous casting
Casting cost	Is relatively low	Height of	Is relatively low
				Site requirements	Is relatively low	Height of	High (a)
Pile forming quality	Height of	Unstable quality	High (a)
				Cost controllability	Controllable	Is not controllable	Controllable
Progress controllability	Controllable	Is not controllable	Controllable
				Controllable piling quality	Is visible and controllable	Is not controllable	Is visible and controllable
Bearing capacity of single pile with same cross section	Height of	Is low in	Height of
				Consumption of water resources	20-25 prescription	25-35 prescription	5-7 prescription

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts of the present invention. The foregoing is only a preferred embodiment of the present invention, and it should be noted that there are objectively infinite specific structures due to the limited character expressions, and it will be apparent to those skilled in the art that a plurality of modifications, decorations or changes may be made without departing from the principle of the present invention, and the technical features described above may be combined in a suitable manner; such modifications, variations, combinations, or adaptations of the invention using its spirit and scope, as defined by the claims, may be directed to other uses and embodiments.

Claims (10)

1. A lifting type variable-diameter self-retaining wall-forming bored concrete pile drill bit comprises a main drill part (1), wherein a drill bit (2) is arranged at the lower end of the main drill part (1), and is characterized in that a retaining wall outer cylinder (5) is sleeved on the outer wall of the main drill part (1); a lifting oil cylinder (8) is arranged on the main drill component (1) and connected with the outer protective wall cylinder (5); notches (10) are distributed on the wall protection outer cylinder (5), and blades (9) which can be vertically turned over are arranged in the notches (10); a pushing piece (17) used for controlling the opening and closing of the blades (9) is arranged on the main drill part (1); a knife edge (93) is arranged on one side of the blade (9), and a slurry outlet hole (94) for outputting concrete slurry and a slurry outlet hole (95) for outputting an accelerating agent are arranged on the other side of the blade; the lower end of the main drilling component (1) is provided with a mud inlet hole (3), and a mud suction pipe (12) communicated with the mud inlet hole (3) is arranged in the main drilling component.

2. The elevating variable-diameter self-retaining bored pile drill bit as claimed in claim 1, wherein the blades (9) are helically distributed on the outer retaining wall cylinder (5).

3. The elevating variable-diameter self-retaining wall-forming bored pile drill bit as claimed in claim 1, wherein the other end of the grout outlet (94) is communicated with the grout pipe (13); the other end of the liquid outlet hole (95) is communicated with the liquid injection pipe (14).

4. The elevating variable-diameter self-retaining wall-forming bored pile drill bit as claimed in claim 1, wherein a chute (91) is provided in the blade (9); the inner wall of the blade (9) is provided with a clamping groove (92); the clamping groove (92) is communicated with the sliding groove (91); a pushing head (18) is arranged at the end of the pushing piece (17); the push head (18) is arranged in the sliding groove (91) in a sliding way.

5. An elevating variable-diameter self-retaining wall-forming bored pile drill bit according to claim 1, wherein the main drill member (1) is of hollow construction with a cavity (19) formed therein.

6. An elevating variable-diameter self-retaining wall-forming bored pile drill bit according to claim 1, wherein the main drill member (1) has vertical grooves (7) distributed in its side wall; convex parts (6) are distributed on the inner wall of the wall protection outer cylinder (5); the protrusions (6) are slidably arranged in corresponding grooves (7).

7. An elevating variable-diameter self-retaining wall-forming bored pile drill bit according to claim 1, wherein the main drill unit (1) is provided with a swivel (16) at its upper end; the mud suction pipe (12) and the grouting pipe (13) are connected with a rotary joint (16).

8. The elevating type variable-diameter self-retaining wall-forming bored concrete pile drill bit according to claim 1, wherein the drill bit (2) is provided with a water outlet hole; the other end of the water outlet hole is connected with a water inlet pipe (11) in the main drill part (1).

9. The method for drilling a hole by using the lifting type variable-diameter self-retaining wall-forming cast-in-place pile drill bit as claimed in claim 1, which is characterized by comprising the following steps:

firstly, diameter changing operation: controlling a lifting oil cylinder (8) to lift according to the diameter of a cast-in-place pile hole, so that a wall protection outer cylinder (5) descends, and driving blades (9) to open according to a set angle;

secondly, drilling operation: the main drill part (1) and the outer protective wall cylinder (5) are driven to synchronously rotate and drill downwards, and soil generated by drilling is sucked away by the main drill part (1) through a mud suction pipe (12) in the drilling process; the opened blades (9) scrape and crush hole wall soil, meanwhile, concrete slurry and an accelerating agent are input into the blades (9) through a main slurry pipe (13), are sprayed out of a slurry outlet hole (94), are uniformly mixed with the crushed soil, and then are solidified to form a concrete retaining wall;

thirdly, hole withdrawing operation: after drilling is finished, stopping injecting concrete slurry and an accelerator, and controlling the outer protective wall cylinder (5) to ascend by the lifting oil cylinder (8) so as to enable the blades (9) to be folded; then the drill bit integrally rises to exit the cast-in-place hole, and a cast-in-place pile hole with a concrete retaining wall is formed.

10. The method for drilling a hole by using the lifting type variable-diameter self-retaining wall-forming cast-in-place pile drill bit as claimed in claim 3, which is characterized by comprising the following steps:

firstly, diameter changing operation: controlling a lifting oil cylinder (8) to lift according to the diameter of the cast-in-place pile hole, so that a wall protection outer cylinder (5) descends, and driving blades (9) to open according to a set angle;

secondly, drilling operation: the main drill part (1) and the outer protective wall cylinder (5) are driven to synchronously rotate and drill downwards, and soil generated by drilling is sucked away by the main drill part (1) through a mud suction pipe (12) in the drilling process; the opened blades (9) scrape and crush hole wall soil, meanwhile, concrete slurry is input into the blades (9) through the main slurry pipe (13) and sprayed out from the slurry outlet holes (94), the accelerating agent is input into the blades (9) through the liquid injection pipe (14) and sprayed out from the liquid outlet holes (95), and the concrete slurry and the accelerating agent are uniformly mixed with the crushed soil and then are solidified to form the concrete retaining wall;

thirdly, hole withdrawing operation: after drilling is finished, stopping injecting concrete slurry and an accelerator, and controlling the outer protective wall cylinder (5) to ascend by the oil cylinder so as to enable the blades (9) to be folded; then the drill bit integrally rises to exit the cast-in-place hole, and a cast-in-place pile hole with a concrete retaining wall is formed.

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