A test device for measuring the influence of pile-soil stress ratio on the deformation adjustment performance of a cushion

Abstract

The utility model relates to the field of foundation engineering, especially relates to a test device for measuring the influence of pile soil stress ratio on mattress layer deformation adjustment performance, including load board, mattress layer, vibrating string type soil pressure box, XPS board, rigid pile, soil between piles and test box, the test box is the hollow square structure of top opening, the bottom end of rigid pile is fixed in the inner chamber bottom center of test box, the outer wall between rigid pile and test box's inner wall is filled with soil between piles, the XPS board is laid in the top of soil between piles, the top of XPS board and rigid pile is equipped with vibrating string type soil pressure box, the top of XPS board is laid with mattress layer, the top of mattress layer is equipped with load board. The utility model can obtain the mattress layer deformation performance data under the condition of various pile soil stress ratios through one-time loading test, and the influence of pile soil stress ratio on the deformation adjustment capacity of mattress layer is convenient to study.

Description

Technical Field

[0001] This utility model relates to the field of foundation engineering, and in particular to a test device for measuring the influence of pile-soil stress ratio on the deformation adjustment performance of cushion layer. Background Technology

[0002] The cushion layer is a crucial component for regulating the coordinated deformation and load distribution of the pile and soil in composite foundations. The theoretical study of the cushion layer's stress and deformation performance is highly complex. Factors influencing the cushion layer's deformation Δ include its thickness h, internal friction angle ϕ, elastic modulus Ec, pile-soil stress ratio n, pile-soil replacement ratio m, and rigid pile diameter d. Theoretical calculations are extremely complex, and measurements are generally performed experimentally, with the pile-soil stress ratio n being a key influencing factor. Currently, there are some shortcomings in experimental measurements of the impact of the pile-soil stress ratio on the cushion layer's deformation performance in composite foundations. This is mainly reflected in traditional rigid pile composite foundation tests, where the pile-soil stress ratio changes relatively little throughout the loading process. Multiple tests are required to determine the cushion layer's deformation performance under different pile-soil stress ratios, which is time-consuming and labor-intensive.

[0003] Based on the above reasons, this utility model designs an experimental device for measuring the influence of pile-soil stress ratio on the deformation adjustment performance of the cushion layer. Utility Model Content

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a test device for measuring the influence of the pile-soil stress ratio on the deformation adjustment performance of the cushion layer. During the loading process, when the XPS plate laid on the soil between the piles reaches the yield strength, the stress of the soil between the piles remains basically unchanged, but the stress of the rigid pile increases rapidly. Through a single loading test, the deformation performance data of the cushion layer under various pile-soil stress ratios can be obtained, which is convenient for studying the influence of the pile-soil stress ratio on the deformation adjustment ability of the cushion layer.

[0005] To achieve the objective of this utility model, the technical solution adopted by this utility model is as follows: This utility model discloses an experimental device for measuring the influence of pile-soil stress ratio on the deformation adjustment performance of a cushion layer. The device includes a load plate, a cushion layer, a vibrating wire earth pressure cell, an XPS plate, a rigid pile, soil between piles, and a test chamber. The test chamber has a hollow square structure with an open top. The bottom end of the rigid pile is fixed to the center of the bottom of the test chamber's inner cavity. The soil between the outer wall of the rigid pile and the inner wall of the test chamber is filled with the soil between the piles. The XPS plate is laid on top of the soil between the piles. The vibrating wire earth pressure cell is located on top of the XPS plate and the rigid pile. The cushion layer is laid on top of the XPS plate, and the load plate is located on top of the cushion layer. A reaction device for applying vertical loads is located on top of the load plate. The rigid pile can be a round pile or a square pile.

[0006] A thin steel plate is provided between the mattress layer and the XPS board.

[0007] The thin steel plate and XPS plate have a through hole in the middle for the top of the rigid pile to pass through; the upper surface of the thin steel plate is flush with the top of the rigid pile.

[0008] The vibrating wire earth pressure box on the top of the thin steel plate is placed at the four corners of the top of the thin steel plate.

[0009] The top of the load plate is equipped with several displacement gauges.

[0010] The top of the thin steel plate is provided with several settlement markers. The settlement markers are rod-shaped structures with bases, and their bottom ends are fixed to the top of the thin steel plate. The load plate is provided with settlement holes for the settlement markers to pass through.

[0011] The reaction device includes a reaction frame and a hydraulic jack. The reaction frame includes a crossbeam and a support column. The crossbeam is positioned above the load plate and connected to the top of the support column. The bottom of the support column is fixed to the ground. The bottom of the hydraulic jack is fixed to the top center of the load plate, and the output end of the hydraulic jack can contact the bottom of the crossbeam.

[0012] The beneficial effects of this utility model are as follows: During the loading process, when the XPS plate laid on the soil between the piles reaches its yield strength, the stress in the soil between the piles remains basically unchanged, but the stress in the rigid piles increases rapidly. Through a single loading test, data on the deformation performance of the cushion layer under various pile-soil stress ratios can be obtained, which is convenient for studying the influence of the pile-soil stress ratio on the deformation adjustment ability of the cushion layer.

[0013] Using the testing device provided by this utility model, the cumbersome test that requires multiple tests in traditional tests to determine the influence of different pile-soil stress ratios on the deformation adjustment performance of the cushion layer can be effectively avoided, significantly reducing the number of tests and greatly improving the efficiency of the test work. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model; Figure 2 This is a schematic diagram showing the placement of the vibrating wire earth pressure box in this utility model; Figure 3 This is a typical stress-strain curve of an XPS board under pressure. Figure 4 The test curves of pile top stress-soil stress in rigid pile composite foundation obtained by the test device described in this utility model are compared with the test curves of pile-soil stress obtained by traditional test methods.

[0015] In the attached diagram, 1-reaction frame, 2-hydraulic jack, 3-load plate, 4-mattress layer, 5-vibrating wire earth pressure cell, 6-thin steel plate, 7-XPS plate, 8-rigid pile, 9-soil between piles, 10-test chamber, 11-beam, 12-support column, 13-displacement gauge, 14-settlement gauge. Detailed Implementation

[0016] The present invention will be further described below: Please see Figures 1-4 , This utility model discloses an experimental device for measuring the effect of pile-soil stress ratio on the deformation adjustment performance of a cushion layer. The device includes a load plate 3, a cushion layer 4, a vibrating wire earth pressure cell 5, a thin steel plate 6, an XPS plate 7, a rigid pile 8, soil between piles 9, and a test chamber 10. The test chamber 10 has a hollow square structure with an open top. The bottom end of the rigid pile 8 is fixed to the center of the bottom of the inner cavity of the test chamber 10. The soil between piles 9 fills the space between the outer wall of the rigid pile 8 and the inner wall of the test chamber 10. The XPS plate 7 is laid on top of the soil between piles 9. A thin steel plate 6 is laid on top of the XPS plate 7. The vibrating wire earth pressure cell 5 is installed on top of the thin steel plate 6 and the rigid pile 8. The cushion layer 4 is laid on top of the thin steel plate 6 and the rigid pile 8. The load plate 3 is installed on top of the cushion layer 4. The reaction device for applying vertical load is installed on top of the load plate 3. During the loading process, when the XPS board 7 laid on the soil between the piles 9 reaches the yield strength, the stress of the soil between the piles 9 remains basically unchanged, but the stress of the rigid pile 8 increases rapidly. Through a single loading test, the deformation performance data of the cushion layer 4 under various pile-soil stress ratios can be obtained, which is convenient for studying the influence of the pile-soil stress ratio on the deformation adjustment ability of the cushion layer 4. This can effectively avoid the cumbersome test that requires multiple tests in traditional tests to obtain the influence of different pile-soil stress ratios on the deformation adjustment performance of the cushion layer, significantly reducing the number of tests and greatly improving the efficiency of the test work. XPS board is short for extruded polystyrene foam board, or simply extruded board.

[0017] Furthermore, the thin steel plate 6 between the mattress layer 4 and the XPS board 7 is placed in sections with aligned seams, and is rectangular in size of 10~15cm. Its function is to prevent the XPS board 7 from being locally crushed by the gravel on the mattress layer 4 above it during the loading process, so as to avoid affecting the overall stress performance of the XPS board 7.

[0018] Furthermore, the thin steel plate 6 and XPS plate 7 are provided with through holes in the middle for the top of the rigid pile 8 to pass through; the upper surface of the thin steel plate 6 is flush with the top of the rigid pile 8, ensuring that the vibrating wire earth pressure cell 5 on the thin steel plate 6 and the rigid pile 8 are at the same height. Preferably, the vibrating wire earth pressure cell 5 on the top of the thin steel plate 6 is placed at the four corners of the top of the thin steel plate 6.

[0019] Furthermore, the top of the load plate 3 is provided with several displacement gauges 13; the top of the thin steel plate 6 is provided with several settlement markers 14, the settlement markers 14 are rod-shaped structures with bases, the bases of which are fixed to the top of the thin steel plate 6, the load plate 3 is provided with holes for the settlement markers 14 to pass through, and the difference between the displacement gauges 13 arranged on the load plate and the settlement markers 14 placed on the thin steel plate is used to represent the deformation performance of the pile-soil stress ratio corresponding to the cushion layer during the loading process.

[0020] Furthermore, the reaction device includes a reaction frame 1 and a hydraulic jack 2. The reaction frame 1 includes a crossbeam 11 and a support column 12. The crossbeam 11 is positioned above the load plate 3, and the crossbeam 11 is connected to the top of each of the support columns 12. The bottom of the support column 12 is fixed to the ground. The bottom of the hydraulic jack 2 is fixed to the top center of the load plate 3, and the output end of the hydraulic jack 2 can contact the bottom center of the top plate 11. When a load needs to be applied to the top of the load plate 3, the hydraulic jack 2 is activated, and its output end extends out and acts on the bottom of the crossbeam 11, thereby generating a reaction force acting on the surface of the load plate 3.

[0021] The testing method of this utility model includes the following steps: S1. First, place the rigid pile 8 in the center of the test chamber 10, and then fill the soil between the piles 9. Each filling height is about 25cm. Use a 5kg heavy iron block to drop freely from a height of 30cm above the sand and compact it evenly twice to make the soil between the piles 9 in a slightly dense state. S2. Place XPS plate 7 horizontally on the surface of soil 9 between piles, place vibrating wire earth pressure cell 5 to measure the stress at the top of the pile, place vibrating wire earth pressure cell 5 around the surface of soil 9 between piles to measure the soil stress of soil 9 between piles, and take the average value of vibrating wire earth pressure cell 5 as the measurement result. S3. Lay the mattress layer 4 and compact it, then cover it with the load plate 3. Use the jack 2 and the reaction frame 1 to apply a vertical load on the load plate 3. Use the vibrating wire earth pressure cell 5, which is embedded in the top of the rigid pile 8 and the surface of the soil between the piles 9 in S2, to measure the stress at the top of the rigid pile and the stress in the soil between the piles. Use the difference between the displacement gauge 13 arranged on the load plate and the settlement gauge 14 placed on the thin steel plate to represent the deformation performance of the mattress layer corresponding to the pile-soil stress ratio. Example

[0022] Two sets of stress tests were conducted on the rigid pile composite foundation model. One set included an XPS plate placed on the soil between the piles, while the other set was a control test without an XPS plate. The test chamber dimensions were 1.10m × 0.83m × 1.05m (length × width × height), with an inner diameter of 0.90m × 0.63m × 1.05m. The load plate dimensions were 0.80m × 0.57m. The model piles were 300mm diameter circular piles, and the cushion layer thickness was... The thickness was 120 mm, and the yield strength of the XPS plate was 120 kPa. The test employed 14 levels of loading with stresses of 33 kPa, 66 kPa, 100 kPa, 200 kPa, 250 kPa, 300 kPa, 350 kPa, 400 kPa, 450 kPa, 500 kPa, 550 kPa, 600 kPa, 700 kPa, and 800 kPa, at a loading rate of 0.5 kN / s. After each load level was applied, the loading pressure was maintained for 5 minutes until the load stabilized before proceeding to the next load level. Figure 3 This is a stress-strain curve of an XPS board under compression. Figure 4 The test curves of pile top stress-soil stress in rigid pile composite foundation obtained by the test device described in this utility model are compared with the test curves of pile-soil stress obtained by traditional test methods. The test results show that in the loading test, the rigid pile composite foundation with only a cushion layer has a pile top stress of 3.160 MPa and a soil stress of 259 kPa when the load reaches 800 kPa. The pile-soil stress ratio remains relatively stable at around 12 during the loading process, with very little variation. In contrast, in the control test with an XPS plate with a yield strength of 120 kPa placed on the soil between the piles, the XPS plate yields when the soil stress reaches 120 kPa, but the stress remains relatively constant. Subsequent loading is borne by the rigid piles. When the load reaches 800 kPa, the pile top stress is 4.1 MPa and the soil stress is only 151 kPa. The pile-soil stress ratio varies from 12 to 27 during the loading process. The comparative test results show that the rigid pile composite foundation test method proposed in this invention can obtain the cushion layer deformation adjustment performance under various pile-soil stress ratios in a single loading test, significantly reducing the number of tests and improving the efficiency of the test work compared to traditional tests.

[0023] The above description is merely an embodiment of this utility model and does not limit the patent scope of this utility model. Any equivalent modifications made based on the content of this utility model specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of this utility model.

Claims

1. A test apparatus for measuring the effect of pile-soil stress ratio on the deformation adjustment performance of a cushion layer, characterized in that: It includes a load plate (3), a cushion layer (4), a vibrating wire earth pressure cell (5), an XPS plate (7), a rigid pile (8), soil between piles (9), and a test chamber (10). The test chamber (10) has a hollow square structure with an open top. The bottom end of the rigid pile (8) is fixed to the center of the bottom of the inner cavity of the test chamber (10). The space between the outer wall of the rigid pile (8) and the inner wall of the test chamber (10) is filled with the inter-pile soil (9). The XPS board (7) is laid on top of the inter-pile soil (9). The XPS plate (7) and the rigid pile (8) are provided with the vibrating wire earth pressure box (5), the XPS plate (7) is covered with the mattress layer (4), the mattress layer (4) is provided with the load plate (3), and the load plate (3) is provided with a reaction device for applying vertical load.

2. The test apparatus for measuring the effect of pile-soil stress ratio on the deformation adjustment performance of cushion layer according to claim 1, characterized in that: A thin steel plate (6) is provided between the mattress layer (4) and the XPS board (7).

3. The test apparatus for measuring the effect of pile-soil stress ratio on the deformation adjustment performance of the cushion layer according to claim 2, characterized in that: The thin steel plate (6) and XPS plate (7) are provided with through holes in the middle for the top of the rigid pile (8) to pass through; the upper surface of the thin steel plate (6) is flush with the top of the rigid pile (8).

4. The test apparatus for measuring the effect of pile-soil stress ratio on the deformation adjustment performance of cushion layer according to claim 3, characterized in that: The vibrating wire earth pressure box (5) on the top of the thin steel plate (6) is placed at the four corners of the top of the thin steel plate (6).

5. The test apparatus for measuring the effect of pile-soil stress ratio on the deformation adjustment performance of cushion layer according to claim 4, characterized in that: The top of the load plate (3) is provided with several displacement gauges (13).

6. The test apparatus for measuring the effect of pile-soil stress ratio on the deformation adjustment performance of the cushion layer according to claim 5, characterized in that: The top of the thin steel plate (6) is provided with a number of settlement markers (14). The settlement markers (14) are rod-shaped structures with bases, and their bottom ends are fixed to the top of the thin steel plate (6). The load plate (3) is provided with holes for the settlement markers (14) to pass through.

7. The test apparatus for measuring the effect of pile-soil stress ratio on the deformation adjustment performance of cushion layer according to claim 1, characterized in that: The reaction device includes a reaction frame (1) and a hydraulic jack (2). The reaction frame (1) includes a crossbeam (11) and a support column (12). The top of the crossbeam (11) is connected to the top of the support column (12), and the bottom of the support column (12) is fixed to the ground. The bottom of the hydraulic jack (2) is fixed to the top center of the load plate (3), and the output end of the hydraulic jack (2) can contact the bottom center of the crossbeam (11).

Images