A recyclable self-balancing static load test detection device and recycling method

Abstract

The present invention provides a recyclable self-balancing static load test detection device, comprising an upper tubular pile, a lower tubular pile, a load box, and a lifting device; the load box includes at least two sub-boxes uniformly distributed circumferentially along the centerline of the upper tubular pile; the upper panel of the sub-box is slidably connected to the lower end surface of the upper tubular pile, and the lower panel of the sub-box is slidably connected to the upper end surface of the lower tubular pile; the side of the sub-box near the centerline of the upper tubular pile is rotatably connected to a diagonal tie rod, the other end of the diagonal tie rod is connected to the lifting rope of the lifting device, and the angle a between the diagonal tie rod and the horizontal direction is acute; the sub-box can move toward the centerline of the upper tubular pile under the lifting action of the lifting device; when the sliding connection between the sub-box and the upper and lower tubular piles is disengaged, the combined sub-boxes can freely pass through the cavity inside the upper tubular pile. The present invention also provides a recovery method for the self-balancing static load test detection device, which can achieve recovery of the load box after the test is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of pile foundation bearing capacity detection technology, and in particular to a recyclable self-balancing static load test detection device and a recycling method. Background Art

[0002] The self-balancing test method is a special device used to test the bearing capacity of pile foundations. Unlike traditional static load testing methods, the self-balancing test method divides the pile into two sections, upper and lower, and installs a load box at the connection between the two sections. During the test, the upper and lower pile sections are subjected to equal and opposite external forces from the load box. The upper section is subject to downward friction from the surrounding soil, while the lower section is subject to upward friction from the surrounding soil and pile end resistance. If the load box is removed, the interaction between the deadweight of the upper section and the lateral friction provided by the surrounding soil and the pile end resistance and lateral friction provided by the surrounding soil of the lower section is equivalent to achieving equilibrium between the internal forces of the pile and the soil as a whole. Compared to traditional static load testing, this method has been widely used in recent years due to its many advantages, including a simple testing process, small footprint, strong applicability, low construction cost, and the ability to test multiple test piles simultaneously.

[0003] Prestressed pipe piles are hollow cylindrical slender concrete prefabricated components made using pre-tensioning or post-tensioning prestressing technology and centrifugal forming. Compared with other types of pipe piles, prestressed pipe piles have many advantages: (1) The bearing capacity of a single pile is high. Its bearing capacity design value is higher than that of cast-in-place piles, bored piles and manually excavated piles of the same diameter. (2) It has a wide range of applications. A variety of soil types can be selected as the bearing layer, and it has strong adaptability to geological conditions with large fluctuations in the bearing layer. (3) The project cost is the cheapest. (4) Professional, factory-based and standardized production ensures mechanical properties.

[0004] The core device of the self-balancing method is its loading device—the load box. The load box's installation location, installation process, and loading capacity are all key factors in determining the success of a static load test. The load box is typically installed at the equilibrium point, where the sum of the side friction of the upper self-balancing pile and its effective deadweight equals the sum of the side friction of the lower pile and its tip resistance.

[0005] Existing load box designs and technical solutions have the following drawbacks: The load box must be welded to the prefabricated tubular piles, which can be difficult to guarantee weld quality, leading to a loose connection between the prefabricated tubular piles and the load box. Furthermore, due to the welding, the load box is essentially impossible to recycle after each test. Load boxes are extremely expensive to manufacture, so designing a recyclable and reusable load box would significantly reduce project costs.

[0006] In summary, there is an urgent need for a recyclable self-balancing static load test detection device and a recycling method to solve the problems existing in the prior art. Summary of the Invention

[0007] The present invention aims to provide a recyclable self-balancing static load test device, which aims to solve the problem that the existing load box is installed by welding and cannot be recycled after the test is completed. The specific technical solution is as follows:

[0008] A recyclable self-balancing static load test device comprises an upper pipe pile, a lower pipe pile, a load box and a lifting device, wherein the lifting device is located directly above the upper pipe pile;

[0009] The load box includes at least two sub-boxes uniformly distributed along the circumferential direction of the center line of the upper pipe pile;

[0010] The upper panel of the sub-box is slidably connected to the lower end surface of the upper pipe pile, and the lower panel of the sub-box is slidably connected to the upper end surface of the lower pipe pile. The side of the sub-box close to the center line of the upper pipe pile is rotatably connected to a diagonal rod, and the other end of the diagonal rod is connected to the lifting rope of the lifting device. The angle a between the diagonal rod and the horizontal direction is an acute angle;

[0011] The sub-box can move toward the center line of the upper pipe pile under the lifting action of the lifting device. When the sliding connection between the sub-box and the upper and lower pipe piles is disengaged, the combined sub-boxes can freely pass through the cavity inside the upper pipe pile.

[0012] Preferably, in the above technical solution, the load box further comprises a connecting member, wherein the connecting member is provided with a plurality of sliding connection parts corresponding to each sub-box one by one, and the sub-boxes are slidably connected to the sliding connection parts;

[0013] When the sub-boxes of the load box are in a dispersed state, the sub-boxes slide along the sliding connection portion to an end away from the center line of the upper pipe pile. At this time, the sub-boxes are respectively slidably connected to the upper pipe pile and the lower pipe pile;

[0014] When the sub-boxes of the load box are in the combined state, the sub-box slides along the sliding connection portion to one end close to the center line of the upper pipe pile, and the sliding connection between the sub-box and the upper and lower pipe piles is disengaged.

[0015] Preferably, in the above technical solution, during the lifting process, when the horizontal component of the force acting on the diagonal tie rod is greater than the sum of the frictional resistances between the sub-box and the upper pipe pile, the lower pipe pile and the sliding connection, the sub-box moves toward the center line of the upper pipe pile.

[0016] Preferably, in the above technical solution, the sliding connection part is inserted into the interior of the sub-box, and a limiting part is provided at one end of the sliding connection part away from the center line of the upper pipe pile.

[0017] Preferably, in the above technical solution, the sub-box and the upper pipe pile and the lower pipe pile are slidably connected through the cooperation of a slide plate and a slideway, and the slide plate is slidably arranged in the slideway.

[0018] Preferably in the above technical solution, the lower end face of the upper pipe pile and the upper end face of the lower pipe pile are provided with pressure plates, the sub-box is slidably connected to the pressure plates on the upper and lower sides, and the compressive strength of the pressure plates is greater than the compressive strength of the upper and lower pipe piles.

[0019] Preferably, in the above technical solution, a connecting ring is provided on the sub-box, and the inclined rod is hinged to the connecting ring; before lifting, the angle a is less than 45°.

[0020] The above technical solution is preferably also provided with a pressurized control box, wherein the hydraulic jack in the sub-box is connected to the pressurized control box through a hydraulic oil pipe, and the upper panel and the lower panel are pushed to move in opposite directions by the hydraulic jack. The upper panel of the sub-box is provided with a through hole allowing the hydraulic oil pipe to pass through.

[0021] The above technical solution preferably further includes a data acquisition system and a displacement sensor. The upper panel and the lower panel of each sub-box are provided with a displacement sensor, and the displacement sensor is connected to the data acquisition system through a data acquisition line.

[0022] The present invention also provides a method for recovering the recoverable self-balancing static load test detection device:

[0023] After the test is completed, the lifting device is used to apply an upward force F. When the horizontal component of the force on the inclined rod is greater than the sum of the frictional resistance of the sub-box, the sub-box moves toward the center line of the upper pipe pile.

[0024] When each sub-box moves to the point where the sliding connection with the upper and lower pipe piles is disengaged, the sub-boxes are in a combined state, and the load box freely passes through the cavity of the upper pipe pile to the ground under the action of the lifting device, thereby realizing the recovery of the load box.

[0025] The application of the technical solution of the present invention has the following beneficial effects:

[0026] (1) By taking advantage of the shape characteristics of the prefabricated pipe piles, the size of the load box can be reduced without affecting the effectiveness of the load box. The load box can be lifted and recovered from the cavity of the upper pipe pile, avoiding the need to pull out the entire pile body and then recover it after the test. This has the advantages of saving time and labor, recycling and reuse, and saving engineering costs. At the same time, the setting of the pressure plate can reduce stress concentration and uneven stress distribution, and evenly transfer the pressure of the load box to the upper and lower pipe piles, thereby improving the accuracy of the static load test.

[0027] (2) The frictional resistance between the upper pipe pile and the soil around the pile is used to reduce the difficulty of recovering the load box. During the test, the upper pipe pile is subjected to the vertical upward thrust of the load box and produces an upward displacement s, which stimulates the frictional resistance of the soil around the pile to the upper pipe pile. When the load box is unloaded, due to the small displacement s between the upper pipe pile and the load box, the frictional resistance will not disappear immediately. At this time, the load box is almost not subjected to the pressure generated by the weight of the upper pipe pile. It only needs to overcome the friction between the sub-box and the pressure plate and the sliding connection. Therefore, only a small horizontal component of force is needed to shrink the dispersed load box to its original state.

[0028] In addition to the above-described objects, features and advantages, the present invention has other objects, features and advantages. The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0030] Figure 1 It is a structural schematic diagram of the detection device;

[0031] Figure 2 is a top view of the detection device;

[0032] Figure 3a It is a schematic diagram of the dispersed state of the sub-box;

[0033] Figure 3b It is a schematic diagram of the sub-box merging state;

[0034] Figure 4 It is a schematic diagram of the sliding structure between the sub-box and the upper pressure plate and the lower pressure plate;

[0035] Figure 5 It is the force decomposition diagram when the load box is recovered;

[0036] Figure 6 Schematic diagram of the load box structure in Example 2 (sub-boxes merged);

[0037] Among them, 1. data acquisition system, 2. pressurization control box, 3. lifting device, 4. reference beam, 5. upper pipe pile, 6. lower pipe pile, 7. load box, 7A, first sub-box, 7B, second sub-box, 7C, third sub-box, 7D, fourth sub-box, 8. upper panel, 9. lower panel, 10. upper pressure plate, 11. lower pressure plate, 12. connector, 12A, limit part, 13. data acquisition line, 14. hydraulic oil pipe, 15. inclined rod, 16. lifting rope, 17. cavity, 18. hydraulic jack, 19. slide plate, 20. slideway, 21. connecting ring. DETAILED DESCRIPTION

[0038] To facilitate understanding of the present invention, the present invention will be described more fully below, along with preferred embodiments thereof. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the disclosure of the present invention.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0040] Example 1:

[0041] See also Figure 1-Figure 5 This embodiment provides a recyclable self-balancing static load test detection device, which includes an upper pipe pile 5, a lower pipe pile 6, a load box 7 and a lifting device 3. During the test, the upper pipe pile, the lower pipe pile and the load box are all located in the foundation, and the lifting device 3 is located on the ground and directly above the pipe pile 5; further, the load box is set at the force balance point between the upper pipe pile and the lower pipe pile.

[0042] Furthermore, the load box 7 includes at least two sub-boxes uniformly distributed along the circumference of the center line of the upper pipe pile 5; the upper panel 8 of the sub-box is slidably connected to the lower end surface of the upper pipe pile 5, and the lower panel 9 of the sub-box is slidably connected to the upper end surface of the lower pipe pile 6. The side of the sub-box close to the center line of the upper pipe pile 5 is rotatably connected to a diagonal rod 15, the other end of the diagonal rod 15 is connected to the lifting rope 16 of the lifting device 3, and the angle a between the diagonal rod 15 and the horizontal direction is an acute angle;

[0043] The sub-boxes can move toward the centerline of the upper pipe pile 5 under the lifting action of the lifting device 3. When the sliding connection between the sub-boxes and the upper and lower pipe piles is disengaged, the combined sub-boxes can freely pass through the cavity 17 inside the upper pipe pile 5.

[0044] In this embodiment, the load box includes a first sub-box 7A and a second sub-box 7B. The first sub-box and the second sub-box are both semi-cylinders. After the first sub-box and the second sub-box are combined, they form a complete cylinder. The diameter of the cylinder should be smaller than the inner diameter of the cavity.

[0045] During lifting (i.e., recovery), the lifting device 3 applies an upward force F through the lifting rope 16. When the horizontal component of the force on the inclined rod 15 is greater than the sum of the frictional resistances on the sub-boxes, the sub-boxes move toward the center line of the upper pipe pile 5, thereby pulling the scattered sub-boxes into a combined state, such as Figure 3a and Figure 3bAs shown, the sub-boxes (i.e., the load box) in the combined state can freely pass through the cavity 17 of the upper pipe pile to reach the ground, thereby realizing the recovery of the load box.

[0046] Furthermore, those skilled in the art will appreciate that controlling the angle a to be an acute angle is intended to ensure that the horizontal component of force is not zero; based on common sense regarding force decomposition, the smaller the angle a, the greater the horizontal component of force, and the stronger the traction effect on the sub-box; in order to achieve smooth traction of the sub-box, this embodiment is configured such that before lifting begins, the angle a is less than 45°.

[0047] See also Figure 1 and Figure 5 It can be understood by those skilled in the art that the initial angle a can be controlled by controlling the sliding stroke of the sub-box, the installation position of the diagonal brace, and the length of the diagonal brace. Furthermore, in order to ensure that the sub-box can be smoothly separated from the upper and lower pipe piles, the horizontal component force should be greater than the frictional resistance of the sub-box during the entire sliding process of the sub-box.

[0048] See also Figure 2 、 Figure 3a and Figure 3b The load box 7 further includes a connecting member 12, wherein the connecting member 12 is provided with a plurality of sliding connection parts corresponding to each sub-box one by one, and the sub-boxes are slidably connected to the sliding connection parts, that is, each sub-box slides along the sliding connection parts to a dispersed state or a merged state;

[0049] See also Figure 3a When the sub-boxes of the load box are in a dispersed state, the sub-boxes slide along the sliding connection portion to the end away from the center line of the upper pipe pile 5. At this time, the sub-boxes are respectively slidably connected to the upper pipe pile and the lower pipe pile; see Figure 3b When the sub-boxes of the load box are in the combined state, the sub-box slides along the sliding connection portion to one end close to the center line of the upper pipe pile 5. At this time, the sliding connection between the sub-box and the upper pipe pile and the lower pipe pile is disengaged.

[0050] Specifically, in this embodiment, when the horizontal component of the force exerted on the inclined rod 15 is greater than the sum of the frictional resistances between the sub-box and the upper pipe pile, the lower pipe pile, and the sliding connection, the sub-box can move toward the center line of the upper pipe pile 5.

[0051] like Figure 5 As shown in this embodiment, F1 is the force exerted by the inclined brace on the first sub-box 7A. When its horizontal component F11 exceeds the sum of the frictional resistances experienced by the first sub-box, the first sub-box begins to move. F2 is the force exerted by the inclined brace on the second sub-box 7B. When its horizontal component F22 exceeds the sum of the frictional resistances experienced by the second sub-box, the second sub-box begins to move. Because the sub-boxes are evenly distributed, the angle a between each inclined brace and the horizontal direction is equal, which means that the horizontal component of force changes uniformly across each sub-box.

[0052] Preferably, the sliding connection is inserted into the sub-box, and a limit portion 12A is provided at one end of the sliding connection away from the centerline of the upper pipe pile 5. The sub-box may have a through hole or a slot that mates with the sliding connection, allowing the sliding connection and the through hole or slot to move relative to each other. The limit portion 12A at the end limits the maximum distance the sub-box can travel from the centerline of the upper pipe pile.

[0053] Preferably, the sub-box is slidably connected to both the upper and lower tubular piles by means of a slide 19 and a slideway 20, wherein the slide 19 is slidably disposed within the slideway 20. Pressure plates are provided on the lower end face of the upper tubular pile 5 and the upper end face of the lower tubular pile 6, and are welded to the annular pile head plates of the upper and lower tubular piles. The sub-box is slidably connected to the upper and lower pressure plates, and the compressive strength of the pressure plates is greater than that of the upper and lower tubular piles to prevent deformation of the pressure plates from causing errors in displacement measurement during the test.

[0054] See also Figure 4 In this embodiment, a slide plate 19 is provided on the upper panel 8 and the lower panel 9 of the sub-box (i.e., the first sub-box and the second sub-box), and a slide groove 20 is provided on the upper pressure plate 10 of the upper pipe pile and the lower pressure plate 11 of the lower pipe pile, so that the sub-box can slide relative to the upper pipe pile and the lower pipe pile; further, a limit portion can also be provided on the slide groove 20, which is used to limit the maximum distance that the sub-box is away from the center line of the upper pipe pile.

[0055] Furthermore, in this embodiment, the parts involving sliding are all made of materials with rough surfaces and high friction coefficients (i.e., sliding between the sub-box and the sliding connection part, and sliding between the sub-box and the upper and lower pipe piles) to generate frictional resistance, which can prevent unnecessary movement between the sub-box and the upper and lower pipe piles; when delivering the piles, the gravity of the lower pipe pile and the load box itself has an increasing effect on the frictional resistance to ensure that the sub-box does not move when delivering the piles, thereby affecting the subsequent test results.

[0056] See also Figure 5 The sub-box is provided with a connecting ring 21, and the inclined rod 15 is hinged to the connecting ring 21. The hinge enables the inclined rod to rotate relative to the sub-box, thereby providing freedom for the change of the angle a during the recovery process.

[0057] See also Figure 1 The detection device also includes a pressurization control box 2. A hydraulic jack in a sub-box is connected to the pressurization control box 2 via a hydraulic oil pipe 14. The hydraulic jacks push the upper panel 8 and lower panel 9 in opposite directions. The upper panel 8 of the sub-box has a through hole to allow the hydraulic oil pipe 14 to pass through. The arrangement of the hydraulic jacks in the sub-box and the structure used to achieve movement of the upper and lower panels can be found in the prior art, such as the prior art load box.

[0058] like Figure 4 As shown, hydraulic jacks are used to apply forces of opposite directions and equal magnitude to the upper panel 8 and the lower panel 9, thereby transmitting the forces to the upper pipe pile 5 and the lower pipe pile 6 through the upper pressure plate 10 and the lower pressure plate 11 respectively.

[0059] See also Figure 1 The detection device also includes a data acquisition system 1 and a displacement sensor. A displacement sensor is provided on the upper panel 8 and the lower panel 9 of each sub-box, which is used to detect the displacement of the upper panel 8 and the lower panel 9 respectively (that is, to measure the displacement of the upper and lower pipe piles during the test). The displacement sensor is connected to the data acquisition system 1 through a data acquisition line 13.

[0060] This embodiment also provides a test and recovery method for the above-mentioned recoverable self-balancing static load test detection device:

[0061] Step 1: Weld an upper pressure plate 10 and a lower pressure plate 11 on the annular pile head plates of the upper pipe pile and the lower pipe pile, respectively. The shapes and sizes of the upper pressure plate 10 and the lower pressure plate 11 are consistent with those of the upper pipe pile and the lower pipe pile, respectively.

[0062] Step 2: Before the test, ensure that the centroids of the upper and lower pipe piles are on the same straight line, and that there is a distance of the load box height between the upper and lower pipe piles; then place the load box between the upper and lower pipe piles, aligning the slides on each sub-box with the slide grooves, and apply force to adjust each sub-box to a dispersed state. Each sub-box moves to the position farthest from the center line of the upper pipe pile and is limited by the limiter. At this point, the load box is installed (after installation, the center lines of the load box, upper pipe pile, and lower pipe pile coincide);

[0063] Step 3: Connect the hydraulic jacks in each sub-box to the pressurized control box on the ground through hydraulic oil pipes to form a loading system; install displacement sensors on the upper and lower panels of each sub-box, and connect the displacement sensors to the ground data acquisition system to measure the displacement of the upper and lower pipe piles during the test;

[0064] Step 4: Delivering and burying piles. When delivering piles, ensure that the pile body plumb bob enters the foundation through the reference beam 4;

[0065] Step 5: The loading system pressurizes the hydraulic jack through the hydraulic oil pipe, records the test data through the data acquisition system, and performs the test in accordance with relevant specifications to complete the self-balancing pile test (during the self-balancing test, each sub-box is located between the upper pipe string 5 and the lower pipe pile 6 and each sub-box is evenly arranged along the center line of the upper pipe string 5. The sub-boxes are in a sliding connection with the upper pipe pile 5 and the lower pipe pile 6);

[0066] Step 6: After the test is completed, the loading system stops applying pressure. At this time, due to the frictional resistance of the soil around the upper and lower pipe piles, the actual pressure on each sub-box is much less than the weight of the upper pipe pile. The lifting device 3 is used to apply an upward force F. When the horizontal component of the force applied to the diagonal tie rod 15 is greater than the sum of the frictional resistance of the sub-box, the sub-box moves toward the centerline of the upper pipe pile 5. When each sub-box moves to the point where the sliding connection between the upper and lower pipe piles is disengaged, each sub-box is in a merged state. Under the action of the lifting device, the load box freely passes through the cavity 17 of the upper pipe pile to reach the ground, and the load box is recovered and can be used for the next test.

[0067] Example 2:

[0068] See also Figure 6 The only difference between this embodiment and embodiment 1 is that the load box in this embodiment is composed of four sub-boxes, namely the first sub-box 7A, the second sub-box 7B, the third sub-box 7C and the fourth sub-box 7D. In this embodiment, the force is applied to the upper pipe pile and the lower pipe pile through the four evenly distributed sub-boxes.

[0069] Those skilled in the art will appreciate that the load box is not limited to the configuration provided in this embodiment, and the load box may also be three sub-boxes, or more sub-boxes, which are evenly distributed between the upper pipe pile and the lower pipe pile.

[0070] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A recyclable self-balancing static load test detection device, characterized in that: It comprises an upper pipe pile (5), a lower pipe pile (6), a load box (7) and a lifting device (3), wherein the lifting device (3) is located directly above the upper pipe pile (5); The load box (7) comprises at least two sub-boxes uniformly distributed along the circumferential direction of the center line of the upper pipe pile (5); The upper panel (8) of the sub-box is slidably connected to the lower end surface of the upper pipe pile (5), and the lower panel (9) of the sub-box is slidably connected to the upper end surface of the lower pipe pile (6). The side of the sub-box close to the center line of the upper pipe pile (5) is rotatably connected to a diagonal tie rod (15), and the other end of the diagonal tie rod (15) is connected to the lifting rope (16) of the lifting device (3). The angle a between the diagonal tie rod (15) and the horizontal direction is an acute angle. The sub-boxes can move toward the centerline of the upper pipe pile (5) under the lifting action of the lifting device (3); when the sliding connection between the sub-boxes and the upper pipe pile and the lower pipe pile is disengaged, the combined sub-boxes can freely pass through the cavity (17) inside the upper pipe pile (5); The load box (7) further comprises a connecting member (12), wherein the connecting member (12) is provided with a plurality of sliding connection parts corresponding to each sub-box one by one, and the sub-boxes are slidably connected to the sliding connection parts; When the sub-boxes of the load box are in a dispersed state, the sub-boxes slide along the sliding connection portion to an end away from the center line of the upper pipe pile (5), and at this time the sub-boxes are respectively slidably connected to the upper pipe pile and the lower pipe pile; When the sub-boxes of the load box are in a combined state, the sub-boxes slide along the sliding connection portion to one end close to the center line of the upper pipe pile (5), and at this time, the sliding connection between the sub-box and the upper pipe pile and the lower pipe pile is disengaged; During the lifting process, when the horizontal component of the force applied to the inclined tie rod (15) is greater than the sum of the frictional resistances between the sub-box and the upper pipe pile, the lower pipe pile, and the sliding connection, the sub-box moves toward the center line of the upper pipe pile (5); It also includes a pressurized control box (2), a hydraulic jack in the sub-box connected to the pressurized control box (2) via a hydraulic oil pipe (14), and the upper panel (8) and the lower panel (9) are pushed to move in opposite directions by the hydraulic jack, and the upper panel (8) of the sub-box is provided with a through hole allowing the hydraulic oil pipe (14) to pass through.

2. The recyclable self-balancing static load test detection device according to claim 1, characterized in that: The sliding connection part is inserted into the interior of the sub-box, and a limiting part (12A) is provided at one end of the sliding connection part away from the center line of the upper pipe pile (5).

3. The recyclable self-balancing static load test detection device according to claim 1, characterized in that: The sub-box and the upper pipe pile and the lower pipe pile are slidably connected through the cooperation of a slide plate (19) and a slideway (20), and the slide plate (19) is slidably arranged in the slideway (20).

4. The recyclable self-balancing static load test detection device according to claim 3, characterized in that: The lower end surface of the upper pipe pile (5) and the upper end surface of the lower pipe pile (6) are both provided with pressure plates, and the sub-box is slidably connected to the pressure plates on the upper and lower sides, and the compressive strength of the pressure plates is greater than the compressive strength of the upper and lower pipe piles.

5. The recyclable self-balancing static load test detection device according to claim 1, characterized in that: A connecting ring (21) is provided on the sub-box, and the inclined tie rod (15) is hinged to the connecting ring (21); before lifting, the angle a is less than 45°.

6. The recyclable self-balancing static load test detection device according to claim 1, characterized in that: It also includes a data acquisition system (1) and a displacement sensor. The upper panel (8) and the lower panel (9) of each sub-box are provided with a displacement sensor, and the displacement sensor is connected to the data acquisition system (1) via a data acquisition line (13).

7. A method for recovering the recoverable self-balancing static load test device according to any one of claims 1 to 6, characterized in that: After the test is completed, the lifting device (3) is used to lift the sub-box and apply an upward force F. When the horizontal component of the force applied to the inclined rod (15) is greater than the sum of the frictional resistances applied to the sub-box, the sub-box moves toward the center line of the upper pipe pile (5); When each sub-box moves to the point where the sliding connection with the upper pipe pile and the lower pipe pile is disengaged, each sub-box is in a combined state, and the load box freely passes through the cavity (17) of the upper pipe pile under the action of the lifting device to reach the ground, thereby realizing the recovery of the load box.

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