A static load test structure of pile foundation using anchor cables to apply prestress

Abstract

The utility model discloses a static load test structure for piles that uses anchor cables to apply prestress, including a test pile, a high-pressure rotary jet anchoring section, an anchor cable assembly, and a test device for providing an upward pulling force to the anchor cable assembly and detecting the strain of the test pile body, wherein the high-pressure rotary jet anchoring section is located below the test pile, the lower end of the anchor cable assembly is fixed in the high-pressure rotary jet anchoring section, a central pipe is provided at the center of the test pile, the upper end of the anchor cable assembly extends upward to the top of the test pile through the central pipe, and is connected to the test device. When the utility model performs a static load test on the test pile, it occupies a small space and does not affect the construction of surrounding structures, has low requirements on the surrounding environment, and has little interference. Compared with the stacking method and the anchor pile method, it reduces the cost of on-site in-situ testing and saves time and effort. At the same time, it has the advantages of convenient construction, high flexibility, and strong adaptability.

Description

Technical Field

[0001] The utility model belongs to the field of foundation structure testing, and in particular relates to a pile static load testing device. Background Art

[0002] The pile static load test is a common engineering testing method used to determine the bearing capacity and deformation characteristics of a single pile or foundation. During the test, vertical pressure, vertical pull or horizontal thrust is applied to the pile or foundation step by step or cyclically. As the load increases, the vertical compressive bearing capacity, vertical pull-out bearing capacity, horizontal bearing capacity and other parameters of the corresponding pile or foundation are determined by regularly observing the settlement, pull-out displacement or horizontal displacement of the top of the pile over time.

[0003] There are two methods used for static load test of foundation piles: pile loading method and anchor pile method. The pile loading method requires a large amount of pile loading for static load test, which has high transportation and hoisting costs, occupies a large area, and has poor adaptability to situations where there are adjacent structures around. The anchor pile method requires on-site testing for static load, and the test process is complicated and requires a large working space. Therefore, it is necessary to provide a foundation pile static load test structure that uses pressure-dispersed anchor cables to apply prestress, which requires a small working space, has low requirements on the surrounding environment, is convenient to construct, and has strong adaptability, so as to solve the problems existing in the existing pile loading method and anchor pile method. Utility Model Content

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a pile static load test structure that uses anchor cables to apply prestress, which requires a small working space, has low requirements on the surrounding environment, is convenient to construct, and has strong adaptability. In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0005] A static load test structure for piles using anchor cables to apply prestress, comprising a test pile, a high-pressure rotary jet anchoring section, an anchor cable assembly, and a test device for providing an upward pulling force to the anchor cable assembly and detecting the strain of the test pile body, wherein the high-pressure rotary jet anchoring section is located below the test pile, the lower end of the anchor cable assembly is fixed in the high-pressure rotary jet anchoring section, a central pipe is provided at the center of the test pile, the upper end of the anchor cable assembly extends upward through the central pipe to above the test pile, and is connected to the test device.

[0006] In the above-mentioned pile foundation static load test structure, preferably, the test pile foundation includes pile foundation concrete and a steel cage arranged in the pile foundation concrete, the central pipe is fixedly arranged at the center of the steel cage, the central pipe is a steel pipe, and the top and bottom of the central pipe are both beyond the steel cage. With the above-mentioned setting, when the bored pile is cast, the bottom of the central pipe can be inserted into the soil at the bottom of the bored pile after the bored pile is formed, so as to prevent the poured concrete from entering the central pipe and causing blockage. At the same time, the top and bottom of the central pipe in the middle of the steel cage are sealed with pipe caps in advance to prevent concrete from entering during casting. After the pile foundation concrete reaches the age, the pile is broken and the central pipe is cut. The central pipe is flush with the pile top elevation, and the pile top is leveled. Finally, the anchor dynamometer is installed and tension loading construction is carried out.

[0007] In the utility model, in order to simulate the static load test by applying force on the test pile with anchor cables, a channel is reserved for the construction of the high-pressure rotary grouting anchoring section to ensure that the high-pressure rotary grouting anchoring section is located directly below the pile bottom so that after the anchor cables are tensioned and stressed, the pile top can be subjected to the vertical downward pressure of the axis. Therefore, a steel pipe is added in the middle of the steel cage.

[0008] In the above pile static load test structure, preferably, the steel cage includes a plurality of vertical main bars, the outer circumferences of the plurality of vertical main bars are fixedly provided with spiral stirrups, the inner circumferences of the plurality of vertical main bars are fixedly provided with a plurality of reinforcing stirrups, transverse steel bars are provided between the reinforcing stirrups, the middle of the transverse steel bars is fixedly connected to the central pipe, and the two ends of the transverse steel bars are arranged at the junction of the reinforcing stirrups and the vertical main bars. More preferably, a pair of inclined steel bars are also provided between the reinforcing stirrups and the central pipe, one end of the inclined steel bars is fixedly connected to the central pipe, and the other end of the inclined steel bars is arranged at the junction of the reinforcing stirrups and the vertical main bars. In order to ensure that the conduit can be lowered from the vacant position between the steel pipe and the steel cage during construction and the pouring can be completed smoothly, the welding accuracy and quality need to be ensured when the steel pipe is welded to the steel cage, so that the steel pipe is in the center of the steel cage. The utility model welds the central pipe to the steel cage by the above welding method, which can ensure the welding accuracy and welding quality of the central pipe.

[0009] In the above-mentioned pile static load test structure, preferably, the high-pressure rotary spraying anchoring section includes a pre-drilled hole body and an anchor body obtained by high-pressure rotary spraying of the pre-drilled hole body, the pre-drilled hole body is arranged just below the central pipe, and the lower end of the anchor cable assembly is located in the pre-drilled hole body and is consolidated with the anchor body as a whole. The pre-drilled hole body is also called a guide hole, and the purpose is to allow the anchor cable assembly to be smoothly pushed down to the designed bottom elevation, otherwise it may be difficult to push down the anchor cable assembly in the harder clay layer and sand layer. After the drilling is completed, the anchor cable assembly is lowered, and then rotary spraying is performed. High-pressure rotary spraying will spray out high-pressure cement slurry. The cement slurry and the soil are stirred and mixed together under high pressure, so that the soil is reinforced, and the cement slurry also wraps the anchor cable assembly. The rotary spraying process is mainly to spray cement slurry while rotating and pulling up the drill rod to reach the elevation, and then the anchor body is applied. At this time, the anchor cable assembly and the anchor body form a whole.

[0010] In the above-mentioned pile static load test structure, preferably, the anchor cable assembly is a pressure-distributed anchor cable structure, including multiple first anchor cables and multiple second anchor cables, the first anchor cables and the second anchor cables have different lengths and the lower ends are located at different elevations, a second bearing body is arranged at the lower end of the second anchor cable, the first anchor cable is arranged through the second bearing body, a first bearing body is arranged at the lower end of the first anchor cable, and the upper ends of the first anchor cable and the second anchor cables are flush.

[0011] In the above-mentioned pile static load test structure, preferably, the test device includes a force-applying part for providing an upward pulling force to the upper end of the anchor cable assembly and a detection part for detecting the strain of the test pile body.

[0012] In the above pile static load test structure, preferably, the force-applying part includes an anchor plate, an anchor dynamometer (intelligent string anchor dynamometer), a locking anchor and a tensioning device (such as a jack) for applying tension to the anchor assembly. The anchor plate is arranged on the top of the test pile, and the upper end of the anchor in the anchor assembly passes through the anchor plate and the anchor dynamometer in sequence and is connected to the locking anchor and exposed. The intelligent string anchor dynamometer is installed at the end of the anchor to measure the anchor force. The anchor dynamometer can be equipped with a monitoring terminal system, which can monitor the prestress of the test pile in real time during the static load test, and can set a prestress loss threshold at the monitoring terminal. When the prestress loss of the anchor reaches the threshold, it will automatically alarm, and existing conventional devices can be used. The above tensioning device is used to act when tension needs to be applied. When tension needs to be applied, the tensioning device is connected to the anchor. After tensioning is completed, the tensioning device can be removed.

[0013] In the above pile static load test structure, preferably, the detection part includes a strain sensing grating fiber sensor (densely distributed at a fixed point), a U-shaped strain sensing grating fiber and a fiber demodulator (densely distributed in a cabinet), the strain sensing grating fiber sensor is arranged on the U-shaped strain sensing grating fiber, the U-shaped strain sensing grating fiber is fixed in the test pile, and the fiber demodulator is connected to the U-shaped strain sensing grating fiber. More preferably, a pair of U-shaped strain sensing grating fibers are vertically crossed, a plurality of strain sensing grating fiber sensors are arranged, and are evenly distributed on the U-shaped strain sensing grating fiber, and the distribution positions of the strain sensing grating fiber sensors on a pair of U-shaped strain sensing grating fibers remain the same.

[0014] In the utility model, the fixed-point densely distributed strain sensing grating fiber optic sensor is arranged on the vertical main reinforcement side wall of the test pile reinforcement cage using a "double U-loop". The two U-shaped loops are perpendicular to each other, and the heights of the fixed-point strain sensors on the left and right sides of the U-shaped loop correspond to each other and are evenly spaced. The spacing between the corresponding sensors on both sides is the diameter of the test pile reinforcement cage. The sensor has good mechanical properties and tensile and compressive properties, and can be well coupled with the concrete structure to achieve spatial non-continuous segmented strain monitoring. The cabinet-type densely distributed fiber optic demodulator has enough channels to integrate all the loops of all the test piles into one, monitor the strain of each sensor in all loops in real time, and can automatically calculate the force and deformation data of the pile body according to the test pile parameters, and can output synchronously in a visual interface such as an image, and can automatically store process data for later export and analysis. The above-mentioned strain sensing grating fiber optic sensor, U-shaped strain sensing grating fiber and fiber optic demodulator can all use existing conventional devices.

[0015] The utility model adopts a pressure dispersion type anchor cable to apply prestressed pile static load test structure, which is used to carry out pile static load test. The test structure is mainly divided into four parts, namely, test pile, high pressure jet grouting anchor section, anchor cable assembly and test device, each part is briefly described as follows:

[0016] The test pile is a pre-designed pile for static load test, which includes a steel cage, and the central welded central pipe (which can be a steel pipe) of the steel cage is used to reserve a drilling channel, high-pressure rotary spraying and anchor cable setting, and the top and bottom of the central steel pipe are both beyond the steel cage. The diameter, wall thickness and length of the steel pipe welded in the center of the steel cage must meet the requirements, and the "transverse steel bar + inclined steel bar welding" method is used to weld it firmly, so that the pre-drilled hole body formed later can be along the axis direction of the test pile. The diameter, pile length and reinforcement of the test pile are determined according to the test conditions, and can be designed according to the test purpose and test environment. The pile static load test structure of the utility model can be applied to test piles of various models and specifications.

[0017] The high-pressure rotary grouting anchoring section uses high-pressure rotary grouting to form a pressure-dispersed anchor body. Through high-pressure rotary grouting, the anchor cable assembly, cement mortar, and surrounding soil form a whole as an anchor body, which is used to fix the lower end of the anchor cable assembly. The high-pressure rotary grouting anchoring section first forms an anchor cable insertion channel through a pre-drilled hole, then inserts the anchor cable and expands the hole with high-pressure rotary grouting to reach the designed position at the bottom of the anchoring section.

[0018] The lower end of the anchor cable assembly is fixed in the high-pressure jet-sprayed anchoring section, and the upper end extends outward and is located above the test pile, and the tensioned anchor cable is locked above. The specific structural form of the anchor cable assembly may include an anchor cable, a spiral rib, a steel bearing body, a limit plate, etc.

[0019] The test device includes a detection part and a force-applying part. The detection part includes a U-shaped strain sensing grating optical fiber tied to the vertical main reinforcement of the test pile reinforcement cage. The U-shaped strain sensing grating optical fiber is densely distributed with strain sensing grating optical fiber sensors at fixed points to monitor the strain of the test pile body. The detection part also includes a cabinet-type densely distributed optical fiber demodulator to automatically monitor and collect the strain test data of the pile body in real time, synchronously calculate the force on the pile body and output it intuitively in the form of images. The force-applying part mainly includes an anchor and an intelligent string anchor dynamometer installed at the anchor, which is used to lock and monitor the cable force value of the tensioned anchor cable.

[0020] The construction method of the pile static load test structure using the pressure dispersion anchor cable to apply prestress in the utility model may include the following steps:

[0021] S1. Design and construction of test piles. Design the diameter, pile length, and reinforcement of the test piles according to the test requirements. Weld a steel pipe in the center of the steel cage to reserve a drilling channel. Tie the fixed-point dense distributed strain sensing grating fiber optic sensor firmly to the vertical main reinforcement of the steel cage. After drilling, lower the steel cage and pour concrete.

[0022] S2. Construction of high-pressure rotary jet anchoring section and anchor cable assembly: After the concrete reaches the specified age (28d), lower the drill rod along the steel pipe channel reserved in the test pile foundation, drill a hole to the designed bottom elevation of the high-pressure rotary jet anchoring section, replace the drill bit and push in the anchor cable assembly until it reaches the designed position at the bottom of the anchor body, and use high-pressure rotary jet cement slurry to expand the hole and construct the anchor body. At the same time, slowly rotate and pull up the drill rod at the designed speed to the designed top elevation of the anchor body.

[0023] S3. Prestress the anchor cables and conduct tests. After the high-pressure rotary grouting anchoring section reaches the specified age (28 days), tension the anchor cables and lock them to the test design value. Install the intelligent string-type anchor cable dynamometer, connect the "double U-loop" grating optical fiber to the cabinet-type densely distributed optical fiber demodulator, connect the dynamometer and demodulator to the integrated control terminal, and monitor the strain of each sensor on the pile body and the anchor cable force in real time.

[0024] More specifically, step S1 specifically includes:

[0025] S11. According to the design drawings, weld the steel cage required for the test pile foundation, and weld the steel pipe firmly in the center of the steel cage. The steel pipe is used as a reserved drilling channel. The bottom of the steel pipe is lower than the bottom of the steel cage, so that the steel pipe is inserted into the soil to a certain depth after the steel cage is lowered. The top of the steel pipe is slightly higher than the steel cage, and the top and bottom of the steel pipe are effectively blocked to prevent concrete from entering the pipe from the bottom or top of the steel pipe when pouring the test pile. Two U-shaped strain sensing sensors are tied to the vertical main reinforcement of the steel cage to form a U-shaped loop. The top (bottom) elevation of the grating fiber optic sensor is located at the top (bottom) reinforcement stirrup of the steel cage. The grating fiber optic sensor at the bottom of the steel cage is arranged circumferentially close to the inner side of the reinforcement stirrup.

[0026] S12. Use mud wall to assist in the construction of bored pile drilling.

[0027] S13. Hoist and lower the steel cage, and check whether the grating fiber optic sensor is firmly tied during the lowering process. In addition, if the steel cage is made in sections, the grating fiber optic sensor needs to be arranged on the bottom cage (the first section of the steel cage, i.e. the bottom section) first, and the remaining reserved grating fiber optic sensors are tied to the steel cage in sequence as the steel cage is overlapped and lowered, and ensure that the main reinforcement tied on one side of the U-shaped loop of each section of the steel cage is the same, and the upper and lower sections are kept corresponding.

[0028] S14. Lower the concrete conduit to pour the foundation piles.

[0029] More specifically, step S2 specifically includes:

[0030] S21. After the test pile reaches the specified age (28 days), lower the drill rod along the reserved steel pipe channel and start drilling downward from the bottom of the test pile according to the drilling diameter and depth designed for the high-pressure jet grouting anchoring section.

[0031] S22. After drilling to the designed depth, pull out the drilling rod, replace the drill bit, and push in and lower the anchor cable assembly until the designed bottom elevation of the anchor body is reached.

[0032] S23, high-pressure rotary jet cement slurry is used to expand the hole, and the soil is reinforced by rotary jet mixing. At the same time, the drill rod is slowly rotated at the designed speed and pulled up to the designed top elevation of the anchor body. The rotary jet can be repeated up and down to achieve a better reinforcement effect.

[0033] S24. After high-pressure jet grouting is completed to form the anchor body, the high-pressure jet grouting drill rod is taken out, and the cavity from the designed top elevation of the anchor body to the pre-drilled hole section at the bottom of the pile and the middle of the steel pipe remains hollow.

[0034] More specifically, step S3 specifically includes:

[0035] S31. After the high-pressure rotary grouting anchoring section reaches the specified age (28 days), the top of the test pile is leveled, and the anchor cable is tensioned and locked to the prestress design value at the top of the pile.

[0036] S32. Install an intelligent string-type anchor force meter to monitor the anchor cable force in real time.

[0037] S33, connect the "double U loop" grating optical fiber to the cabinet-type dense distributed optical fiber demodulator.

[0038] S34. Connect the intelligent string-type anchor force gauge and the cabinet-type densely distributed optical fiber demodulator to the integrated control terminal to conduct real-time monitoring, transmission and early warning of the strain of each sensor on the pile body and the anchor cable force.

[0039] Compared with the prior art, the advantages of the utility model are:

[0040] 1. The utility model adopts the anchor cable to apply prestress to the pile foundation static load test structure. When the test pile foundation is subjected to static load test, it occupies a small space and does not affect the construction of surrounding buildings. It has low requirements on the surrounding environment and little interference. Compared with the pile loading method and the anchor pile method, it reduces the on-site in-situ test cost and saves time and labor.

[0041] 2. The utility model adopts anchor cables to apply prestress to the pile foundation static load test structure, which is convenient to construct, highly flexible, and highly adaptable. The high-pressure rotary grouting anchoring section and the tension value can be flexibly adjusted according to the test requirements and the test stratum.

[0042] 3. The utility model adopts anchor cable to apply prestressed pile static load test structure, which has strong adaptability to the stratum. The bottom of the pile static load test structure is a high-pressure rotary jet anchoring section. High-pressure rotary jet is particularly suitable for loose soil, soft soil, silt and other unfavorable geological soil layers. When such static load test is needed under such stratum conditions and the site conditions are limited, the structure is used for loading with strong adaptability and good effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 It is a structural schematic diagram of the pile static load test structure of the embodiment.

[0045] Figure 2 It is a schematic structural diagram of a reinforcement cage and a central pipe of an embodiment.

[0046] Figure 3 for Figure 2 Section view of the AA plane.

[0047] Figure 4 Schematic diagram of the welding structure of the steel cage and the central pipe in the embodiment.

[0048] Figure 5 It is a schematic diagram of the structure of the pile static load test structure in the embodiment after omitting some components.

[0049] Figure 6 for Figure 5 Sectional view of the BB plane.

[0050] Figure 7 for Figure 5 Section view of the CC plane.

[0051] Figure 8 Schematic diagram of the construction and testing process of the static load test structure of the pile foundation in the embodiment (in the figure, (a) is the welding of the steel cage and the arrangement of the optical fiber; (b) is the lowering of the steel cage; (c) is the pouring of the concrete for the test pile body; (d) is the lead hole; (e) is the high-pressure rotary spraying to make the anchor body; (f) is the tensioning of the anchor cable and the installation of the anchor cable dynamometer and the locking of the anchor; (g) is the connection control terminal for integrated testing).

[0052] Legend:

[0053] 1. Test pile; 11. Pile concrete; 2. Steel cage; 21. Center pipe; 22. Reinforced stirrups; 23. Vertical main reinforcement; 24. Spiral stirrups; 25. Transverse reinforcement; 26. Inclined reinforcement; 3. High-pressure rotary spray anchoring section; 31. Anchor body; 32. Pre-drilled body; 4. Anchor cable assembly; 41. First anchor cable; 42. Second anchor cable; 43. Second bearing body; 44. First bearing body; 5. Test device; 51. Strain sensing grating fiber sensor; 52. U-shaped strain sensing grating fiber; 53. Anchor cable dynamometer; 54. Anchor pad; 55. Fiber demodulator; 56. Locking anchor. DETAILED DESCRIPTION

[0054] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and carefully below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0055] Unless otherwise defined, all professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present utility model.

[0056] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0057] Example:

[0058] like Figure 1 As shown, the static load test structure of the pile using anchor cables to apply prestress in this embodiment includes a test pile 1, a high-pressure rotary spraying anchoring section 3, an anchor cable assembly 4 and a test device 5 for providing an upward pulling force to the anchor cable assembly 4 and detecting the strain of the pile body of the test pile 1. The high-pressure rotary spraying anchoring section 3 is located below the test pile 1, and the lower end of the anchor cable assembly 4 is fixed in the high-pressure rotary spraying anchoring section 3. A central pipe 21 is provided in the center of the test pile 1, and the upper end of the anchor cable assembly 4 extends upward through the central pipe 21 to the top of the test pile 1 and is connected to the test device 5.

[0059] like Figure 2 , Figure 3 As shown, in this embodiment, the test pile 1 includes a pile concrete 11 and a steel cage 2 arranged in the pile concrete 11, and a central pipe 21 is fixed at the center of the steel cage 2. The central pipe 21 is a steel pipe, and the top and bottom of the central pipe 21 both exceed the steel cage 2.

[0060] like Figure 4 As shown, in this embodiment, the steel cage 2 includes a plurality of vertical main bars 23, spiral stirrups 24 are fixedly provided on the outer circumference of the plurality of vertical main bars 23, a plurality of reinforcing stirrups 22 are fixedly provided on the inner circumference of the plurality of vertical main bars 23, transverse steel bars 25 are provided between the reinforcing stirrups 22, the middle of the transverse steel bars 25 is fixedly connected to the central pipe 21, and the two ends of the transverse steel bars 25 are arranged at the junction of the reinforcing stirrups 22 and the vertical main bars 23. A pair of inclined steel bars 26 are also provided between the reinforcing stirrups 22 and the central pipe 21, one end of the inclined steel bars 26 is fixedly connected to the central pipe 21, and the other end of the inclined steel bars 26 is arranged at the junction of the reinforcing stirrups 22 and the vertical main bars 23.

[0061] like Figure 1 , Figure 5 As shown, in this embodiment, the high-pressure rotary spraying anchoring section 3 includes a pre-drilled body 32 and an anchor body 31 obtained by high-pressure rotary spraying of the pre-drilled body 32. The pre-drilled body 32 is arranged just below the central pipe 21, and the lower end of the anchor cable assembly 4 is located in the pre-drilled body 32 and is consolidated into a whole with the anchor body 31.

[0062] like Figure 5 , Figure 6 , Figure 7As shown, in this embodiment, the anchor cable assembly 4 is a pressure-distributing anchor cable structure, including multiple first anchor cables 41 and multiple second anchor cables 42. The first anchor cables 41 and the second anchor cables 42 have different lengths and their lower ends are located at different elevations. A second carrier 43 is arranged at the lower end of the second anchor cable 42, the first anchor cable 41 is arranged through the second carrier 43, the first carrier 44 is arranged at the lower end of the first anchor cable 41, and the upper ends of the first anchor cable 41 and the second anchor cable 42 are flush.

[0063] like Figure 1 , Figure 5 As shown, in this embodiment, the testing device 5 includes a force-applying part for providing an upward pulling force to the upper end of the anchor cable assembly 4 and a detection part for detecting the strain of the pile body of the test pile 1 .

[0064] Specifically, the force-applying part includes an anchor plate 54, an anchor dynamometer 53, a locking anchor 56 and a tensioning device for applying tension to the anchor assembly 4. The anchor plate 54 is arranged on the top of the test pile 1, and the upper end of the anchor in the anchor assembly 4 passes through the anchor plate 54 and the anchor dynamometer 53 in sequence and is connected to the locking anchor 56 and exposed.

[0065] Specifically, the detection part includes a strain sensing grating fiber sensor 51, a U-shaped strain sensing grating fiber 52 and a fiber demodulator 55. The strain sensing grating fiber sensor 51 is arranged on the U-shaped strain sensing grating fiber 52, the U-shaped strain sensing grating fiber 52 is fixed in the test pile 1, and the fiber demodulator 55 is connected to the U-shaped strain sensing grating fiber 52. A pair of U-shaped strain sensing grating fibers 52 are vertically crossed, and a plurality of strain sensing grating fiber sensors 51 are arranged, which are evenly distributed on the U-shaped strain sensing grating fiber 52, and the distribution positions of the strain sensing grating fiber sensors 51 on a pair of U-shaped strain sensing grating fibers 52 remain the same.

[0066] like Figure 8 As shown, the construction method of the pile static load test structure using the pressure dispersion anchor cable to apply prestress in this embodiment may include the following steps:

[0067] S1. Design and construction of the test pile 1. The diameter, pile length, reinforcement, etc. of the test pile 1 are designed according to the test requirements. A steel pipe is welded in the center of the steel cage 2 to reserve a drilling channel. The fixed-point dense distributed strain sensing grating fiber optic sensor 51 is firmly tied to the vertical main reinforcement 23 of the steel cage 2. After the hole is formed, the steel cage 2 is lowered and concrete is poured.

[0068] S2. Construction of high-pressure rotary spraying anchor section 3 and anchor cable assembly 4. After the concrete reaches the specified age (28d), lower the drill rod along the steel pipe channel reserved in the test pile 1 to drill a hole to the designed bottom elevation of the high-pressure rotary spraying anchor section 3. Pull out the drill rod, replace the drill bit, and push in and lower the anchor cable assembly 4 until it reaches the designed position at the bottom of the anchor body 31. Use high-pressure rotary spraying cement slurry to expand the hole and construct the pressure-dispersed anchor body 31. At the same time, slowly rotate at the designed speed and pull up the drill rod to the designed top elevation of the anchor body 31.

[0069] S3, tensioning anchor cables to apply prestress and test, after the high-pressure rotary grouting anchoring section 3 reaches the specified age (28d), tension the anchor cables and lock them to the test design value, install the intelligent string-type anchor cable dynamometer 53, connect the "double U-loop" grating optical fiber to the cabinet-type dense distributed optical fiber demodulator 55, connect the dynamometer and demodulator to the integrated control terminal, and monitor the strain of each sensor on the pile body and the anchor cable force in real time.

[0070] The above description is only the preferred embodiment of the utility model, and is not intended to limit the utility model. For those skilled in the art, the utility model can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the utility model shall be included in the protection scope of the utility model.

Claims

1. A pile static load test structure using anchor cables to apply prestress, characterized in that: The invention comprises a test pile (1), a high-pressure rotary grouting anchoring section (3), an anchor cable assembly (4), and a testing device (5) for providing an upward pulling force to the anchor cable assembly (4) and detecting the strain of the pile body of the test pile (1); the high-pressure rotary grouting anchoring section (3) is located below the test pile (1); the lower end of the anchor cable assembly (4) is fixed in the high-pressure rotary grouting anchoring section (3); a central pipe (21) is provided at the center of the test pile (1); the upper end of the anchor cable assembly (4) extends upward through the central pipe (21) to the top of the test pile (1) and is connected to the testing device (5).

2. The pile static load test structure according to claim 1, characterized in that: The test pile foundation (1) comprises pile foundation concrete (11) and a steel cage (2) arranged in the pile foundation concrete (11); the central pipe (21) is fixed at the center of the steel cage (2); the central pipe (21) is a steel pipe; the top and bottom of the central pipe (21) both extend beyond the steel cage (2).

3. The pile static load test structure according to claim 2, characterized in that: The steel cage (2) comprises a plurality of vertical main bars (23), the outer circumferences of the plurality of vertical main bars (23) are fixedly provided with spiral stirrups (24), the inner circumferences of the plurality of vertical main bars (23) are fixedly provided with a plurality of reinforcing stirrups (22), transverse steel bars (25) are provided between the reinforcing stirrups (22), the middle portion of the transverse steel bars (25) is fixedly connected to the central pipe (21), and the two ends of the transverse steel bars (25) are provided at the junction of the reinforcing stirrups (22) and the vertical main bars (23).

4. The pile static load test structure according to claim 3, characterized in that: A pair of inclined steel bars (26) are also provided between the reinforcing stirrups (22) and the central pipe (21), one end of the inclined steel bar (26) is fixedly connected to the central pipe (21), and the other end of the inclined steel bar (26) is arranged at the junction of the reinforcing stirrups (22) and the vertical main reinforcement (23).

5. The pile static load test structure according to any one of claims 1 to 4, characterized in that: The high-pressure rotary spraying anchoring section (3) comprises a pre-drilled body (32) and an anchor body (31) obtained by high-pressure rotary spraying of the pre-drilled body (32); the pre-drilled body (32) is arranged just below the central pipe (21); the lower end of the anchor cable assembly (4) is located in the pre-drilled body (32) and is fixed to the anchor body (31) as a whole.

6. The pile static load test structure according to any one of claims 1 to 4, characterized in that: The anchor cable assembly (4) is a pressure-dispersed anchor cable structure, comprising a plurality of first anchor cables (41) and a plurality of second anchor cables (42); the first anchor cables (41) and the second anchor cables (42) have different lengths and their lower ends are located at different elevations; a second bearing body (43) is arranged at the lower end of the second anchor cable (42); the first anchor cable (41) passes through the second bearing body (43); a first bearing body (44) is arranged at the lower end of the first anchor cable (41); and the upper ends of the first anchor cable (41) and the second anchor cable (42) are flush.

7. The pile static load test structure according to any one of claims 1 to 4, characterized in that: The testing device (5) comprises a force-applying part for providing an upward pulling force to the upper end of the anchor cable assembly (4) and a detection part for detecting the strain of the pile body of the test pile (1).

8. The pile static load test structure according to claim 7, characterized in that: The force-applying part comprises an anchor plate (54), an anchor dynamometer (53), a locking anchor (56) and a tensioning device for applying tension to the anchor assembly (4); the anchor plate (54) is arranged on the top of the test pile (1); the upper end of the anchor in the anchor assembly (4) passes through the anchor plate (54) and the anchor dynamometer (53) in sequence and is connected to the locking anchor (56) and exposed.

9. The pile static load test structure according to claim 7, characterized in that: The detection unit comprises a strain sensing grating optical fiber sensor (51), a U-shaped strain sensing grating optical fiber (52) and an optical fiber demodulator (55); the strain sensing grating optical fiber sensor (51) is arranged on the U-shaped strain sensing grating optical fiber (52); the U-shaped strain sensing grating optical fiber (52) is fixed in the test pile (1); and the optical fiber demodulator (55) is connected to the U-shaped strain sensing grating optical fiber (52).

10. The pile static load test structure according to claim 9, characterized in that: A pair of U-shaped strain sensing grating optical fibers (52) are vertically crossed, a plurality of strain sensing grating optical fiber sensors (51) are provided and evenly distributed on the U-shaped strain sensing grating optical fibers (52), and the distribution positions of the strain sensing grating optical fiber sensors (51) on the pair of U-shaped strain sensing grating optical fibers (52) remain the same.

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