Indoor model test device and method for post-grouting of pile foundation

Abstract

The invention discloses a pile foundation post-grouting indoor model test device and method.The pile foundation post-grouting indoor model test device comprises a model box and a model pile, a permeable stone layer is arranged at the bottom of the model box, a permeable plate is arranged on the permeable stone layer, a plurality of permeable holes are formed in the permeable plate, a test soil body is arranged above the permeable plate, and a plurality of soil pressure boxes are embedded in the test soil body; an annular water filling capsule is arranged above the test soil body and is connected with a hydraulic water injection system; a limiting steel plate is arranged on the water filling capsule; a grouting pipe is arranged in the model pile, and the input end of the grouting pipe is connected with a model pile grouting system. The water filling capsule is used for vertically pressurizing the test soil body and can be in good contact with a soil layer, and hydraulic pressure is applied to the soil body through the water filling capsule to uniformly apply pressure to the soil body, so that the contact pressure is equal everywhere, the soil body consolidation pressure is uniform, and the test result is more controllable.

Description

Technical Field

[0001] The invention relates to the technical field of pile foundation post-grouting, and in particular to a pile foundation post-grouting indoor model test device and method. Background Art

[0002] Indoor model tests for post-grouting pile foundations often require consolidating soil samples to meet certain physical and mechanical specifications, such as strength and moisture content, to simulate the properties of undisturbed soil. The core goal of preparing consolidated soil samples is to simulate the structure and stress state of natural soil, ensuring that the test results reflect the actual engineering properties. For large-scale tests, it is difficult to produce undisturbed consolidated samples that meet both the quantity and state requirements. Furthermore, typical indoor model tests do not consider the effect of soil self-weight stress on soil consolidation, resulting in the following problems: 1. Indoor model experiments for pile-end post-grouting typically manipulate soil properties by controlling moisture content, density, and other methods. These experiments fail to simulate deeper soil layers, which in turn fail to simulate the variations in post-grouting effectiveness that occur with varying soil depths. Furthermore, most indoor model tests for pile-end post-grouting often fail to consider the changes in soil state caused by the soil's own weight in actual engineering situations. This means they fail to fully account for the actual ground pressure conditions, which can also lead to variations in grouting effectiveness.

[0003] 2. It is difficult to ensure that the pressure is evenly applied to the soil layer when consolidating the soil in the model box. In actual engineering, the soil layer is distributed over a large range, so the soil layer at the same depth is subjected to evenly distributed pressure. The existing technology mostly adopts methods such as hard plate pressurization or fixed point pressurization, which will lead to different consolidation pressures at various positions in the soil layer, and it is impossible to form the evenly consolidated soil required by the experiment. Summary of the Invention

[0004] In response to the above-mentioned deficiencies in the prior art, the present invention provides an indoor model test device and method for pile foundation post-grouting, which can be used to change the consolidation pressure of the soil, change the soil layer depth, and then conduct indoor model tests of pile foundation post-grouting. At the same time, it is designed with a good grouting sealing environment and loading and measurement functions for the test piles to explore the changes in the effects of post-grouting of the pile foundation at different soil layer depths.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is: Provided is a model test device for post-grouting of pile foundations, comprising a model box and a model pile, wherein a permeable stone layer is provided at the bottom of the model box, a permeable plate is provided on the permeable stone layer, a plurality of permeable holes are provided on the permeable plate, a test soil body is provided above the permeable plate, a plurality of soil pressure boxes are buried in the test soil body, an annular water-filled capsule is provided above the test soil body, and the water-filled capsule is used to apply uniform consolidation pressure to the test soil body; a limiting steel plate is provided on the water-filled capsule, and vertical through holes cooperating with the model pile are provided on the water-filled capsule and the limiting steel plate, and the model pile is arranged in the test soil body through the vertical through holes; a grouting pipe is provided in the model pile, and an input end of the grouting pipe is connected to a model pile grouting system, and the model pile grouting system is used to simulate the grouting operation of the model pile.

[0006] Furthermore, the model pile grouting system includes a grouting pipe, a stainless steel pressure barrel and an air compressor. The stainless steel pressure barrel is provided with an air pressure valve. The input end of the grouting pipe passes through the bottom of the stainless steel pressure barrel. The top of the stainless steel pressure barrel is connected to the air compressor through a pipeline.

[0007] Furthermore, the water-filled capsule is connected to a hydraulic water injection system, which includes a water filling pipe and a hydraulic pump. One end of the water filling pipe is connected to the water-filled capsule, and the other end is connected to the hydraulic pump.

[0008] Furthermore, a stainless steel shell is provided in the vertical through hole, the model pile is installed in the stainless steel shell, the stainless steel shell is sealed to the limiting steel plate, and the model pile is sealed to the stainless steel shell.

[0009] Furthermore, a loading pressure head is provided above the model box to cooperate with the hydraulic loading equipment to perform pressure loading on the model pile.

[0010] Furthermore, a radial outlet opening cooperating with the grouting pipe is provided at the top of the model pile.

[0011] Furthermore, a drain pipe is provided at the bottom of the model box, and a switch valve is provided on the drain pipe.

[0012] Furthermore, a water-permeable gauze layer is provided on the lower side of the water-filled capsule, and a plurality of exhaust holes are provided on the model box, and the plurality of exhaust holes and the water-permeable gauze layer are located on the same horizontal plane.

[0013] Furthermore, a plurality of limiting beams are provided above the limiting steel plates, and limiting holes matching the ends of the limiting beams are provided on the model box.

[0014] A test method for a pile foundation post-grouting indoor model test device comprises the following steps: S1: Before filling, lay a permeable stone layer at the bottom of the model box and bury the drainage pipe; S2: Install a permeable board on top of the permeable stone and fill the permeable board with test soil. During the process of filling the test soil, bury the model piles and place the grouting pipes in the model piles. S3: Bury several earth pressure cells at the top of the test soil layer and near the model piles, and then continue to fill the test soil; S4: Place a permeable gauze layer on top of the test soil and open several vents on the model box. The vents and the permeable gauze layer are located on the same plane. S5: Place the stainless steel shell over the model pile and continue burying it. Place a water-filled capsule above the test soil and fill it with water. Use a hydraulic water injection system to control the pressure exerted by the water-filled capsule on the test soil. Place a limiting steel plate above the water-filled capsule and pass the model pile through the vertical through-holes of the water-filled capsule and the limiting steel plate. S6: Install several limit beams above the limit steel plate to limit the upward displacement of the limit steel plate; S7: The limiting steel plate cooperates with the water-filled capsule to apply the pressure inside the test soil to the required consolidation pressure; S8. During the test, the test soil is consolidated. The actual pressure transmitted to the soil layer is determined by the soil pressure data fed back by the soil pressure cell to control the pressure to the required value. The pressure of the water-filled capsule is adjusted. Each load level is maintained until the deformation is stable and the test soil consolidation is completed. S9: Conduct grouting experiments. The hydraulic loading equipment cooperates with the loading head to load the model pile. The slow-maintained load method is used, and supplementary loading is performed. The grouting pipe cooperates with the model pile grouting system to complete the grouting experiment. The soil pressure change during the grouting process is tested using the soil pressure cell. S10: Apply load to the upper loading head, start the pile foundation load test, and collect stress and deformation data of the pile foundation and foundation.

[0015] The beneficial effects of the present invention are: The present invention uses water-filled capsules to vertically pressurize the test soil, which can ensure good contact with the soil layer. The water-filled capsules apply hydraulic pressure to uniformly pressurize the soil, so that the contact pressure is equal everywhere, so as to achieve uniform soil consolidation pressure and make the test results more controllable.

[0016] By varying the water pressure in the water-filled capsules, the present invention can simulate the actual self-weight stress state of soil layers at different depths. Since the self-weight stress is closely related to the soil layer properties and the post-grouting effect, the consolidation and stress state of the stratum can be simulated to the greatest extent possible. By taking into account the effect changes brought about by the self-weight stress of the soil, relevant tests can also be conducted on the soil under different consolidation states (normal consolidation, underconsolidation, and overconsolidation).

[0017] The present invention can change the consolidation pressure of the soil and change the depth of the soil layer. It can carry out indoor model tests of pile foundation post-grouting. At the same time, it is designed with a good grouting sealing environment and an integrated system for loading and measuring test piles to explore the changes in the effects of post-grouting of pile foundations at different soil layer depths.

[0018] The indoor model test device for post-grouting of pile foundation of the present invention can realize a closed pressurized environment of the soil layer area through the comprehensive application of pressurization and sealing measures, while at the same time, the test pile is deeply penetrated into the stratum and operations such as pile foundation bearing capacity measurement can be carried out.

[0019] This invention enables testing of soils in various consolidation states (normal, underconsolidated, and overconsolidated). The water-filled capsules ensure uniform soil consolidation. The drainage boundary of the consolidation method also allows for saturated and partially saturated engineering environments. By varying the pressure applied to the soil layer, the method can be extended to other deep soil mechanics studies. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a structural diagram of the limiting steel plate and the limiting beam; The main components in the figure are described as follows: 1. Upper loading head; 2. Hydraulic pump; 3. Limiting beam; 4. Water-filled capsule; 5. Model pile; 6. Model box; 7. Permeable stone layer; 8. Drain pipe; 9. Permeable board; 10. Grouting pipe; 11. Air pressure valve; 12. Slurry; 13. Stainless steel pressure barrel; 14. Air compressor; 15. Limiting steel plate; 16. Stainless steel shell; 17. Soil pressure box; 18. Switch valve; 19. Permeable gauze layer. DETAILED DESCRIPTION

[0021] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0022] like Figure 1As shown, the indoor model test device for post-grouting of pile foundations includes a model box 6 and a model pile 5. The bottom of the model box 6 is provided with a permeable stone layer 7, and a permeable plate 9 is provided on the permeable stone layer 7. The permeable plate 9 is provided with a plurality of permeable holes. A test soil is provided above the permeable plate 9. Several soil pressure cells 17 are embedded in the test soil. An annular water-filled capsule 4 is provided above the test soil. The water-filled capsule 4 is used to apply uniform consolidation pressure to the test soil. A limiting steel plate 15 is provided on the water-filled capsule 4. The water-filled capsule 4 and the limiting steel plate 15 are provided with vertical through-holes that cooperate with the model pile 5. The model pile 5 is set in the test soil through the vertical through-holes. A stainless steel shell 16 is provided in the vertical through-holes. The model pile 5 is installed in the stainless steel shell 16. The stainless steel shell 16 and the limiting steel plate 15 are sealed together, and the model pile 5 and the stainless steel shell 16 are sealed together. A grouting pipe 10 is installed within the model pile 5. The input end of the grouting pipe 10 is connected to the model pile grouting system, which is used to simulate the grouting operation of the model pile 5. A drain pipe 8 is installed at the bottom of the model box 6, and an on / off valve 18 is installed on the drain pipe 8. The drain pipe 8 cooperates with the on / off valve 18 to facilitate drainage of the interior of the model box 6. A permeable gauze layer 19 is provided on the underside of the water-filled capsule 4. The model box 6 is provided with several vents, which are located on the same horizontal plane as the permeable gauze layer 19. The vents cooperate with the permeable gauze layer 19 to discharge gas / liquid from the soil during the grouting process.

[0023] The model pile grouting system includes a grouting pipe 10, a stainless steel pressure barrel 13, and an air compressor 14. The stainless steel pressure barrel 13 is equipped with an air pressure valve 11. The input end of the grouting pipe 10 extends through the bottom of the stainless steel pressure barrel 13. The air compressor 14 is connected to the top of the stainless steel pressure barrel 13 via a pipe. The stainless steel pressure barrel 13 is filled with slurry, which cooperates with the air compressor 14 to inject the slurry into the pile end of the model pile 5.

[0024] The water-filled capsule 4 is connected to a hydraulic water injection system, which includes a water filling pipe and a hydraulic pump 2. One end of the water filling pipe is connected to the water-filled capsule 4, and the other end is connected to the hydraulic pump 2. A pressure valve and a solenoid valve are provided on the water filling pipe to facilitate the detection and control of the water pressure in the water-filled capsule 4.

[0025] An upper loading head 1 is provided above the model box 6, and the upper loading head 1 cooperates with the hydraulic loading equipment to pressure load the model pile 5. A radial lead-out opening that cooperates with the grouting pipe 10 is provided on the top of the model pile 5. The radial lead-out opening facilitates the lead-out of the grouting pipe 10 and does not affect the pressure loading operation of the model pile 5. The upper loading head 1 cooperates with the hydraulic loading equipment to load the model pile 5. After the experimental device and data acquisition device for post-grouting are prepared, the water-filled capsule 4 is hydraulically operated, and the actual pressure transmitted to the soil layer is determined by the soil pressure box 17 to control the pressure to reach the required value. After consolidation is completed, a post-grouting test is carried out, and the loading is completed by a jack. Finally, the experimental data can be obtained and conclusions can be made.

[0026] like Figure 2 As shown, a number of limiting beams 3 are provided above the limiting steel plate 15, and limiting holes are provided on the model box 6 to match the ends of the limiting beams 3. The limiting holes are preferably strip-shaped holes that can be adjusted up and down. There are preferably four limiting beams 3, and the four limiting beams 3 are grouped in pairs, stacked in pairs to form a well shape. Eight limiting holes are provided on the model box 6 to match the limiting beams 3. Under the limiting action of the limiting beams 3, the limiting steel plate 15 applies hydraulic pressure to the water-filled capsules 4 through the hydraulic pump 2, so that the water-filled capsules 4 can apply a large pressure to the soil layer to achieve the required consolidation pressure. The water-filled capsules 4 used are soft structures and have good contact with the soil layer, so that a relatively uniform consolidation pressure can be applied to the soil layer.

[0027] A test method for a pile foundation post-grouting indoor model test device comprises the following steps: S1: Before filling, lay a permeable stone layer 7 at the bottom of the model box 6 and bury the drainage pipe 8; S2: Install the permeable plate 9 above the permeable stone 7 and fill the test soil on the permeable plate 9. During the filling of the test soil, bury the model pile 5 and place the grouting pipe 10 in the model pile 5. S3: Bury several earth pressure cells 17 at the top of the test soil layer and near the model pile 5, and then continue to fill the test soil; S4: Place a permeable gauze layer 19 on the test soil and open a number of vent holes on the model box 6. The vent holes and the permeable gauze layer 19 are located on the same plane. S5: The stainless steel shell 6 is placed over the model pile 5 and continues to be buried. A water-filled capsule 4 is placed above the test soil and filled with water. The pressure exerted by the water-filled capsule 4 on the test soil is controlled by a hydraulic water injection system. A limiting steel plate 15 is placed above the water-filled capsule 4, and the model pile 5 is passed through the vertical through-holes of the water-filled capsule 4 and the limiting steel plate 15. S6: Install a plurality of limiting beams 3 above the limiting steel plate 15. The limiting beams 3 are used to limit the upward displacement of the limiting steel plate 15. S7: The limiting steel plate 15 cooperates with the water-filled capsule 4 to apply the pressure inside the test soil to the required consolidation pressure; S8. During the test, the test soil is consolidated. The actual pressure transmitted to the soil layer is determined by the soil pressure data fed back by the soil pressure cell 17 to control the pressure to the desired value. The pressure of the water-filled capsule 4 is adjusted. The preload pressure and subsequent loading stage design are set according to the specific test conditions. Each load stage is maintained until the deformation is stable, such as the deformation change is less than 0.01 mm within 1 hour. The consolidation of the test soil is completed. S9: Perform grouting experiment. The hydraulic loading equipment cooperates with the loading head 1 to load the model pile 5. The slow load maintenance method is used, and the additional load is performed. The grouting pipe 10 cooperates with the model pile grouting system to complete the grouting experiment. The pressure change of the soil during the grouting process is tested through the soil pressure cell 17. S10: Apply a load to the upper loading head 1 to start the pile foundation load test and collect stress and deformation data of the pile foundation and the foundation.

Claims

1. A pile foundation post-grouting indoor model test device, characterized in that: The invention comprises a model box (6) and a model pile (5), wherein a permeable stone layer (7) is provided at the bottom of the model box (6), a permeable plate (9) is provided on the permeable stone layer (7), a plurality of permeable holes are provided on the permeable plate (9), a test soil body is provided above the permeable plate (9), a plurality of soil pressure boxes (17) are buried in the test soil body, and an annular water-filled capsule (4) is provided above the test soil body, and the water-filled capsule (4) is used to apply uniform consolidation pressure to the test soil body; A limiting steel plate (15) is provided on the water-filled capsule (4), and vertical through holes cooperating with the model pile (5) are provided on the water-filled capsule (4) and the limiting steel plate (15), and the model pile (5) is set in the test soil through the vertical through holes; A grouting pipe (10) is provided in the model pile (5), and an input end of the grouting pipe (10) is connected to a model pile grouting system, and the model pile grouting system is used to simulate the grouting operation of the model pile (5).

2. The indoor model test device for pile foundation post-grouting according to claim 1, characterized in that: The model pile grouting system comprises a grouting pipe (10), a stainless steel pressure barrel (13) and an air compressor (14); the stainless steel pressure barrel (13) is provided with an air pressure valve (11); the input end of the grouting pipe (10) passes through the bottom of the stainless steel pressure barrel (13); and the top of the stainless steel pressure barrel (13) is connected to the air compressor (14) via a pipeline.

3. The indoor model test device for pile foundation post-grouting according to claim 2, characterized in that: The water-filled capsule (4) is connected to a hydraulic water injection system, which comprises a water-filling pipe and a hydraulic pump (2). One end of the water-filling pipe is connected to the water-filled capsule (4), and the other end is connected to the hydraulic pump (2).

4. The indoor model test device for pile foundation post-grouting according to claim 3, characterized in that: A stainless steel shell (16) is provided in the vertical through hole, the model pile (5) is installed in the stainless steel shell (16), the stainless steel shell (16) and the limiting steel plate (15) are sealed together, and the model pile (5) and the stainless steel shell (16) are sealed together.

5. The indoor model test device for pile foundation post-grouting according to claim 4, characterized in that: An upper loading pressure head (1) is provided above the model box (6), and the upper loading pressure head (1) cooperates with a hydraulic loading device to perform pressure loading on the model pile (5).

6. The indoor model test device for pile foundation post-grouting according to claim 5, characterized in that: The top of the model pile (5) is provided with a radial outlet opening that cooperates with the grouting pipe (10).

7. The indoor model test device for pile foundation post-grouting according to claim 6, characterized in that: A drainage pipe (8) is provided at the bottom of the model box (6), and a switch valve (18) is provided on the drainage pipe (8).

8. The indoor model test device for pile foundation post-grouting according to claim 7, characterized in that: A water-permeable gauze layer (19) is provided on the lower side of the water-filled capsule (4), and a plurality of exhaust holes are provided on the model box (6), wherein the plurality of exhaust holes and the water-permeable gauze layer (19) are located on the same horizontal plane.

9. The indoor model test device for pile foundation post-grouting according to claim 8, characterized in that: A plurality of limiting cross beams (3) are provided above the limiting steel plate (15), and limiting holes matching the ends of the limiting cross beams (3) are provided on the model box (6).

10. A test method using the indoor model test device for pile foundation post-grouting according to claim 9, characterized in that: The steps include: S1: Before filling, lay a permeable stone layer (7) at the bottom of the model box (6) and bury the drainage pipe (8); S2: Install a permeable plate (9) above the permeable stone (7), and fill the permeable plate (9) with test soil. During the process of filling the test soil, bury the model pile (5) and place the grouting pipe (10) in the model pile (5). S3: burying a number of soil pressure boxes (17) at the top of the soil layer of the test soil and near the model pile (5), and then continue to fill the test soil; S4: placing a permeable gauze layer (19) above the test soil, and opening a plurality of vent holes on the model box (6), wherein the vent holes and the permeable gauze layer (19) are located on the same plane; S5: The stainless steel shell (6) is placed outside the model pile (5) and continues to be buried. A water-filled capsule (4) is placed above the test soil, and the water-filled capsule (4) is filled with water. The pressure exerted by the water-filled capsule (4) on the test soil is controlled by a hydraulic water injection system. A limiting steel plate (15) is placed above the water-filled capsule (4), and the model pile (5) is passed through the vertical through-holes of the water-filled capsule (4) and the limiting steel plate (15); S6: Installing a plurality of limiting beams (3) above the limiting steel plate (15), wherein the limiting beams (3) are used to limit the upward displacement of the limiting steel plate (15); S7: The limiting steel plate (15) cooperates with the water-filled capsule (4) to apply the pressure inside the test soil to the required consolidation pressure; S8, during the test, the test soil is consolidated, and the pressure actually transmitted to the soil layer is determined by the soil layer pressure data fed back by the soil pressure box (17) to control the pressure to reach the required value, and the pressure of the water-filled capsule (4) is adjusted. Each load level is maintained until the deformation is stable and the test soil consolidation is completed, thus completing the consolidation of the test soil; S9: Conduct grouting experiment. The hydraulic loading equipment cooperates with the loading head (1) to load the model pile (5). The slow load maintenance method is used and the additional load is performed. The grouting pipe (10) cooperates with the model pile grouting system to complete the grouting experiment. The pressure change of the experimental soil during the grouting process is tested through the soil pressure box (17); S10: Apply load to the upper loading head (1), start the pile foundation load test, and collect stress and deformation data of the pile foundation and the foundation.

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