CN113550311B - Subway vehicle unfavorable geology CFG pile foundation treatment construction method - Google Patents

Abstract

The application discloses a subway vehicle unfavorable geology CFG pile foundation treatment construction method which comprises the following steps that S1, a drilling machine drills holes to reach a designed elevation; s2, after drilling to the designed elevation, stopping drilling, and lifting the drill rod while pouring concrete into the pile hole until the concrete reaches the designed elevation of the pile top; s3, excavating soil among piles, determining the pile cutting position of a pile head after cleaning the soil among the piles, installing a pile head cutting device after a hole coaxial with the CFG pile is formed in the pile top, starting the pile head cutting device after the installation is finished, cutting the pile head cutting device in the direction from the inside of the hole to the outer wall of the pile head along the radial direction of the pile head and in the direction from the outer wall of the pile head to the inside of the hole, stopping cutting along the radial direction of the pile head when the sum of the cutting depths of the two cutting directions is greater than the difference value between the radius of the pile head and the radius of the hole, and cutting the pile head cutting device in the 360-degree circumferential mode around the circumferential direction of the pile head. This application has promoted work efficiency, has shortened construction period's effect.

Description

Subway vehicle unfavorable geology CFG pile foundation treatment construction method

Technical Field

The invention relates to the field of foundation treatment, in particular to a subway vehicle unfavorable geology CFG pile foundation treatment construction method.

Background

In the process of foundation treatment construction, foundation treatment is divided into different areas according to different foundation bearing capacity requirements and settlement control standards of each functional partition, and then a foundation treatment mode suitable for the areas, such as CFG pile composite foundation treatment, is selected. The CFG pile is a low-strength concrete pile, can fully utilize the combined action of bearing capacity of soil among piles, and can transmit load to a deep foundation.

In the related art, after excavation and removal of soil between piles are completed, when a pile head is cut off, a pile cutter is usually pushed manually to transversely cut the pile head, three steel nails are inserted into the same horizontal plane at the joint cut of the pile head after cutting, the pile head is cut off by beating with tools such as a hammer, and then the pile head is flattened manually, so that the pile head is cut.

With respect to the related art among the above, the inventors consider that the following drawbacks exist: the CFG pile foundations arranged at intervals are usually arranged in the same area, and the pile head cutting process in the related technology is complicated, so that the construction period is long, and a certain improvement space exists.

Disclosure of Invention

In order to improve the working efficiency and shorten the construction period, the application provides a subway vehicle unfavorable geology CFG pile foundation treatment construction method.

The application provides a subway vehicle unfavorable geology CFG stake foundation treatment construction method adopts following technical scheme:

a subway vehicle unfavorable geology CFG pile foundation treatment construction method comprises the following steps:

s1, drilling a hole to a designed elevation by a drilling machine;

s2, after drilling to a designed elevation, stopping drilling, pouring concrete into the pile hole while lifting the drill rod until the concrete reaches the designed elevation of the pile top, and constructing the CFG piles one by one according to a set sequence;

s3, excavating soil among the piles, determining the pile cutting position of the pile head after cleaning the soil among the piles, installing a pile head cutting device after a hole coaxial with the CFG pile is formed in the pile top, starting the pile head cutting device after the installation is finished, cutting the pile head cutting device in the direction from the inside of the hole to the outer wall of the pile head along the radial direction of the pile head and in the direction from the outer wall of the pile head to the inside of the hole, stopping cutting along the radial direction of the pile head when the sum of the cutting depths of the two cutting directions is greater than the difference value between the radius of the pile head and the radius of the hole, and cutting the pile head cutting device in the 360-degree circumferential mode around the circumferential direction of the pile head;

s4, pile cap construction;

s5, backfilling soil among the piles;

and S6, constructing a mattress layer.

Through adopting above-mentioned technical scheme, when excision pile head, through along the radial excision from inside to outside and outside-in of pile head, after excision to the predetermined degree of depth, again through the mode that carries out the circular cutting to the pile head, the pile head that will cut more than the pile position is cut, need not the cooperation of resection device and peg, can realize cutting the stake, whole process of cutting is comparatively simple, and then the efficiency of construction of this process of cutting off the pile head has been promoted, holistic construction period has been shortened, in addition, this kind of pile head cuts off mode easy operation, provide good reference effect for subsequent similar engineering.

Preferably, the pile head cutting device comprises an inner cutting blade for cutting from the inside of the cut hole to the direction of the outer wall of the pile head and an outer cutting blade for cutting from the outside of the pile head to the inside of the cut hole, and in step S3, when the pile head cutting device cuts along the radial direction of the pile head, the inner cutting blade and the outer cutting blade move simultaneously and in the same direction along the radial direction of the pile head.

By adopting the technical scheme, the collision of the inner cutting piece and the outer cutting piece is avoided by the inner cutting piece and the outer cutting piece which move in the same direction, the simultaneous movement of the inner cutting piece and the outer cutting piece is realized, the construction efficiency of cutting off along the radial direction of the pile head is improved, and the whole construction period is further shortened.

Preferably, in the step S3, after the pile cutting position of the pile head is determined, a steel plate is first laid on the ground outside the pile head so that the steel plate is fitted on the outside of the pile head, and then the pile head cutting device is installed on the steel plate.

Through adopting above-mentioned technical scheme, the setting up of steel sheet has promoted the intensity and the roughness on the ground in the pile head outside, and then has increased levelness and stability among the pile head resection device excision process.

Preferably, pile head resection device is still including setting firmly the support body in the pile head outside, it is connected with the connecting piece and is used for driving the connecting piece around the axis direction pivoted power unit of cutting the hole to rotate on the support body, it is connected with the crossbeam to slide along the distribution direction of interior cutting piece and outer cutting piece on the connecting piece, be provided with on the crossbeam and be used for locking it in the locking Assembly of connecting piece, interior cutting piece rotates through the interior connecting rod and connects in the crossbeam, outer cutting piece rotates through the outer connecting rod and connects in the crossbeam, be provided with on the crossbeam and be used for driving interior connecting rod and outer connecting rod pivoted actuating mechanism, be provided with on the support body and be used for driving the driving piece that the crossbeam removed, the output of driving piece can be dismantled through coupling assembling and connect in the crossbeam.

By adopting the technical scheme, when the pile head is cut off, the limitation of the locking assembly on the cross beam is removed, the cross beam can move relative to the connecting piece, the output end of the driving piece is detachably connected to the cross beam through the connecting assembly, the driving piece is started to drive the cross beam to drive the inner connecting rod and the outer connecting rod to move, and meanwhile, the driving mechanism is started to drive the inner connecting rod and the outer connecting rod to respectively drive the inner cutting piece and the outer cutting piece to rotate, so that the inner cutting piece and the outer cutting piece in high-speed rotation move along the radial direction of the pile head and are cut off along the radial direction of the pile head; and after the pile head is cut into the preset depth, the driving piece is disconnected with the cross beam, the cross beam is locked through the locking assembly, the movement of the cross beam relative to the connecting piece is limited, and then the power mechanism and the driving mechanism are started, so that the inner cutting piece and the outer cutting piece which rotate at high speed rotate around the circumferential direction of the pile head, and the pile head is circumferentially cut by 360 degrees.

Preferably, the connecting piece sets up to the sleeve pipe, the sleeve pipe bottom stretches into in cutting the hole with cut the hole coaxial, the sleeve pipe top is fixed with the apron, the apron rotates through the gag lever post to be connected in the support body, the internal connection connects the pole top to slide and wears to locate the apron.

Through adopting above-mentioned technical scheme, realized being connected between connecting piece and the support body, simple structure, the processing and the installation of the connecting piece of being convenient for.

Preferably, the outer wall of the sleeve is rotatably connected with a vertically arranged roller shaft, and the outer wall of the roller shaft is in contact with the inner wall of the cutting hole.

Through adopting above-mentioned technical scheme, promoted sheathed tube straightness that hangs down, reduced the frictional force between roller and the cut hole simultaneously, the sleeve pipe of being convenient for rotates.

Preferably, the power mechanism comprises a first motor fixedly arranged on the pile top and a first belt transmission assembly arranged between the first motor and the sleeve.

By adopting the technical scheme, the driving to the sleeve is realized, the structure is simple, and the installation is convenient.

Preferably, the driving mechanism comprises a second motor fixedly arranged on the cross beam, the second motor is used for driving the inner connecting rod to rotate, and a second belt transmission assembly is arranged between the inner connecting rod and the outer connecting rod.

By adopting the technical scheme, the second motor is started, the inner connecting rod drives the inner cutting piece to rotate under the action of the second motor, so that the second belt transmission assembly is driven to act, the outer connecting rod drives the outer cutting piece to rotate under the action of the second belt transmission assembly, and the drive of the inner cutting piece and the outer cutting piece is realized.

Preferably, the drive element is configured as a hydraulic cylinder.

In summary, the present application includes at least one of the following beneficial technical effects:

1. the whole pile head cutting process is simple, so that the construction efficiency of the pile head cutting process is improved, the whole construction period is shortened, and in addition, the pile head cutting mode is simple to operate, and a good reference effect is provided for subsequent similar projects;

2. the inner cutting piece and the outer cutting piece which move in the same direction avoid collision of the inner cutting piece and the outer cutting piece, the inner cutting piece and the outer cutting piece can move simultaneously, the construction efficiency of cutting off along the radial direction of the pile head is improved, and the whole construction period is further shortened.

Drawings

Fig. 1 is a schematic top view of a CFG pile foundation shown in the present application.

Fig. 2 is a schematic view showing the overall construction of the pile head removing device in the present application.

Figure 3 is a schematic partial cross-sectional view of the pile head removing device shown in this application.

Fig. 4 is a partially enlarged schematic view of a portion a in fig. 3.

Figure 5 is a schematic partial cross-sectional view of the locking assembly configuration shown in the present application.

Fig. 6 is a partially enlarged schematic view of a portion B in fig. 3.

Description of reference numerals:

1. CFG piles; 11. cutting a hole; 2. a steel plate; 3. a pile head cutting device; 31. a frame body; 311. a limiting ring; 4. a slice supporting mechanism; 41. an inner connecting rod; 42. an outer connecting rod; 43. a cross beam; 431. an inner connecting sleeve; 432. an outer connecting sleeve; 4321. an extension rod; 433. a connecting beam; 44. a locking assembly; 441. supporting a lug; 442. a locking block; 443. locking the bolt; 51. an inner cutting sheet; 52. externally cutting the sheet; 6. a sleeve; 61. a cover plate; 611. a sliding hole; 612. a locking groove; 62. a limiting rod; 621. a limiting clamping block; 63. a roll shaft; 7. a power mechanism; 71. a support; 72. a first motor; 73. a first belt drive assembly; 731. a first drive wheel; 732. a first driven wheel; 733. a first belt; 8. a drive mechanism; 81. a support; 82. a second motor; 83. a second belt drive assembly; 831. a second drive wheel; 832. a second driven wheel; 833. a second belt; 9. a hydraulic cylinder; 10. a connecting assembly; 101. a collar; 102. and pressing the bolt.

Detailed Description

The present application is described in further detail below with reference to figures 1-6.

The embodiment of the application discloses a subway vehicle unfavorable geology CFG pile foundation treatment construction method, combines fig. 1 to 3, includes the following steps:

s1, measurement and setting:

according to a drawing, positioning and paying off are carried out through a control point and an axis, the specific position of each CFG pile 1 is measured and paid out, a steel pipe is driven into the ground to a certain depth, white lime is added after the CFG pile is pulled out, and the center of a white lime hole is used as the center of a pile position.

S2, positioning a drilling machine and drilling a hole:

after the CFG pile drilling machine is in place, the position is corrected, the drill rod is vertically aligned to the center of the pile position, and the side face of the rack beside the pile is provided with a level elevation mark of the drilling depth by red paint. When drilling begins, the valve of the drill bit is closed, the drill rod is moved downwards until the drill bit touches the ground, and the motor is started to drill. When the drill bit reaches the designed pile length elevation, the corresponding drilling machine tower body position of the stop position of the power head bottom surface is marked and recorded, the pile bottom reaches the middle and light weathered limestone top and the pile length are subjected to double control in actual construction, the pile bottom reaches the limestone top mainly, and the pile length is assisted.

S3, pouring and drawing the concrete:

the strength grade of the pile body concrete is C20 underwater concrete, and the slump of the pumping pressure mixture in the pipe during pile forming construction is preferably 180-220 mm. And after the CFG pile 1 is drilled to the designed elevation, stopping drilling and starting pumping the mixture. During construction, concrete is poured into the hole under pressure, and the drill rod is lifted until the concrete reaches the designed pile top elevation. And starting to pull the pipe after the drill pipe core pipe is filled with the mixture. In order to ensure the quality of the pile head, the height of the pile top is designed to be higher than the height of the pile top by 50 cm.

S4, moving the machine:

and after the previous pile is constructed, the drilling machine is shifted to carry out the construction of the next pile.

S5, pile head cutting:

s51, excavating soil among the piles, wherein the small excavator is matched with manpower to excavate concrete with the pile top being more than 0.2m and peripheral soil before initial setting of the pile head concrete and then timely clean the pile out of the field, the small excavator should leave the pile edge for 20cm when excavating the soil, and the residual soil is manually removed.

And S52, determining the pile cutting position, measuring the actual pile top elevation by a field technician, and marking the pile cutting line by using red paint at the position 10cm above the pile top.

S53, pile head cutting, manually leveling the ground outside the pile head of the CFG pile 1, laying a steel plate 2 on the ground, prefabricating the steel plate 2 in a factory, arranging a yielding hole for the CFG pile 1 to penetrate through on the steel plate 2, adjusting the steel plate 2 to be in a horizontal state, and enabling the upper surface of the steel plate 2 to be located below the pile cutting position of the CFG pile 1.

The top wall of the pile head is vertically downwards provided with a cut hole 11 through the hole drilling equipment, the depth of the cut hole 11 reaches the pile cutting position of the CFG pile 1, and the cut hole 11 is a round hole and is coaxially arranged with the CFG pile 1.

Installing a pile head cutting device 3 on the upper surface of the steel plate 2, cutting off the pile head through the pile head cutting device 3 to cut off the upper pile body, and after the upper pile body is cut off, completely removing floating slag at the top end of the CFG pile 1 until a fresh concrete surface is exposed, wherein the effective length of the pile after removing the floating slag meets the design requirement;

s6, pile cap construction:

the strength grade of the cast-in-situ pile cap concrete is C30, and commercial concrete is adopted for pouring. And after the concrete pouring is finished, the whole body is covered with geotextile and is watered for maintenance. And (4) removing the top cap round die after the concrete is initially set, and continuing to cover and maintain by adopting geotextile, wherein the watering and maintaining time is not less than 7 days.

S7, backfilling soil among piles:

backfilling soil materials among piles in two layers, and tamping each layer by using a tamping machine.

S8, constructing a mattress layer:

and after the strength of the pile cap reaches 70% of the designed strength, filling 300mm medium coarse sand at the top of the pile cap, sandwiching a layer of bidirectional steel-plastic composite geogrid in the middle of the cushion layer, and tamping the cushion layer by adopting a layered laying water tamping method.

With reference to fig. 2 and 3, the pile head cutting device 3 comprises a slice supporting mechanism 4, an inner cutting blade 51 for cutting from the inner wall of the cut hole 11 outwards and an outer cutting blade 52 for cutting from the outer wall of the pile head inwards, wherein the inner cutting blade 51 and the outer cutting blade 52 are both located at the pile cutting position of the CFG pile 1, and the sum of the maximum cutting depth of the inner cutting blade 51 in the radial direction of the pile head and the maximum cutting depth of the outer cutting blade 52 in the radial direction of the pile head is greater than the difference between the radius of the pile head and the radius of the cut hole 11. When the pile head is cut off, the inner cutting sheet 51 and the outer cutting sheet 52 which rotate at a high speed simultaneously act in the same direction by driving the cutting sheet supporting mechanism 4, firstly, the pile head is cut into the maximum cutting depth along the radial direction of the pile head, and then 360-degree circumferential cutting is carried out around the circumferential direction of the pile head, so that the pile head is cut off.

In order to avoid friction between the cut hole 11 and the inner cutting piece 51 during actual construction, the bottom wall of the cut hole 11 is usually lower than the pile cutting position of the pile head.

Pile head resection device 3 is still including being fixed in support body 31 on the steel sheet 2, and it is connected with sleeve pipe 6 to rotate on the support body 31, and sleeve pipe 6 and the coaxial setting of cutting hole 11, 6 bottoms of sleeve pipe stretch into in cutting hole 11.

A limiting ring 311 is fixed on the frame body 31, and the limiting ring 311 is coaxially arranged with the sleeve 6 and is located above the sleeve 6. The top end of the sleeve 6 is coaxially fixed with a cover plate 61, a limiting rod 62 is fixed at the outer edge of the upper surface of the cover plate 61, and the limiting rod 62 is vertically arranged. The top end of the limiting rod 62 is fixed with a limiting fixture block 621 used for being matched with the limiting ring 311, the limiting fixture block 621 is slidably sleeved on the inner side of the limiting ring 311 to limit the vertical movement of the sleeve 6, and the sleeve 6 is rotatably connected with the frame body 31.

Referring to fig. 3, the outer circumferential surface of the sleeve 6 is rotatably connected with a roller 63 through a vertically arranged rotating shaft, the outer wall of the roller 63 contacts with the inner wall of the cutting hole 11, the roller 63 is uniformly distributed along the circumferential direction of the sleeve 6 at intervals, and in the embodiment, the number of the roller 63 is three. The arrangement of the roll shaft 63 has a certain centering effect on the sleeve 6, the perpendicularity of the sleeve 6 is ensured, and meanwhile, the friction force between the roll shaft 63 and the inner wall of the cut hole 11 is reduced.

The top end of the pile head is fixedly provided with a power mechanism 7 for driving the sleeve 6 to rotate, the power mechanism 7 comprises a support 71 fixed on the top wall of the pile head, a first motor 72 vertically arranged is fixed on the support 71, and a first belt transmission assembly 73 is arranged between the first motor 72 and the sleeve 6. The first belt transmission assembly 73 includes a first driving wheel 731 coaxially fixed to the outer side of the output shaft of the first motor 72, a first driven wheel 732 coaxially fixed to the outer wall of the sleeve 6, and a first belt 733 sleeved on the outer sides of the first driven wheel 732 and the first driving wheel 731.

The sliced sheet supporting mechanism 4 includes an inner connecting rod 41 coaxially fixed to the inner cutting sheet 51, an outer connecting rod 42 coaxially fixed to the outer cutting sheet 52, and a cross beam 43 for connecting the inner connecting rod 41 and the outer connecting rod 42. The cover plate 61 is provided with a sliding hole 611, the sliding hole 611 extends along the radial direction of the sleeve 6, the top end of the inner connecting rod 41 slides and penetrates through the sliding hole 611, and the outer wall of the inner connecting rod 41 contacts with the inner wall of the sliding hole 611. The cross beam 43 comprises an inner connecting sleeve 431, an outer connecting sleeve 432 and a connecting beam 433 fixed between the inner connecting sleeve 431 and the outer connecting sleeve 432, wherein the inner connecting sleeve 431 is rotatably connected to the outer side of the inner connecting rod 41 and always keeps the relative rest in the vertical direction, the bottom wall of the inner connecting sleeve 431 is in contact with the upper surface of the cover plate 61, and the outer connecting sleeve 432 is rotatably connected to the outer side of the outer connecting rod 42 and always keeps the relative rest in the vertical direction.

Referring to fig. 4 and 5, the cross beam 43 is provided with a locking assembly 44, the locking assembly 44 includes two support lugs 441 extending outwards on the outer wall of the inner connecting sleeve 431, and the two support lugs 441 are symmetrically arranged on two sides of the sliding hole 611. The lower surface of the support lug 441 is integrally formed with a locking block 442, and the locking block 442 is configured as a trapezoidal block. The upper surface of the cover plate 61 is provided with a locking groove 612 for accommodating the locking block 442, and the locking groove 612 is arranged along the length direction of the sliding hole 611. The same locking bolt 443 is commonly screwed on the support lug 441 and the locking block 442, the locking bolt 443 is vertically arranged, the bottom end of the locking bolt 443 abuts against the bottom wall of the locking groove 612, the locking bolt 443 is screwed, and relative movement between the cross beam 43 and the sleeve 6 is limited.

Referring to fig. 2 and 3, the frame body 31 is provided with a driving mechanism 8 for driving the inner connecting rod 41 and the outer connecting rod 42 to rotate. The driving mechanism 8 includes a support 81 fixed to the two support lugs 441, and a second motor 82 for driving the inner connecting rod 41 to rotate around its own axis is fixed to the support 81. The driving mechanism 8 further includes a second belt transmission assembly 83, the second belt transmission assembly 83 includes a second driving wheel 831 coaxially fixed to the outer side of the inner connecting rod 41, a second driven wheel 832 coaxially fixed to the outer side of the outer connecting rod 42, and a second belt 833 sleeved on the outer sides of the second driven wheel 832 and the second driving wheel 831.

Referring to fig. 3 and 6, a hydraulic cylinder 9 for driving the slice supporting mechanism 4 to move is fixed on the frame body 31, and the hydraulic cylinder 9 is arranged along the radial direction of the pile head. An extension rod 4321 extends outwards from the outer side of the outer connecting sleeve 432 along the length direction of the connecting beam 433. A connecting assembly 10 is arranged between the extension rod 4321 and the rod end of the hydraulic cylinder 9, the connecting assembly 10 comprises a lantern ring 101 fixed at one end, away from the sleeve 6, of the extension rod 4321, the lantern ring 101 is used for being matched with the rod end of the hydraulic cylinder 9, and a pressing bolt 102 used for pressing the rod end of the hydraulic cylinder 9 is connected to the lantern ring 101 in a threaded mode.

Referring to fig. 1 to 6, in step S6, after the cut hole 11 is cut, the pile head cutting device 3 is installed to fix the frame body 31 on the upper surface of the steel plate 2, the inner cutting piece 51 extends into the bottom end of the cut hole 11 and contacts with the inner wall of the cut hole 11, and the outer cutting piece 52 abuts against the outer wall of the pile head.

When the pile head cutting device 3 cuts the pile head, the locking bolt 443 is released from limiting the cross beam 43, so that the cross beam 43 can move relative to the sleeve 6, the rod end of the hydraulic cylinder 9 is matched with the sleeve ring 101, and the hold-down bolt 102 is tightened, the hydraulic cylinder 9 is started to enable the rod part to extend outwards, the slicing support mechanism 4 moves away from the hydraulic cylinder 9 along the axial direction of the rod part of the hydraulic cylinder 9 under the action of the hydraulic cylinder 9, and when the hydraulic cylinder 9 is started, the second motor 82 is started, the inner connecting rod 41 drives the inner cutting blade 51 to rotate under the action of the second motor 82, the second belt transmission component 83 drives the outer connecting rod 42 to rotate under the action of the second motor 82, thereby driving the outer cutting blade 52 to rotate, so that in the process of moving the cutting blade supporting mechanism 4 along the radial direction of the pile head, the inner cutting blade 51 and the outer cutting blade 52 respectively rotate around the axial direction of the pile head at high speed, and the cutting is carried out along the radial direction of the pile head.

After the pile head is cut into the maximum cutting depth along the radial direction of the pile head, the compression bolt 102 is unscrewed, the rod part of the hydraulic cylinder 9 is controlled to retract, the rod end of the hydraulic cylinder 9 is separated from the sleeve ring 101, the cross beam 43 is locked and fixed on the sleeve 6 through the locking bolt 443, relative movement between the cross beam 43 and the sleeve 6 is limited, the first motor 72 is started, the first belt transmission assembly 73 drives the sleeve 6 to rotate under the action of the first motor 72, the second motor 82 is started while the first motor 72 is started, so that the inner cutting piece 51 and the outer cutting piece 52 rotate around the circumferential direction of the pile head, the inner cutting piece 51 and the outer cutting piece 52 rotate around the axial direction of the pile head at a high speed respectively, 360-degree circumferential cutting is carried out on the pile head, and the pile head is cut off.

The above embodiments are preferred embodiments of the present application, and the protection scope of the present application is not limited by the above embodiments, so: all equivalent changes made according to the structure, shape and principle of the present application shall be covered by the protection scope of the present application.

Claims (5)

1. A subway vehicle unfavorable geology CFG pile foundation treatment construction method is characterized by comprising the following steps:

s1, drilling a hole to a designed elevation by a drilling machine;

s2, drilling to a designed elevation, stopping drilling, lifting the drill rod while pouring concrete into the pile hole until the concrete reaches the designed pile top elevation, and constructing the CFG piles (1) one by one according to a set sequence;

s3, excavating soil among piles, determining the pile cutting position of a pile head after cleaning the soil among piles, installing a pile head cutting device (3) after a hole (11) coaxial with the CFG pile (1) is formed in the pile top, starting the pile head cutting device (3) after the installation is finished, cutting the pile head cutting device (3) from the direction from the inside of the hole (11) to the outer wall of the pile head along the radial direction of the pile head and from the outer wall of the pile head to the inside of the hole (11), stopping cutting along the radial direction of the pile head when the sum of the cutting depths of the two cutting directions is greater than the difference between the radius of the pile head and the radius of the hole (11), and cutting the pile head cutting device circumferentially for 360 degrees around the circumferential direction of the pile head;

s4, pile cap construction;

s5, backfilling soil between piles;

s6, constructing a mattress layer;

the pile head cutting device (3) comprises an inner cutting piece (51) used for cutting from the inner side of the cutting hole (11) to the outer wall of the pile head and an outer cutting piece (52) used for cutting from the outer wall of the pile head to the inner side of the cutting hole (11), and in the step S3, when the pile head cutting device cuts along the radial direction of the pile head, the inner cutting piece (51) and the outer cutting piece (52) move simultaneously and simultaneously along the radial direction of the pile head;

the pile head cutting device (3) further comprises a frame body (31) fixedly arranged outside the pile head, a connecting piece and a power mechanism (7) used for driving the connecting piece to rotate around the axis direction of the cutting hole (11) are rotatably connected to the frame body (31), a cross beam (43) is connected to the connecting piece in a sliding mode along the distribution direction of an inner cutting sheet (51) and an outer cutting sheet (52), a locking assembly used for locking the cross beam (43) to the connecting piece is arranged on the cross beam, the inner cutting sheet (51) is rotatably connected to the cross beam (43) through an inner connecting rod (41), the outer cutting sheet (52) is rotatably connected to the cross beam (43) through an outer connecting rod (42), a driving mechanism (8) used for driving the inner connecting rod (41) and the outer connecting rod (42) to rotate is arranged on the cross beam (43), and a driving piece used for driving the cross beam (43) to move is arranged on the frame body (31), the output end of the driving piece is detachably connected to the cross beam (43) through a connecting assembly (10);

the connecting piece is arranged as a sleeve (6), the bottom end of the sleeve (6) extends into the cut hole (11) and is coaxial with the cut hole (11), a cover plate (61) is fixed at the top end of the sleeve (6), the cover plate (61) is rotatably connected to the frame body (31) through a limiting rod (62), and the top end of the inner connecting rod (41) is slidably arranged on the cover plate (61);

the outer wall of sleeve pipe (6) is gone up to rotate and is connected with vertical roller (63) that set up, the outer wall of roller (63) contacts with the inner wall of cutting hole (11).

2. The subway vehicle unfavorable geological CFG pile foundation treatment construction method according to claim 1, characterized in that: in the step S3, after the pile cutting position of the pile head is determined, the steel plate (2) is laid on the ground outside the pile head, the steel plate (2) is sleeved outside the pile head, and the pile head cutting device (3) is installed on the steel plate (2).

3. The subway vehicle unfavorable geology CFG pile foundation treatment construction method according to claim 1, characterized in that: the power mechanism (7) comprises a first motor (72) fixedly arranged on the pile top and a first belt transmission assembly (73) arranged between the first motor (72) and the sleeve (6).

4. The subway vehicle unfavorable geological CFG pile foundation treatment construction method according to claim 1, characterized in that: the driving mechanism (8) comprises a second motor (82) fixedly arranged on the cross beam (43), the second motor (82) is used for driving the inner connecting rod (41) to rotate, and a second belt transmission assembly (83) is arranged between the inner connecting rod (41) and the outer connecting rod (42).

5. The subway vehicle unfavorable geological CFG pile foundation treatment construction method according to claim 1, characterized in that: the drive is configured as a hydraulic cylinder (9).

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