System and method for testing vertical compressive bearing capacity of single super-long large-diameter cast-in-place pile

Abstract

The invention discloses a system and method for testing the vertical compressive bearing capacity of a single super-long large-diameter cast-in-place pile. The system comprises a bearing system, a jack, an inhaul cable, an axial force transmission column, a horizontal force transmission rod, an anchor pile and the like. The bearing system comprises an upper bearing system and a lower bearing system, the base plate is located between the two bearing systems, the two bearing systems are fixed together and then arranged at the top of the jack, the jack is arranged at the top of the axial force transmission column, the base plate is arranged at the bottom of the axial force transmission column, and loads applied by the jack are transmitted to the test pile through the base plate. The four anchor piles are uniformly arranged on the periphery of the test pile, four horizontal dowel bars are arranged at the tops of the four anchor piles, two oppositely arranged horizontal dowel bars are connected through a first group of inhaul cables, and the first group of inhaul cables penetrate through the upper bearing system in the front-back direction; the other two oppositely-arranged horizontal dowel bars are connected through a second set of inhaul cables, and the second set of inhaul cables penetrate through the lower bearing system in the left-right direction. The datum line beam is arranged on the horizontal dowel bar, and a sensor used for measuring the settlement amount of the test pile is arranged on the datum line beam.

Description

Technical Field

[0001] The invention belongs to the technical field of civil engineering testing, and in particular relates to a vertical compressive bearing capacity testing system for a super-long diameter cast-in-place pile. Background Art

[0002] The single pile static load test is the most reliable method for determining the vertical compressive bearing capacity of a single pile. It is widely used to test the bearing capacity of pile foundations because of its advantages such as its stress conditions are closer to reality and the test results are intuitive and accurate. During the test, vertical pressure is applied step by step to the top of the pile body, and the change of pile top settlement over time is observed to determine the corresponding vertical compressive bearing capacity of the single pile, providing a design basis for the project, or sampling inspection and evaluation of the bearing capacity of anchor piles to ensure the safety and stability of the project.

[0003] Common methods for single pile static load test are stacking method and anchor pile reaction method. In the stacking method, a load-bearing platform is set up above the top of the pile body with steel beams, and heavy objects are piled on the platform. The platform is gradually lifted up by the jack placed on the pile head, so that force is applied to the pile body. In the anchor pile reaction method, several anchor piles symmetrically around the tested pile are connected to the reaction beam with anchor bars, and the reaction beam is lifted up by the jack above the pile top. The connected anchor piles provide reaction force to apply force to the pile body. However, these two methods have the following defects that cannot be avoided: in the stacking method, first, the installation work of the test device is too large. If concrete prefabricated blocks are used for stacking weights, the installation time will be greatly reduced, but transportation vehicles and cranes are required, and the test cost is high. If water tank counterweights are used, water needs to be drained after the test, which will affect the cleanliness of the test site. At the same time, if the operation is improper during the test, it is very easy to cause a major safety accident, which seriously threatens the personal safety of the on-site test personnel. Second, before the test begins, the weight of the pile is transferred from the support pier to the ground, which will have a certain impact on the soil around the pile. The disturbance of the soil around the pile will affect the anchor pile and the test pile. The current national "Technical Specifications for Building Foundation Pile Inspection" (JGJ106-2014) stipulates that the distance between the center of the anchor pile and the test pile must meet ≥4D and ≥2.0m (D is the design diameter of the test pile or anchor pile) to reduce this impact. In the test, the larger of the two values ​​is taken. In addition, due to the large upper load and long installation time, technical treatment is required to prevent the load-bearing platform from bulging and collapsing. As for the anchor pile reaction method, although the installation volume is smaller than that of the pile loading method, the load centering during installation is not easy to control. During the test, eccentric compression is easily generated, causing deformation and damage of the test device and affecting the test results. At the same time, this method involves the overlap or welding of the primary and secondary reaction beams and the anchor piles, which poses a great safety hazard.

[0004] At present, there are many methods and devices for carrying out bearing capacity testing in the disclosed similar technologies. CN118601057A discloses a new test device in which an inclination sensor is added to the load-bearing platform to cooperate with the arc groove and the arc structure, which solves the problem of the load-bearing platform tilting caused by the eccentric placement of the piled objects or the local settlement of the pier, but it is still necessary to pile heavy objects on the load-bearing platform to apply force to the pile body, which cannot effectively solve the problem that the installation amount of the test device is too large and the test cycle is too long; CN114197544A discloses a reaction force device and a reaction force application method for a single pile vertical static load test. This method can use multiple jacks to apply loads at the same time, and can disperse the reaction force generated by the jacks, but this method involves the overlap or welding of the main and secondary reaction beams and the anchor piles, and there is a hidden danger that eccentric pressure is easily generated during the test, causing the test device to deform, damage and affect the test results; CN118563847A discloses a static load test method and a test device for existing piles, by drilling a test hole above the existing pile and placing a hard The purpose of static load test on existing piles is achieved by pipe and grouting, but it is still necessary to pile heavy objects on the load-bearing platform to apply force to the pile body, which cannot effectively solve the problem of too large installation engineering and safety hazards of the test device, and the weight of the piled heavy objects is transferred from the supporting pier to the ground, which will cause certain disturbance to the soil around the pile, and the disturbance of the soil around the pile will affect the anchor pile and the test pile; CN111894049A discloses a loading device for static load test of pile foundation, which can quickly perform compressive bearing capacity test, but the device uses bolts and chains to transmit the reaction force generated by the jack, and its tensile strength cannot meet the needs of super-large tonnage bearing capacity test, and the test device does not have a device for transmitting horizontal component force at the pile head of the reaction pile, which cannot effectively protect the pile head from shear damage after being subjected to a large horizontal component force during the test, and cannot perform super-large tonnage single pile bearing capacity test, and at the same time, the balance structure in the device is not easy to be completely centered, and the imbalance generated during the super-large tonnage bearing capacity test will be more obvious, thereby affecting the stability of the test process. Summary of the invention

[0005] In order to solve the technical problems existing in the prior art, the present invention discloses a single pile vertical compressive bearing capacity testing system for super-long long diameter cast-in-place piles. The testing system can quickly and flexibly perform single pile vertical compressive bearing capacity testing on super-long long diameter cast-in-place piles, and the testing device can be recycled, thereby solving the problems of complex installation, high testing cost, low work efficiency, long testing cycle, etc. when performing single pile vertical compressive bearing capacity testing on super-long long diameter cast-in-place piles, and has significant economic benefits.

[0006] In order to achieve the above object, the present invention proposes the following scheme:

[0007] In a first aspect, the present invention provides a vertical compressive bearing capacity test system for a single super-long diameter cast-in-place pile, characterized in that it includes a bearing system, a pad, a jack, a cable, an axial force transmission column, a pad, a reference beam, a horizontal force transmission rod, and an anchor pile;

[0008] The bearing system comprises an upper bearing system and a lower bearing system arranged up and down, and a pad is located between the two bearing systems, and the two bearing systems are fixed together and arranged on the top of the jack, the jack is arranged on the top of the axial force transmission column, and a pad is arranged at the bottom of the axial force transmission column, and the load applied by the jack is transmitted to the test pile through the pad;

[0009] The anchor piles include four anchor piles, which are evenly arranged around the test piles. Four horizontal force transmission rods are arranged on the tops of the four anchor piles, wherein two of the horizontal force transmission rods arranged opposite to each other are connected by a first set of cables, and the first set of cables passes through the upper bearing system from the front and rear directions; the other two horizontal force transmission rods arranged opposite to each other are connected by a second set of cables, and the second set of cables passes through the lower bearing system from the left and right directions.

[0010] The reference beam is arranged on a horizontal force transmission rod, on which a sensor for measuring the settlement of the test pile is arranged.

[0011] As a further technical solution, the upper bearing system and the lower bearing system have the same structure, and are each composed of a bearing system body and a bearing system baffle welded together. The bearing system baffles are located at both ends of the bearing system body, and the bearing system baffles are inclined relative to the bearing system body.

[0012] As a further technical solution, the upper bearing system body includes three parts welded together: upper and lower steel plates, left and right steel plates, and partitions; the upper and lower steel plates and the left and right steel plates are welded together to form a rectangular frame, and within the rectangular frame, multiple partitions are arranged along the front and rear directions, and the multiple partitions are parallel to each other.

[0013] As a further technical solution, the main body of the lower bearing system includes three parts welded together: upper and lower steel plates, front and rear steel plates, and partitions; the upper and lower steel plates and the front and rear steel plates are welded together to form a rectangular frame, and within the rectangular frame, multiple partitions are arranged along the left and right directions, and the multiple partitions are parallel to each other.

[0014] As a further technical solution, each cable includes three sections, and the three cable sections are connected by a cable anchoring clamp.

[0015] As a further technical solution, the anchor pile and the horizontal force transfer rod are cast in one piece.

[0016] As a further technical solution, the centers of the axial force transmission column, the pad and the test pile are aligned.

[0017] As a further technical solution, the diameter of the axial force transmission column is slightly larger than the diameter of the test pile.

[0018] As a further technical solution, the centers of the upper bearing plate, the lower bearing system and the pad coincide with each other.

[0019] In a second aspect, the present invention also provides a construction method for a super-long diameter cast-in-place pile single pile vertical compressive bearing capacity test system, as follows:

[0020] Step 1. Construction of test piles;

[0021] Step 2. Construct anchor piles and horizontal force transfer rods around the test pile; the anchor piles and the horizontal force transfer rods are integrally formed, and a certain length of cable needs to be pre-buried in advance during casting of the horizontal force transfer rods, and the pre-buried cable is 1.5m outside the horizontal force transfer rods, and the end of the horizontal force transfer rod is close to the pile head part of the test pile that is higher than the ground elevation, so that the horizontal force component generated during the test can be transmitted to the pile head of the test pile by the horizontal force transfer rod, and the connection part between the horizontal force transfer rod and the anchor pile is prevented from being damaged due to deformation and displacement of the horizontal force transfer rod;

[0022] Step 3. Install the axial force transmission column

[0023] When the concrete of the test pile, horizontal force transfer rod and anchor pile is fully hardened, place the pad on the top surface of the test pile, and then place the prefabricated axial force transfer column on the pad;

[0024] Step 4. Install the cable

[0025] Pass the cable through the load-bearing system, and use the cable anchoring fixture to anchor the two ends of the cable to the cable pre-buried on the horizontal force transmission rod, so that the two parts of the cable are closely connected and firmly fixed through the cable anchoring fixture to ensure that the cable can transmit the reaction force generated by the jack to the horizontal force transmission rod and the anchor pile during the test without being damaged;

[0026] Step 5. Install the load-bearing system, pads, and jacks

[0027] Place the jack, lower bearing system, pad, and upper bearing system on the axial force transmission column from bottom to top to complete the installation of the test device;

[0028] Step 6. Install the reference beam

[0029] A reference beam is installed on the top of the horizontal force transmission rod, and a displacement meter is installed on the reference beam. Two reference beams are provided, and the two reference beams are located on both sides of the test pile;

[0030] Step 7: Perform the test.

[0031] The beneficial effects of the present invention are as follows:

[0032] The present invention proposes a vertical compressive bearing capacity test system for a single pile of super-long long diameter bored piles. The present invention does not need to pile heavy objects on the upper part to apply pressure to the test pile, but uses 4 anchor piles to provide reaction force for the test pile through cables, which can significantly reduce the installation workload and installation time, greatly shorten the test cycle, and does not require the cooperation of transportation vehicles and cranes, which significantly reduces the test cost. At the same time, there is almost no load on the upper part, which will not affect the soil around the pile, so the anchor pile and the test pile will not be affected by the disturbance of the soil around the pile. The cable has extremely high tensile strength, and the unbonded prestressed cable has the advantages of corrosion resistance, good relaxation performance, easy operation, and ability to work in a high temperature environment. At the same time, the test system is provided with a horizontal force transmission rod, which can transmit the horizontal force transmitted by the cable to the pile head of the test pile during the test, so as to avoid shear damage of the anchor pile caused by excessive horizontal component force during the test, and can perform super-large tonnage single pile bearing capacity test. A load-bearing system is arranged above the axial force transmission column to allow the cable to pass through it. The load-bearing system has extremely high rigidity, can fix the position of the cable and can withstand the force transmitted from the cable without deformation. When the load-bearing system body and the load-bearing system baffle are welded, the load-bearing system baffle and the steel plate under the load-bearing system body are not perpendicular, and a certain inclination angle is required to ensure that the cable will not be damaged due to stress concentration during the test. The installation of the test device is fast, flexible and relatively simple, and can well align the centroid of the load-bearing system, pad, jack, axial force transmission column, pad and test pile to ensure that the test components will not be damaged due to eccentric compression during the test, thereby ensuring the accuracy and reliability of the test results. The test device can be flexibly disassembled and recycled, which meets the development needs of the dual carbon goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a top view of the main structural principle of the present invention;

[0034] Figure 2 It is a front view of the main structure principle of the present invention;

[0035] Figure 3 It is a schematic diagram of the structural principle of the axial force transmission column of the present invention;

[0036] Figure 4 It is a schematic diagram of the structural principle of the bearing system of the present invention;

[0037] Figure 5 It is a schematic diagram of the main structural principle of the bearing system of the present invention;

[0038] In the figure: 1-bearing system, 1-1-bearing system body, 1-2-bearing system baffle, 1-3-upper and lower steel plates of the bearing system body, 1-4-left and right (front and back) steel plates of the bearing system body, 1-5-bearing system body partition, 2-shim, 3-jack, 4-cable, 5-axial force transfer column, 6-cable anchoring fixture, 7-shim, 8-reference beam, 9-horizontal force transfer rod, 10-test pile, 11-anchor pile. DETAILED DESCRIPTION

[0040] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0041] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless otherwise explicitly stated in the present invention, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "include" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof;

[0042] For the convenience of description, if the words "up", "down", "left" and "right" appear in the present invention, they only indicate that they are consistent with the up, down, left and right directions of the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0043] In order to better illustrate the technical means, creative features, objectives and effects achieved by this patent, the specific implementation method is further elaborated below in conjunction with the accompanying drawings.

[0044] The present embodiment discloses a vertical compressive bearing capacity test system for a single super-long diameter bored pile, comprising: a bearing system 1, a pad 2, a jack 3, a cable 4, an axial force transmission column 5, a cable anchoring fixture 6, a pad 7, a reference beam 8, a horizontal force transmission rod 9, a test pile 10, and an anchor pile 11.

[0045] The anchor piles 11 include four anchor piles 11, which are evenly arranged around the test pile 10. Four horizontal force transmission rods 9 are arranged on the tops of the four anchor piles 11, and reference beams 8 are arranged on the tops of two of the horizontal force transmission rods 9. The horizontal force transmission rods 9 are connected to the bearing system 1 through two groups of cables 4, and two cable anchoring fixtures 6 are arranged on each group of cables 4.

[0046] The bearing system 1 includes two bearing systems 1, which are arranged up and down, and the pad 2 is located between the two bearing systems 1, and the two bearing systems 1 are fixed together and placed on the top of the jack 3, the jack 3 is arranged on the top of the axial force transmission column 5, and a pad 7 is arranged at the bottom of the axial force transmission column 5, and the load applied by the jack is transmitted to the test pile 10 through the pad 7;

[0047] The above-mentioned cables 4 include two groups, one group of cables 4 passes through the front and rear directions of the upper bearing system 1 and is connected to two oppositely arranged horizontal force transmission rods 9; the other group of cables 4 passes through the left and right directions of the lower bearing system 1 and is connected to two oppositely arranged horizontal force transmission rods 9.

[0048] Specifically, the upper bearing system 1 is welded by a bearing system body 1-1 and a bearing system baffle 1-2, wherein the bearing system body 1-1 is welded by three parts: upper and lower steel plates 1-3 of the bearing system body, left and right steel plates 1-4 of the bearing system body, and a bearing system body partition 1-5. The specific welding method is as follows: Figure 5 As shown, the bearing system body 1-1 and the bearing system baffle 1-2 can be made of Q235B or Q335B steel. The specific size is determined according to the test needs. The thickness of the steel plate of each part of the bearing system 1 can be between 8 and 12 mm. The compartment separated by the steel partition can allow the cable 4 required for the test to pass through. It should be noted that the size of the bearing system baffle 1-2 must ensure that it can be coupled with the compartments of the bearing system body 1-1. At the same time, the bearing system baffle 1-2 and the upper and lower steel plates 1-3 of the bearing system body are not vertical when welded. There is a certain inclination angle between the two to ensure that the cable 4 will not be damaged due to stress concentration during the test. The inclination angle can be between 40° and 60° and can be adjusted according to the specific size of the test device. In the present invention, the bearing system body 1-1 and the bearing system baffle 1-2 are made of Q335B steel, wherein the bearing system baffle 1-2 has a thickness of 10 mm, the upper and lower steel plates 1-3 of the bearing system body have a size of 1.7 m × 1.7 m, and a steel plate thickness of 10 mm, the left and right steel plates 1-4 of the bearing system body have a size of 1.7 m × 0.5 m, and a steel plate thickness of 10 mm, the bearing system body partition 1-5 has a size of 1.7 m × 0.48 m, and a steel plate thickness of 5 mm, and the angle between the upper and lower steel plates 1-3 of the bearing system body and the bearing system baffle 1-2 is 45°.

[0049] Similarly, the lower bearing system body 1-1 is also composed of a bearing system body 1-1 and a bearing system baffle 1-2 welded together; wherein the bearing system body 1-1 is composed of three parts welded together, namely, the upper and lower steel plates 1-3 of the bearing system body, the front and rear steel plates 1-4 of the bearing system body, and the bearing system body partition 1-5. That is, the main difference between the lower bearing system body 1-1 and the upper bearing system body 1-1 is that the lower bearing system body 1-1 has no steel plates on the left and right, allowing a group of cables 4 to pass through the left and right directions of the lower bearing system 1; the upper bearing system body 1-1 has no steel plates on the front and back, allowing another group of cables 4 to pass through the front and back directions of the upper bearing system 1; and the corresponding bearing system baffles 1-2 are also set in different positions, the bearing system baffles 1-2 of the lower bearing system body 1-1 are set at its left and right ends; the bearing system baffles 1-2 of the upper bearing system body 1-1 are set at its front and back ends; the rest of the structural designs of the two are basically the same, which will not be repeated here.

[0050] In this embodiment, the pad 2 can be made of Q235B or Q335B steel, with the length and width slightly larger than the load-bearing system 1, and the plate thickness can be between 15 and 30 mm. The pad 2 is located between the two load-bearing systems 1, so that the force can be evenly applied to the load-bearing system 1 during the test, thereby providing a certain degree of protection for the load-bearing system 1 and ensuring that the load-bearing system 1 will not be deformed or damaged due to uneven force. The pad 2 and the two load-bearing systems 1 need to be centrally aligned to ensure that the test device will not be damaged due to eccentric pressure during the test. In the present invention, the pad 2 is made of Q335B steel and is made of a square steel plate of 2m×2m and 20mm thick.

[0051] In this embodiment, the jack 3 is a hydraulic jack, and the rated force of the selected jack is not less than 1.5 times the estimated maximum test load. The rated force of the jack 3 in the present invention is 60000 kN.

[0052] In this embodiment, each group of cables 4 is made of unbonded prestressed steel strands twisted by 7 steel wires with a diameter of 5 mm, with an overall diameter of 15.2 mm. Compared with ordinary steel wires, it has the advantages of high tensile strength, corrosion resistance, good relaxation performance, easy operation, and can work in high temperature environments. Each cable of each group of cables 4 includes three sections, wherein the middle section passes through the above-mentioned bearing system 1, and the first and last sections are respectively pre-buried in two oppositely arranged horizontal force transmission rods 9, and the first and last sections of the cable 4 are connected to the middle section through a cable anchoring fixture 6.

[0053] In this embodiment, the axial force transmission column 5 can be made of concrete with a strength grade of C30 or C35, and the overall shape is cylindrical. The cross-sectional size is determined according to the size of the test pile 10 in the test, and the diameter is slightly larger than the diameter of the test pile 10. The length can be 2 to 4 meters. In the present invention, the axial force transmission column 5 is made of concrete with a strength grade of C35, with an overall length of 4 meters and a cross-sectional diameter of 1.7 meters.

[0054] In this embodiment, the reference beam 8 is made of 28A hot-rolled ordinary I-beam with an overall size of 280mm×124mm×8.5mm. The reference beam 8 can record the reference position and measure the settlement of the test pile 10 by a displacement meter (dividual indicator). The settlement measurement plane should be set at a position 200mm below the pile top. The measuring point should be fixed on the test pile 10. The fixture that fixes and supports the displacement meter (dividual indicator) and the reference beam 8 shall not be affected by temperature, vibration and other external factors. When the reference beam is exposed to sunlight, shielding measures should be taken.

[0055] In this embodiment, the horizontal dowel rod 9 is made of concrete with a strength grade not less than C40, and its size is determined according to the size of the anchor pile 11. In the present invention, the horizontal dowel rod 9 is made of concrete with a strength grade of C35, and its size is 5m×2m×0.5m.

[0056] The specific construction methods are as follows:

[0057] 1. Construction of test pile 10

[0058] The test loading limit value was preliminarily determined based on the geological survey data of the line and combined with the vertical compressive bearing capacity test results of similar single piles nearby. The test adopted a "4 anchors in 1" layout, that is, 4 anchor piles 11 were used to provide reaction force for the middle test pile 10 to test the vertical compressive bearing capacity of the test pile 10. The reaction force that the anchor pile 11 and the loading reaction force device can provide is not less than 1.2 times the estimated maximum load. After determining the test load limit and completing the pre-test preparation, the pouring of the test pile 10 begins. The mud wall construction method is used when pouring the test pile 10. It should be noted that the test pile 10 needs to be 80-100cm higher than the ground elevation so that the horizontal component force generated during the test can be transmitted to the head of the test pile 10 by the horizontal force transmission rod 9. The top of the test pile 10 should be strengthened. 2-3 layers of dense steel mesh can be configured on the top of the pile, or a thin steel plate cylinder can be used to make a reinforcing hoop and cast it into one with the concrete on the top of the pile, and the top of the pile should be smoothed with high-grade mortar; the center position distance between the test pile 10 and the anchor pile 11 should comply with the provisions of the "Technical Specifications for Building Foundation Pile Inspection" (JGJ106-2014), that is, ≥4D and ≥2.0m, where D is the design diameter of the test pile 10 or the anchor pile 11, and the larger of the two values ​​is taken. In this experiment, the diameter of the test pile 10 is 1.5m, the length is 80m, and the diameter of the anchor pile 11 is 2.0m, and the length is 85m.

[0059] 2. Construction of anchor pile 11 and horizontal force transmission rod 9

[0060] The anchor pile 11 is integrally formed with the horizontal force transmission rod 9. When the horizontal force transmission rod 9 is cast, a certain length of cable 4 needs to be pre-buried in advance. The portion of the cable 4 outside the horizontal force transmission rod 9 is 1.5m. The end of the horizontal force transmission rod 9 needs to be close to the pile head of the test pile 10 that is higher than the ground elevation, so that the horizontal force component generated during the test can be transmitted to the pile head of the test pile 10 by the horizontal force transmission rod 9, and the connection between the horizontal force transmission rod 9 and the anchor pile 11 can be prevented from being damaged due to deformation and displacement of the horizontal force transmission rod 9.

[0061] 3. Install the axial force transmission column 5

[0062] When the concrete of the test pile 10, the horizontal force transfer rod 9 and the anchor pile 11 is fully hardened, generally 28 days after the concrete pouring, the test can be continued. First, place the pad 7 on the top surface of the test pile 10, and then place the prefabricated axial force transfer column 5 on the pad 7. When placing, it is necessary to pay attention to aligning the centers of the axial force transfer column 5, the pad 7 and the test pile 10 from top to bottom to avoid damage to the axial force transfer column 5 and the test pile 10 due to eccentric compression during the test.

[0063] 4. Install the cable 4

[0064] The cable 4 of a length that can ensure that the cable 4 is straight but not too tight is passed through the load-bearing system 1, and the two ends of the cable 4 are anchored together with the cable 4 pre-buried in the horizontal force transfer rod 9 through the cable anchoring clamp 6, so that the two parts of the cable 4 are tightly connected and firmly fixed through the cable anchoring clamp 6, ensuring that the cable 4 can transmit the reaction force generated by the jack 3 to the horizontal force transfer rod 9 and the anchor pile 11 without being damaged during the test, thereby ensuring the stability and safety of the test process and the accuracy of the test results.

[0065] 5. Install the bearing system 1, pad 2, jack 3

[0066] Place the jack 3, lower bearing system 1, pad 2, and upper bearing system 1 on the axial force transmission column 5 from bottom to top to complete the installation of the test device. It should be noted that the centroid of the cross section of the bearing system 1, pad 2, jack 3 and axial force transmission column 5 should be aligned during placement to ensure that each device will not be damaged by eccentric pressure during the test, so as to ensure the stability and safety of the test process and the accuracy of the test results.

[0067] 6. Install the reference beam

[0068] A reference beam 8 is installed on the top of the horizontal force transmission rod 9 , and a displacement meter is installed on the reference beam 8 . Two reference beams 8 are provided, and the two reference beams are located at both sides of the test pile 10 .

[0069] 7. Conduct testing

[0070] After all the test devices are installed, the test begins. The test adopts a step-by-step equal loading method. The graded load should be the maximum load value or an estimated 1 / 10. The first-level load can be twice the graded load. According to the current national "Technical Specifications for Testing of Building Foundation Pile" (JGJ106-2014), the single pile vertical compressive static load test that provides a basis for design should adopt a slow maintenance load method. After each level of load is applied, the pile top settlement should be measured at 5, 15, 30, 45, and 60 minutes, and then measured every 30 minutes. When the pile top settlement rate reaches a relatively stable standard, that is, the pile top settlement does not exceed 0.1mm per hour and occurs twice in succession, the next level of load can be applied. When one of the following situations occurs, the loading should be terminated: (1) Under a certain level of load, the pile top settlement is greater than 5 times the settlement under the previous level of load, and the total pile top settlement exceeds 40mm. (2) Under a certain load level, the settlement of the pile top is greater than twice the settlement under the previous load level, and has not reached the above-mentioned relative stability standard after 24 hours. (3) The maximum load value required by the design has been reached and the settlement of the pile top has reached the relative stability standard. (4) When the engineering pile is used as anchor pile 11, the pull-out amount of anchor pile 11 has reached the allowable value. When the load-settlement curve is a slow-changing type, the pile top can be loaded to a total settlement of 60mm-80mm. When the pile end resistance has not been fully exerted, the pile top can be loaded to a cumulative settlement of more than 80mm. When unloading, each load level should be maintained for 1 hour. After the pile top settlement is measured at 15, 30, and 60 minutes, the next load level can be unloaded; after unloading to 0, the residual settlement of the pile top should be measured and read, and the maintenance time shall not be less than 3 hours. The measurement time is 15 and 30 minutes respectively, and the residual settlement of the pile top is measured every 30 minutes thereafter. The test ends after the unloading is completed and all test data are recorded.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A vertical compressive bearing capacity test system for a single super-long diameter cast-in-place pile, characterized in that: It includes the bearing system, pad, jack, cable, axial force transmission column, pad, reference beam, horizontal force transmission rod and anchor pile; The bearing system comprises an upper bearing system and a lower bearing system arranged up and down, and a pad is located between the two bearing systems, and the two bearing systems are fixed together and arranged on the top of the jack, the jack is arranged on the top of the axial force transmission column, and a pad is arranged at the bottom of the axial force transmission column, and the load applied by the jack is transmitted to the test pile through the pad; The anchor piles include four anchor piles, which are evenly arranged around the test piles. Four horizontal force transmission rods are arranged on the tops of the four anchor piles, wherein two of the horizontal force transmission rods arranged opposite to each other are connected by a first set of cables, which pass through the upper bearing system from the front and rear directions; the other two horizontal force transmission rods arranged opposite to each other are connected by a second set of cables, which pass through the lower bearing system from the left and right directions. The reference beam is arranged on a horizontal force transmission rod, on which a sensor for measuring the settlement of the test pile is arranged.

2. The vertical compressive bearing capacity testing system for a single super-long diameter cast-in-place pile according to claim 1, characterized in that: The upper bearing system and the lower bearing system have the same structure, and are each composed of a bearing system body and a bearing system baffle welded together. The bearing system baffles are located at both ends of the bearing system body, and the bearing system baffles are inclined relative to the bearing system body.

3. The vertical compressive bearing capacity testing system for a single super-long diameter cast-in-place pile according to claim 1, characterized in that: The upper bearing system body comprises three welded parts, namely, upper and lower steel plates, left and right steel plates, and partitions; the upper and lower steel plates and the left and right steel plates are welded together to form a rectangular frame, in which a plurality of partitions are arranged along the front and rear directions, and the plurality of partitions are parallel to each other.

4. The vertical compressive bearing capacity testing system for a super-long diameter cast-in-place pile as claimed in claim 1, characterized in that: The lower bearing system body comprises three welded parts, namely, upper and lower steel plates, front and rear steel plates, and partitions; the upper and lower steel plates and the front and rear steel plates are welded together to form a rectangular frame, in which a plurality of partitions are arranged along the left and right directions, and the plurality of partitions are parallel to each other.

5. The vertical compressive bearing capacity testing system for a single super-long diameter bored pile according to claim 1, characterized in that: Each cable comprises three sections, and the first and last sections are connected to the middle section through cable anchoring clamps.

6. The vertical compressive bearing capacity testing system for a super-long diameter cast-in-place pile as claimed in claim 1, characterized in that: The anchor pile and the horizontal force transmission rod are integrally cast and formed.

7. The vertical compressive bearing capacity testing system for a super-long diameter cast-in-place pile as claimed in claim 1, characterized in that: The centers of the axial force transmission column, the pad and the test pile are aligned.

8. The vertical compressive bearing capacity testing system for a single super-long diameter cast-in-place pile according to claim 1, characterized in that: The diameter of the axial force transmission column is slightly larger than the diameter of the test pile.

9. The vertical compressive bearing capacity testing system for a super-long diameter cast-in-place pile as claimed in claim 1, characterized in that: The centers of the upper bearing plate, the lower bearing system and the pad coincide with each other.

10. The construction method of the vertical compressive bearing capacity test system of a super-long diameter cast-in-place pile according to any one of claims 1 to 9, characterized in that: as follows: Step 1. Construction of test piles; Step 2. construct anchor piles and horizontal force transfer rods around the test pile; the anchor piles and horizontal force transfer rods are integrally formed, and a certain length of cable needs to be pre-buried in advance during casting of the horizontal force transfer rods. The pre-buried cables on the two relatively arranged horizontal force transfer rods serve as the first and last sections of a group of cables, and the pre-buried cables outside the horizontal force transfer rods are 1.5m long. The end of the horizontal force transfer rod is close to the pile head part of the test pile that is higher than the ground elevation, so that the horizontal force component generated during the test can be transmitted to the pile head of the test pile by the horizontal force transfer rod, and the connection part between the horizontal force transfer rod and the anchor pile is prevented from being damaged due to deformation and displacement of the horizontal force transfer rod; Step 3. Install the axial force transmission column When the concrete of the test pile, horizontal force transfer rod and anchor pile is fully hardened, place the pad on the top surface of the test pile, and then place the prefabricated axial force transfer column on the pad; Step 4. Install the cable Pass the middle section of the cable through the load-bearing system, and use the cable anchoring fixture to anchor the two ends of the middle section of the cable to the first and last sections of the cable pre-buried on two oppositely arranged horizontal force transmission rods, so that the three parts of the cable are closely connected and firmly fixed through the cable anchoring fixture to ensure that the cable can transmit the reaction force generated by the jack to the horizontal force transmission rod and the anchor pile during the test without being damaged; Step 5. Install the load-bearing system, pads, and jacks Place the jack, lower bearing system, pad, and upper bearing system on the axial force transmission column from bottom to top to complete the installation of the test device; Step 6. Install the reference beam A reference beam is installed on the top of the horizontal force transmission rod, and a displacement meter is installed on the reference beam. Two reference beams are provided, and the two reference beams are located on both sides of the test pile; Step 7: Perform the test.

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