A test system and method for vertical bearing capacity of a foundation pile

Abstract

The present application relates to the technical field of building construction, and particularly relates to a foundation pile vertical bearing capacity test system and a detection method, the foundation pile vertical bearing capacity test system comprises a load box body, a loading module and an oil pipe, the load box comprises a disc-shaped upper force applying plate and a lower force applying plate, through holes for concrete circulation are arranged on the upper force applying plate and the lower force applying plate, and a hydraulic oil cylinder is further arranged between the upper force applying plate and the lower force applying plate; a plurality of fixing sleeves corresponding to the main reinforcement parts of the reinforcement cage are further arranged on the upper force applying plate and the lower force applying plate, and the main reinforcement of the reinforcement cage is threadedly connected with the fixing sleeves. The present application arranges a plurality of fixing sleeves on the upper force applying plate and the lower force applying plate, so that the main reinforcement of the reinforcement cage is threadedly connected with the fixing sleeves, the connection quality of the reinforcement cage and the load box body can be ensured, in the test, the load generated by the load box body can be effectively transmitted to the cast-in-place pile, and the accuracy of the foundation pile bearing capacity test is improved.

Description

Technical Field

[0001] This invention relates to the field of building construction technology, and in particular to a test system and method for testing the vertical bearing capacity of foundation piles. Background Technology

[0002] Pile foundations are a long-standing and ancient form of foundation. The function of pile foundations is to transfer loads to the inner soil or rock layers with low deformation and high strength through the piles, thus addressing the issue that shallow soil or rock layers cannot meet the deformation and strength requirements of the building foundation, thereby reducing the adverse effects of shallow, weak soil layers.

[0003] With the rapid development of my country's construction industry, high-rise and super high-rise buildings are becoming increasingly common, demanding higher bearing capacity from pile foundations. Higher pile bearing capacity places greater demands on the load or reaction system capacity of static load tests, leading to a sharp increase in testing costs. Furthermore, in actual construction, site limitations may prevent the conduct of single-pile static load tests on certain special pile locations, resulting in incomplete pile bearing capacity data, affecting the accuracy of pile bearing capacity testing, and preventing the effective realization of the pile's bearing potential.

[0004] To address the aforementioned problems, a new method for determining the bearing capacity of pile foundations has emerged in the existing technology: the self-balancing pile test method. Its testing principle involves embedding a specially designed loading device, a "load box," along with the reinforcing cage into the pile at a corresponding location before concrete pouring. The pressure pipe of the loading box and other necessary testing equipment are led from the pile body to the ground, and then the pile is poured. A pressure pump applies pressure to the load box from the ground, generating a loading force within the pile body. By calculating and analyzing the relationship between the loading force and these parameters, we can obtain not only the pile foundation bearing capacity but also a series of data such as the lateral resistance coefficient of each soil layer, the lateral resistance of the pile, and the end bearing capacity of the pile.

[0005] For example, Chinese invention patent application number CN201910219678.1 discloses a load cell and its measurement method. The load cell includes an upper plate, a stiffening plate, a lower plate, a lower displacement rod, an upper displacement rod, an outer cylinder of the load cell cylinder, and an inner plug of the load cell cylinder. The inner plug of the load cell cylinder is disposed on the lower plate. The outer cylinder of the load cell cylinder is sleeved on the upper end of the inner plug of the load cell cylinder, and an oil cavity is provided between the outer cylinder of the load cell cylinder and the inner plug of the load cell cylinder. The stiffening plate is disposed on the side of the outer cylinder of the load cell cylinder. The upper plate is disposed on the top of the outer cylinder of the load cell cylinder. The stiffening plate is connected to the upper plate or the lower plate. The lower displacement rod passes through the upper plate and the outer cylinder of the load cell cylinder and connects to the top of the inner plug of the load cell cylinder. The upper displacement rod passes through the upper plate and connects to the top of the outer cylinder of the load cell cylinder. This invention provides a sufficiently large load cell output value while maintaining a structural design that does not affect displacement measurement. It can meet the requirements for measuring small-diameter pipe piles and also achieves good force balance during measurement. The detection of the load cell's downward displacement follows the movement of the jack piston's base plate, eliminating the need for a ring-shaped jack structure and effectively detecting the load cell's downward displacement. Furthermore, for the issue of small pipe pile diameters, the load cell can employ a single jack design, with the piston having a large hydraulic contact area, ensuring a large output force within a relatively low oil pressure range. However, some shortcomings remain, as detailed below: In existing technologies, the steel reinforcement cage and the load cell are usually connected by welding. However, in actual construction, the welding skills of workers vary, and the quality of the welding is difficult to guarantee. This may result in the load generated by the hydraulic cylinder of the load cell not being effectively transferred to the pile foundation during the test, thus affecting the accuracy of the pile bearing capacity test.

[0006] Therefore, how to improve the connection quality between the reinforcing cage and the load cell, ensure that the load generated by the hydraulic cylinder of the load cell is effectively transferred to the pile foundation during the test, and improve the accuracy of the pile bearing capacity test are technical problems that urgently need to be solved in the existing technology. Summary of the Invention

[0007] The purpose of this invention is to address the problem that existing technologies typically use welding to connect the reinforcing cage and the load cell. However, in actual construction, the welding skills of workers vary, making it difficult to guarantee the quality of the welds. This can lead to the load generated by the hydraulic cylinder of the load cell not being effectively transferred to the pile foundation during testing, thus affecting the accuracy of the pile bearing capacity test. This invention provides a pile vertical bearing capacity testing system and method.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A vertical bearing capacity testing system for foundation piles includes a load cell body, a loading module, and oil pipes. The load cell body is connected to a reinforcing cage, and the central axis of the load cell body coincides with the central axis of the reinforcing cage. The load cell body is positioned at the equilibrium point of the side friction and end friction of the cast-in-place pile. The load cell body includes a disc-shaped upper force-applying plate and a lower force-applying plate. The upper force-applying plate is connected to the reinforcing cage on one side of the pile top of the cast-in-place pile, and the lower force-applying plate is connected to the reinforcing cage on one side of the pile bottom of the cast-in-place pile. The diameters of the upper force-applying plate and the lower force-applying plate match the diameter of the reinforcing cage. The upper force-applying plate and the lower force-applying plate are provided with through holes for concrete flow, and a hydraulic cylinder is also provided between the upper force-applying plate and the lower force-applying plate. One end of the oil pipe is connected to the loading module, and the other end is connected to the hydraulic cylinder. The loading module is used to input hydraulic oil into the hydraulic cylinder, so that the hydraulic cylinder extends, and then the upper force plate and the lower force plate can apply load on the pile body of the cast-in-place pile. The upper force-applying plate and the lower force-applying plate are also provided with a number of fixing sleeves corresponding to the main reinforcement of the steel cage, and the main reinforcement of the steel cage and the fixing sleeves are threadedly connected. The bearing capacity testing system also includes a data acquisition module and a measurement module. When the load cell body applies a load to the cast-in-place pile, the measurement module detects the pressure in the hydraulic cylinder and the vertical displacement of the cast-in-place pile. The data acquisition module is wirelessly connected to the measurement module and / or wiredly connected. The data acquisition module is used to receive the pressure data and displacement data collected by the measurement module.

[0009] Preferably, the fixing sleeve includes a first cylindrical section and a second cylindrical section. The first cylindrical section is respectively disposed on the surfaces opposite to the upper force-applying plate and the lower force-applying plate. The first cylindrical section has a receiving cavity inside, into which the main reinforcement bars of the steel cage can be inserted. The second cylindrical section includes a first threaded portion and a second threaded portion. The first threaded portion is threadedly connected to the first cylindrical section, and the second threaded portion is threadedly connected to the main reinforcement bars of the steel cage.

[0010] Preferably, the diameter of the receiving cavity matches the diameter of the main reinforcing bar of the steel cage.

[0011] Preferably, the interior of the reinforcing cage corresponding to the upper force-applying plate is provided with a plurality of protective ribs. One end of the protective rib is connected to the upper force-applying plate and the other end is connected to the reinforcing cage. The plurality of protective ribs surround the through hole to form a flared structure. The joint connecting the oil pipe and the hydraulic cylinder is provided between the protective rib and the reinforcing cage.

[0012] Preferably, the area of ​​the reinforcing cage adjacent to the load cell body is provided with a structural reinforcement zone, and the density of the stirrups in the structural reinforcement zone is greater than the density of the stirrups in the rest of the reinforcing cage.

[0013] Preferably, the upper force-applying plate includes a first plate and a second plate arranged in parallel. The fixing sleeve is disposed on the first plate, and the hydraulic cylinder is connected to the second plate. A plurality of first force-transmitting columns and second force-transmitting columns are disposed between the first plate and the second plate. The second force-transmitting columns are disposed in areas corresponding to the hydraulic cylinders. A plurality of puncture holes are disposed on the second plate, and the first force-transmitting columns are disposed corresponding to the puncture holes. The first force transmission column includes a sleeve section and a telescopic section. Both the sleeve section and the second force transmission column are perpendicularly connected to the first plate. The length of the sleeve section is less than the gap width between the first and second plates, and the diameter of the sleeve section is greater than the diameter of the puncture hole. The length of the second force transmission column is equal to the length of the sleeve section. The telescopic section is fitted inside the sleeve section, and a push spring is also provided between the sleeve section and the telescopic section. Under the action of the push spring, the telescopic section can be pushed out of the sleeve section by the push spring. A sealing plug is provided at the end of the telescopic section facing the second plate. The sealing plug is used to seal the puncture hole. When the hydraulic cylinder extends, the sealing plug protrudes from the puncture hole under pressure. The edges of the first plate and the second plate, as well as the edge of the through hole, are also provided with baffles. The baffles are integrally formed with the first plate, and the second plate and the baffles are slidably sealed together. The baffles are used to create a sealed environment between the first plate and the second plate.

[0014] Preferably, the surface of the sealing plug is provided with a plurality of fins, the fins being arranged vertically, and the fins being used to improve the tightness of the fit between the sealing plug and the puncture hole.

[0015] Preferably, the density of the first force transmission column and the puncture hole at the edge of the first plate and the second plate is greater than that at other locations.

[0016] Preferably, the first plate is further provided with a plurality of snap-fit ​​sleeves, the bottom of which is provided with an elastic rubber pad. The sleeve section and the second force transmission column are inserted into the snap-fit ​​sleeves for fixation. The first plate is also provided with a splitting hole at the part corresponding to the snap-fit ​​sleeve. The sleeve section and the second force transmission column are provided with a spike structure at the ends corresponding to the first plate. The diameter of the spike structure matches the diameter of the splitting hole. The spike structure is snapped into the splitting hole. When the hydraulic cylinder extends, the second plate squeezes the sleeve section and the second force transmission column, causing the spike structure at their ends to pass through the splitting hole.

[0017] Preferably, the surfaces of the sleeve section and the second force transmission column are further provided with a plurality of grout passage grooves, through which concrete grout can enter the snap-fit ​​sleeve and flow out from the split hole.

[0018] Preferably, the surface of the sleeve section is further provided with a plurality of grout passage holes, through which concrete grout can enter the cavity of the sleeve section.

[0019] Preferably, the elastic deformation force of the elastic pad is greater than the frictional resistance of the sealing plug passing through the puncture hole.

[0020] Preferably, the outer surface of the first plate is further provided with a patch, the size of which matches the size of the first plate, the edge of which is connected to the first plate, and the spike structure provided at the end of the sleeve section and the second force transmission column can pierce the patch when it passes through the splitting hole.

[0021] Preferably, the lower force-applying plate has a lifting ring; the lifting ring is detachably connected to the lower force-applying plate.

[0022] A method for testing the vertical bearing capacity of foundation piles includes the following steps: Step 1: Test pile hole formation: Excavate the pile hole according to the design drawings, and seal the bottom of the pile with concrete with a strength higher than that of the pile body after the hole is formed; Step 2, Installation of the load cell body: Connect the load cell body to the reinforcing cage of the cast-in-place pile. The load cell body is set at the equilibrium point of the side friction and end friction of the cast-in-place pile. Step 3: Installation and testing of the loading module, data acquisition module, and measurement module: Connect the loading module and measurement module to the load cell body, test whether the load provided by the loading module meets the test requirements, and test whether the test data collected by the measurement module is accurate; connect the data acquisition module to the measurement module, and test whether the data acquisition module can accurately receive the data collected by the measurement module. Step 4: Reinforcing cage installation and concrete pouring: Use hoisting equipment to place the reinforcing cage into the pile hole. After adjusting the position of the reinforcing cage, use a guide pipe to gradually pour concrete from the bottom of the pile to the top of the pile to the design elevation. Step 5: Vertical compressive static load test of cast-in-place piles: After the concrete strength of the cast-in-place piles reaches the set value, a vertical compressive static load test is conducted. The test adopts the slow sustained load method, with graded loading. Each grade of loading is one-tenth of the estimated value. When the load reaches the predetermined maximum value, unloading begins. Unloading is also carried out in stages, with each unloading amount being the load value of two loading stages, for a total of 5 stages. The test data are collected using a measurement module during the loading and unloading tests.

[0023] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. The vertical bearing capacity testing system for foundation piles of the present invention comprises several fixed sleeves provided on the upper and lower force-applying plates, so that the main reinforcement bars of the reinforcing cage are threadedly connected to the fixed sleeves. On the one hand, this ensures the connection quality between the reinforcing cage and the load cell body, and in the test, the load generated by the load cell body can be effectively transferred to the cast-in-place pile, thereby improving the accuracy of the foundation pile bearing capacity test. On the other hand, this structural arrangement can improve the convenience of connecting the reinforcing cage and the load cell body, and can also speed up the connection and assembly speed of the reinforcing cage and the load cell body to a certain extent, thereby improving the efficiency of the test. 2. The vertical bearing capacity testing system for foundation piles described in this invention, wherein the load cell body expands the pile body while the jacking spring pushes the expansion joint out of the sleeve section, causing the expansion joint to stand upright in the cracks of the pile. Several expansion joints can form a "barrier structure," effectively suppressing the inflow of mud and sand into the pile cross-section and preventing contamination. This results in better bonding between the old and new concrete during subsequent grouting repair work, thus improving the quality of the grouting repair of the cracks in the pile. Furthermore, the expansion joint standing upright in the pile... The cracks can also form a skeleton structure, which can improve the structural strength of the cracked parts of the cast-in-place pile after grouting repair. On the other hand, in this embodiment, the load applied by the hydraulic cylinder in the initial stage of pressurization is mainly used to push the second plate towards the first plate and to make the sealing plug pass through the puncture hole under pressure. This effectively avoids uneven load applied to the cast-in-place pile body, which could cause the cast-in-place pile body to deviate and / or cause the cast-in-place pile body structure to be damaged. This reduces the adverse effects of the self-balancing test on the bearing capacity of the cast-in-place pile. 3. The vertical bearing capacity testing system for foundation piles of the present invention includes spike structures at the ends of the sleeve section and the second force transmission column corresponding to the first plate. The first plate has splitting holes. When the hydraulic cylinder extends, the second plate compresses the sleeve section and the second force transmission column, causing the spike structures at their ends to protrude through the splitting holes. During this process, the spike structures can split the concrete of the cast-in-place pile, allowing for better connection between the first plate and the cast-in-place pile. This ensures that during high-pressure grouting, the cement grout fills the gap between the first plate and the cast-in-place pile completely, thereby ensuring the quality of the cast-in-place pile's formation. Furthermore, in this embodiment, the setting of the splitting hole also forms a plurality of grouting holes on the surface of the first plate. The concrete grout enters the snap-fit ​​sleeve through the grouting groove set on the surface of the sleeve section and the second force transmission column, and under the action of pressure, it flows out from the splitting hole to fill the gap formed between the first plate and the cast-in-place pile. This solves the problem in the prior art that the gap formed between the first plate and the cast-in-place pile is too small, making it difficult for cement grout to penetrate into the gap between the first plate and the cast-in-place pile. 4. The vertical bearing capacity testing system for foundation piles described in this invention, wherein the patch is provided on the outer surface of the first plate, which can seal the splitting hole on the first plate, preventing concrete from seeping into the closed space formed between the first plate and the second plate during the casting of the pile body, thus avoiding damage to the load box structure of this invention and improving the practicality of this invention; on the other hand, when the spike structure provided at the end of the sleeve section and the second force transmission column pierces the patch through the splitting hole, the patch undergoes a certain deformation, which can widen the gap formed between the first plate and the cast-in-place pile, further reducing the difficulty of cement grout seeping into the gap between the first plate and the cast-in-place pile, ensuring that the cement grout can fill the gap between the first plate and the cast-in-place pile tightly; at the same time, the deformation of the patch can also better separate from the cast-in-place pile concrete, so that the gap between the first plate and the cast-in-place pile can be better connected, further ensuring the density of the cement grout filling the gap between the first plate and the cast-in-place pile. Attached Figure Description

[0024] Figure 1 This is a structural schematic diagram of a vertical bearing capacity testing system for foundation piles; Figure 2 This is a schematic diagram showing the connection between the steel cage and the load cell body; Figure 3 This is a cross-sectional structural diagram of the fixed sleeve; Figure 4 This is a cross-sectional structural diagram of the load cell body in its first state. Figure 5yes Figure 4 A schematic diagram of the structure of A in the middle; Figure 6 This is a cross-sectional structural diagram of the load cell body in its second state; Figure 7 yes Figure 6 A schematic diagram of the structure of B in the middle; Figure 8 This is a schematic diagram of the cross-sectional structure of the first force transmission column; Figure 9 This is a schematic diagram of the construction process for a method of testing the vertical bearing capacity of foundation piles.

[0025] The diagram is labeled as follows: 1-Load box body, 2-Loading module, 3-Oil pipe, 4-Reinforcing cage, 5-Upper force plate, 6-Lower force plate, 7-Through hole, 8-Hydraulic cylinder, 9-Fixing sleeve, 10-Data acquisition module, 11-Measurement module, 12-First cylinder section, 13-Second cylinder section, 14-First threaded part, 15-Second threaded part, 16-Protective rib, 17-Structural reinforcement area, 18-First plate, 19-Second plate, 20-First force transmission column, 21-Second force transmission column, 22-Piercing hole, 23-Sleeve section, 24-Telescopic section, 25-Push spring, 26-Sealing plug, 27-Blocking plate, 28-Fin, 29-Snap-fit ​​sleeve, 30-Elastic rubber pad, 31-Split hole, 32-Spike structure, 33-Grouting groove, 34-Grouting hole, 35-Pattern, 36-Lifting ring. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings.

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0028] Therefore, the following detailed description of embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely illustrates some embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0029] It should be noted that, unless otherwise specified, the embodiments and features and technical solutions in the present invention can be combined with each other.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] In the description of this invention, it should be noted that the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. These terms are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0032] Example 1 like Figure 1 and Figure 2 As shown, the vertical bearing capacity testing system for foundation piles according to the present invention includes a load cell body 1, a loading module 2, and an oil pipe 3. The load cell body 1 is connected to a reinforcing cage 4, and the central axis of the load cell body 1 coincides with the central axis of the reinforcing cage 4. The load cell body 1 is positioned at the equilibrium point of the side friction and end friction of the cast-in-place pile. The load cell body 1 includes a disc-shaped upper force-applying plate 5 and a lower force-applying plate 6. The upper force-applying plate 5 is connected to the reinforcing cage 4 on one side of the pile top of the cast-in-place pile, and the lower force-applying plate 6 is connected to the reinforcing cage 4 on one side of the pile bottom of the cast-in-place pile. The diameters of the upper force-applying plate 5 and the lower force-applying plate 6 are matched with the diameter of the reinforcing cage 4. The upper force-applying plate 5 and the lower force-applying plate 6 are provided with through holes 7 for concrete flow, and a hydraulic cylinder 8 is also provided between the upper force-applying plate 5 and the lower force-applying plate 6. One end of the oil pipe 3 is connected to the loading module 2, and the other end is connected to the hydraulic cylinder 8. The loading module 2 is used to input hydraulic oil into the hydraulic cylinder 8, so that the hydraulic cylinder 8 extends, and then the upper force plate 5 and the lower force plate 6 can apply load on the pile body of the cast-in-place pile. The upper force-applying plate 5 and the lower force-applying plate 6 are also provided with a number of fixing sleeves 9 corresponding to the main reinforcement of the steel cage 4. The main reinforcement of the steel cage 4 and the fixing sleeves 9 are threadedly connected. The bearing capacity testing system also includes a data acquisition module 10 and a measurement module 11. When the load box body 1 applies a load to the cast-in-place pile, the measurement module 11 detects the pressure in the hydraulic cylinder 8 and the vertical displacement of the cast-in-place pile. The data acquisition module 10 is wirelessly connected to the measurement module 11 and / or wiredly connected. The data acquisition module 10 is used to receive the pressure data and displacement data collected by the measurement module 11.

[0033] The pile vertical bearing capacity testing system of the present invention employs a plurality of fixed sleeves 9 on the upper force-applying plate 5 and the lower force-applying plate 6, so that the main reinforcement of the reinforcing cage 4 is threadedly connected to the fixed sleeves 9. On the one hand, this ensures the connection quality between the reinforcing cage 4 and the load box body 1, and the load generated by the load box body 1 can be effectively transferred to the cast-in-place pile during the test, thereby improving the accuracy of the pile bearing capacity test. On the other hand, this structural arrangement can improve the convenience of connecting the reinforcing cage 4 and the load box body 1, and can also speed up the connection and assembly speed of the reinforcing cage 4 and the load box body 1 to a certain extent, thereby improving the efficiency of the test.

[0034] Specifically, in this embodiment, the loading module 2 is a high-pressure oil pump; the measuring module 11 includes an oil pressure sensor, a displacement sensor, and a displacement rod component; the oil pressure sensor is located at the end of the oil pipe 3, and the oil pressure sensor measures the pressure inside the oil pipe 3, thereby reflecting the pressure in the hydraulic cylinder 8; A reference steel beam is set on the construction site at the top of the cast-in-place pile. The reference steel beam is used to set the horizontal elevation, and the displacement sensor is installed on the reference steel beam. The displacement rod component includes a displacement rod body and a sheath. The displacement rod body is welded to the load box body 1, and the sheath is sleeved on the outside of the displacement rod body to protect the displacement rod body from mud erosion. When the load box body 1 applies a load to the cast-in-place pile, the height of the top of the displacement rod component can change with the rise / fall of the cast-in-place pile. The displacement sensor measures the change in the elevation of the top of the displacement rod component to accurately reflect the displacement of the cast-in-place pile. The length of the displacement rod body and the sheath extends 500mm above the top of the cast-in-place pile. Four sets of displacement sensors and displacement rod components are set, two sets for measuring the displacement of the cast-in-place pile on one side of the upper force plate 5, and the other two sets for measuring the displacement of the cast-in-place pile on one side of the lower force plate 6.

[0035] The test pile foundations should be constructed strictly according to the design drawings. In addition, due to the requirements of the pile self-balancing test method, the following points should also be noted: 1) After the test pile is drilled, its verticality should be checked using reliable testing equipment; 2) After the pile hole is excavated, the bottom of the pile shall be sealed with concrete of the designed strength, and the thickness of the sealing concrete shall not be less than 150mm.

[0036] 3) After connecting the steel cage 4 to the load box body 1, use a tower crane or crane to put the load box into the pile hole.

[0037] 4) Connect the four displacement rod bodies (main reinforcement of the pile body with the same diameter) and the four sheath pipes (Ф50 steel pipes) to the load box body 1, and tie the sheath pipes to the reinforcing cage 4 as a whole to ensure that the sheath pipes do not leak mud; the length of the four displacement rod bodies and the four sheath pipes should be 500mm higher than the top of the pile.

[0038] 5) Before placing the load cell body 1 and the reinforcing cage 4, check the pile diameter, pile length, oil pipe 3 and displacement rod component length; the concrete elevation of the test pile is the design height.

[0039] 6) After placing the load cell body 1 and the reinforcing cage 4, protect the end caps of the oil pipe 3 and the displacement bar component to prevent them from being buried by concrete. 7) Before formal testing, the integrity of the test piles must be tested using the sonic projection method.

[0040] 8) Power supply (380V and 220A) should be guaranteed during the test, and there should be no significant vibration within 10 meters of the test pile; Example 2 like Figures 1 to 3 As shown, the vertical bearing capacity test system for foundation piles of the present invention, based on the above-mentioned method, further includes a fixed sleeve 9 comprising a first cylindrical section 12 and a second cylindrical section 13. The first cylindrical section 12 is respectively disposed on the surfaces opposite to the upper force-applying plate 5 and the lower force-applying plate 6. The interior of the first cylindrical section 12 is provided with a receiving cavity, into which the main reinforcement of the reinforcing cage 4 can be inserted. The second cylindrical section 13 includes a first threaded portion 14 and a second threaded portion 15. The first threaded portion 14 is threadedly connected to the first cylindrical section 12, and the second threaded portion 15 is threadedly connected to the main reinforcement of the reinforcing cage 4.

[0041] Specifically, in this embodiment, before connecting the reinforcing cage 4 to the load cell body 1, the second cylindrical section 13 is first connected to the main reinforcing bars of the reinforcing cage 4. Then, the main reinforcing bars of the reinforcing cage 4 are inserted into the receiving cavity provided inside the first cylindrical section 12. The second cylindrical section 13 is then screwed to connect the first threaded portion 14 of the second cylindrical section 13 to the first cylindrical section 12. This structural arrangement allows for the direct connection and assembly of the bound reinforcing cage 4 structure to the load cell body 1. Thus, the fabrication of the reinforcing cage 4 and the production of the load cell body 1 can be carried out separately and independently, thereby further improving the efficiency of the pile foundation test.

[0042] As a preferred embodiment, based on the above method, the diameter of the receiving cavity is further matched with the diameter of the main reinforcement of the reinforcing cage 4. With this structural arrangement, the first cylindrical section 12 and the main reinforcement of the reinforcing cage 4 can form a tighter fit, improving the connection stability between the reinforcing cage 4 and the load box body 1. Furthermore, with this structural arrangement, the main reinforcement of the reinforcing cage 4 can fully fill the receiving cavity, effectively preventing the formation of cavities inside the cast-in-place pile after molding, thereby ensuring the molding quality of the cast-in-place pile.

[0043] Example 3 like Figure 1 and Figure 2 As shown, the vertical bearing capacity test system for foundation piles of the present invention, based on the above method, further includes a plurality of protective ribs 16 inside the reinforcing cage 4 corresponding to the upper force-applying plate 5. One end of each protective rib 16 is connected to the upper force-applying plate 5, and the other end is connected to the reinforcing cage 4. The plurality of protective ribs 16 surround the through hole 7 to form a flared structure. The joint connecting the oil pipe 3 and the hydraulic cylinder 8 is located between the protective ribs 16 and the reinforcing cage 4.

[0044] With this structural arrangement, the flared structure formed by the protective ribs 16 can protect the joint connecting the oil pipe 3 and the hydraulic cylinder 8. During the concrete pouring of the cast-in-place pile, it effectively avoids damage caused by the concrete guide pipe colliding with the joint connecting the oil pipe 3 and the hydraulic cylinder 8 when it is being lifted, thereby reducing the risk of pile test failure. On the other hand, in this embodiment, the protective ribs 16 can also improve the structural strength of the cast-in-place pile to a certain extent.

[0045] Specifically, in this embodiment, one end of the protective rib 16 is welded to the upper force-applying plate 5, and the other end is tied to the reinforcing cage 4; or, one end of the protective rib 16 is welded to the upper force-applying plate 5, and the other end is welded to the reinforcing cage 4; or, one end of the protective rib 16 is welded to the upper force-applying plate 5, and the other end overlaps the reinforcing cage 4.

[0046] As a preferred embodiment, based on the above method, a structural reinforcement zone 17 is further provided in the area of ​​the reinforcing cage 4 adjacent to the load cell body 1. The density of the stirrups in the structural reinforcement zone 17 is greater than the density of the stirrups in the other parts of the reinforcing cage 4. This structural arrangement can improve the structural strength of the cast-in-place pile in the area of ​​the load cell body 1, and minimize the risk of structural damage to the cast-in-place pile during the test.

[0047] Example 4 like Figures 4 to 8As shown, the vertical bearing capacity testing system for foundation piles of the present invention, based on the above-described method, further includes an upper force-applying plate 5 comprising a first plate 18 and a second plate 19 arranged in parallel. A fixing sleeve 9 is disposed on the first plate 18. A hydraulic cylinder 8 is connected to the second plate 19. A plurality of first force-transmitting columns 20 and second force-transmitting columns 21 are disposed between the first plate 18 and the second plate 19. The second force-transmitting columns 21 are disposed corresponding to the area of ​​the hydraulic cylinder 8. A plurality of puncture holes 22 are disposed on the second plate 19, and the first force-transmitting columns 20 are disposed corresponding to the puncture holes 22. The first force transmission column 20 includes a sleeve section 23 and a telescopic section 24. Both the sleeve section 23 and the second force transmission column 21 are vertically connected to the first plate 18. The length of the sleeve section 23 is less than the gap width between the first plate 18 and the second plate 19. The diameter of the sleeve section 23 is greater than the diameter of the puncture hole 22. The length of the second force transmission column 21 is equal to the length of the sleeve section 23. The telescopic section 24 is fitted inside the sleeve section 23. A push spring 25 is also provided between the sleeve section 23 and the telescopic section 24. Under the action of the push spring 25, the telescopic section 24 can be pushed out of the sleeve section 23. A sealing plug 26 is provided at the end of the telescopic section 24 facing the second plate 19. The sealing plug 26 is used to block the puncture hole 22. When the hydraulic cylinder 8 extends, the sealing plug 26 passes through the puncture hole 22 under pressure. The edges of the first plate 18 and the second plate 19, as well as the edge of the through hole 7, are also provided with a baffle plate 27. The baffle plate 27 is integrally formed with the first plate 18, and the second plate 19 and the baffle plate 27 are slidably sealed together. The baffle plate 27 is used to create a sealed environment between the first plate 18 and the second plate 19.

[0048] Specifically, in this embodiment, when the load box body 1 applies a load to the pile body, the hydraulic cylinder 8 extends and pushes the second plate 19 to move towards the first plate 18; when the second plate 19 is not in contact with the sleeve section 23 and the second force transmission column 21, the jacking force applied by the second plate 19 mainly acts on the first force transmission column 20; when the jacking force applied by the second plate 19 on the first force transmission column 20 is greater than the frictional resistance between the sealing plug 26 and the puncture hole 22, the sealing plug 26 passes through the puncture hole 22 under pressure, and the jacking spring 25 can normally release its elastic potential energy; when When the second plate 19 abuts against the ends of the sleeve section 23 and the second force transmission column 21, the sleeve section 23 and the second force transmission column 21 transmit the jacking force applied by the first plate 18 to the first plate 18. The load generated by the load box body 1 acts entirely on the pile body of the cast-in-place pile. When the load applied by the load box body 1 is greater than the bearing capacity limit of the cast-in-place pile itself, the pile body of the cast-in-place pile cracks from the load box body 1 to form two parts. At the same time, the jacking spring 25 pushes the telescopic section 24 out of the sleeve section 23, so that the sealing plug 26 provided at the end of the telescopic section 24 abuts against the fracture surface of the cast-in-place pile.

[0049] In this embodiment, while the load box body 1 expands the pile body, the jacking spring 25 pushes the telescopic section 24 out from the sleeve section 23, so that the telescopic section 24 stands upright in the crack of the pile. Several telescopic sections 24 can form a "barrier structure" to effectively suppress the inflow of mud and sand into the cross-section of the pile and avoid pollution of the cross-section of the pile. In this way, when grouting repair is carried out later, the bonding between the old and new concrete is better, thereby improving the quality of the later grouting repair of the crack in the pile. On the other hand, the telescopic section 24 standing upright in the crack of the pile can also form a skeleton structure, which can improve the structural strength of the crack in the pile after later grouting repair. On the other hand, in this embodiment, the hydraulic cylinders 8 are composed of multiple cylinders connected in series. The synchronization and stability of the hydraulic cylinders 8 fluctuate during the initial pressurization phase. If the load of the load cell body 1 is applied to the cast-in-place pile at this time, the pile body may become skewed due to uneven stress, and / or the pile structure may be damaged, adversely affecting the bearing capacity of the cast-in-place pile. However, in this embodiment, during the initial pressurization phase, the load applied by the hydraulic cylinders 8 is mainly used to push the second plate 19 towards the first plate 18 and to allow the sealing plug 26 to pass through the puncture hole 22 under pressure. This effectively avoids uneven load application to the cast-in-place pile, preventing skewness and / or damage to the pile structure, thereby reducing the adverse effects of the self-balancing test on the bearing capacity of the cast-in-place pile.

[0050] As a preferred embodiment, based on the above method, the surface of the sealing plug 26 is provided with a plurality of fins 28, the fins 28 being arranged vertically, and the fins 28 being used to improve the tightness of the fit between the sealing plug 26 and the puncture hole 22.

[0051] The fins 28 described in this embodiment can, on the one hand, improve the tightness of the fit between the sealing plug 26 and the puncture hole 22, thus effectively reducing the risk of concrete slurry leaking from the puncture hole 22 into the sealed cavity formed between the first plate 18 and the second plate 19 during the concrete pouring process of the cast-in-place pile; on the other hand, after the sealing plug 26 passes through the puncture hole 22, the fins 28 unfold to fill the gap between the expansion sections 24, further preventing mud and sand from flowing into the cross-section of the cast-in-place pile and causing pollution, and improving the quality of the later grouting repair of the cracked parts of the cast-in-place pile.

[0052] As a preferred embodiment, based on the above method, the density of the first force transmission columns 20 and the puncture holes 22 at the edges of the first plate 18 and the second plate 19 is greater than that at other locations. This structural arrangement reduces the interval width of the expansion joints 24, further preventing mud and sand from flowing into the cross-section of the cast-in-place pile and causing pollution, thus improving the quality of subsequent grouting repairs of cracks in the cast-in-place pile.

[0053] Example 5 like Figures 4 to 8 As shown, the vertical bearing capacity testing system for foundation piles of the present invention, based on the above-described method, further includes a plurality of snap-fit ​​sleeves 29 on the first plate 18, with an elastic rubber pad 30 at the bottom of each snap-fit ​​sleeve 29. The sleeve section 23 and the second force transmission column 21 are inserted into and fixed within the snap-fit ​​sleeves 29. The first plate 18 corresponding to the snap-fit ​​sleeves 29 is also provided with a splitting hole 31. The sleeve section 23 and the second force transmission column 21 corresponding to the ends of the first plate 18 are provided with spike structures 32. The diameter of the spike structure 32 matches the diameter of the splitting hole 31. The spike structure 32 is engaged in the splitting hole 31. When the hydraulic cylinder 8 extends, the second plate 19 squeezes the sleeve section 23 and the second force transmission column 21, causing the spike structure 32 at their ends to pass through the splitting hole 31. The surfaces of the sleeve section 23 and the second force transmission column 21 are also provided with a plurality of grout passage grooves 33. Concrete grout can enter the engaging sleeve 29 through the grout passage grooves 33 and gush out from the splitting hole 31.

[0054] In this embodiment, it is considered that when the first plate 18 transfers the load to the pile body, under the strong squeezing action of the hydraulic cylinder 8, the connection between the first plate 18 and the pile concrete may delaminate, resulting in a gap between the first plate 18 and the pile. Later, air and water seep into the gap, causing corrosion of the pile reinforcement and / or the load cell body 1, thus affecting the structural strength of the pile. Existing technology typically uses high-pressure grouting to seal the gap between the first plate 18 and the pile. However, because the gap between the first plate 18 and the cast-in-place pile is too small, the cement grout has difficulty penetrating into the gap. Furthermore, because the forces applied to the first plate 18 by the sleeve section 23 and the two force transmission columns are not uniform, the gap between the first plate 18 and the cast-in-place pile may not be connected. This results in insufficient and incomplete filling of the gap between the first plate 18 and the cast-in-place pile during high-pressure grouting, affecting the stability of the cast-in-place pile structure.

[0055] In this embodiment, spike structures 32 are provided at the ends of the sleeve section 23 and the second force transmission column 21 corresponding to the first plate 18. Splitting holes 31 are provided on the first plate 18. When the hydraulic cylinder 8 extends, the second plate 19 presses against the sleeve section 23 and the second force transmission column 21, causing the spike structures 32 at their ends to pass through the splitting holes 31. During this process, the spike structures 32 can split the concrete of the cast-in-place pile, allowing for better connection between the first plate 18 and the cast-in-place pile. This ensures that during high-pressure grouting, the cement grout fills the gap between the first plate 18 and the cast-in-place pile completely, thereby ensuring the quality of the cast-in-place pile's formation. Furthermore, in this embodiment, the splitting hole 31 also creates several grouting holes on the surface of the first plate 18. Concrete grout enters the snap-fit ​​sleeve 29 through the grouting groove 33 on the surface of the sleeve section 23 and the second force transmission column 21, and under pressure, it flows out from the splitting hole 31, filling the gap between the first plate 18 and the cast-in-place pile. This solves the problem in the prior art where the gap between the first plate 18 and the cast-in-place pile is too small, making it difficult for cement grout to penetrate. It should be noted that in this embodiment, the sleeve section 23, the second force transmission column 21, and the snap-fit ​​sleeve 29 are connected and fitted by friction.

[0056] As a preferred embodiment, based on the above method, the surface of the sleeve section 23 is further provided with a plurality of grout passage holes 34, through which concrete grout can enter the cavity of the sleeve section 23. With this structural arrangement, the concrete grout can fill the cavity inside the sleeve section 23, thereby further improving the forming quality of the cast-in-place pile.

[0057] As a preferred embodiment, based on the above method, the elastic deformation force of the elastic pad 30 is greater than the frictional resistance of the sealing plug 26 passing through the puncture hole 22.

[0058] As a preferred embodiment, based on the above method, the outer surface of the first plate 18 is further provided with a patch 35, the size of the patch 35 is matched with the size of the first plate 18, the edge of the patch 35 is connected to the first plate 18, and the spike structure 32 provided at the end of the sleeve section 23 and the second force transmission column 21 can pierce the patch 35 when it passes through the split hole 31.

[0059] Specifically, the patch 35 is made of steel sheet, and the edge of the patch 35 is welded to the edge of the first plate 18. In this embodiment, the patch 35 is provided on the outer surface of the first plate 18, which can seal the splitting hole 31 on the first plate 18, avoiding concrete seepage into the closed space formed between the first plate 18 and the second plate 19 during the pouring of the cast-in-place pile, thus preventing damage to the structure of the load box body 1 of the present invention and improving the practicality of the present invention; on the other hand, when the spike structure 32 provided at the end of the sleeve section 23 and the second force transmission column 21 pierces the patch 35 through the splitting hole 31, the patch 35... The deformation of plate 5 can widen the gap between the first plate 18 and the cast-in-place pile, further reducing the difficulty of cement grout penetrating the gap between the first plate 18 and the cast-in-place pile, ensuring that the cement grout can fill the gap between the first plate 18 and the cast-in-place pile tightly; at the same time, the deformation of the patch 35 can also better separate it from the cast-in-place pile concrete, so that the gap between the first plate 18 and the cast-in-place pile can be better connected, further ensuring the tightness of the cement grout filling the gap between the first plate 18 and the cast-in-place pile.

[0060] As a preferred embodiment, based on the above method, a lifting ring 36 is further provided on the lower force-applying plate 6; the lifting ring 36 is detachably connected to the lower force-applying plate 6. This structural arrangement facilitates the hoisting of the load box body 1 and improves the practicality of the invention in actual construction applications.

[0061] Example 6 like Figures 1 to 8 As shown, the method for detecting the vertical bearing capacity of foundation piles according to the present invention includes the following steps: Step 1: Test pile hole formation: Excavate the pile hole according to the design drawings, and seal the bottom of the pile with concrete with a strength higher than that of the pile body after the hole is formed; Step 2, Installation of Load Box Body 1: Connect the load box body 1 to the reinforcing cage 4 of the cast-in-place pile. The load box body 1 is set at the equilibrium point of the side friction and end friction of the cast-in-place pile. Step 3: Installation and testing of loading module 2, data acquisition module 10 and measurement module 11: Connect loading module 2 and measurement module 11 to the load cell body 1, test whether the load provided by loading module 2 meets the test requirements, and test whether the test data collected by measurement module 11 is accurate; connect data acquisition module 10 to measurement module 11, and test whether the data acquisition module can accurately receive the data collected by measurement module 11. Step 4, Reinforcing Cage 4 Installation and Concrete Pouring: Use hoisting equipment to put the reinforcing cage 4 into the pile hole. After adjusting the position of the reinforcing cage 4, use the guide pipe to gradually pour concrete from the bottom of the pile to the top of the pile to the design elevation. Step 5, Vertical Compression Static Load Test of Cast-in-Place Piles: After the concrete strength of the cast-in-place piles reaches the set value, a vertical compression static load test is conducted. The test adopts the slow sustained load method, with graded loading. Each grade of loading is one-tenth of the estimated value. When the load reaches the predetermined maximum value, unloading begins. Unloading is also carried out in stages, with each unloading amount being the load value of two loading stages, for a total of 5 stages. The test data are collected using measurement module 11 during the loading and unloading tests.

[0062] The specific method for the vertical compressive static load test of cast-in-place piles in this embodiment is as follows: 1. Loader A slow sustained loading test was adopted.

[0063] 2. Add / Unload Classification Loading levels: Each loading level has a load value of 1 / 10 of the estimated value. Once the maximum value has been loaded, the unloading process begins.

[0064] Unloading is also carried out in stages, with each stage unloading the amount of two loading stages, for a total of 5 stages.

[0065] 3. Observation procedures, a. Loading measurement: After each loading stage, readings should be taken at 5, 10, 15, and 30 minutes within the first hour, and then every 30 minutes thereafter.

[0066] b. Unloading Measurement: After each load level is unloaded, the rebound amount at the top of the pile should be observed, using the same method as for loading. After unloading to zero, observations should be taken at least every 30 minutes for at least 2 hours.

[0067] c. Stability standard: The displacement of the pile does not exceed 0.1 mm per hour, and this occurs twice consecutively.

[0068] d. Termination of loading conditions: Loading will terminate when one of the following conditions is met: 1. Under a certain load level, the displacement under the subsequent load level is 5 times the displacement under the previous load level. 2. Under a certain load, the displacement of the pile is more than twice the displacement under the previous load, and it has not yet reached relative stability after 24 hours. 3. The maximum load capacity of the load cell body 1 has been reached; 4. When the load-displacement curve changes gradually, the load can be applied up to a displacement of 60mm-80mm; under special circumstances, depending on specific requirements, the load can be applied up to a cumulative displacement of more than 80mm.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A vertical bearing capacity testing system for foundation piles, characterized in that, The system includes a load cell body, a loading module, and oil pipes. The load cell body is connected to the reinforcing cage, and the central axis of the load cell body coincides with the central axis of the reinforcing cage. The load cell body is positioned at the equilibrium point of the side friction and end friction of the cast-in-place pile. The load cell body includes a disc-shaped upper force-applying plate and a lower force-applying plate. The upper force-applying plate is connected to the reinforcing cage on one side of the pile top of the cast-in-place pile, and the lower force-applying plate is connected to the reinforcing cage on one side of the pile bottom of the cast-in-place pile. The diameters of the upper force-applying plate and the lower force-applying plate match the diameter of the reinforcing cage. The upper force-applying plate and the lower force-applying plate are provided with through holes for concrete flow, and a hydraulic cylinder is also provided between the upper force-applying plate and the lower force-applying plate. One end of the oil pipe is connected to the loading module, and the other end is connected to the hydraulic cylinder. The loading module is used to input hydraulic oil into the hydraulic cylinder, so that the hydraulic cylinder extends, and then the upper force plate and the lower force plate can apply load on the pile body of the cast-in-place pile. The upper force-applying plate and the lower force-applying plate are also provided with a number of fixing sleeves corresponding to the main reinforcement of the steel cage, and the main reinforcement of the steel cage and the fixing sleeves are threadedly connected. The bearing capacity testing system also includes a data acquisition module and a measurement module. When the load cell body applies a load to the cast-in-place pile, the measurement module detects the pressure in the hydraulic cylinder and the vertical displacement of the cast-in-place pile. The data acquisition module is wirelessly connected to the measurement module and / or wiredly connected. The data acquisition module is used to receive the pressure data and displacement data collected by the measurement module. The upper force-applying plate includes a first plate and a second plate arranged in parallel. A fixing sleeve is disposed on the first plate. The hydraulic cylinder is connected to the second plate. A plurality of first and second force-transmitting columns are disposed between the first and second plates, with the second force-transmitting columns corresponding to the areas of the hydraulic cylinder. A plurality of puncture holes are provided on the second plate, with the first force-transmitting columns corresponding to the puncture holes. The first force transmission column includes a sleeve section and a telescopic section. Both the sleeve section and the second force transmission column are perpendicularly connected to the first plate. The length of the sleeve section is less than the gap width between the first and second plates, and the diameter of the sleeve section is greater than the diameter of the puncture hole. The length of the second force transmission column is equal to the length of the sleeve section. The telescopic section is fitted inside the sleeve section, and a push spring is also provided between the sleeve section and the telescopic section. Under the action of the push spring, the telescopic section can be pushed out of the sleeve section by the push spring. A sealing plug is provided at the end of the telescopic section facing the second plate. The sealing plug is used to seal the puncture hole. When the hydraulic cylinder extends, the sealing plug protrudes from the puncture hole under pressure. The edges of the first plate and the second plate, as well as the edge of the through hole, are also provided with baffles. The baffles are integrally formed with the first plate, and the second plate and the baffles are slidably sealed together. The baffles are used to create a sealed environment between the first plate and the second plate.

2. The pile vertical bearing capacity testing system according to claim 1, characterized in that, The fixing sleeve includes a first cylindrical section and a second cylindrical section. The first cylindrical section is respectively disposed on the surfaces opposite to the upper force-applying plate and the lower force-applying plate. The first cylindrical section has a receiving cavity inside, into which the main reinforcement bars of the reinforcing cage can be inserted. The second cylindrical section includes a first threaded portion and a second threaded portion. The first threaded portion is threadedly connected to the first cylindrical section, and the second threaded portion is threadedly connected to the main reinforcement bars of the reinforcing cage. The diameter of the receiving cavity matches the diameter of the main reinforcement bars of the reinforcing cage.

3. The pile vertical bearing capacity testing system according to claim 2, characterized in that, The upper force-applying plate corresponds to a reinforcing cage with several protective ribs inside. One end of each protective rib is connected to the upper force-applying plate, and the other end is connected to the reinforcing cage. The protective ribs surround the through hole to form a flared structure. The joint connecting the oil pipe and the hydraulic cylinder is located between the protective ribs and the reinforcing cage. A structural reinforcement zone is provided in the area of ​​the reinforcing cage near the load box body. The density of the stirrups in the structural reinforcement zone is greater than the density of the stirrups in the rest of the reinforcing cage.

4. The pile vertical bearing capacity testing system according to claim 3, characterized in that, The surface of the sealing plug is provided with a plurality of fins, which are arranged vertically and are used to improve the tightness of the fit between the sealing plug and the puncture hole; the density of the first force transmission column and the puncture hole at the edge of the first plate and the second plate is greater than that at other parts.

5. The pile vertical bearing capacity testing system according to claim 4, characterized in that, The first plate is also provided with several snap-fit ​​sleeves, and the bottom of each snap-fit ​​sleeve is provided with an elastic rubber pad. The sleeve section and the second force transmission column are inserted into the snap-fit ​​sleeves for fixation. The first plate is also provided with a splitting hole at the part corresponding to the snap-fit ​​sleeve. The sleeve section and the second force transmission column are provided with a spike structure at the end corresponding to the first plate. The diameter of the spike structure matches the diameter of the splitting hole. The spike structure is snapped into the splitting hole. When the hydraulic cylinder extends, the second plate squeezes the sleeve section and the second force transmission column, causing the spike structure at their ends to pass through the splitting hole. The surface of the sleeve section and the second force transmission column is also provided with several grout passage grooves. Concrete grout can enter the snap-fit ​​sleeve through the grout passage grooves and gush out from the splitting hole.

6. The pile vertical bearing capacity testing system according to claim 5, characterized in that, The surface of the sleeve section is also provided with several grout passage holes, through which concrete grout can enter the cavity of the sleeve section.

7. The pile vertical bearing capacity testing system according to claim 6, characterized in that, The elastic deformation force of the elastic pad is greater than the frictional resistance of the sealing plug passing through the puncture hole.

8. The pile vertical bearing capacity testing system according to claim 7, characterized in that, The outer surface of the first plate is also provided with a patch, the size of which matches the size of the first plate. The edge of the patch is connected to the first plate. When the spike structure provided at the end of the sleeve section and the second force transmission column passes through the split hole, it can pierce the patch.

9. A method for testing the vertical bearing capacity of foundation piles, characterized in that, The pile vertical bearing capacity testing system as described in any one of claims 1-8 includes the following steps: Step 1: Test pile hole formation: Excavate the pile hole according to the design drawings, and seal the bottom of the pile with concrete with a strength higher than that of the pile body after the hole is formed; Step 2, Installation of the load cell body: Connect the load cell body to the reinforcing cage of the cast-in-place pile. The load cell body is set at the equilibrium point of the side friction and end friction of the cast-in-place pile. Step 3: Installation and testing of the loading module, data acquisition module, and measurement module: Connect the loading module and measurement module to the load cell body, test whether the load provided by the loading module meets the test requirements, and test whether the test data collected by the measurement module is accurate; connect the data acquisition module to the measurement module, and test whether the data acquisition module can accurately receive the data collected by the measurement module. Step 4: Reinforcing cage installation and concrete pouring: Use hoisting equipment to place the reinforcing cage into the pile hole. After adjusting the position of the reinforcing cage, use a guide pipe to gradually pour concrete from the bottom of the pile to the top of the pile to the design elevation. Step 5: Vertical compressive static load test of cast-in-place piles: After the concrete strength of the cast-in-place piles reaches the set value, a vertical compressive static load test is conducted. The test adopts the slow sustained load method, with graded loading. Each grade of loading is one-tenth of the estimated value. When the load reaches the predetermined maximum value, unloading begins. Unloading is also carried out in stages, with each unloading amount being the load value of two loading stages, for a total of 5 stages. The test data are collected using a measurement module during the loading and unloading tests.

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