Full-length bonding type anti-pulling anchor rod group anchor bearing capacity testing system and testing method

Abstract

The invention discloses a full-length bonding type anti-pulling anchor rod group anchor bearing capacity testing system and testing method. The system comprises an upper pulling screw rod, a counter-force pier, a steel beam, a jack and an upper pulling screw rod. The counter-force piers are arranged on the two sides of the anchor rod group, and the steel beams are arranged on the tops of the counter-force piers. Base plates are arranged on the steel beams; a jack is arranged at the top of the load sensor; the tops of the jacks are connected with bearing plates; a plurality of up-pulling screw rods sequentially penetrate through the bearing plate, the base plate and the connecting plate from top to bottom, the top ends of the plurality of up-pulling screw rods are fixed on the bearing plate, and the bottom ends of the plurality of up-pulling screw rods are fixed on the connecting plate; the top of the anchor rod group is fixed on the connecting plate; and a fiber grating strain sensor is fixed on each anchor rod of the anchor rod group. All parts of the whole test system are mechanically connected, compared with a conventional connection mode, mechanical connection has the advantages of being stable, reliable, easy and convenient to operate, high in construction speed and the like, and meanwhile pollution and fire hazards are avoided in the installation process.

Description

Technical Field

[0001] The invention belongs to the field of foundation engineering, and in particular relates to a full-length bonded pull-out anchor group anchor bearing capacity testing system and testing method. Background Art

[0002] The foundation pullout problem has always been an important issue in geotechnical engineering. The focus is on how to resist the pullout load of the building to ensure the stability of the building foundation. The foundation pullout problem is widely present in underground garages, subway stations, sunken squares, super high-rise buildings, offshore dock platforms, suspension bridges, cable-stayed bridges, and power line towers. At present, the common method to solve the pullout problem is to set up pullout piles to bear the pullout load of buildings (structures). However, engineering practice shows that for foundation conditions dominated by bedrock, pullout piles have a series of problems such as construction difficulties and low efficiency. In the face of these problems, setting up full-length bonded pullout anchor rods is a good solution. It has the advantages of strong stratum adaptability, good seismic performance, simple construction, and low cost. Therefore, full-length bonded pullout anchor rods are widely used in pullout projects with bedrock as the main foundation conditions.

[0003] In the prior art, the design of full-length bonded pull-out anchors focuses more on the calculation of the pull-out bearing capacity of a single anchor and the control of influencing factors, but pays little attention to the deformation characteristics and failure mechanism of the anchor. Therefore, full-length bonded pull-out anchors are often designed by increasing the safety factor, which is very blind. In most cases, the design of anchors needs to be controlled by deformation. In actual engineering, the study of the deformation mechanism and failure mechanism of anchors is very important, which is of great significance for studying the failure causes of anchors and improving the strength and long-term service performance of anchors. At the same time, in the current research, there are more tests on single full-length bonded pull-out anchors, while there are few tests and studies on the bearing capacity, deformation characteristics and failure mechanism of full-length bonded pull-out anchor groups. In actual engineering, the mutual influence between the anchors in the group and the superposition effect of the pull-out load will also seriously affect the pull-out bearing capacity and long-term service performance of the full-length bonded pull-out anchor. Therefore, seeking to design a full-length bonded pull-out anchor group bearing capacity test system to test and study the bearing capacity, deformation mechanism and failure mechanism of full-length bonded pull-out anchor groups has very important social and economic significance.

[0004] At present, there are many methods for testing the bearing capacity and deformation of pull-out anchor rods in similar technologies that have been disclosed. CN221572143U discloses a new type of anchor pull-out bearing capacity detection device, but it can only test the pull-out bearing capacity of a single anchor rod, without considering the mutual influence between anchor rods in the anchor rod group and the influence of the superposition effect of the pull-out load on the anchor group. CN115573405A discloses an anchor pull-out bearing capacity detection device, which can test the bearing capacity and deformation of one or more anchor rods at the same time, but it can only measure the deformation of the anchor rod head, and cannot measure the deformation of the entire anchor rod, so it cannot test and study the deformation characteristics and failure mechanism of the anchor rod. CN215253056U discloses an anchor pull-out bearing capacity testing device, which can test the bearing capacity of a group of anchors and takes into account the mutual influence between the anchors in the anchor group. However, it only tests the pull-out bearing capacity and the deformation of the anchor head, and does not test the overall deformation of the group of anchors. It is impossible to test and study the bearing capacity, deformation mechanism and failure mechanism of the group of anchors. In addition, the testing device applies a pull-out load through two jacks. During the test, it is difficult to ensure that the axis of the anchor is pulled, which is inconsistent with the actual service condition of the anchor group. Summary of the invention

[0005] In order to solve the technical problems existing in the prior art, the present invention discloses a full-length bonded pull-out anchor group anchor bearing capacity testing system, which solves the problem that the test device in the current group anchor bearing capacity detection is unable to provide a large pull-out load, and can perform group anchor bearing capacity detection on anchor groups with a larger number, a larger diameter, and a longer anchoring length; it solves the problem that the pull-out load applied in the current group anchor bearing capacity testing process is difficult to ensure that the anchor axis is tensile, which is more in line with the actual service conditions of the anchor group and, at the same time, the test device will not be deformed or damaged due to eccentric compression during the test, which will affect the test results, thereby ensuring the stability and safety of the test process and the test results. The accuracy of the method is improved; the problem that only the bearing capacity and the deformation of the anchor head can be tested in the current group anchor bearing capacity detection, but the overall deformation of the anchor cannot be measured. The overall deformation of the anchor can be detected while the bearing capacity of the group anchor is detected, ensuring that the pull-out load on the anchor during the test corresponds to the overall deformation, and then the bearing capacity, deformation mechanism and failure mechanism of the full-length bonded pull-out anchor group can be tested and studied. At the same time, the bearing capacity test results of the group anchor can be compared with the bearing capacity of a single anchor, providing a reference for the design of the group anchor in actual engineering in terms of the mutual influence between the anchors in the anchor group and the influence of the superposition effect of the pull-out load on the group anchor.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention discloses a full-length bonded pull-out anchor group anchor bearing capacity testing system, comprising a pull-out screw, a reaction pier, a steel beam, a jack and a pull-out screw;

[0008] The reaction piers are arranged around the anchor rod group, and a steel beam is arranged on the top of the reaction pier; a pad is arranged on the steel beam; a jack is arranged on the pad, and a load sensor is arranged at the bottom of the jack; the top of the jack is connected to the pressure plate; a plurality of pull-up screws pass through the pressure plate, the pad, and the connecting plate from top to bottom in sequence, the top ends of the plurality of pull-up screws are fixed on the pressure plate, and the bottom ends of the plurality of pull-up screws are fixed on the connecting plate; and the top of the anchor rod group is fixed on the connecting plate; a fiber grating strain sensor is fixed on each anchor rod of the anchor rod group.

[0009] As a further technical solution, the pull-up screw is connected to the pressure plate through a first nut, and a first pad is arranged between the first nut and the pressure plate; the pull-up screw is connected to the connecting plate through a third nut, and a third pad is arranged between the third nut and the connecting plate.

[0010] As a further technical solution, the anchor rod is connected to the connecting plate through a second nut, and a second pad is arranged between the second nut and the connecting plate.

[0011] As a further technical solution, the fiber Bragg grating strain sensors should be arranged on the anchor rod in a dense manner at the top and sparse manner at the bottom.

[0012] As a further technical solution, the connection position between the pull-up screw rod and the connection plate is located outside the connection position between the anchor rod and the connection plate.

[0013] As a further technical solution, the fiber Bragg grating strain sensor is fixed by a base bracket, an anchoring clamp and a clamp screw; the base bracket is fixed to the anchor rod body by welding, and the clamp screw fixes the anchoring clamp and the optical fiber to the base bracket.

[0014] As a further technical solution, the connecting plate is made of Q335B steel, and a set distance is reserved between the center point of the outer reserved hole and the edge of the connecting plate; a set distance is reserved between the center point of the inner reserved hole and the edge of the connecting plate.

[0015] As a further technical solution, the steel beam is two box sections welded from three I-beams; two holes need to be reserved at the center of the top plate and the bottom plate of each box section, and the diameter of the holes is larger than the pull-up screw.

[0016] As a further technical solution, the strength point of the jack is located at the center of the anchor rod group.

[0017] In a second aspect, the present invention also provides a testing method for a full-length bonded pull-out anchor group anchor bearing capacity testing system, as follows:

[0018] Step 1: Install the optical fiber and the fiber grating strain sensor on the anchor rod;

[0019] A location with suitable foundation conditions is selected as the test site. After the test site is completed, the base bracket is fixed to the anchor rod body by welding, and the anchor clamp and the optical fiber are fixed to the base bracket using clamp screws to ensure that the optical fiber and the fiber grating strain sensor can deform in coordination with the anchor rod body to accurately measure the deformation of each position of the anchor rod body;

[0020] Step 2: Install the anchor rod

[0021] After the installation of the optical fiber and fiber Bragg grating strain sensor is completed, the anchor rod body is placed in the center of the anchor hole, the gap between the anchor rod body and the anchor hole wall at each position is measured, the anchor rod body is adjusted to the center, and then grouting is performed in the anchor hole;

[0022] Step 3: Install the connecting plate

[0023] After the grouting body is completely solidified, the I-beam is placed on both sides of the anchor hole to place the connecting plate and fix its position. After the I-beam is placed in a suitable position, the connecting plate is passed through the four reserved holes on the inner periphery through the anchor rod body and the connecting plate is placed on the I-beam. The second gasket is passed through the anchor rod body and placed on the connecting plate, and then the second nut is installed to ensure that the second nut is tightly connected and firmly fixed to the anchor rod body through threads;

[0024] Step 4: Install steel beams and reaction piers

[0025] Place the reaction piers on both sides of the anchor hole. The distance between the reaction piers and the anchor hole is determined according to the length of the steel beam. Make the end of the steel beam exceed the reaction piers. Then place the steel beam on the reaction. When placing the steel beam and the reaction piers, ensure that the reserved holes are aligned with the four reserved holes on the outer periphery of the connecting plate.

[0026] Step 5: Install the pressure plate, jack, load sensor, and pad

[0027] Place the pad, load sensor, jack, and pressure plate on the steel beam in sequence, and align the pressure plate, pad, steel beam, and four reserved holes on the periphery of the connecting plate to ensure that the pull-up screw can pass freely during installation;

[0028] Step 6: Install the pull-out screw

[0029] The pull-up screw is passed through the reserved holes from top to bottom in turn through the pressure plate, pad, steel beam and connecting plate. After reserving a suitable length above the pressure plate and below the connecting plate, the first gasket and the third gasket are passed through the pull-up screw and placed on the pressure plate and the connecting plate respectively. Then, the pull-up screw is tightly connected and firmly fixed to the pressure plate and the connecting plate through the first nut and the third nut respectively to ensure that the pull-up screw can transfer the pull-up load applied by the jack to the connecting plate during the test, and then the connecting plate transfers the pull-up load to the anchor rod body.

[0030] Step 7: Calibrate the jack to ensure the accuracy of the load applied at each level during the test, and ensure that the strength of the grouting consolidation body in the anchoring section reaches 15MPa or 75% of the design strength; during the test, the pull-out load applied by the jack is transmitted to the anchor rod body through the pull-out screw and the connecting plate, and the reaction force generated by the jack is transmitted to the ground by the steel beam and the reaction pier. The pull-out load applied by the jack to the anchor rod body during the loading process is tested by the load sensor, and the deformation of the anchor rod body during the loading process is tested by the optical fiber and fiber grating strain sensor;

[0031] Step 8 After the test is completed, the test results are further processed. The bearing capacity obtained from the group anchor bearing capacity test, the deformation of each anchor position, and the deformation mechanism and failure mechanism of each anchor in the group anchor are compared with those of a single anchor. If the difference is large, it means that the mutual influence between the anchors in the anchor group and the superposition effect of the pull-out load have a great influence on the group anchor. In the design of the group anchor in actual engineering, it is necessary to reduce such influence by increasing the spacing between the anchors in the anchor group, so as to optimize the design of the group anchor.

[0032] The beneficial effects of the present invention are as follows:

[0033] The present invention proposes a full-length bonded pull-out anchor group anchor bearing capacity testing system, which takes into account the mutual influence between the anchors in the group anchor and the influence of the superposition effect of the pull-out load, and transmits the pull-out load applied by the jack to the anchor rod body of the group anchor through the pull-out screw, the connecting plate, the first nut, the second nut, and the third nut, and utilizes the steel beam and the reaction pier to transmit the reaction force generated by the jack to the ground, so as to perform a bearing capacity test, and utilizes the load sensor to measure the pull-out load applied by the jack to measure the bearing capacity of the anchor rod body. The connecting plate has extremely high rigidity and is an important test component in the test system that directly transmits the pull-out load applied by the jack to the anchor rod body, and can withstand huge loads without deformation and damage. At the same time, the deformation of the anchor rod at different positions is measured by arranging a fiber Bragg grating strain sensor consisting of four parts: optical fiber, base bracket, anchor clamp and clamp screw. The main parameters, working environment conditions and error correction of the fiber Bragg grating strain sensor are strictly in accordance with the provisions of the current national "Fiber Bragg grating strain sensor for civil engineering" (JG / T 422-2013). The components of the entire test device are mechanically connected. Compared with the conventional connection method, the mechanical connection has the advantages of stability, reliability, simple operation and fast construction speed. At the same time, it will not cause pollution and fire hazards during the installation process. After the test is completed, the deformation of the full-length bonded anti-pullout anchor group measured by the test system corresponds to the bearing capacity, so as to study the deformation mechanism and failure mechanism of the group anchor, which is of great significance for evaluating the bearing capacity and long-term service performance of the full-length bonded anti-pullout anchor group. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Attached Figure 1 It is a schematic diagram of the main structural principle of the present invention;

[0035] Attached Figure 2 It is a schematic diagram of the principle of the anchor and anchor rod connection structure of the present invention (AA section);

[0036] Attached Figure 3 It is a schematic diagram of the cross-sectional structure principle of the reaction beam of the present invention (BB section);

[0037] Attached Figure 4 It is a schematic diagram of the principle of the connecting plate anchor and anchor rod connection structure of the present invention (CC section);

[0038] Attached Figure 5 A schematic diagram of the structural principle of a fiber Bragg grating strain sensor according to the present invention;

[0039] In the figure: 1-pull-up screw, 2-first nut, 2-1-first gasket, 3-pressure plate, 4-jack, 5-load sensor, 6-gasket, 7-steel beam, 8-reaction pier, 9-second nut, 9-1-second gasket, 10-connecting plate, 11-third nut, 11-1-third gasket, 12-I-beam, 13-fiber grating strain sensor, 13-1-optical fiber, 13-2-base bracket, 13-3-anchor clamp, 13-4-clamp screw, 14-anchor rod body, 15-anchor hole.

[0040] Specific construction method

[0041] 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.

[0042] 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;

[0043] In order to solve the deficiencies in the prior art, the present invention proposes a full-length bonded pull-out anchor group anchor bearing capacity testing system, which takes into account the mutual influence between the anchors in the group anchor and the influence of the superposition effect of the pull-out load, and transmits the pull-out load applied by the jack 4 to the anchor rod body 14 of the group anchor through the pull-out screw 1, the connecting plate 10, the first nut 2, the second nut 9, and the third nut 11, and transmits the reaction force generated by the jack 4 to the ground by using the steel beam 7 and the reaction pier 8, so as to perform a bearing capacity test, and uses the load sensor 5 to measure the pull-out load applied by the jack 4 to measure the bearing capacity of the anchor rod body 14. The connecting plate 10 has extremely high rigidity. As an important test component in the test system that directly transmits the pull-out load applied by the jack 4 to the anchor rod body 14, it can withstand huge loads without deformation and damage. At the same time, the deformation of the anchor rod body 14 at different positions is measured by arranging a fiber Bragg grating strain sensor 13 composed of four parts: optical fiber 13-1, base bracket 13-2, anchor clamp 13-3 and clamp screw 13-4. The main parameters, working environment conditions, error correction, etc. of the fiber Bragg grating strain sensor 13 are strictly in accordance with the provisions of the current national "Fiber Bragg grating strain sensor for civil engineering" (JG / T 422-2013). All components of the entire test device are mechanically connected. Compared with conventional connection methods, mechanical connection has the advantages of stability, reliability, simple operation, and fast construction speed. At the same time, it will not cause pollution during the installation process and there is no fire hazard. After the test is completed, the deformation of the full-length bonded anti-pullout anchor group anchor measured by the test system corresponds to the bearing capacity, so as to study the deformation mechanism and failure mechanism of the group anchor, which is of great significance for evaluating the bearing capacity and long-term service performance of the full-length bonded anti-pullout anchor group anchor.

[0044] The full-length bonded anti-pullout anchor group anchor bearing capacity testing system disclosed in this embodiment includes an upper pull-out screw 1, a first nut 2, a first gasket 2-1, a pressure plate 3, a jack 4, a load sensor 5, a pad 6, a steel beam 7, a reaction pier 8, a second nut 9, a second gasket 9-1, a connecting plate 10, a third nut 11, a third gasket 11-1, an I-beam 12, a fiber grating strain sensor 13, an optical fiber 13-1, a base bracket 13-2, an anchoring clamp 13-3, a clamp screw 13-4, an anchor rod body 14, and an anchor hole 15;

[0045] The reaction pier 8 is arranged around the anchor rod group, and the steel beam 7 is arranged on the top of the reaction pier 8; the steel beam 7 is provided with a pad 6; the pad 6 is provided with a jack 4, and the bottom of the jack 4 is a load sensor 5; the jack 4 is connected to the pressure plate 3, and the bearing plate 3 is connected to the connecting plate 10 located below the steel beam 7 through four pull-up screws 1, and the four pull-up screws 1 pass through the pressure plate 3, the pad 6, and the connecting plate 10 from top to bottom in sequence, and the top end is fixed on the pressure plate 3, and the bottom end is fixed on the connecting plate 10; the top of the anchor rod group is fixed on the connecting plate 10;

[0046] Furthermore, a fiber Bragg grating strain sensor 13 is fixed on each anchor rod of the anchor rod group.

[0047] Furthermore, the pull-up screw rod 1 is a finely rolled threaded steel bar with a diameter of 18 mm to 32 mm, and the diameter of the finely rolled threaded steel bar can be adjusted according to the tensile strength required for the test. In the present invention, a 25 mm finely rolled threaded steel bar is used as the pull-up screw rod 1 .

[0048] The first nut 2 and the third nut 11 are made of Q235B or Q335B steel, with a wall thickness of 4 mm to 8 mm and an inner diameter of 18 mm to 32 mm. They are adjusted according to the diameter of the pull-up screw 1 and need to be coupled with the pull-up screw 1. The inner side is provided with threads, so that the first nut 2, the third nut 11 and the pull-up screw 1 can be tightly connected and firmly fixed through threads. The first gasket 2-1 and the third gasket 11-1 are respectively arranged between the first nut 2 and the pressure plate 3, and between the third nut 11 and the connecting plate 10. The first gasket 2 -1 and the third gasket 11-1 are made of Q235B or Q335B steel, with a thickness of 4mm to 8mm. The overall shape is a ring, and the inner diameter of the ring is the same as the diameter of the reserved hole on the pressure plate 3. The outer diameter of the ring can be between 60mm and 80mm, which can be adjusted according to the test needs. The first gasket 2-1 and the third gasket 11-1 can play a role in dispersing the load during the test, thereby protecting the pressure plate 3 and the connecting plate 10 from damage, ensuring the stability of the test system and the accuracy of the test results. The first nut 2 is located above the pressure plate 3 and plays a role in fixing the position of the pressure plate 3 to ensure that the pressure plate 3 can withstand and transmit the pressure applied by the jack 4 during the test; the third nut 11 is located below the connecting plate 10 and plays a role in fixing the position of the connecting plate 10 to ensure that the connecting plate 10 can withstand and transmit the pressure applied by the jack 4 during the test. In the present invention, the first nut 2 and the third nut 11 are made of Q335B steel with an inner diameter of 25 mm and a wall thickness of 6 mm. The first gasket 2-1 and the third gasket 11-1 are made of Q335B steel with an inner diameter of 27 mm, an outer diameter of 70 mm and a thickness of 6 mm.

[0049] The pressure plate 3 and the pad 6 are square steel plates of 500mm×500mm×60mm as a whole, made of Q235B or Q335B steel, and four holes need to be reserved at the four corners. The vertical distance between the center point of each reserved hole and the edge of the pressure plate 3 and the pad 6 can be between 60mm and 100mm, which can be adjusted according to the test needs. The diameter of the reserved hole is adjusted according to the diameter of the pull-up screw 1. The hole diameter needs to be 2mm larger than the diameter of the pull-up screw 1, so that the pull-up screw 1 can freely pass through the reserved hole without bending and deformation, ensuring the stability of the test system and the accuracy of the test results. After installation, the pressure plate 3 is located between the first nut 2 and the jack 4; the pad 6 is located between the jack 4 and the steel beam 7 after installation. In the present invention, the pressure plate 3 and the pad 6 are made of Q335B steel, the diameter of the reserved hole is 27mm, and the vertical distance between the center point of each reserved hole and the edge of the pressure plate 3 and the pad 6 is 80mm.

[0050] Furthermore, the jack 4 in this embodiment adopts a handheld hydraulic through-hole jack. Compared with ordinary jacks, it has a more convenient and flexible working state, and has the advantages of high strength, light weight, and easy operation. It can accurately control the applied load. When pressure is applied during the test, it is placed between the pressure plate 3 and the load sensor 5, and the steel beam 7 is used to apply an upward pull load to the anchor rod body 14, and the load sensor 5 is used to accurately measure the load applied by the jack 4, thereby accurately measuring the bearing capacity of the anchor rod body 14.

[0051] Furthermore, the steel beam 7 in this embodiment is two box sections welded from three I-beams, wherein the I-beams are hot-rolled I-beams made of Q335B material, with an overall size of 560mm×168mm×14.5mm. Two holes need to be reserved at the center of each box section top plate and bottom plate, with a total of eight reserved holes. The positions of the reserved holes can be consistent with the positions of the reserved holes on the pressure plate 3 and the pad 6. The diameter of the reserved holes is adjusted according to the diameter of the pull-up screw 1. The hole diameter needs to be 2mm larger than the diameter of the pull-up screw 1, so that the pull-up screw 1 can freely pass through the reserved holes without bending and deformation, ensuring the stability of the test system and the accuracy of the test results. During the test, the steel beam 7 is placed on the reaction pier 8 to bear the reaction force generated when the jack 4 applies the pull-up load.

[0052] Furthermore, the second nut 9 in this embodiment is made of Q235B or Q335B steel, with a wall thickness of 3 mm to 6 mm and an inner diameter of 32 mm to 40 mm. It is adjusted according to the diameter of the anchor rod body 14 and needs to be coupled with the diameter of the anchor rod body 14. A thread is provided on the inner side, so that the second nut 9 can be tightly connected and firmly fixed to the anchor rod body 14 through the thread. The second nut 9 is located above the connecting plate 10, which can fix the connecting plate 10 and transfer the pull-out load applied by the jack 4 to the anchor rod body 14. A second gasket 9-1 is provided between the second nut 9 and the connecting plate 10. The second gasket 9-1 is made of Q235B or Q335B steel, with a thickness of 4 mm to 8 mm. The overall shape is an annular ring, and the inner diameter of the annular ring is the same as the diameter of the four reserved holes on the inner periphery of the connecting plate 10. The outer diameter of the annular ring can be between 60 mm and 80 mm, which can be adjusted according to the test needs. The second gasket 9-1 can play a role in dispersing the load during the test, thereby protecting the connecting plate 10 from damage, ensuring the stability of the test system and the accuracy of the test results. In the present invention, the second nut 9 is made of Q335B steel, with an inner diameter of 15 mm and a wall thickness of 5 mm. The second gasket 9-1 is made of Q335B steel, with an inner diameter of 22 mm, an outer diameter of 70 mm, and a thickness of 6 mm.

[0053] Furthermore, the connecting plate 10 in this embodiment is located between the second nut 9 and the third nut 11 after installation. The whole is a square steel plate of 600mm×600mm×80mm, made of Q235B or Q335B steel. Eight holes need to be reserved at the four corners. The diameter of the four reserved holes on the periphery is adjusted according to the diameter of the pull-up screw 1. The hole diameter needs to be 2mm larger than the diameter of the pull-up screw 1, so that the pull-up screw 1 can freely pass through the reserved holes without bending and deformation, ensuring the stability of the test system and the accuracy of the test results. The vertical distance between the center point of the reserved hole and the edge of the connecting plate 10 can be between 110mm and 150mm, which can be adjusted according to the test needs; the diameter of the four inner holes is adjusted according to the diameter of the anchor rod body 14, and the hole diameter needs to be 2mm larger than the diameter of the anchor rod body 14, so that the anchor rod body 14 can freely pass through the reserved holes without bending and deformation, ensuring the stability of the test system and the accuracy of the test results. The vertical distance between the center point of each reserved hole and the edge of the connecting plate 10 can be between 150mm and 200mm, which can be adjusted according to the test needs. It should be noted that during the test, the connecting plate 10 is an important test component in the test system that directly transfers the pull-out load applied by the jack 4 to the anchor rod body 14, and needs to withstand huge loads. Therefore, the connecting plate 10 needs to have great rigidity to ensure that it will not be damaged during the test. In the present invention, the connecting plate 10 is made of Q335B steel, the diameter of the outer reserved hole is 27mm, and the vertical distance between the center point of each reserved hole and the edge of the connecting plate 10 is 130mm; the diameter of the inner reserved hole is 22mm, and the vertical distance between the center point of each reserved hole and the edge of the connecting plate 10 is 170mm.

[0054] Further, such as Figure 5 As shown, the fiber Bragg grating strain sensor 13 in this embodiment is composed of four parts: an optical fiber 13-1, a base bracket 13-2, an anchoring clamp 13-3 and a clamp screw 13-4, wherein the base bracket 13-2, the anchoring clamp 13-3 and the clamp screw 13-4 are all made of Q235B or Q335B steel, the base bracket 13-2 is fixed to the anchor rod body 14 by welding, and the anchoring clamp 13-3 and the optical fiber 13-1 are fixed to the base bracket 13-2 by using the clamp screw 13-4, so that the optical fiber 13-1 in the fiber Bragg grating strain sensor 13 can cooperate with the anchor rod body 14 to deform so as to accurately measure the deformation of each position of the anchor rod body 14.

[0055] The specific construction methods are as follows:

[0056] Step 1: Install the fiber Bragg grating strain sensor 13

[0057] Select a location with suitable foundation conditions as the test site. After determining the test site, first make a test foundation. The construction process can be summarized as follows: First, remove the overburden on the surface of the bedrock and level the undulating rock surface; then drill holes according to the foundation plan. When the drilling reaches the designed depth, stop drilling, and then use the pneumatic force of the air compressor to flush and clean the hole. After the test foundation is completed, fix the base bracket 13-2 to the anchor rod body 14 by welding, and use the clamp screw 13-4 to firmly fix the anchor clamp 13-3 and the optical fiber 13-1 to the base bracket 13-2 to ensure that the optical fiber 13-1 in the fiber grating strain sensor 13 can cooperate with the deformation of the anchor rod body 14 to accurately measure the deformation of each position of the anchor rod body 14, such as Figure 5 It should be noted that the fiber Bragg grating strain sensors 13 should be arranged in a dense manner at the top and sparse manner at the bottom. In this embodiment, the anchoring section length of the anchor rod body 14 is 4.5 m. Starting from 0.2 m away from the opening of the anchor hole 15, four fiber Bragg grating strain sensors 13 are arranged on the anchor rod body 14 at a spacing of 0.6 m, and two more fiber Bragg grating strain sensors 13 are arranged at a spacing of 0.8 m, for a total of 6.

[0058] Step 2: Install the anchor rod body 14

[0059] After the fiber Bragg grating strain sensor 13 is installed, the anchor rod body 14 is placed in the center of the anchor hole 15 , the gap between the anchor rod body 14 and the wall of the anchor hole 15 at each position is measured, the anchor rod body 14 is adjusted to be centered, and then grouting is performed in the anchor hole 15 .

[0060] Step 3: Install the connecting plate 10

[0061] After the grouting body is completely solidified, the I-beam 12 is placed on both sides of the anchor hole 15 to place the connecting plate 10 and fix its position. After the I-beam 12 is placed in the appropriate position, the connecting plate 10 is passed through the four reserved holes on the inner periphery through the anchor rod body 14 and the connecting plate 10 is placed on the I-beam 12. The second gasket 9-1 is passed through the anchor rod body 14 and placed on the connecting plate 10, and then the second nut 9 is installed to ensure that the second nut 9 is tightly connected and firmly fixed to the anchor rod body 14 through threads.

[0062] Step 4: Install the steel beam 7 and the reaction pier 8

[0063] Place the reaction pier 8 on both sides of the anchor hole 15. The distance between the reaction pier 8 and the anchor hole 15 is determined according to the length of the steel beam 7, so that the end of the steel beam 7 exceeds the reaction pier 8 by 1m, and then place the steel beam 7 on the reaction pier 8. It should be noted that when placing the steel beam 7 and the reaction pier 8, the reserved holes must be aligned with the four reserved holes on the outer periphery of the connecting plate 10 to ensure that the pull-out screw 1 can pass freely during installation.

[0064] Step 5: Install the pressure plate 3, jack 4, load sensor 5, and pad 6

[0065] Place the pad 6, load sensor 5, jack 4 and pressure plate 3 on the steel beam 7 in sequence. It should be noted that during the above installation process, the pressure plate 3, pad 6, steel beam 7 and four reserved holes on the periphery of the connecting plate 10 need to be aligned to ensure that the pull-up screw 1 can pass freely during installation.

[0066] Step 6: Install the pull-up screw 1

[0067] After all the above components are installed, the pull-up screw 1 is passed through the reserved holes from top to bottom, through the pressure plate 3, the pad 6, the steel beam 7, and the connecting plate 10. After reserving a suitable length above the pressure plate 3 and below the connecting plate 10, the first gasket 2-1 and the third gasket 11-1 are passed through the pull-up screw 1 and placed on the pressure plate 3 and the connecting plate 10, respectively. Then, the pull-up screw 1 is tightly connected and firmly fixed to the pressure plate 3 and the connecting plate 10 through the first nut 2 and the third nut 11, respectively, to ensure that the pull-up screw 1 can transfer the pull-up load applied by the jack 4 to the connecting plate 10 during the test, and then the connecting plate 10 transfers the pull-up load to the anchor rod body 14. After the pull-up screw 1 is installed, the test system is installed. After the test system is installed, the components should be in close contact and no shaking occurs to ensure the safety during the test and the accuracy of the test results. Before use, the present invention needs to calibrate the jack 4 to ensure the accuracy of the load applied at each level during the test, and to ensure that the strength of the grouting consolidation body in the anchoring section reaches 15MPa or 75% of the design strength; during the test, the pull-out load applied by the jack 4 is transmitted to the anchor rod body 14 through the pull-out screw 1 and the connecting plate 10, and the reaction force generated by the jack 4 is transmitted to the ground by the steel beam 7 and the reaction pier 8. The pull-out load applied by the jack 4 to the anchor rod body 14 during the loading process is tested by the load sensor 5, and the deformation of the anchor rod body 14 during the loading process is tested by the fiber grating strain sensor 13, so as to study and analyze the bearing capacity, deformation mechanism and failure mechanism of the anchor rod body 14 during the loading process. After the test, the test results can be further processed by comparing the bearing capacity obtained from the group anchor bearing capacity test, the deformation of each anchor position, and the deformation mechanism and failure mechanism of each anchor in the group anchor with those of a single anchor. If the difference is large, it means that the mutual influence between the anchors in the anchor group and the superposition effect of the pull-out load have a great influence on the group anchor. In the design of the group anchor in actual engineering, it is necessary to reduce such influence by increasing the spacing between the anchors in the anchor group, so as to optimize the design of the group anchor.

[0068] Finally, it should be noted that relational terms such as first and second are merely used to distinguish one entity or operation from another entity or operation, but do not necessarily require or imply any actual relationship or order between these entities or operations.

[0069] 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 full-length bonded pull-out anchor group anchor bearing capacity testing system, characterized in that: It includes a pull-up screw rod, a reaction pier, a steel beam, a jack and a pull-up screw rod; The reaction piers are arranged on both sides of the anchor rod group, and a steel beam is arranged on the top of the reaction pier; a pad is arranged on the steel beam; a load sensor is arranged on the pad, and a jack is arranged on the top of the load sensor; The top of the jack is connected to the pressure plate; multiple pull-up screws pass through the pressure plate, the pad, and the connecting plate from top to bottom in sequence, the top ends of the multiple pull-up screws are fixed on the pressure plate, and the bottom ends of the multiple pull-up screws are fixed on the connecting plate; and the top of the anchor rod group is fixed on the connecting plate; a fiber grating strain sensor is fixed on each anchor rod of the anchor rod group.

2. The full-length bonded pull-out anchor group anchor bearing capacity testing system according to claim 1, characterized in that: The pull-up screw rod is connected to the pressure plate through a first nut, and a first pad is arranged between the first nut and the pressure plate; the pull-up screw rod is connected to the connecting plate through a third nut, and a third pad is arranged between the third nut and the connecting plate.

3. The full-length bonded pull-out anchor group anchor bearing capacity testing system according to claim 1, characterized in that: The anchor rod is connected to the connecting plate through a second nut, and a second pad is arranged between the second nut and the connecting plate.

4. The full-length bonded pull-out anchor group anchor bearing capacity testing system according to claim 1, characterized in that: The fiber Bragg grating strain sensors should be arranged on the anchor rod in a dense manner at the top and sparse manner at the bottom.

5. The full-length bonded pull-out anchor group anchor bearing capacity testing system according to claim 1, characterized in that: The connection position between the pull-up screw rod and the connection plate is located outside the connection position between the anchor rod and the connection plate.

6. The full-length bonded pull-out anchor group anchor bearing capacity testing system according to claim 1, characterized in that: The fiber grating strain sensor is fixed by a base bracket, an anchoring clamp and a clamp screw; the base bracket is fixed to the anchor rod body by welding, and the clamp screw fixes the anchoring clamp and the optical fiber to the base bracket.

7. The full-length bonded pull-out anchor group anchor bearing capacity testing system according to claim 1, characterized in that: The connecting plate is made of Q335B steel, and a set distance is reserved between the center point of the outer reserved hole and the edge of the connecting plate; a set distance is reserved between the center point of the inner reserved hole and the edge of the connecting plate.

8. The full-length bonded pull-out anchor group anchor bearing capacity testing system according to claim 1, characterized in that: The steel beam is two box sections welded from three I-beams; two holes need to be reserved at the center of the top plate and the bottom plate of each box section, and the diameter of the holes is larger than the pull-up screw.

9. The full-length bonded pull-out anchor group anchor bearing capacity testing system according to claim 1, characterized in that: The strength point of the jack is located at the center of the anchor rod group.

10. The testing method of the full-length bonded pull-out anchor group anchor bearing capacity testing system according to any one of claims 1 to 9, characterized in that: Step 1: Install the optical fiber and the fiber grating strain sensor on the anchor rod; A location with suitable foundation conditions is selected as the test site. After the test site is completed, the base bracket is fixed to the anchor rod body by welding, and the anchor clamp and the optical fiber are fixed to the base bracket using clamp screws to ensure that the optical fiber and the fiber grating strain sensor can deform in coordination with the anchor rod body to accurately measure the deformation of each position of the anchor rod body; Step 2: Install the anchor rod After the installation of the optical fiber and fiber Bragg grating strain sensor is completed, the anchor rod body is placed in the center of the anchor hole, the gap between the anchor rod body and the anchor hole wall at each position is measured, the anchor rod body is adjusted to the center, and then grouting is performed in the anchor hole; Step 3: Install the connecting plate After the grouting body is completely solidified, the I-beam is placed on both sides of the anchor hole to place the connecting plate and fix its position. After the I-beam is placed in a suitable position, the connecting plate is passed through the four reserved holes on the inner periphery through the anchor rod body and the connecting plate is placed on the I-beam. The second gasket is passed through the anchor rod body and placed on the connecting plate, and then the second nut is installed to ensure that the second nut is tightly connected and firmly fixed to the anchor rod body through threads; Step 4: Install steel beams and reaction piers Place the reaction piers on both sides of the anchor hole. The distance between the reaction piers and the anchor hole is determined according to the length of the steel beam. Make the end of the steel beam exceed the reaction piers. Then place the steel beam on the reaction. When placing the steel beam and the reaction piers, ensure that the reserved holes are aligned with the four reserved holes on the outer periphery of the connecting plate. Step 5: Install the pressure plate, jack, load sensor, and pad Place the pad, load sensor, jack, and pressure plate on the steel beam in sequence, and align the pressure plate, pad, steel beam, and four reserved holes on the periphery of the connecting plate to ensure that the pull-up screw can pass freely during installation; Step 6: Install the pull-out screw The pull-up screw is passed through the reserved holes from top to bottom in turn through the pressure plate, pad, steel beam and connecting plate. After reserving a suitable length above the pressure plate and below the connecting plate, the first gasket and the third gasket are passed through the pull-up screw and placed on the pressure plate and the connecting plate respectively. Then, the pull-up screw is tightly connected and firmly fixed to the pressure plate and the connecting plate through the first nut and the third nut respectively to ensure that the pull-up screw can transfer the pull-up load applied by the jack to the connecting plate during the test, and then the connecting plate transfers the pull-up load to the anchor rod body. Step 7: Calibrate the jack to ensure the accuracy of the load applied at each level during the test, and ensure that the strength of the grouting consolidation body in the anchoring section reaches 15MPa or 75% of the design strength; during the test, the pull-out load applied by the jack is transmitted to the anchor rod body through the pull-out screw and the connecting plate, and the reaction force generated by the jack is transmitted to the ground by the steel beam and the reaction pier. The pull-out load applied by the jack to the anchor rod body during the loading process is tested by the load sensor, and the deformation of the anchor rod body during the loading process is tested by the optical fiber and fiber grating strain sensor; Step 8 After the test is completed, the test results are further processed. The bearing capacity obtained from the group anchor bearing capacity test, the deformation of each anchor position, and the deformation mechanism and failure mechanism of each anchor in the group anchor are compared with those of a single anchor. If the difference is large, it means that the mutual influence between the anchors in the anchor group and the superposition effect of the pull-out load have a great influence on the group anchor. In the design of the group anchor in actual engineering, it is necessary to reduce such influence by increasing the spacing between the anchors in the anchor group, so as to optimize the design of the group anchor.

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