Test device and method for stress characteristics of inclined anchor short pile composite foundation node

Abstract

The present application relates to the technical field of characteristic test, in particular to a kind of inclined anchor short pile composite foundation node stress characteristic test device and method thereof;Including test module, loading module and data acquisition module;Test module includes bottom plate, counterforce frame, angle steel, beam, screw rod, anchor rod and rib plate, using inclined anchor short pile composite foundation node stress characteristic test device for load measurement, displacement measurement, steel strain measurement and crack measurement, realize the test research of different foundation size, inclined anchor structure, inclined anchor material, inclined anchor quantity, inclined anchor angle and inclined anchor anchoring form of inclined anchor short pile composite foundation type, observe node failure mode and the deformation and displacement of structure, study the influence of different factors on its failure mechanism, and then determine the reasonable inclined anchor short pile composite foundation structure form.

Description

Technical Field

[0001] This invention relates to the field of characteristic testing technology, and in particular to a test device and method for the stress characteristics of inclined anchor short pile composite foundation nodes. Background Technology

[0002] As a crucial pillar of the national internet communication network, high-voltage transmission line projects are increasingly becoming key projects in the construction field, with tower foundations accounting for approximately half of the total engineering volume of the entire transmission line. Currently, facing longer transmission distances, more complex terrain conditions, and harsher geological conditions, past tower foundation construction is increasingly revealing problems such as low overall construction efficiency, high construction costs, long construction periods, high material consumption, and unreasonable foundation selection. Ordinary foundation types can no longer meet the needs of social development and industry progress, and contradict the requirements of green development and green construction in the construction industry. Against this backdrop, the inclined anchor short pile foundation type, through the combined action of a central short pile and multiple surrounding anchors, utilizes the downward bearing capacity provided by the short pile foundation and relies on the inclined anchor rods to obtain greater pull-out and horizontal forces. It fully utilizes the bearing capacity of the rock and the structural stress characteristics, reduces the constraints of upward control loads on the diameter and height of the pile foundation, reduces foundation excavation dimensions, and effectively reduces material consumption.

[0003] For composite foundations consisting of short piles and anchor bolts, current research both domestically and internationally mainly focuses on straight-anchored short pile composite foundations, while research on inclined-anchored short pile composite foundations is relatively limited, especially in terms of experimental studies on their stress performance. The stress characteristics of the joints in inclined-anchored short pile composite foundations are crucial factors affecting the foundation's bearing capacity and stability. Due to the influence of connection structure and material properties, experimental results on the stress of inclined-anchored short pile composite foundation joints are significantly affected by size effects. Furthermore, field pile testing is time-consuming, economical, and inconvenient for data collection and observation of failure modes at joints. Therefore, it is essential to propose a suitable indoor full-scale test apparatus and method for assessing the stress characteristics of inclined-anchored short pile composite foundation joints. Summary of the Invention

[0004] The purpose of this invention is to provide a test device and method for the stress characteristics of inclined anchored short pile composite foundation nodes, enabling experimental research on different foundation dimensions, inclined anchor structures, inclined anchor materials, number of inclined anchors, inclined anchor inclination angles, and inclined anchor anchoring forms of inclined anchored short pile composite foundation types. It also allows for observation of node failure modes and structural deformation and displacement, study of the influence of different factors on its failure mechanism, and determination of a reasonable inclined anchored short pile composite foundation structural form.

[0005] To achieve the above objectives, the present invention employs a test device for the stress characteristics of a composite foundation node with inclined anchor short piles, comprising a test module, a loading module, and a data acquisition module. The loading module is connected to the test module, and the data acquisition module is located on the outside of the test module.

[0006] The test module includes a base plate, a reaction frame, angle steel, a pressure beam, a screw, an anchor, and a rib. The reaction frame is positioned above the base plate, and the loading module is positioned above the base plate. Both ends of the angle steel are fixedly connected to the reaction frame. The screw passes through the pressure beam and is inserted into the base plate. The rib is fixedly connected to the base plate and is located above the base plate. One end of the anchor is fixedly connected to the rib.

[0007] The loading module includes a jack, an oil pipe, and an oil pump. The jack is mounted on the base plate and located above the base plate. The two ends of the oil pipe are connected to the output ends of the jack and the oil pump, respectively.

[0008] The data acquisition module includes a load sensor, a dial gauge, a displacement gauge, a strain gauge, an image acquisition unit, and a data processing terminal. The load sensor is integrally formed with the jack. The dial gauge, the displacement gauge, and the strain gauge are respectively disposed above the base plate. The image acquisition unit is disposed on one side of the reaction frame. The load sensor, the dial gauge, the displacement gauge, the strain gauge, and the image acquisition unit are electrically connected to the data processing terminal.

[0009] The present invention also provides a test method for the stress characteristics of inclined anchor short pile composite foundation nodes, using the aforementioned test device for load measurement, displacement measurement, steel bar strain measurement, and crack measurement.

[0010] Before performing load measurement, displacement measurement, steel bar strain measurement, and crack measurement:

[0011] The 4000kN jack and the matching 3000kN load sensor are assembled into a whole. After the jack is pressurized and raised to a certain height, the pile body is hoisted above the jack, and then the jack is depressurized.

[0012] After the distance between the end of the anchor rod and the base plate meets the welding requirements, the anchor rod and the base plate are reinforced and welded together using the rib plate.

[0013] The data acquisition module is deployed.

[0014] Among the steps involved in load measurement:

[0015] The load changes are recorded using the 3000kN load sensor and the data processing terminal of model DH5902. The load sensor is calibrated before loading.

[0016] The precise load value applied by the jack is obtained by inputting the calibration coefficient into the data processing terminal.

[0017] Among the steps involved in displacement measurement:

[0018] The dial gauge and the displacement gauge are respectively installed at the top of the pile and on the non-anchored section of the anchor rod reinforcement.

[0019] The data processing terminal is used to monitor the vertical displacement of the pile body;

[0020] The data processing terminal is used to monitor the relative displacement between the anchor rod reinforcement and the pile concrete.

[0021] Among the steps involved in measuring the strain of reinforcing bars:

[0022] Before pouring the pile body, the strain gauges are attached to the inside of the reinforcing bars at the adjacent points of the anchor rod, longitudinal reinforcement and stirrups;

[0023] The strain of the anchor rod, longitudinal reinforcement and stirrups is measured using strain gauges with a sensitive grid size of 2mm×3mm, and the strain gauges are arranged at 10cm intervals.

[0024] Among the steps involved in crack measurement:

[0025] Artificial speckle patterns are created in the measurement area by evenly spraying matte white automatic hand spray paint onto the measurement area on the surface of the pile.

[0026] The marker pen was used to manually apply dots, randomly and evenly applied to the concrete surface of the pile, resulting in a surface speckled distribution.

[0027] This invention discloses a test device and method for the stress characteristics of inclined anchored short pile composite foundation nodes, comprising a test module, a loading module, and a data acquisition module. The test module includes a base plate, a reaction frame, angle steel, a pressure beam, threaded rods, anchor rods, and ribs. The test device is used to perform load measurements, displacement measurements, steel bar strain measurements, and crack measurements. This allows for experimental research on different foundation dimensions, inclined anchor structures, inclined anchor materials, number of inclined anchors, inclined anchor inclination angles, and inclined anchor anchoring methods in inclined anchored short pile composite foundation types. It also allows for observation of node failure modes and structural deformation and displacement, studying the influence of different factors on the failure mechanism, and ultimately determining a reasonable inclined anchored short pile composite foundation structural form. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structural characteristics test device for the joint stress characteristics of the inclined anchor short pile composite foundation of the present invention.

[0030] Figure 2 This is a flowchart of the preliminary preparation steps for the present invention.

[0031] Figure 3 This is a flowchart of the load measurement steps of the present invention.

[0032] Figure 4 This is a flowchart of the displacement measurement steps of the present invention.

[0033] Figure 5 This is a flowchart of the steps for measuring the strain of reinforcing bars according to the present invention.

[0034] Figure 6 This is a flowchart of the crack measurement steps of the present invention.

[0035] 11-Base plate, 12-Reaction frame, 13-Angle steel, 14-Pressure beam, 15-Screw rod, 16-Anchor rod, 17-Rib plate, 21-Jack, 22-Oil pipe, 23-Oil pump, 31-Image acquisition unit, 32-Data processing terminal, 40-Longitudinal reinforcement, 50-Pile body. Detailed Implementation

[0036] Please see Figure 1 ,in Figure 1 This is a schematic diagram of the structural characteristics test device for the joint stress characteristics of inclined anchor short pile composite foundation.

[0037] This invention provides a test device for the stress characteristics of a joint in a composite foundation with inclined anchor short piles, comprising a test module, a loading module, and a data acquisition module. The loading module is connected to the test module, and the data acquisition module is located outside the test module.

[0038] The test module includes a base plate 11, a reaction frame 12, an angle steel 13, a pressure beam 14, a screw 15, an anchor 16, and a rib plate 17. The reaction frame 12 is disposed above the base plate 11, and the loading module is disposed above the base plate 11. Both ends of the angle steel 13 are fixedly connected to the reaction frame 12. The screw 15 passes through the pressure beam 14 and is inserted into the base plate 11. The rib plate 17 is fixedly connected to the base plate 11 and is located above the base plate 11. One end of the anchor 16 is fixedly connected to the rib plate 17.

[0039] In this embodiment, the test module, the loading module, and the data acquisition module are used. The test module includes a base plate 11, a reaction frame 12, an angle steel 13, a pressure beam 14, a screw rod 15, an anchor rod 16, and a rib plate 17. The stress characteristic test device for inclined anchor short pile composite foundation nodes is used to perform load measurement, displacement measurement, steel bar strain measurement, and crack measurement. This enables experimental research on different foundation dimensions, inclined anchor structures, inclined anchor materials, inclined anchor quantities, inclined anchor inclination angles, and inclined anchor anchoring forms of inclined anchor short pile composite foundation types. The failure modes of nodes and the deformation and displacement of the structure are observed, and the influence of different factors on its failure mechanism is studied, thereby determining a reasonable inclined anchor short pile composite foundation structural form.

[0040] Furthermore, the loading module includes a jack 21, an oil pipe 22, and an oil pump 23. The jack 21 is mounted on the base plate 11 and is located above the base plate 11. The two ends of the oil pipe 22 are respectively connected to the output ends of the jack 21 and the oil pump 23.

[0041] Furthermore, the data acquisition module includes a load sensor, a dial gauge, a displacement gauge, a strain gauge, an image acquisition unit 31, and a data processing terminal 32. The load sensor is integrally formed with the jack 21. The dial gauge, the displacement gauge, and the strain gauge are respectively disposed above the base plate 11. The image acquisition unit 31 is disposed on one side of the reaction frame 12. The load sensor, the dial gauge, the displacement gauge, the strain gauge, and the image acquisition unit 31 are electrically connected to the data processing terminal 32.

[0042] In this embodiment, the jack 21 and the matching load sensor are assembled into a whole to apply axial load to the concrete pile, thereby simulating the pile being subjected to pull-out load. The anchor rod 16 is reinforced and welded to the base plate 11 using rib plates 17. The edge of the base plate 11 is restricted from uneven excessive warping by the pressure beam 14. Each pressure beam 14 is fixed in the ground anchor groove by two 12.9 grade bolts 15 with a diameter of 48mm. Simultaneously, two angle steels 13 are welded and fixed to the reaction frame 12 on the upper part of the pile 50 as horizontal supports to limit the possible large horizontal tilt of the pile 50. The load measurement, displacement measurement, steel bar strain measurement and crack measurement are carried out using the stress characteristic test device of the inclined anchor short pile composite foundation node. This allows for experimental research on different foundation dimensions, inclined anchor structures, inclined anchor materials, inclined anchor quantities, inclined anchor inclination angles and inclined anchor anchoring forms of the inclined anchor short pile composite foundation type. The failure mode of the node and the deformation and displacement of the structure are observed, and the influence of different factors on its failure mechanism is studied, thereby determining a reasonable inclined anchor short pile composite foundation structural form.

[0043] Please see Figures 2-6 The present invention also provides a test method for the stress characteristics of inclined anchor short pile composite foundation nodes, using the aforementioned test device for load measurement, displacement measurement, steel bar strain measurement, and crack measurement.

[0044] Furthermore, before performing load measurements, displacement measurements, rebar strain measurements, and crack measurements:

[0045] S11: Assemble the 4000kN jack 21 and the matching 3000kN load sensor into a whole. After the jack 21 is pressurized and raised to a certain height, the pile body 50 is hoisted above the jack 21. Then the jack 21 is depressurized.

[0046] S12: After the distance between the end of the anchor rod 16 and the base plate 11 meets the welding requirements, the anchor rod 16 and the base plate 11 are reinforced and welded together using the rib plate 17.

[0047] S13: Deploy the data acquisition module.

[0048] In this embodiment, the stress characteristic test device for the inclined anchor short pile composite foundation node can be used to measure load, displacement, steel bar strain, and cracks. Before measurement, preliminary preparations are required. First, the 4000kN jack 21 and the matching 3000kN load sensor are assembled into a whole. After the jack 21 is pressurized and raised to a certain height, the pile body 50 is hoisted above the jack 21, and then the jack 21 is depressurized. Then, after the distance between the end of the anchor rod 16 and the base plate 11 meets the welding requirements, the anchor rod 16 and the base plate 11 are reinforced and welded using the rib plate 17. Finally, the load sensor, the dial gauge, the displacement gauge, the strain gauge, the image acquisition unit 31, and the data processing terminal 32 are set up.

[0049] Furthermore, in the process of performing load measurements:

[0050] S21: The load change is recorded using the 3000kN load sensor and the data processing terminal 32 of model DH5902. The load sensor is calibrated before loading.

[0051] S22: By inputting calibration coefficients into the data processing terminal 32, the precise load value applied by the jack 21 is obtained;

[0052] S23: Record load changes and keep accurate measurement records.

[0053] In this embodiment, the load measurement is performed using the stress characteristic test device for the inclined anchor short pile composite foundation node. First, the load change is recorded using the 3000kN load sensor and the data processing terminal 32 (model DH5902). The load sensor is calibrated before loading. By inputting the calibration coefficient into the data processing terminal 32, the accurate load value applied by the jack 21 is obtained. During the test loading process, the load value needs to be measured and recorded. Special attention should be paid to the cracking, yielding, and ultimate load of the pile 50 during the loading process, and corresponding measurement records should be made.

[0054] Furthermore, in the displacement measurement step:

[0055] S31: Install the dial gauge and the displacement gauge at the top of the pile body 50 and the non-anchored section of the anchor rod 16 steel bar, respectively.

[0056] S32: Use the data processing terminal 32 to monitor the vertical displacement of the pile body;

[0057] S33: Use the data processing terminal 32 to monitor the relative displacement between the anchor rod reinforcement and the pile concrete.

[0058] In this embodiment, the dial gauge and the displacement gauge are first installed at the top of the pile 50 and the non-anchored section of the anchor rod 16 reinforcement, respectively; the data processing terminal 32 is used to monitor the vertical displacement of the pile body; and the data processing terminal 32 is used to monitor the relative displacement between the anchor rod reinforcement and the concrete.

[0059] Furthermore, in the procedure of measuring the strain of the reinforcing steel:

[0060] S41: Before pouring the pile body 50, attach the strain gauge to the inside of the reinforcing bars at the adjacent points of the anchor rod 16, longitudinal bar 40 and stirrup;

[0061] S42: The strain of the anchor rod 16, longitudinal reinforcement 40 and stirrup is measured by the strain gauge with a sensitive grid size of 2mm×3mm, and the strain gauge is arranged at 10cm intervals;

[0062] S43: The strain gauge is connected to the strain testing system via a wire, and the strain of the steel bar is systematically measured and analyzed by means of continuous transmission of dynamic signals.

[0063] In this embodiment, before pouring the pile body 50, strain gauges are attached to the inner side of the reinforcing bars at the adjacent locations of the anchor rod 16, longitudinal reinforcement 40, and stirrups. The strain of the anchor rod 16, longitudinal reinforcement 40, and stirrups is measured using strain gauges with a sensitive grid size of 2mm×3mm. The strain gauges are arranged at 10cm intervals and are connected to a strain testing system (DH3816N) via wires. The system measurement and analysis of the reinforcing bar strain is achieved by means of continuous transmission of dynamic signals (DHDAS).

[0064] Furthermore, in the step of crack measurement:

[0065] S51: Construct pile body 50;

[0066] S52: Create an artificial random speckle field on the surface of the area to be observed on the pile 50. If the surface texture pattern of the pile 50 is good, speckle processing is not required.

[0067] S53: Before loading, the image acquisition unit 31 is used to record the speckle area image of the pile body 50 before deformation;

[0068] S54: Set a reasonable acquisition interval according to the test time span, and record the images of the pile body before and after deformation during the loading process;

[0069] S55: After the experiment, import the data processing terminal 32 before and after deformation into the image processing software for calibration, and set the sub-region size, region of interest and virtual mesh step size required for calculation;

[0070] S56: Submit calculation;

[0071] S57: Output relevant deformation information as needed.

[0072] In this embodiment, the image acquisition unit 31 is a DIC high-speed camera. Since a single DIC high-speed camera cannot fully cover all three nodes, the method of observing the expansion trend of cracks on the concrete surface of one node area with the naked eye and using the DIC high-speed camera to capture the formation and development of cracks in the other two node areas of the pile 50 during loading can be adopted. First, the pile 50 is constructed; then, an artificial random speckle field is created on the surface of the area to be observed on the pile 50. If the surface texture pattern of the pile 50 is good, speckle processing is not required; before loading, the image acquisition unit 31 is used to record the speckle area image of the pile 50 before deformation; then, a reasonable acquisition interval is set according to the test time span, and the images of the pile 50 before and after deformation during loading are recorded; after the test, the data processing terminal 32 before and after deformation is imported into the image processing software for calibration, and the required sub-region size, region of interest, and virtual mesh step size are set; then the calculation is submitted; finally, the relevant deformation information is output as needed.

[0073] The above description discloses only one preferred embodiment of the present invention, and should not be construed as limiting the scope of the present invention. Those skilled in the art will understand that all or part of the processes of the above embodiments can be implemented, and equivalent changes made in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A test device for the stress characteristics of a joint in a composite foundation with inclined anchor short piles, characterized in that, It includes a test module, a loading module, and a data acquisition module. The loading module is connected to the test module, and the data acquisition module is located outside the test module. The test module includes a base plate, a reaction frame, angle steel, a pressure beam, a screw rod, an anchor rod, and a rib plate. The reaction frame is positioned above the base plate, and the loading module is positioned above the base plate. Both ends of the angle steel are fixedly connected to the reaction frame. The screw rod passes through the pressure beam and is inserted into the base plate. The rib plate is fixedly connected to the base plate and is located above the base plate. One end of the anchor rod is fixedly connected to the rib plate, and the other end of the anchor rod is connected to the pile body. The loading module includes a jack, an oil pipe, and an oil pump. The jack is mounted on the base plate and located above the base plate. The two ends of the oil pipe are connected to the output ends of the jack and the oil pump, respectively. The pile is hoisted above the jack, and two angle steels are welded and fixed to the reaction frame on the upper part of the pile as horizontal supports to limit the pile from tilting too much in the horizontal direction. The data acquisition module includes a load sensor, a dial gauge, a displacement gauge, a strain gauge, an image acquisition unit, and a data processing terminal. The load sensor is integrally formed with the jack. The dial gauge and the displacement gauge are respectively installed at the top of the pile and on the non-anchored section of the anchor rod reinforcement. Before pouring the pile, the strain gauge is attached to the inside of the reinforcement at the adjacent points of the anchor rod, longitudinal reinforcement, and stirrups. The image acquisition unit is located on one side of the reaction frame. The load sensor, the dial gauge, the displacement gauge, the strain gauge, and the image acquisition unit are electrically connected to the data processing terminal.

2. A method for testing the stress characteristics of a joint in a composite foundation with inclined anchored short piles, using the stress characteristic testing device for the joint of the composite foundation with inclined anchored short piles as described in claim 1 to perform load measurement, displacement measurement, steel reinforcement strain measurement, and crack measurement.

3. The test method for the stress characteristics of inclined anchored short pile composite foundation nodes as described in claim 2, characterized in that, Before performing load measurement, displacement measurement, rebar strain measurement, and crack measurement: The 4000kN jack and the matching 3000kN load sensor are assembled into a whole. After the jack is pressurized and raised to a certain height, the pile body is hoisted above the jack, and then the jack is depressurized. After the distance between the end of the anchor rod and the base plate meets the welding requirements, the anchor rod and the base plate are reinforced and welded together using the rib plate. The data acquisition module is deployed.

4. The test method for the stress characteristics of inclined anchored short pile composite foundation nodes as described in claim 3, characterized in that, In the steps of load measurement: The load changes are recorded using the 3000kN load sensor and the data processing terminal of model DH5902. The load sensor is calibrated before loading. The precise load value applied by the jack is obtained by inputting the calibration coefficient into the data processing terminal.

5. The test method for the stress characteristics of inclined anchored short pile composite foundation nodes as described in claim 3, characterized in that, In the steps of performing displacement measurement: The dial gauge and the displacement gauge are respectively installed at the top of the pile and on the non-anchored section of the anchor rod reinforcement. The data processing terminal is used to monitor the vertical displacement of the pile body; The data processing terminal is used to monitor the relative displacement between the anchor rod reinforcement and the pile concrete.

6. The test method for the stress characteristics of the joint of the inclined anchor short pile composite foundation as described in claim 3, characterized in that, In the steps of performing steel bar strain measurement: Before pouring the pile body, the strain gauges are attached to the inside of the reinforcing bars at the adjacent points of the anchor rod, longitudinal reinforcement and stirrups; The strain of the anchor rod, longitudinal reinforcement and stirrups is measured using strain gauges with a sensitive grid size of 2mm×3mm, and the strain gauges are arranged at 10cm intervals.

7. The test method for the stress characteristics of the joint of the inclined anchor short pile composite foundation as described in claim 3, characterized in that, In the steps of crack measurement: Artificial speckle patterns are created in the measurement area by evenly spraying matte white automatic hand spray paint onto the measurement area on the surface of the pile. The marker pen was used to manually apply dots, randomly and evenly applied to the concrete surface of the pile, resulting in a surface speckled distribution.

Images