Recyclable spiral steel pile and construction method thereof

Abstract

The application discloses a recyclable spiral steel pile and a construction method thereof. The recyclable spiral steel pile comprises a main pile body and an expanded bottom pile tip. The expanded bottom pile tip comprises a conical bottom, a transition pile body and a plurality of fan-shaped cutting arms. The upper end of the transition pile body is connected with the lower end of the main pile body through a thread. The transition pile body is fixed above the conical bottom. The fan-shaped cutting arms are movably arranged on the upper surface of the conical bottom. A plurality of arc-shaped notches are arranged at the joint of the transition pile body and the conical bottom, and are used for the outward extension of the fan-shaped cutting arms. A pressure bearing assembly is arranged in the transition pile body, and is used for the outward extension of the fan-shaped cutting arms through the arc-shaped notches under the grouting pressure. A grouting hole is arranged below the transition pile body. The recyclable spiral steel pile adopts a separable pile body and an expanded bottom pile tip. The expanded bottom pile tip is discarded during recycling, and the pile body is recycled. The recyclable spiral steel pile can meet the requirements of high bearing capacity and high recycling rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of underground foundation, and particularly relates to a pile foundation and a construction method thereof. BACKGROUND

[0002] In the field of geotechnical engineering and foundation construction, there has been a long-standing contradiction between permanent pile foundations and recyclable pile foundations. Although traditional cast-in-place piles and PHC prestressed pipe piles have high bearing capacity, they have problems such as high pollution, non-recyclable materials, high cost, and so on. Especially in temporary engineering, these pile foundations can only be abandoned in the ground after service, which not only causes a lot of material waste, but also forms underground obstacles, affecting subsequent development.

[0003] To solve this problem, recyclable spiral steel piles have emerged. This type of pile foundation is rotated into the ground and recycled by reversing rotation, realizing the recycling of materials. However, the existing recyclable spiral piles have obvious limitations: first, their bearing capacity mainly depends on the side friction of the pile body, and in soft soil or conditions requiring high bearing capacity, the pile length or diameter often needs to be increased, which is not economical; second, the expansion or grouting reinforcement components set to achieve bearing capacity enhancement often lead to the inability to recycle the steel pile, resulting in a decrease in actual recycling rate.

[0004] Therefore, there is an urgent need for a new type of spiral steel pile system that can meet the requirements of high bearing capacity and green construction recycling. SUMMARY

[0005] The technical problem to be solved by the present application is to overcome the deficiencies and defects mentioned in the background art, and to provide a recyclable spiral steel pile that can meet the requirements of high bearing capacity and high recycling rate, and a construction method thereof. The recyclable spiral steel pile adopts a separable pile body and an expanded bottom pile tip, and the expanded bottom pile tip is discarded during recycling, and the pile body is recycled, which can meet the requirements of high bearing capacity and high recycling rate.

[0006] To solve the above technical problems, the technical solution proposed by the present application is as follows:

[0007] The application discloses a recyclable spiral steel pile, which comprises a main pile body and an expanded bottom pile tip, wherein the expanded bottom pile tip comprises a conical bottom, a transition pile body and a plurality of fan-shaped cutting arms; the main pile body and the transition pile body are both hollow tubular structures; the upper end of the transition pile body is connected with the lower end of the main pile body through screw threads; the transition pile body is fixed above the conical bottom; the fan-shaped cutting arms are movably arranged on the upper surface of the conical bottom; a plurality of arc-shaped notches are arranged at the connecting position of the transition pile body and the conical bottom, and the arc-shaped notches are used for the outward extension of the fan-shaped cutting arms; a pressure-bearing assembly is arranged in the transition pile body and used for the outward extension of the fan-shaped cutting arms through the arc-shaped notches under grouting pressure; and a grouting hole is arranged below the transition pile body; when the pressure-bearing assembly moves downward under grouting pressure and makes the fan-shaped cutting arms extend to the limit position, the pressure-bearing assembly is located below the grouting hole.

[0008] In the application, the main pile body and the expanded bottom pile tip can both be made of stainless steel; the length and thickness of the main pile body are not limited, for example, the length is 300-500 cm, and the wall thickness is 10-16 mm; continuous spiral blades are welded on the outer side of the main pile body, the thickness of the blades can be 12-20 mm, and the lower end of the main pile body can be provided with internal screw threads. The conical bottom of the expanded bottom pile tip can be a solid structure, and the transition pile body is a hollow structure, and the upper end of the transition pile body is provided with external screw threads, which are matched with the internal screw threads of the lower end of the main pile body, so that the main pile body is convenient to recycle. The outer periphery of the fan-shaped cutting arm can be thinned, so that the fan-shaped cutting arm can cut the soil under grouting pressure and extend outward; and the number of the fan-shaped cutting arms is not limited, for example, the number is four. When the main pile body and the expanded bottom pile tip are driven into the soil, the pressure-bearing plate of the pressure-bearing assembly is located above the grouting hole; when the design depth is reached and grouting is performed, the grouting pressure drives the pressure-bearing assembly to move downward, and the pressure-bearing plate is located below the grouting hole; at this time, the grouting liquid can seep into the foundation through the grouting hole, and finally, the conical bottom, the transition pile body and the expanded fan-shaped cutting arms jointly form a dense and stable permanent underground reinforcing body.

[0009] Preferably, the conical bottom upper surface is provided with a plurality of sector-shaped partitions for separating a plurality of independent spaces, the plurality of sector-shaped cutting arms are respectively located in the plurality of independent spaces, and the shape of the sector-shaped cutting arm matches the independent space; when grouting is not performed, the outer periphery of the sector-shaped cutting arm is located at the arc-shaped notch and closes the arc-shaped notch, and the sector-shaped cutting arm cannot move inward. The conical bottom can be connected to the transition pile body through the sector-shaped partitions, and the transition pile body can be welded above the sector-shaped partitions. The sector-shaped openings between adjacent sector-shaped partitions are the arc-shaped notches. The shape of the sector-shaped cutting arm can match the independent space, that is, the shape of the combination of the plurality of sector-shaped cutting arms and the plurality of sector-shaped partitions is approximately circular. This arrangement can ensure the stability of the sector-shaped cutting arm during construction. The outer diameter of the sector-shaped cutting arm in the contracted state is consistent with the outer diameter of the main pile body, and the sector-shaped cutting arm cannot move inward. In the fully expanded state, the diameter of the sector-shaped cutting arm is greater than the diameter of the main pile body. After the sector-shaped cutting arm is expanded, the stress area is increased, thereby forming an enlarged bearing body.

[0010] Preferably, the pressure bearing assembly includes a pressure bearing plate and a hinge shaft. The pressure bearing plate is movably arranged in the transition pile body. One end of the hinge shaft is hingedly arranged below the pressure bearing plate. The other end of the hinge shaft is hingedly arranged on the sector-shaped cutting arm. The number of hinge shafts matches the number of sector-shaped cutting arms. When grouting is not performed, the pressure bearing plate is located above the grouting hole. When the pressure bearing plate bears the grouting pressure, the pressure bearing plate moves downward, the hinge shaft rotates, and the sector-shaped cutting arm extends outward. Each sector-shaped cutting arm can be connected to the pressure bearing plate through a hinge shaft.

[0011] Preferably, the sector-shaped cutting arm is provided with a baffle for limiting the outward extension position of the sector-shaped cutting arm. The hinge shaft is hingedly arranged on the baffle. When the sector-shaped cutting arm extends to the limit position, the baffle is attached to the inner wall of the transition pile body. In the present application, the sector-shaped cutting arm is driven by grouting pressure to expand. The expansion stroke is precisely controlled by the pressure bearing plate. When the sector-shaped cutting arm expands to the maximum design angle (i.e., the limit position), the baffle closely fits the inner wall of the main pile body, forming mechanical limiting, ensuring that the expansion size is stable and controllable, and avoiding overtravel damage.

[0012] Preferably, the shape of the pressure bearing plate matches the shape of the inner cavity of the transition pile body, and the outer periphery of the pressure bearing plate is provided with a sealing rubber ring. The inner cavity of the transition pile body can be circular, and the shape of the pressure bearing plate can also be circular. The sealing rubber ring is arranged on the outer periphery of the pressure bearing plate, so that the pressure bearing plate is basically sealed and slidably arranged in the inner cavity of the transition pile body. The grout injected above the pressure bearing plate forms pressure to drive the pressure bearing plate to move downward.

[0013] Preferably, the fan-shaped cutting arm is provided with a plurality of through holes.

[0014] Preferably, the slurry outlet hole is uniformly provided with a plurality of taper holes along the outer periphery of the transition pile body, the slurry outlet hole is a taper hole, the slurry outlet of the slurry outlet hole is larger than the slurry inlet, and the slurry outlet hole is provided with a soil stopper when no grouting is performed, the shape of the soil stopper is a taper shape matched with the taper hole. During the process of driving the main pile body and the expanded pile tip into the soil body, the soil stopper is used to close the slurry outlet hole to prevent the soil or underground water from entering the expanded pile tip through the slurry outlet hole. The shape of the slurry outlet hole and the shape of the soil stopper are optimized in the present application, the taper-shaped slurry outlet hole is adopted, and the taper-shaped soil stopper is adopted, during the process of driving the main pile body and the expanded pile tip into the soil body, the soil stopper is limited in the slurry outlet hole, under the pressure of the slurry, the soil stopper moves outward to separate from the slurry outlet hole, and the slurry exosmosis is facilitated.

[0015] Preferably, the outer surface of the main pile body is provided with a continuous spiral blade, and the upper end surface of the transition pile body is also provided with a spiral blade. The thickness of the spiral blade can be 12-20mm, and the spiral blade is used to cut the soil when the main pile body and the expanded pile tip uniformly penetrate into the soil body, so as to better drive the main pile body and the expanded pile tip into the soil body, and the spiral blade on the upper end surface of the transition pile body can limit the transition of the slurry upward to the connection between the main pile body and the expanded pile tip. The pitch of the spiral blade can be optimized by fluid mechanics, and the value range is 0.8-1.2 times of the diameter of the pile body, which can ensure the penetration efficiency and provide sufficient uplift resistance.

[0016] As a general technical concept, the present application also provides a construction method of the recyclable spiral steel pile.

[0017] S1: connecting the main pile body and the expanded pile tip, connecting the hydraulic power head with the upper end of the main pile body, starting the hydraulic power head to rotate forward, uniformly penetrating the main pile body and the expanded pile tip into the soil body until reaching the designed depth; during the process of penetrating the main pile body and the expanded pile tip into the soil body, the outer periphery of the fan-shaped cutting arm is located at the arc-shaped notch and closes the arc-shaped notch;

[0018] S2: connecting the grouting equipment with the main pile body, injecting the slurry into the hollow inner cavity of the main pile body, under the grouting pressure, the pressure-bearing assembly moves downward to extend the fan-shaped cutting arm to the limit position, and the slurry exosmosis through the slurry outlet hole, the slurry wraps the expanded pile tip and solidifies to form an expanded load-bearing body, and the recyclable spiral steel pile is obtained.

[0019] The initial pressure of the grouting device can be set to 3 MPa, and when the grouting pressure reaches 3 MPa, the pressure-bearing assembly drives the fan-shaped cutting arm to automatically open. The subsequent pressure of the grouting device can be increased so that the slurry can be exuded through the slurry outlet hole, the amount of grouting can be controlled, and excessive slurry can be prevented from seeping upward to the connection between the main pile body and the expanded pile tip, thereby affecting the subsequent recovery of the main pile body. The grouting device can use a special high-pressure grouting device, and the grouting pressure accuracy is controlled within ±0.5 MPa, and the grouting amount measurement accuracy reaches ±2%. After grouting is completed, quality inspection is required, and ultrasonic detection method or core drilling sampling method is used to inspect the quality of the grouting body, so as to ensure that the strength of the grouting body meets the design requirements.

[0020] When the main pile body and the expanded pile tip are uniformly penetrated into the soil body, for underwater construction conditions, a special underwater grouting device and sealing device are used to ensure that the grouting process is normally carried out underwater, and the grouting pressure is correspondingly increased by 10-20%. During the penetration construction process, a real-time positioning monitoring system is used to ensure that the verticality deviation of the pile body is not more than 1%, and the position deviation is not more than 50 mm.

[0021] The grouting slurry of the present application can use existing conventional concrete slurry, and for special geological conditions, an appropriate amount of additive can be added to the grouting slurry, including early strength agent, expanding agent or corrosion inhibitor, and the addition amount is 1-5% of the weight of cement.

[0022] In the above construction method, preferably, the method further comprises the following recycling steps:

[0023] S3: When the service life of the recyclable spiral steel pile ends, the hydraulic power head is connected with the upper end of the main pile body, the hydraulic power head is started in reverse rotation, the main pile body and the expanded pile tip are separated, the main pile body is recycled, and the expanded pile tip is permanently left in the ground.

[0024] The inner wall of the main pile body of the present application is preferably subjected to special polishing treatment, so as to facilitate the recycling of the main pile body. The recycling of the main pile body can use existing conventional means.

[0025] After the main pile body of the present application is recycled, comprehensive quality detection is required, including diameter measurement, straightness detection, wall thickness measurement and surface damage inspection, and the qualified standards are that the diameter deviation is not more than ±1%, the straightness deviation is not more than 1 ‰, the wall thickness thinning amount is not more than 10% of the original thickness, and the surface is free of cracks and other defects.

[0026] In the present application, the hydraulic power head can adopt existing conventional equipment, and the hydraulic power head is used to provide power output for forward driving and reverse recovery, and a torque adjusting control module can be integrated inside. A standardized quick connection interface is arranged at the upper end of the main pile body for docking with the hydraulic power head. The torque adjusting module can include an electric telescopic drive device, a spring resistance block assembly and a pressure sensing device, which can monitor and accurately control the output torque in real time, the maximum output torque can be 200kN·m, and the output rotation speed can be steplessly adjusted in the range of 2-10 revolutions per minute. When the main pile body and the expanded bottom pile tip are uniformly penetrated into the soil, the pile body is uniformly penetrated into the soil at an initial rotation speed of 3-5 revolutions per minute, and the stratum change is fed back in real time through the torque monitoring system, and when the torque is abnormally increased, the rotation speed is automatically adjusted or the penetration is paused to prevent equipment damage. After the engineering service period is over, the recovery operation is carried out, the soil around the pile top is cleaned, the hydraulic power head is reconnected, the reverse rotation mode is started, a low-speed torque of 2-3 revolutions per minute is initially applied slowly, and when the torque reaches a preset separation threshold of 45-60kN·m, the threaded connection is accurately opened, the main pile body and the expanded bottom pile tip assembly are separated, the reverse rotation is continued and the main pile body is synchronously lifted at a speed of 0.3-0.5m / min, the main pile body is completely pulled out of the ground, the recovered main pile body is cleaned and detected, and after being qualified, it can be reused.

[0027] The recyclable spiral steel pile of the present application can realize the core target of "high bearing capacity" and "high recovery rate", and integrates a grouting pressure driven fan-shaped cutting arm and a spiral connection design separable connection mechanism. The specific structure and principle are as follows:

[0028] (I) Grouting pressure driven fan-shaped cutting arm:

[0029] The fan-shaped cutting arm is made of stainless steel. When not grouting, the fan-shaped cutting arm is stored in the transition pile body, and its outer contour is flush with the outer wall of the transition pile body, so as to ensure that the pile body has the minimum resistance when penetrating into the soil and smoothly reaches the design elevation. Its action process is controlled by grouting pressure. When the grouting equipment is started and the pressure reaches the set opening value of 3MPa, the hydraulic pressure drives the pressure plate to move downward, drives the fan-shaped cutting arm to unfold outward around the hinge point, cuts the surrounding soil, and forms the designed bearing body. When the baffle contacts with the inner wall of the transition pile body, it stops. At this time, the pressure plate is below the grouting hole, and the injected grout can exude in the foundation to form an enlarged bearing body, which can also provide friction force for the separation of the expanded bottom pile tip and the main pile body, so that the expanded bottom pile tip and the main pile body are separated smoothly. After the service of the pile body is over, the fan-shaped cutting arm, the conical bottom, the transition pile body and the grouting concrete are permanently left in the ground as part of the reinforcing body, and are completely separated from the main pile body, so as to ensure that the main pile body can be smoothly pulled out without obstruction when reverse rotating, and complete recovery is realized.

[0030] (II) Spiral connection design separable connection mechanism:

[0031] The expanded bottom pile tip and the main pile body are connected by a screw connection design to ensure construction reliability; when driving, the expanded bottom pile tip is tightly locked with the main pile body through the screw connection; when recycling, the torque generated by the reverse rotation of the hydraulic power head overcomes the pre-tightening force of the screw connection, so that the expanded bottom pile tip is not recycled with the main pile body, but remains in the soil.

[0032] The construction method of the present application includes three key stages: penetration construction, grouting operation and recycling operation. The first step in the penetration construction stage is to locate the site, connect the hydraulic power head to the upper end of the main pile body, check the connection reliability, and then start the hydraulic power head to rotate in the forward direction, and uniformly penetrate the main pile body with the expanded bottom pile tip into the soil. After the pile body penetrates to the designed elevation, grouting operation is carried out. The grouting pressure triggers the pressure plate to push the hinged shaft, drives the fan-shaped cutting arm to unfold around the hinged shaft, and when the pressure plate reaches below the grouting hole, the grouting concrete can exude into the foundation to form an enlarged bearing body. After the service period of the project is over, first clean the soil around the pile top, reconnect the hydraulic power head, start the reverse rotation mode, and initially apply a low-speed and slow torque. When the torque reaches the preset separation threshold, the torque overcomes the pre-tightening force of the screw connection, the main pile body and the expanded bottom pile tip are separated, and the main pile body is continuously rotated in the reverse direction and lifted simultaneously to pull it out of the ground. The recycled pile body is cleaned and inspected, and can be reused after passing the inspection.

[0033] Compared with the prior art, the present application has the following advantages:

[0034] The recyclable spiral steel pile and its construction method of the present application realize reliable separation of the "permanent reinforcement body" and the "recyclable main body" through the separable screw thread connection of the main pile body and the expanded bottom pile body, solving the technical problem of the difficulty in recycling the traditional main pile body. At the same time, the fan-shaped cutting arm is driven by the grouting pressure to cut and disturb the soil, and expand the bearing area. When the fan-shaped cutting arm is fully unfolded, the grouting concrete can exude into the foundation, and the grouting concrete can continuously penetrate into the soil gaps, tightly cement with the soil particles, and finally form a dense and stable permanent underground reinforcement body together with the expanded bottom pile tip, greatly improving the bearing stability of the foundation.

[0035] The recyclable spiral steel pile and its construction method of the present application have significant economic benefits, the main pile body can be completely recycled and reused multiple times, greatly reducing the engineering cost. According to the actual engineering calculation, compared with the traditional cast-in-place pile scheme, the cost can be saved by more than 40%.

[0036] The recyclable spiral steel pile and its construction method of the present application successfully solve the long-standing technical bottleneck in the recyclable pile field, have high bearing capacity, full recycling rate and environmental friendliness, provide a high-performance, high-economy and environmentally friendly foundation solution for temporary engineering construction, and are particularly suitable for temporary engineering, wind power foundation, ecologically sensitive areas and other scenes with strict requirements for foundation performance and green construction, having important popularization value and broad application prospect. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the recyclable spiral steel pile in the embodiment.

[0039] Figure 2 This is a schematic diagram of the connection between the enlarged base of the recyclable helical steel pile and the main pile body in the embodiment (the helical blades are not shown).

[0040] Figure 3 This is a schematic diagram of the expanded-base pile tip of the recyclable spiral steel pile in the embodiment (the soil stop plug and baffle are not shown; only the through holes on part of the fan-shaped cutting arm are shown).

[0041] Figure 4 This is a schematic diagram of the conical bottom of the recyclable spiral steel pile in the embodiment.

[0042] Figure 5 This is a schematic diagram of the structure in the embodiment where the fan-shaped cutting arm is not fully extended.

[0043] Figure 6 This is a schematic diagram of the structure in the embodiment where the fan-shaped cutting arm is fully extended.

[0044] Figure 7 This is a schematic diagram of the grout outlet and soil stopper of the recyclable spiral steel pile in the embodiment.

[0045] Legend

[0046] 1. Main pile body; 2. Expanded pile tip; 21. Conical bottom; 22. Transition pile body; 23. Fan-shaped cutting arm; 231. Through hole; 24. Fan-shaped partition; 3. Pressure-bearing component; 31. Pressure-bearing plate; 32. Hinge shaft; 33. Baffle; 4. Grout outlet hole; 5. Soil stop plug; 6. Spiral blade; 7. Hydraulic power head. Detailed Implementation

[0047] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0048] It should be noted that when a component is described as being "fixed to, attached to, connected to or connected to" another component, it can be directly fixed to, attached to, connected to or connected to the other component, or it can be indirectly fixed to, attached to, connected to or connected to the other component through other intermediate connectors.

[0049] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0050] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0051] Example:

[0052] like Figures 1-4 As shown, the recyclable spiral steel pile of this embodiment includes a main pile body 1 and an enlarged-base pile tip 2. The enlarged-base pile tip 2 includes a conical bottom 21, a transition pile body 22, and multiple fan-shaped cutting arms 23 (specifically four in this embodiment). Both the main pile body 1 and the transition pile body 22 are hollow tubular structures. The upper end of the transition pile body 22 and the lower end of the main pile body 1 are connected by threads (the upper end of the transition pile body 22 has internal threads, and the lower end of the main pile body 1 has external threads). The transition pile body 22 is fixed above the conical bottom 21, and the fan-shaped cutting arms 23 are movable. Located on the upper surface of the conical bottom 21, the transition pile body 22 and the conical bottom 21 are provided with multiple arc-shaped slots (corresponding to the fan-shaped cutting arm 23, there are also four) for the fan-shaped cutting arm 23 to extend outward. The transition pile body 22 is provided with a pressure-bearing component 3 for the fan-shaped cutting arm 23 to extend outward through the arc-shaped slots under grouting pressure. The transition pile body 22 is provided with a grout outlet hole 4 below it. When the pressure-bearing component 3 moves downward under grouting pressure to extend the fan-shaped cutting arm 23 to the limit position, the pressure-bearing component 3 is located below the grout outlet hole 4.

[0053] like Figure 4 As shown, in this embodiment, the upper surface of the conical bottom 21 is provided with multiple fan-shaped partitions 24 for separating multiple independent spaces, and multiple fan-shaped cutting arms 23 are located in multiple independent spaces respectively, and the shape of the fan-shaped cutting arms 23 matches the independent spaces; when grouting is not performed, the outer periphery of the fan-shaped cutting arms 23 is located at the arc-shaped groove and closes the arc-shaped groove, and the fan-shaped cutting arms 23 cannot move inward.

[0054] like Figure 3 , Figure 5 , Figure 6As shown, in this embodiment, the pressure-bearing assembly 3 includes a pressure-bearing plate 31 movably arranged in the transition pile body 22 and a hinge shaft 32 hingedly arranged at the lower side of the pressure-bearing plate 31 and at the fan-shaped cutting arm 23, the number of the hinge shaft 32 matching that of the fan-shaped cutting arm 23; and the pressure-bearing plate 31 is located above the grouting hole 4 when no grouting is performed.

[0055] As shown in Figure 5 , Figure 6 As shown, in this embodiment, the fan-shaped cutting arm 23 is provided with a baffle 33 for limiting the outward extension position thereof, and the hinge shaft 32 is hingedly arranged at the baffle 33; when the fan-shaped cutting arm 23 is extended to the limit position, the baffle 33 is attached to the inner wall of the transition pile body 22.

[0056] In this embodiment, the pressure-bearing plate 31 has an outer shape matching that of the inner cavity of the transition pile body 22, and the outer periphery of the pressure-bearing plate 31 is provided with a sealing rubber ring.

[0057] In this embodiment, the fan-shaped cutting arm 23 is provided with a plurality of through holes 231 penetrating upward and downward. Each fan-shaped cutting arm 23 is made of stainless steel and has a high hardness, and is embedded with stainless steel teeth on the surface, so as to ensure effective cutting of the soil in various types of strata.

[0058] As shown in Figure 7 In this embodiment, a plurality of the grouting holes 4 are uniformly arranged along the outer periphery of the transition pile body 22, the grouting hole 4 is a frustoconical hole, the grouting outlet of the grouting hole 4 is larger than the grouting inlet, and the grouting hole 4 is provided with a soil-stopping plug 5 when no grouting is performed, the soil-stopping plug 5 has a frustoconical shape matching that of the frustoconical hole. The diameter of the grouting hole 4 can be 3-5 mm, and the grouting holes 4 are symmetrically arranged to ensure uniform distribution of the slurry.

[0059] In this embodiment, the outer surface of the main pile body 1 is provided with continuous spiral blades 6, and the upper end surface of the transition pile body 22 is also provided with spiral blades 6.

[0060] The construction method of the above-mentioned recyclable spiral steel pile of this embodiment includes the following steps:

[0061] S1: connecting the main pile body 1 and the expanded tip 2, and connecting the hydraulic power head 7 with the upper end of the main pile body 1, starting the hydraulic power head 7 to rotate in the forward direction, and uniformly penetrating the main pile body 1 and the expanded tip 2 into the soil until the designed depth is reached; during the penetration of the main pile body 1 and the expanded tip 2 into the soil, the outer periphery of the fan-shaped cutting arm 23 is located at the arc-shaped notch and closes the arc-shaped notch;

[0062] S2: connecting the grouting equipment with the main pile body 1, and injecting the slurry into the hollow inner cavity of the main pile body 1, under the grouting pressure, the pressure-bearing assembly 3 moves downward to extend the fan-shaped cutting arm 23 to the limit position, and the slurry exudes through the grouting hole 4, the slurry wraps the expanded tip 2 and solidifies to form an expanded bearing body, and a recyclable spiral steel pile is obtained.

[0063] The recycling step in this embodiment also includes the following steps:

[0064] S3: When the service life of the recyclable spiral steel pile ends, the hydraulic power head 7 is connected to the upper end of the main pile body 1, the hydraulic power head 7 is started in reverse rotation, the main pile body 1 and the expanded pile tip 2 are separated, the main pile body 1 is recycled, and the expanded pile tip 2 is permanently left in the ground.

[0065] The construction method of this embodiment takes "precise control, efficient construction, and reliable recycling" as the core, and realizes the penetration of the pile body, the reinforcement of the foundation, and the recycling of the main pile body 1 in stages. More specifically, it includes the following detailed steps:

[0066] Before construction, the system assembly and preliminary debugging need to be completed to ensure the reliable cooperation of all equipment and components. First, the hydraulic power head 7, the main pile body 1, and the expanded pile tip 2 are comprehensively inspected for appearance and size, with a focus on checking the flexibility of the fan-shaped cutting arm 23 to eliminate initial defects. Then, a special torque wrench is used to check the fastening state of all connection parts to avoid loosening risks during construction.

[0067] During the pile body penetration construction phase, precise positioning and torque dynamic control are required to ensure stable penetration of the pile body to the designed elevation. First, use a total station to accurately position the pile, with a pile position deviation controlled within ±50mm. Then, the hydraulic power head 7 is reliably connected to the standardized quick connection interface at the upper end of the main pile body 1. This interface uses trapezoidal thread design with a precision of 6g level. After connection, the connection firmness is checked again. Then, the hydraulic power head 7 is started in forward rotation program, with an initial rotation speed of 3-5 revolutions per minute to uniformly penetrate the main pile body 1 and the expanded pile tip 2 into the soil. During the penetration process, the torque monitoring system feeds back the formation changes in real time with a sampling frequency of 100Hz. When an abnormal increase in torque is detected, the system automatically reduces the rotation speed to 1-2 revolutions per minute or pauses the penetration to prevent spiral blade deformation or equipment damage. At the same time, the double-axis inclination sensor installed on the hydraulic power head 7 monitors the pile body perpendicularity in real time to ensure that the deviation does not exceed 1%, until the pile body penetrates to the designed elevation.

[0068] A high-pressure grouting pipe is placed in the hollow cavity of the main pile body 1, the grouting pipe is selected from a high-strength flexible pipe, the burst pressure of the high-strength flexible pipe is not less than 50 MPa, then a segmented pressurization mode is adopted to inject a cement-based slurry, the initial grouting pressure is controlled at 3 MPa, the segmented pressurization mode is used to extend the fan-shaped cutting arm 23 outward through the pressure-bearing plate 31, then the working pressure is gradually increased to 25-30 MPa, so that the slurry is seeped outward through the slurry outlet hole 4. The water-cement ratio of the slurry is controlled between 0.4-0.5, if the construction stratum is sandy clay, marine saline soil or other special geology, early strength agent, expansive agent or corrosion inhibitor can be added to the slurry, the addition amount is 1-5% of the weight of cement, the specific proportion needs to be determined through field test, the grouting amount is controlled in real time by a high-precision electromagnetic flowmeter, the measurement accuracy of the flowmeter is ±0.5%, the grouting is stopped immediately after the design amount is reached; the system pressure needs to be maintained for 5 minutes after the grouting is completed, so as to ensure that the grouting concrete passing through the slurry outlet hole 4 is fully diffused to the cavity of the expanded bottom and the pores of the surrounding soil, and finally a permanent foundation reinforcement body is formed.

[0069] After the engineering service period is over, the pile body recycling operation stage is entered, and the main pile body 1 is recycled by controllable torque separation. First, the soil within a range of at least 2 times the pile diameter around the pile top is cleaned, the upper end connection part of the main pile body 1 is fully exposed, then the hydraulic power head 7 is reconnected and the connection reliability is checked; then the hydraulic power head 7 is started in the reverse rotation mode, the torque is slowly applied at a low speed of 2-3 revolutions per minute, the torque growth rate is controlled at 5 kN·m / min, when the torque reaches the preset separation threshold of 45-60 kN·m, the torque generated by the reverse rotation of the hydraulic power head 7 overcomes the helical connection pre-tightening force, so that the main pile body 1 is separated from the expanded bottom pile tip 2; after the main pile body 1 is separated from the expanded bottom pile tip 2, the reverse rotation is continued, and the main pile body 1 is synchronously lifted at a speed of 0.3-0.5 m / min, the lifting force is monitored in real time by a load sensor during the lifting process, to ensure that it does not exceed the allowable stress range of the pile body, and finally the main pile body 1 is completely pulled out of the ground; the main pile body 1 after recycling needs to be cleaned first, and then overall quality detection is carried out, the diameter is measured by an electronic digital caliper, to ensure that the deviation is not more than ±1%; the straightness is detected by a laser collimator, to ensure that the deviation is not more than 1 ‰; the wall thickness is verified by an ultrasonic thickness gauge, to ensure that the thinning amount is not more than 10% of the original thickness; at the same time, surface damage is checked by magnetic particle testing or penetration testing, to ensure that there is no crack or other defects, after the detection is qualified, a corrosion-resistant coating can be sprayed, and the main pile body 1 is stored for subsequent reuse.

[0070] For special working conditions such as underwater construction, special adaptation measures and whole-process quality assurance means need to be taken additionally. When underwater construction is carried out, special underwater grouting equipment and double-sealed grouting pipeline meeting the IP68 waterproof level are used, the grouting pressure is increased by 10-20% compared with the conventional working condition, so as to overcome the influence of water pressure on the grouting process, and the underwater positioning system is used to ensure the positioning accuracy of the pile body; in the whole construction process, the grouting pressure accuracy needs to be strictly controlled within ±0.5MPa, the grouting quantity measurement accuracy reaches ±2%, and after the grouting is completed, the ultrasonic detection method or the core drilling sampling method is used to inspect the quality of the grouting body, so as to ensure that the grouting body is continuous and complete and the 28-day compressive strength reaches the design requirement; when the recovery operation is carried out, the intelligent torque control system is started, and when the torque reaches 95% of the preset separation threshold, the rotation speed is automatically reduced, so as to ensure that the separation process is stable and controllable, and the engineering quality and construction safety are comprehensively guaranteed.

[0071] The recyclable spiral steel pile and the construction method thereof in the embodiment are specifically applied to the following application scenarios and effects:

[0072] Application scenario 1: building deep foundation pit support engineering

[0073] In a deep foundation pit support engineering in a city center, the recyclable spiral steel pile of the embodiment is used as a support pile. After the foundation pit is used for 2 years, the recovery operation is carried out, and it is calculated that the recovery rate of the main pile body 1 of 125 support piles reaches 100%, and about 200 tons of steel material is saved, which has significant economic benefits.

[0074] Application scenario 2: offshore wind power temporary working platform

[0075] In the construction of a certain offshore wind power project, the recyclable spiral steel pile of the embodiment is used as the foundation pile of the temporary working platform. Considering the corrosiveness of the marine environment and the requirement of high bearing capacity, the main pile body 1 is made of corrosion-resistant steel material and the surface is subjected to special corrosion prevention treatment. The grouting material uses sulfate-resistant cement. After the project is completed, the recovery operation is carried out by the ship-mounted hydraulic system, and all the main pile bodies 1 are successfully recovered (the recovery rate is 100%), which avoids pollution of the marine environment and saves the cost of the project by about 35%.

[0076] Application scenario 3: river regulation temporary cofferdam engineering

[0077] In a river regulation project, the recyclable spiral steel pile of the embodiment is used as the support pile of the temporary cofferdam. During construction, the pile body is directly penetrated into the riverbed from the construction ship, and after the grouting forms the reinforced body, it can effectively resist the impact of water flow. After the project is completed, all the main pile bodies 1 are successfully recovered, which avoids leaving obstacles in the river and ensures the safety of navigation.

[0078] Application scenario 4: temporary observation tower foundation in ecologically sensitive area

[0079] In the temporary foundation engineering of an ecological observation tower in a national wetland park, in order to minimize the damage to the original topography and meet the requirement of complete recovery of the foundation, the recyclable spiral steel pile of the embodiment is used. After the 18-month observation task is completed, the main pile body 1 is completely pulled out. After detection, the straightness deviation of the main pile body 1 is only 0.8‰, and the surface is not damaged, meeting the reuse standard. The project realizes 100% recovery of the foundation structure, and the site is restored as before, fully verifying the excellent applicability of the invention in the ecological sensitive environment.

Claims

1. A recyclable spiral steel pile characterized by, The utility model provides a kind of pile, including main pile body (1) and expanded base pile tip (2), the expanded base pile tip (2) includes conical bottom (21), transition pile body (22) and multiple pieces of fan-shaped cutting arm (23), the main pile body (1) and the transition pile body (22) are hollow tubular structure, the transition pile body (22) upper end and the main pile body (1) lower end are connected by thread, the transition pile body (22) is fixed on the conical bottom (21) upper side, the fan-shaped cutting arm (23) is movably arranged on the conical bottom (21) upper surface, the transition pile body (22) and the conical bottom (21) junction is equipped with multiple arc-shaped notches for the fan-shaped cutting arm (23) outward extension, the transition pile body (22) is equipped with pressure-bearing component (3) for the fan-shaped cutting arm (23) outward extension by the arc-shaped notch under the grouting pressure, the transition pile body (22) lower side is equipped with grouting hole (4);When the pressure-bearing component (3) moves downward under the grouting pressure and makes the fan-shaped cutting arm (23) outward extension to limit position, the pressure-bearing component (3) is located below the grouting hole (4); The conical bottom (21) upper surface is equipped with multiple fan-shaped partitions (24) for separating multiple independent spaces, multiple fan-shaped cutting arms (23) are located in multiple independent spaces respectively, and the shape of the fan-shaped cutting arm (23) is matched with the independent space;When not grouting, the outer periphery of the fan-shaped cutting arm (23) is located at the arc-shaped notch and closes the arc-shaped notch, and the fan-shaped cutting arm (23) cannot move inward; The pressure-bearing component (3) includes pressure-bearing plate (31) and hinged shaft (32), the pressure-bearing plate (31) is movably arranged in the transition pile body (22), one end of the hinged shaft (32) is hingedly arranged below the pressure-bearing plate (31), the other end of the hinged shaft (32) is hingedly arranged on the fan-shaped cutting arm (23), and the number of the hinged shaft (32) is matched with the fan-shaped cutting arm (23);When not grouting, the pressure-bearing plate (31) is located above the grouting hole (4); The fan-shaped cutting arm (23) is equipped with baffle (33) for limiting its outward extension position, and the hinged shaft (32) is hingedly arranged on the baffle (33);When the fan-shaped cutting arm (23) outward extension to limit position, the baffle (33) is attached to the inner wall of the transition pile body (22); The shape of the pressure-bearing plate (31) is matched with the shape of the inner cavity of the transition pile body (22), and the outer periphery of the pressure-bearing plate (31) is equipped with sealing rubber ring; The fan-shaped cutting arm (23) is equipped with multiple through holes (231) penetrating up and down.

2. The recyclable screw steel pile according to claim 1, characterized in that, The grouting hole (4) is evenly provided with multiple along the outer periphery of the transition pile body (22), the grouting hole (4) is frustum-shaped hole, the grouting outlet of the grouting hole (4) is larger than the grouting inlet, and the grouting hole (4) is equipped with soil stopper (5) when not grouting, and the shape of the soil stopper (5) is matched with the frustum-shaped hole.

3. The recyclable screw steel pile according to claim 1, characterized in that, The outer surface of the main pile body (1) is provided with continuous spiral blades (6), and the upper end surface of the transition pile body (22) is also provided with spiral blades (6).

4. A method of constructing a recyclable screw steel pile according to any one of claims 1 to 3, characterized in that, The method comprises the following steps: S1: connecting the main pile body (1) and the expanded bottom pile tip (2), connecting the hydraulic power head (7) with the upper end of the main pile body (1), starting the hydraulic power head (7) to rotate forward, and uniformly penetrating the main pile body (1) and the expanded bottom pile tip (2) into the soil body until the designed depth is reached; during the penetration of the main pile body (1) and the expanded bottom pile tip (2) into the soil body, the outer periphery of the fan-shaped cutting arm (23) is located at the arc-shaped notch and closes the arc-shaped notch; S2: connecting the grouting equipment with the main pile body (1), injecting slurry into the hollow inner cavity of the main pile body (1), under the grouting pressure, the pressure-bearing assembly (3) moves downward to make the fan-shaped cutting arm (23) extend to the limit position, and the slurry is exuded through the slurry outlet hole (4), the slurry wraps the expanded bottom pile tip (2) and solidifies to form an expanded bearing body, and a recyclable spiral steel pile is obtained.

5. The construction method according to claim 4, characterized in that, The method further comprises the following recycling steps: S3: after the service life of the recyclable spiral steel pile ends, the hydraulic power head (7) is connected with the upper end of the main pile body (1) again, the hydraulic power head (7) is started to rotate reversely, the separation of the main pile body (1) and the expanded bottom pile tip (2) is realized, the main pile body (1) is recycled, and the expanded bottom pile tip (2) is permanently left in the ground.

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