Construction method for reinforcing a round pile by expanding its diameter

Abstract

The application discloses a construction method of a round pile diameter expansion reinforcement, and steps are as follows: (1) installing a diameter expansion pile machine on a construction surface; (2) driving a spiral drill bit to rotate to cut the soil body around the round pile, simultaneously starting a driving mechanism to drive the cutting part to reciprocatingly rotate around the first axis, so that the drill holes formed by the adjacent spiral drill bits are overlapped with each other to form an annular pile hole; while cutting the soil body, water is injected into the cut soil through a liquid inlet pipe to form a plain soil slurry, and the plain soil slurry is discharged from the annular pile hole; (3) when the drill tip of the spiral drill bit reaches a first set position downwards, the cutting of the soil body is stopped, and the cutting part is lifted upwards; the coagulable material is poured into the annular pile hole through the liquid inlet pipe to form a plain pile, and the plain pile and the round pile form a composite pile body. The composite pile formed by the application can be adapted to a construction area where the prefabricated round pile is not suitable for large-scale use, and the construction of the building structure can be carried out in advance to shorten the construction period.

Description

Technical Field

[0001] This invention relates to a construction method for reinforcing circular piles by expanding their diameter. Background Technology

[0002] Precast concrete round piles, including hollow pipe piles, solid pipe piles, and solid round piles, are widely used in the foundation piles of buildings. Due to their good quality and convenient construction, precast round piles are widely used. However, precast round piles can cause soil squeezing when they sink, which can seriously affect existing buildings around the construction area. In addition, due to the limitations of the processing technology, the diameter of precast round piles is mainly controlled between 0.3 and 1 meter.

[0003] In some construction areas, due to site requirements or surrounding environmental requirements, it is not possible to use precast round piles in large quantities. Instead, they can only be combined with some cast-in-place piles or sheet piles to form composite piles. However, sheet piles have relatively low end bearing capacity and are not effective in some soft soil areas, so they cannot be used as foundation piles. Even if cast-in-place piles are used, they are treated as independent piles. Furthermore, the mixed construction of precast piles and cast-in-place piles is difficult and results in low construction efficiency.

[0004] In addition, sometimes it is necessary to re-pile in areas where the circular piles have been completed to make up for exploration or design defects, or to adapt to changes in the building design. However, re-pile can only be carried out in areas that are far from the original bearing point, which requires the corresponding expansion of the pile cap and thus the need to adjust the corresponding area.

[0005] Therefore, it is necessary to enlarge and reinforce the existing round piles that have already been sunk to improve their bearing capacity. Summary of the Invention

[0006] To address the aforementioned issues, this application proposes a construction method for expanding the diameter of a circular pile for reinforcement. The circular pile is one that has been driven into the ground and extends vertically. The construction method employs a diameter-expanding pile driver, which includes a base, a cutting section, and a driving section. The base has a worktable with an upper surface extending horizontally, and a through-shaft hole is provided on the worktable.

[0007] The cutting section includes a hollow shaft extending vertically, an annular body fixedly installed at the lower end of the hollow shaft, and at least four spiral drill bits installed at the lower end of the annular body. The hollow shaft and the annular body are coaxially arranged, and the central axes of the hollow shaft and the annular body are collinear with a first axis. The first inner cavity of the hollow shaft and the second inner cavity of the annular body together form a through hole extending vertically. The first axis extends vertically. The worktable is freely fitted onto the hollow shaft through the through hole.

[0008] Each auger drill includes a auger bit connected together and a motor that drives the auger bit to rotate. Corresponding to each motor, a motor chamber is provided inside the annular body, and the motor is installed in the corresponding motor chamber. The auger bit is located on the lower side of the annular body.

[0009] The auger drill bits are evenly spaced around the first axis. When viewed vertically, all the auger drill bits are located within a virtual annular surface. The outer diameter of the hollow shaft and the outer diameter of the annular body are not greater than the outer diameter of the virtual annular surface, and the inner diameter of the hollow shaft and the inner diameter of the annular body are not less than the inner diameter of the virtual annular surface.

[0010] The drive unit includes a swing wheel and a drive mechanism mounted on the worktable. The swing wheel is movably supported on the upper surface of the worktable and connected to the drive mechanism. The drive mechanism can drive the swing wheel to reciprocate about a first axis as the central axis.

[0011] The oscillating wheel is sleeved on the hollow shaft, and the oscillating wheel and the hollow shaft are held together by grooves and teeth, and the hollow shaft can reciprocate relative to the oscillating wheel in the vertical direction; when the oscillating wheel reciprocates, it can drive the cutting part to reciprocate synchronously through the hollow shaft; when the cutting part reciprocates, it can make the drill holes formed by adjacent spiral drill bits overlap each other.

[0012] A liquid inlet pipe and a slurry outlet pipe extending vertically are fixedly installed on the annular body. Both the liquid inlet pipe and the slurry outlet pipe pass freely through the swing wheel and the through shaft hole and are then fixedly connected to the annular body. The liquid outlet of the liquid inlet pipe and the slurry inlet of the slurry outlet pipe both penetrate downward through the lower end face of the annular body, and neither the liquid outlet nor the slurry inlet extends downward beyond the drill tip of the auger bit.

[0013] The construction method includes the following steps:

[0014] (1) Install the expansion pile driver on the construction surface and make the first axis collinear with the central axis of the circular pile, and the outer diameter of the circular pile is less than or equal to the inner diameter of the virtual annular surface;

[0015] (2) Start the motor to drive the auger bit to rotate and cut the soil around the round pile. Simultaneously start the drive mechanism to drive the cutting part to reciprocate around the first axis, so that the drill holes formed by adjacent auger bits overlap each other to form a ring pile hole.

[0016] While the soil is being cut, water is injected into the cut soil through the inlet pipe to form plain soil slurry. The plain soil slurry is then discharged from the annular pile hole through the slurry discharge pipe. When the plain soil slurry cannot be discharged from the annular pile hole smoothly, a slurry pump needs to be connected to the top of the slurry discharge pipe to assist in discharging the plain soil slurry from the annular pile hole.

[0017] (3) When the tip of the auger bit reaches the first set position downwards, the cutting of the soil is stopped, and the cutting part is lifted upwards; while the cutting part is lifted upwards, the solidifiable material is poured into the annular pile hole through the liquid inlet pipe; the cutting part is continuously lifted upwards until the auger bit reaches the top of the round pile, forming a plain pile, which forms a composite pile body with the round pile. The solidifiable material is preferably cement-soil, cement mortar, or fine stone concrete. Preferably, the liquid outlet and the grout inlet are located between the lower end face of the annular body and the upper end of the auger blade on the auger bit. The cement-soil is made by mixing cement, soil, and water evenly, and no other materials need to be added before it can be used to cast the plain pile. The round pile is a precast concrete round pile such as a hollow pipe pile, a solid pipe pile, or a solid round pile.

[0018] In this application, during the drilling of the annular pile hole, the auger bit forms an annular pile hole around the circular pile by utilizing the self-weight of the cutting part or by applying an additional load to the top of the hollow shaft. The noise generated during construction is minimal and has no impact on the surrounding environment. During construction, due to the sealing effect of the annular body, the annular pile hole at the bottom of the annular body forms a relatively sealed cavity. Under the pressure of water, the cut soil is discharged from the annular pile hole in the form of plain soil slurry. When pouring the solidifiable material, it is poured gradually from the bottom of the annular pile hole upwards, allowing the plain soil slurry inside the annular pile hole to continue to be discharged outwards. Only a small amount of plain soil slurry is mixed into the solidifiable material, which does not affect the overall structural performance of the plain pile and requires no mixing. Since the majority of the soil inside the annular pile hole is discharged in the form of plain soil slurry, the plain pile in this application is mainly composed of solidifiable material, with the proportion of solidifiable material in the formed plain pile being ≥95wt%.

[0019] Since the material forming the plain pile in this application is mainly a solidifiable material, there is no need to stir the solidifiable material in the annular pile hole multiple times, nor is it necessary to use a auger drill bit to stir the solidifiable material. Of course, during the upward lifting of the cutting part, the auger drill bit can be kept rotating to stir the solidifiable material so that the plain soil slurry can be more evenly dispersed in the solidifiable material. However, in actual operation, it was found that keeping the auger drill bit rotating did not increase the strength of the plain pile, mainly due to the low proportion of plain soil slurry.

[0020] After the solidifiable material is poured into the annular pile hole, it can penetrate through the soil layer between the annular pile hole and the round pile, and wrap around the round pile. After solidification, it forms a ring-shaped plain pile. The plain pile and the round pile form a composite pile body. The new composite pile body has a higher bearing capacity than the existing round pile.

[0021] The aforementioned circular piles already sunk underground can be the original design circular piles. However, due to geological exploration or design defects, or to adapt to modifications in the building design, it is necessary to add foundation piles. By adopting this application, the existing circular piles can be enlarged and reinforced while retaining their location and quantity, thereby increasing their bearing capacity. This does not require increasing the number of circular piles or their placement area, and can effectively reduce the amount of modifications to the completed building design.

[0022] The aforementioned circular piles already sunk underground can be used in construction areas where soil squeezing is severe, making large-scale use of precast circular piles impossible; only partial use is permitted. This application, however, allows for the maximum use of precast circular piles, with plain piles formed around the outer perimeter to create composite piles. Using composite piles not only ensures pile strength but also increases the pile's side friction resistance due to the increased contact area between the pile and soil, thus guaranteeing the pile's bearing capacity and reducing the soil squeezing effect associated with large-diameter foundation piles. The composite piles formed using this application are suitable for construction areas where large-scale use of precast circular piles is not advisable. By combining precast circular piles with cast-in-place piles, the strength provided by the precast piles allows for construction of the superstructure without requiring the plain piles to reach their curing period. In the initial stages of construction, the precast circular piles can withstand the loads generated by the building structure. As construction progresses, since the curing period of the plain piles is much shorter than the construction period of the building structure, there is no need to worry about the piles failing to provide sufficient bearing capacity during the construction period. Therefore, by utilizing this application, the construction of the building structure can be carried out in advance, thereby shortening the construction period.

[0023] Furthermore, the first designated position is 0.3-1.5 meters above the bottom end of the circular pile. This design avoids disturbing the bearing stratum at the pile tip, ensuring the bearing capacity of the bearing stratum for the circular pile.

[0024] Furthermore, the difference between the outer diameter of the circular pile and the inner diameter of the virtual annular surface is 3-20mm. This ensures the outer diameter of the circular pile is smaller than the inner diameter of the virtual annular surface. If the difference in inner diameter is too small, the spiral blades of the auger bit will easily come into contact with the circular pile, damaging the auger bit. If the difference in inner diameter is too large, the amount of coagulating material that can penetrate through the soil layer between the annular pile hole and the circular pile will be reduced, resulting in insufficient bond strength between the plain pile and the circular pile.

[0025] Furthermore, when the cutting section reciprocates, the overlap rate of the boreholes formed by adjacent auger bits is 20-100%. The overlap rate refers to the ratio of the overlap length between the boreholes formed by two adjacent auger bits to the borehole diameter. For example, if the borehole diameter is 500mm and the overlap length between the boreholes formed by two adjacent auger bits is 200mm, then the overlap rate is 200 / 500 = 40%. When the overlap rate is 100%, the inner and outer walls of the annular pile hole are smooth. When the overlap rate is less than 100%, both the inner and outer walls of the annular pile hole have numerous grooves, resulting in corresponding grooves on the inner and outer walls of the formed plain pile. This improves the friction of the plain pile and enhances the bearing capacity of the cylindrical pile.

[0026] Specifically, the inner circumferential surface of the oscillating wheel is provided with an internal spline, and the outer circumferential surface of the hollow shaft is provided with an external spline that meshes with the internal spline. The keyways on both the hollow shaft and the oscillating wheel are formed as grooves, and the key teeth on both are formed as convex teeth. The meshing spline structure of the oscillating wheel and the hollow shaft ensures smooth meshing and the transmission of large torques, preventing damage to the key teeth under high torques, ensuring a stable connection between the two, and extending the service life of the equipment.

[0027] Specifically, the drive mechanism includes 2-5 drivers mounted on the upper surface of the worktable. Each driver includes a hydraulic cylinder. Corresponding to each hydraulic cylinder, a radial rod extending outward in a radial direction is fixedly provided on the swing wheel. All the radial rods are evenly arranged around the first axis. Along the circumferential direction of the swing wheel, each hydraulic cylinder is located on the same side of the circumferential direction of its corresponding radial rod.

[0028] For each radial rod, a sliding groove is fixedly installed on the upper surface of the worktable. The sliding groove is located on the radial outer side of the swing wheel. An arc-shaped groove is formed on each sliding groove. The arc-shaped groove is formed by the side of the sliding groove facing the swing wheel and recessed radially away from the swing wheel. The arc-shaped grooves on all sliding grooves are located in the same virtual annular groove. The central axis of the virtual annular groove coincides with the first axis. The radial outer end of the radial rod extends movably into the arc-shaped groove on the corresponding sliding groove.

[0029] For each hydraulic cylinder, a guide rail is fixedly installed on the upper surface of the worktable. The hydraulic cylinder is slidably installed on the corresponding guide rail. The piston rod of the hydraulic cylinder extends horizontally and is perpendicular to the installed guide rail. The piston rod of the hydraulic cylinder is hinged to the corresponding radial rod.

[0030] This design allows the oscillating wheel to be movably supported within the arcuate groove via a radial rod. In this application, the piston rod is preferably hinged to the radially outer end of the radial rod to provide greater torque.

[0031] In this design, a hydraulic cylinder is used to provide driving force. This not only ensures the stability of the driving force but also allows for flexible adjustment of the piston rod extension length as needed, thereby adjusting the rotation angle of the cutting section and the overlap length of the boreholes formed by adjacent auger bits. Using the worktable as a mounting base for the hydraulic cylinder ensures radial stability between the cutting section and the drive mechanism, eliminating the need for a ground-based mounting base. This also allows for rapid movement and positioning of the entire auger during relocation, improving operational efficiency and ultimately enhancing construction efficiency.

[0032] Specifically, the annular body includes an inner cylinder and an outer cylinder nested together, with the outer cylinder located outside the inner cylinder. A distance exists between the inner and outer cylinders, forming an annular space. A top plate is sealed and installed on top of the inner and outer cylinders. A bottom plate is sealed and detachably installed at the bottom of the inner and outer cylinders, and both the top and bottom plates are annular. The space enclosed by the inner cylinder, outer cylinder, top plate, and bottom plate forms a receiving cavity. This receiving cavity forms a motor chamber, and a motor is fixedly installed within it. The motor's drive shaft extends vertically downwards and is sealed beyond the bottom plate, where the auger drill bit is mounted. The inner and outer cylinders are coaxially arranged.

[0033] In this design, the receiving cavity forms the motor chamber for installing the motor. Since the receiving cavity is a large internal cavity, it has a large operating space, which facilitates the installation, debugging and replacement of the motor. At the same time, multiple motor installation positions can be preset on the base plate, and different combinations of motor groups can be installed as needed to adjust the model, quantity and distance of the auger drill bit.

[0034] Furthermore, a radially outward protrusion is provided at the lower end of the hollow shaft, forming an upward-facing stepped surface between the protrusion and the outer circumference of the hollow shaft. The swing wheel can be detachably supported on this stepped surface. This design facilitates the movement of the diameter-expanding pile driver. Because the swing wheel can be detachably supported on this stepped surface, after the diameter-expanding pile driver completes the drilling of a ring-shaped pile hole, lifting the hollow shaft upward allows the swing wheel to be supported on the stepped surface, and the swing wheel simultaneously lifts the base upward, thereby lifting the entire diameter-expanding pile driver off the ground and transferring it to the next construction position. When the cutting part moves underground to cut the soil, the swing wheel's position in height remains unchanged, allowing the swing wheel to leave the stepped surface.

[0035] Furthermore, the drive unit also includes a connecting ring located above the swing wheel and fixedly mounted on the top of the hollow shaft. The liquid inlet pipe and the slurry outlet pipe are fixedly connected to the connecting ring.

[0036] The connecting ring ensures that the inlet pipe and the outlet pipe extend vertically between the connecting ring and the annular body, preventing tilting. When the expanding pile driver is operating, the connecting ring remains above the swing wheel, effectively preventing the inlet pipe and outlet pipe from impacting the annular pile hole's perimeter without restraint, thus maintaining the hole's stability.

[0037] Furthermore, the outer diameter of the virtual annular surface is 20-60 mm larger than the outer diameter of the annular body, while the inner diameter of the virtual annular surface is 20-60 mm smaller than the inner diameter of the annular body. The outer diameter of the hollow shaft is less than or equal to the outer diameter of the annular body, and the inner diameter of the hollow shaft is greater than or equal to the outer diameter of the annular body. This design avoids the inner and outer circumferential surfaces of the annular body and the hollow shaft from contacting the sidewall of the annular pile hole, thus preventing the annular pile hole from affecting its stability. Simultaneously, it allows the annular pile hole below the annular body to form a relatively sealed chamber, enabling the plain soil slurry to be smoothly discharged through the slurry discharge pipe. Attached Figure Description

[0038] Figure 1 It is a 3D diagram of a pile driver with an enlarged diameter.

[0039] Figure 2 This is the front view of the diameter expansion pile driver.

[0040] Figure 3 yes Figure 2 Top view.

[0041] Figure 4 yes Figure 2 A view from the center AA direction.

[0042] Figure 5 yes Figure 2 A view from the center (BB direction).

[0043] Figure 6 yes Figure 2 A view directed towards the center (CC).

[0044] Figure 7 yes Figure 6 Enlarged view of section D.

[0045] Figure 8 yes Figure 6 Enlarged view of section E in the middle.

[0046] Figure 9 This is a diagram showing the positional relationship between the virtual annular surface where the auger bit is located and the cutting section.

[0047] Figure 10 This is a schematic diagram of the construction process for expanding the diameter of circular piles for reinforcement. Detailed Implementation

[0048] The following section first describes the structure of the diameter-expanding pile driver. Please refer to [link / reference]. Figures 1-8It includes a base 10, a drive unit 20, and a cutting unit 40. The base 10 includes a support leg 11 and a worktable 12 fixedly mounted on the top of the support leg. The upper surface 121 of the worktable 12 is a planar shape extending horizontally. A through hole 122 is formed on the worktable 12, and the through hole 122 extends vertically through the worktable 12.

[0049] The cutting section 40 includes a hollow shaft 41 extending vertically, an annular body 42 fixedly installed at the lower end of the hollow shaft, and eight spiral drill bits 50 installed at the lower end of the annular body 42. The hollow shaft and the annular body are coaxially arranged, and the central axes of the hollow shaft and the annular body are both collinear with the first axis 91. The first inner cavity of the hollow shaft and the second inner cavity of the annular body together form a through hole 412 extending vertically. The first axis 91 extends vertically. The worktable is freely fitted onto the hollow shaft through the through hole. A lifting hole 413 is provided at the top end of the hollow shaft 41.

[0050] In this embodiment, the annular body 42 includes an inner cylinder 421 and an outer cylinder 422 coaxially sleeved together. Both the inner and outer cylinders extend vertically, with the outer cylinder located outside the inner cylinder. A distance exists between the inner and outer cylinders, forming an annular space between them. Please also refer to... Figure 7 A first inner arc-shaped plate 426 and a first outer arc-shaped plate 424 are respectively installed on the top of the inner cylinder and the outer cylinder. The first inner arc-shaped plate 426 extends from the inner cylinder to the outer cylinder, and the first outer arc-shaped plate 424 extends from the outer cylinder to the inner cylinder. The top plate 428 is annular. The radial inner end and radial outer end of the top plate are respectively detachably fixed to the upper side of the first inner arc-shaped plate 426 and the first outer arc-shaped plate 424 with bolts, so that the top plate is sealed and fixedly installed on the top of the inner cylinder and the outer cylinder, sealing the upper part of the annular space.

[0051] Please also refer to Figure 8 A second inner arc-shaped plate 427 and a second outer arc-shaped plate 425 are respectively installed at the bottom of the inner cylinder and the outer cylinder. The second inner arc-shaped plate 427 extends from the inner cylinder towards the outer cylinder, and the second outer arc-shaped plate 425 extends from the outer cylinder towards the inner cylinder. The bottom plate 429 is annular. The radially inner end and radially outer end of the bottom plate are respectively bolted and detachably installed on the lower side of the second inner arc-shaped plate 427 and the second outer arc-shaped plate 425, so that the bottom plate is detachably and detachably installed at the bottom of the inner cylinder and the outer cylinder, sealing the upper part of the annular space. The space enclosed by the inner cylinder, the outer cylinder, the top plate, and the bottom plate forms a receiving cavity 423.

[0052] Please see Figure 7A protrusion 44 protruding radially outward is provided at the lower end of the hollow shaft 41. The protrusion is a hollow cylinder welded to the lower end of the hollow shaft. The hollow cylinder extends vertically, and its lower end is welded to the top plate. The inner diameter of the hollow cylinder is larger than the inner diameter of the hollow shaft, and its outer diameter is larger than the outer diameter of the hollow shaft but smaller than the outer diameter of the annular body. A stepped surface 43 is formed between the outer circumferential surface of the hollow cylinder and the hollow shaft. The stepped surface 43 extends radially outward from the outer circumferential surface of the hollow shaft and faces upward.

[0053] Each auger drill bit 50 includes a auger drill bit 52 connected together and a motor 51 that drives the auger drill bit to rotate. Corresponding to each motor, a motor chamber is provided in the annular body. Specifically, in this embodiment, the receiving cavity is also formed as the motor chamber, and the motor is fixedly installed in the receiving cavity. Corresponding to each motor, a motor shaft hole is opened on the base plate. The output shaft 511 of the motor 51 passes through the motor shaft hole, exits the base plate 429, and is connected to the drill rod 521 of the auger drill bit 52. A spiral blade 522 is welded on the outer peripheral surface of the drill rod 521, and the drill tip 523 of the drill rod 52 faces downward.

[0054] The packing flange 512 is fitted onto the output shaft 511 and is sealed on the base plate. A sealing ring 513 is installed between the packing flange and the output shaft to seal the gap between the packing flange and the output shaft.

[0055] It is understood that, in another embodiment, the annular body may be a solid structure, and a motor chamber may be provided within the annular body for each motor.

[0056] Please also refer to Figure 9 Eight spiral drill bits 52 are evenly spaced around the first axis 91. For clarity, in Figure 9 In the diagram, the first axis 91 is represented by a small circle. When viewed vertically, all the auger bits are located within a virtual annular surface 420. The outer diameter of the hollow shaft and the outer diameter of the annular body are both no greater than the outer diameter of the virtual annular surface, and the inner diameter of the hollow shaft and the inner diameter of the annular body are both no less than the inner diameter of the virtual annular surface.

[0057] Specifically, in this embodiment, the inner diameter DA of the virtual annular surface 420 is 605 mm, the outer diameter DB of the virtual annular surface 420 is 1245 mm, the inner diameter DC of the annular body 42 is 640 mm, and the outer diameter DD of the annular body is 1220 mm. The inner circumferential surface of the hollow shaft is coplanar with the inner circumferential surface of the annular body, and the outer circumferential surface of the annular body extends outward beyond the outer circumferential surface of the hollow shaft. Figure 9 In the diagram, 101 represents the inner edge of the virtual annular surface 420, 102 represents the outer edge of the virtual annular surface 420, 4201 represents the inner circumferential surface of the annular body 42, and 4202 represents the outer circumferential surface of the annular body 42.

[0058] It is understood that in other embodiments, the outer peripheral surface of the hollow shaft and the outer peripheral surface of the annular body may both be located on the same circular surface as the outer edge of the virtual annular surface, and the inner peripheral surface of the hollow shaft and the inner peripheral surface of the annular body may both be located on another circular surface as the inner edge of the virtual annular surface.

[0059] The drive unit 20 includes a swing wheel 21, a connecting ring 22 and a drive mechanism. The swing wheel 21 and the connecting ring 22 are arranged at intervals in the vertical direction. Both the swing wheel and the connecting ring are circular. The swing wheel is sleeved on a hollow shaft, and the connecting ring 22 is located on the upper side of the swing wheel and welded to the top of the hollow shaft.

[0060] Five vertically extending pipes are fixedly connected to the connecting ring 22. All five pipes are steel pipes, including one liquid inlet pipe 241, one slurry discharge pipe 242, and three sheath pipes 23. The connecting ring 22 is welded to the five pipes. Corresponding to the five pipes, the swing wheel has five through holes 212, through which each of the five pipes can freely pass.

[0061] The inlet pipe has an inlet and an outlet, and the discharge pipe has an inlet and an outlet. Both the inlet pipe 241 and the discharge pipe 242 penetrate the annular body vertically and extend out of the base plate 429 in a sealed manner, so that both the outlet and inlet extend downwards from the base plate. In this embodiment, the outlet and inlet are located between the base plate and the spiral blade, and the inlet and outlet extend upwards from the connecting ring. The upper openings of the three sheathed tubes extend upwards from the connecting ring, and the lower openings of the three sheathed tubes extend into the receiving cavity. The cables enter the receiving cavity through the three sheathed tubes 23 respectively, and then connect to the respective motors.

[0062] A radial rod 32 is provided on each of the two symmetrical sides of the swing wheel 21. The radial rods are fixedly connected to the outer circumferential surface of the swing wheel and extend outward along the radial direction of the swing wheel. That is, the radial rods are evenly distributed around the first axis.

[0063] The drive mechanism includes two actuators 30 mounted on the upper surface of the worktable, each actuator corresponding to a radial rod 32. The two actuators have identical structures, and each actuator 30 includes a hydraulic cylinder 35. That is, a hydraulic cylinder is provided for each radial rod. It is understood that in other embodiments, when the number of radial rods is 3, 4, or 5, the corresponding number of actuators is 3, 4, or 5.

[0064] For each hydraulic cylinder, two parallel T-shaped guide rails 356 are fixedly installed on the upper surface of the worktable. The hydraulic cylinder 35 has a cylinder barrel 351 and a front end plate 354 and a rear end plate 355 installed at both ends of the cylinder barrel in the axial direction. The hydraulic cylinder 35 is placed horizontally. A sliding member 357 is installed at the lower end of both the front end plate 354 and the rear end plate 355. This sliding member has a groove that can be engaged with the T-shaped guide rail. The two sliding members are slidably engaged with one T-shaped guide rail via this groove, allowing the hydraulic cylinder to slide along the length of the T-shaped guide rail. The piston rod of the hydraulic cylinder extends horizontally and is perpendicular to the installed T-shaped guide rail.

[0065] Corresponding to each radial rod 32, each actuator also includes a sliding member 34, which is fixedly mounted on the upper surface of the worktable and located radially outward of the swing wheel 21. Each sliding member has an arc-shaped groove 341 formed by a radial indentation of the sliding member 34 towards the swing wheel 21. The arc-shaped groove 341 has a radially outwardly projecting arc-shaped bottom. The radially outer end of the radial rod 32 is formed as a hemispherical end 321, which movably extends into the arc-shaped groove of the corresponding sliding member. All the arc-shaped grooves on the sliding members are located within the same virtual annular groove, the central axis of which coincides with the first axis. The swing wheel is movably supported within the arc-shaped groove via the radial rod, thus movably supporting the swing wheel on the upper surface of the worktable via the sliding member. It can be understood that, in another embodiment, the end may also be spherical.

[0066] The hydraulic cylinder is located on one side of its corresponding radial rod. A hinge rod 33 is fixedly installed at the outer end of the radial rod facing the corresponding hydraulic cylinder. This hinge rod 33 is hinged to the piston rod 353 of the hydraulic cylinder via a pin. For clarity, the pin is not shown in the attached drawing; only the pin hole 331 for inserting the pin is shown. That is, the piston rod 353 is indirectly hinged to the swing wheel 21 via the hinge rod 33 and the radial rod 32. Along the circumferential direction of the swing wheel, the hydraulic cylinders are all located on the same side of the circumferential direction of their corresponding radial rods.

[0067] In this embodiment, an inner spline 211 is provided on the inner circumferential surface of the swing wheel, and an outer spline 411 that meshes with the inner spline 211 is provided on the outer circumferential surface of the hollow shaft. The key teeth and keyways on the inner and outer splines extend in the vertical direction, so that the hollow shaft can reciprocate in the vertical direction relative to the swing wheel.

[0068] Both the internal and external splines have convex teeth, and the keyways are formed as grooves into which the convex teeth extend. That is, the inner circumferential surface of the oscillating wheel has convex teeth, and the outer circumferential surface of the hollow shaft has grooves into which these convex teeth extend. Alternatively, it can be understood that the inner circumferential surface of the oscillating wheel has grooves, and the outer circumferential surface of the hollow shaft has convex teeth that extend into these grooves.

[0069] Driven by the piston rod, the swing wheel reciprocates around the first axis as the central axis, and drives the entire cutting part to reciprocate synchronously via the hollow shaft, while the hydraulic cylinder moves back and forth along the T-shaped guide rail.

[0070] It is understood that in other embodiments, it is not necessary to use a spline-shaped swing wheel and a hollow shaft. It is only necessary to provide grooves or protrusions on a local outer peripheral surface of the hollow shaft and provide corresponding protrusions or grooves in the corresponding area of ​​the inner peripheral surface of the swing wheel, so that the hollow shaft can perform corresponding reciprocating rotation under the drive of the swing wheel.

[0071] In this embodiment, eight auger drill bits are used. All eight auger drill bits have identical structures, with their tips 523 located on a circle with a diameter of 925 mm. Each auger drill bit has a diameter of 320 mm. When the cutting part reciprocates, the angle of reciprocating rotation is 45°, allowing the holes formed by adjacent auger drill bits to overlap, thus forming a complete circular annular pile hole. That is, in this embodiment, the overlap rate between the holes formed by adjacent auger drill bits is 100%. It can be understood that in other embodiments, adjusting the angle of reciprocating rotation of the cutting part can also make the overlap rate between the holes formed by adjacent auger drill bits 20%, 30%, 40%, 50%, 80%, or other ratios between 20% and 100%. The overlap rate refers to the ratio of the overlap length between two adjacent auger drill bits to the diameter of the drill hole. For example, in this embodiment, the diameter of the drill hole is 320mm. When the drill holes formed by two adjacent auger drill bits completely overlap, that is, the overlap length is 320mm, the overlap rate is 320 / 320=100%.

[0072] The following describes the construction method for expanding the diameter of a circular pile for reinforcement. In this embodiment, the circular pile is a concrete pipe pile 90, which has been sunk into the ground. The concrete pipe pile extends vertically, with an outer diameter of 600 mm and an inner diameter DA of the virtual annular surface 420 of 605 mm. The difference between the outer diameter of the circular pile and the inner diameter of the virtual annular surface is 5 mm.

[0073] Please see Figure 10 The construction method includes the following steps:

[0074] (1) Please refer to Figure 10 In step (a), the expansion pile driver is installed on the construction surface 500 via the base, and the first axis is collinear with the central axis of the concrete pipe pile 90, with the pile hole facing the concrete pipe pile.

[0075] (2) Please refer to Figure 10In steps (b) and (c), the motor is started to drive the auger drill bit to rotate and cut the soil around the concrete pipe pile. The drive mechanism is started simultaneously to drive the cutting part to reciprocate around the first axis, so that the drill holes formed by adjacent auger drill bits overlap each other to form an annular pile hole 80.

[0076] While cutting the soil, water is injected into the cut soil through the inlet pipe. The auger drill bit cuts the soil, turning the cut soil into raw soil slurry. Due to the sealing effect of the annular structure, the annular pile hole below the annular structure forms a relatively closed cavity. Under water pressure, the raw soil slurry is discharged from the annular pile hole through the slurry discharge pipe. In this embodiment, the depth of the annular pile hole is 18 meters, and the water pressure is 0.7 MPa. When the raw soil slurry cannot be smoothly discharged from the annular pile hole, a slurry pump needs to be connected to the top of the slurry discharge pipe to assist in discharging the raw soil slurry from the annular pile hole.

[0077] (3) Please refer to Figure 10 In steps (d) and (e), when the drill tip of the auger reaches the first set position, the cutting of the soil is stopped, and the cutting section is lifted upwards. Simultaneously, cement-soil 81 is poured into the annular pile hole through the inlet pipe. The cutting section is continuously lifted upwards until the auger reaches the top of the concrete pipe pile 90, forming a cement-soil pile 93. This cement-soil pipe pile 93 and the concrete pipe pile 90 form a composite pile body 100. Since the cement-soil pile 93 is formed solely of cement and soil without reinforcement such as a steel cage or prestressed steel bars, it is called a plain pile.

[0078] When lifting the cutting section upwards, the rotation of the auger bit and the reciprocating rotation of the cutting section are maintained to stir the cement-soil entering the annular pile hole, so that a small amount of plain soil slurry can be evenly distributed into the cement-soil mixture. Alternatively, in another embodiment, when lifting the cutting section upwards, only the auger bit can rotate, or the cutting section can reciprocate, or both the auger bit and the cutting section can be stopped rotating.

[0079] In this embodiment, the first designated position is 1.0 meter above the bottom end of the concrete pipe pile 90. It can be understood that in other embodiments, the first designated position may also be 0.3 meters, 0.5 meters, 0.8 meters, 1.2 meters, or 1.5 meters above the bottom end of the concrete pipe pile.

[0080] It is understood that in other embodiments, the circular pile may also be a solid concrete circular pile or a solid concrete pipe pile.

[0081] In this embodiment, cement-based solidifying material is used. It is understood that in other embodiments, the solidifying material may also be cement mortar or fine aggregate concrete, etc.

Claims

1. A method for construction of a pile diameter expansion reinforcement, characterized by, The circular pile is a circular pile that has been sunk into the ground and extends vertically. The construction method uses a diameter-expanding pile machine, which includes a base, a cutting part and a driving part. The base has a worktable with an upper surface that extends horizontally and a through-shaft hole is provided on the worktable. The cutting section includes a hollow shaft extending vertically, an annular body fixedly installed at the lower end of the hollow shaft, and at least four spiral drill bits installed at the lower end of the annular body. The hollow shaft and the annular body are coaxially arranged, and the central axes of the hollow shaft and the annular body are collinear with a first axis. The first inner cavity of the hollow shaft and the second inner cavity of the annular body together form a through hole extending vertically. The first axis extends vertically. The worktable is freely fitted onto the hollow shaft through the through hole. Each auger drill includes a auger bit connected together and a motor that drives the auger bit to rotate. Corresponding to each motor, a motor chamber is provided inside the annular body, and the motor is installed in the corresponding motor chamber. The auger bit is located on the lower side of the annular body. The auger drill bits are evenly spaced around the first axis. When viewed vertically, all the auger drill bits are located within a virtual annular surface. The outer diameter of the hollow shaft and the outer diameter of the annular body are not greater than the outer diameter of the virtual annular surface, and the inner diameter of the hollow shaft and the inner diameter of the annular body are not less than the inner diameter of the virtual annular surface. The drive unit includes a swing wheel and a drive mechanism mounted on the worktable. The swing wheel is movably supported on the upper surface of the worktable and connected to the drive mechanism. The drive mechanism can drive the swing wheel to reciprocate about a first axis as the central axis. The oscillating wheel is sleeved on the hollow shaft, and the oscillating wheel and the hollow shaft are held together by grooves and teeth, and the hollow shaft can reciprocate relative to the oscillating wheel in the vertical direction; when the oscillating wheel reciprocates, it can drive the cutting part to reciprocate synchronously through the hollow shaft; when the cutting part reciprocates, it can make the drill holes formed by adjacent spiral drill bits overlap each other. A liquid inlet pipe and a slurry outlet pipe extending vertically are fixedly installed on the annular body. Both the liquid inlet pipe and the slurry outlet pipe pass freely through the swing wheel and the through shaft hole and are then fixedly connected to the annular body. The liquid outlet of the liquid inlet pipe and the slurry inlet of the slurry outlet pipe both penetrate downward through the lower end face of the annular body, and neither the liquid outlet nor the slurry inlet extends downward beyond the drill tip of the auger bit. The construction method includes the following steps: (1) Install the expansion pile driver on the construction surface and make the first axis collinear with the central axis of the circular pile, and the outer diameter of the circular pile is less than or equal to the inner diameter of the virtual annular surface; (2) Start the motor to drive the auger bit to rotate and cut the soil around the round pile. Simultaneously start the drive mechanism to drive the cutting part to reciprocate around the first axis, so that the drill holes formed by adjacent auger bits overlap each other to form a ring pile hole. While the soil is being cut, water is injected into the cut soil through the inlet pipe to form plain soil slurry, which is then discharged from the annular pile hole through the slurry outlet pipe. (3) When the tip of the auger bit reaches the first set position downwards, stop cutting the soil and lift the cutting part upwards; while the cutting part is lifted upwards, pour solidifiable material into the annular pile hole through the liquid inlet pipe; continue to lift the cutting part upwards until the auger bit reaches the top of the round pile to form a plain pile, which forms a composite pile with the round pile.

2. The construction method according to claim 1, characterized in that, The first designated position is 0.3-1.5 meters above the bottom end of the circular pile.

3. The construction method according to claim 1, characterized in that, The difference between the outer diameter of the circular pile and the inner diameter of the virtual annular surface is 3-20mm.

4. The construction method according to claim 1, characterized in that, When the cutting part reciprocates, the overlap rate of the drill holes formed by adjacent auger bits is 20-100%.

5. The construction method according to claim 1, characterized in that, The inner circumferential surface of the oscillating wheel is provided with an internal spline, and the outer circumferential surface of the hollow shaft is provided with an external spline that meshes with the internal spline.

6. The construction method according to claim 1, characterized in that, The drive mechanism includes 2-5 drivers mounted on the upper surface of the worktable. Each driver includes a hydraulic cylinder. Corresponding to each hydraulic cylinder, a radial rod extending outward in a radial direction is fixedly installed on the swing wheel. All the radial rods are evenly arranged around the first axis. Along the circumferential direction of the swing wheel, each hydraulic cylinder is located on the same side of the circumferential direction of its corresponding radial rod. For each radial rod, a sliding groove is fixedly installed on the upper surface of the worktable. The sliding groove is located on the radial outer side of the swing wheel. An arc-shaped groove is formed on each sliding groove. The arc-shaped groove is formed by the side of the sliding groove facing the swing wheel and recessed radially away from the swing wheel. The arc-shaped grooves on all sliding grooves are located in the same virtual annular groove. The central axis of the virtual annular groove coincides with the first axis. The radial outer end of the radial rod extends movably into the arc-shaped groove on the corresponding sliding groove. For each hydraulic cylinder, a guide rail is fixedly installed on the upper surface of the worktable. The hydraulic cylinder is slidably installed on the corresponding guide rail. The piston rod of the hydraulic cylinder extends horizontally and is perpendicular to the installed guide rail. The piston rod of the hydraulic cylinder is hinged to the corresponding radial rod.

7. The construction method according to claim 1, characterized in that, The annular body includes an inner cylinder and an outer cylinder nested together, with the outer cylinder located outside the inner cylinder. There is a distance between the inner and outer cylinders, forming an annular space between them. A top plate is sealed and installed on the top of the inner and outer cylinders. A bottom plate is sealed and detachably installed on the bottom of the inner and outer cylinders. Both the top and bottom plates are annular. The space enclosed by the inner cylinder, outer cylinder, top plate, and bottom plate forms a receiving cavity. The cavity is formed as a motor chamber, and the motor is fixedly installed inside the cavity. The drive shaft of the motor extends vertically downwards and is sealed out of the base plate before the auger drill bit is installed.

8. The construction method according to claim 1, characterized in that, A protrusion that protrudes radially outward is provided at the lower end of the hollow shaft. The protrusion and the outer peripheral surface of the hollow shaft form an upward-facing stepped surface, and the swing wheel can be detachably supported on the stepped surface.

9. The construction method according to claim 1, characterized in that, The drive unit also includes a connecting ring located on the upper side of the swing wheel and fixedly mounted on the top of the hollow shaft. The liquid inlet pipe and the slurry outlet pipe are fixedly connected to the connecting ring.

10. The construction method according to claim 1, characterized in that, The outer diameter of the virtual annular surface is 20-60 mm larger than the outer diameter of the annular body, and the inner diameter of the virtual annular surface is 20-60 mm smaller than the inner diameter of the annular body; the outer diameter of the hollow shaft is less than or equal to the outer diameter of the annular body, and the inner diameter of the hollow shaft is greater than or equal to the outer diameter of the annular body.

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