Test device and installation method for stability of buried pipeline in unsaturated soil

Abstract

The application discloses a kind of test device and installation method of buried pipeline stability in unsaturated soil, solve the problems in the prior art, with beneficial effect, specific scheme is as follows: a kind of test device of buried pipeline stability in unsaturated soil, including support, support support counterforce beam;Visual model box is supported by support, water inlet and outlet pipe is led into visual model box, water inlet and outlet pipe has water seepage hole, water seepage hole outside is covered with water seepage layer, visual model box is filled with soil body in the side of water seepage layer, and pipeline is buried in soil body;Matrix suction control unit, matrix suction control unit includes the first water tank and second water tank, the height of first water tank is higher than pipeline and second water tank, and matrix suction measuring piece is connected with first water tank to obtain soil body suction;Loading unit, loading unit includes radial loading component and axial loading component respectively connected with pipeline;Data acquisition unit, data acquisition unit includes particle trapping component.

Description

Technical Field

[0001] This invention relates to the field of pipeline stability testing, and in particular to a testing device and installation method for the stability of buried pipelines in unsaturated soil. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Pipelines, as vital infrastructure for transporting oil, natural gas, and domestic water, play a crucial role in economic development. Typically, to achieve efficient pipeline transport, the internal environment is under high pressure, which easily causes pipeline expansion and yielding deformation, resulting in relative displacement between the pipeline and the surrounding soil until a stable equilibrium is reached. Furthermore, oil and gas pipelines are long-distance engineering structures, often traversing diverse geological and environmental conditions. Therefore, underground soil displacement caused by external factors such as surface subsidence, periodic deformation cycles in expansive and frozen soil regions, geological activity, subsidence in mining areas, and urban underground engineering excavation can also lead to pipeline-soil interaction problems, posing a significant threat to the safe operation of the pipeline.

[0004] Pipe-soil interaction typically occurs in both radial (upward yielding) and axial (horizontal shear slip) directions. When the relative displacement between the pipe and soil is large, it can easily lead to pipeline cracking, instability, and failure, resulting in major accidents such as crude oil leaks, explosions, and poisoning, which can cause significant casualties and property damage in severe cases. In-situ stability of oil and gas pipelines has become a key concern in pipeline engineering construction. For onshore pipelines, the burial depth is generally between 0.8m and 2m. Under these conditions, the surrounding soil is often unsaturated. Due to the presence of soil suction within the soil, the shear strength of unsaturated soil will be greater than that of completely dry and completely saturated soil under the same density conditions. However, existing pipeline peak resistance design methods and criteria are based on completely dry and completely saturated soil conditions. These existing design methods cannot reasonably evaluate the mechanical performance of pipeline systems buried in unsaturated soil.

[0005] The inventors discovered that although there are currently experimental devices and methods for studying the interaction between unsaturated soil and structures, there is still no reliable experimental device for studying the stability of buried pipelines in unsaturated soil with controllable soil suction. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a test device for the stability of buried pipelines in unsaturated soil, which can intuitively reveal the mechanical behavior of pipelines in unsaturated soil and is conducive to establishing a reliable theory for calculating the peak resistance of pipelines in unsaturated soil.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] A test apparatus for the stability of buried pipelines in unsaturated soil, comprising:

[0009] The bracket supports the reaction beam.

[0010] The visualization model box is supported by a bracket. Inlet and outlet pipes are introduced into the visualization model box. The inlet and outlet pipes have seepage holes. The outside of the seepage holes is covered with a seepage layer. The visualization model box is filled with soil on one side of the seepage layer, and the pipes are buried in the soil.

[0011] The matrix suction control unit includes a first water tank and a second water tank connected together. The height of the first water tank is higher than the pipe and the second water tank. The height of the second water tank is adjustable. The inlet and outlet pipes are connected to the first water tank. The matrix suction measuring device is connected to the first water tank to obtain the soil suction.

[0012] The loading unit includes a radial loading component and an axial loading component that are respectively connected to the pipeline. The radial loading component drives the pipeline to move arbitrarily within a radially set range, and the axial loading component drives the pipeline to move axially.

[0013] The data acquisition unit includes a particle capture component located outside the visualization model box to acquire the displacement of soil particles in the soil during loading.

[0014] The experimental setup described above uses a visual model box to embed soil and pipes. The matrix suction control unit contains two water tanks. The first water tank is located at a higher height to form a suspended water supply source. The loading unit can drive the pipes to move radially and axially, maximizing the simulation of the pipes' real environment. This achieves a full-condition simulation of the radial and axial pipe-soil interactions that may occur during pipe operation. The data acquisition unit acquires relevant data to establish relevant calculation theories.

[0015] As described above, the test device for the stability of buried pipelines in unsaturated soil includes a data acquisition unit that further comprises a matrix suction distribution measurement component, a pipeline displacement measurement component, and a stress measurement component. The matrix suction distribution measurement component is buried in the soil, the pipeline displacement measurement component acquires the radial and axial displacements of the pipeline, and the stress measurement component acquires the pipeline resistance under the radial and axial displacement modes.

[0016] The data acquisition unit, matrix suction control unit, and loading unit are connected to the control unit, which controls the lifting and lowering of the second water tank, the operation of the loading unit, and can store the data.

[0017] The above-described test device for the stability of buried pipelines in unsaturated soil includes a pipeline displacement measurement component comprising a positioning and displacement measurement mechanism and an axial displacement measurement mechanism.

[0018] The radial loading component includes a power mechanism fixed to the reaction beam. The power mechanism is detachably connected to one end of the pipe via a first pulley mounted on the bracket, thereby driving the pipe to rotate within a radially set range. The pipe is also connected to a positioning and displacement measuring mechanism. The first pulley is movable relative to the bracket, and the positioning and displacement measuring mechanism is movable relative to the reaction beam, so as to determine the positions of the first pulley and the positioning and displacement measuring mechanism according to the position of the pipe.

[0019] The axial loading component includes a second pulley, which is mounted on the bracket. The power mechanism is detachably connected to one end of the pipe through the second pulley. The power mechanism also serves as a power source, driving the pipe to move axially.

[0020] As described above, a test device for the stability of buried pipelines in unsaturated soil includes an axial displacement measuring mechanism comprising an axial displacement sensor, which is supported by the bracket. The measuring end of the displacement sensor is connected to the pipeline, and the axial displacement of the pipeline is obtained by the axial displacement sensor.

[0021] The positioning and displacement measuring mechanism is installed on the reaction beam to obtain the radial displacement of the pipeline, and the measuring end of the positioning and displacement measuring mechanism is set towards the radial direction of the pipeline.

[0022] The positioning and displacement measuring mechanism is a damper that enables displacement measurement.

[0023] As described above, the test device for the stability of buried pipelines in unsaturated soil includes a stress measurement component comprising a tension sensor and a spoke sensor. The tension sensor is connected to the pipeline and the power mechanism. The tension sensor acquires tension data, and the damper acquires resistance data. The difference between the two is the pipeline pull-out force. The pipeline pull-out force data is used to characterize the pipeline's pull-out performance.

[0024] A spoke sensor is installed at the end of the pipe to obtain the pipe resistance in axial displacement mode, and the spoke sensor is connected to the power mechanism.

[0025] The experimental device for testing the stability of buried pipelines in unsaturated soil as described above uses a tensiometer as the matrix suction distribution measuring component. The tensiometer is used to measure the matrix suction distribution in the soil.

[0026] The test device for the stability of buried pipelines in unsaturated soil as described above includes a data acquisition unit that further includes strain gauges. The strain gauges are fixed to the surface of the pipeline to measure the radial strain of the pipeline, and the axial stress distribution on the pipeline surface is calculated based on the longitudinal cross-sectional area of ​​the pipeline.

[0027] As described above, a test device for the stability of buried pipelines in unsaturated soil is provided for pipelines that need to be moved axially. To ensure the axial movement of the pipeline, the pipeline includes a pipe and a connector installed in the visualization model box. One end of the pipe is inserted into the connector, and a sealing ring is provided at one end of the connector to prevent water and soil particles from entering the pipe. The other end of the pipe is connected to the visualization model box through a fixed shaft, and the pipe can move relative to the connector and the fixed shaft.

[0028] The pipes are positioned close to the side wall of the visualization model box.

[0029] As described above, a test device for the stability of buried pipelines in unsaturated soil includes a second water tank placed on a platform, the platform being connected to a lifting mechanism, the lifting mechanism being fixed to a mounting frame, and the mounting frame having scale lines set in the vertical direction to read the displacement of the second water tank.

[0030] The matrix suction measuring device is a U-shaped water pressure gauge, which is connected to a horizontal reading tube, and the horizontal reading tube is connected to the visualization model box.

[0031] Secondly, the present invention also provides a method for installing a test device for the stability of buried pipelines in unsaturated soil, comprising the following:

[0032] The visualization model box is supported by a bracket, and pipes are installed inside the visualization model box. The pipes are connected to the loading unit to conduct a pre-loading test.

[0033] Remove the pipes and install inlet and outlet pipes inside the visualization model box. The inlet and outlet pipes are connected to the first water tank through a water pressure gauge. The first water tank is connected to the second water tank.

[0034] A permeable layer is laid on one side of the inlet and outlet pipes, and soil is filled on the other side of the permeable layer opposite the inlet and outlet pipes to the set first height.

[0035] Adjust the position of the loading unit and reinstall the pipes;

[0036] Continue filling the soil to the second height;

[0037] A closed visualization model box is filled with water through inlet and outlet pipes until the water level exceeds the filling height, thus expelling air bubbles from the soil and allowing it to stand for a set time.

[0038] The soil suction force is adjusted to a preset value by adjusting the height of the second water tank, and the soil suction force is measured by a water pressure gauge.

[0039] Install the data acquisition unit and conduct a loading test using the loading unit.

[0040] The beneficial effects of the present invention are as follows:

[0041] 1) This invention provides an experimental device in which soil and pipelines are buried in a visual model box. Two water tanks are set in the matrix suction control unit. The first water tank is set at a higher height to form a suspended water supply source. The loading unit can drive the pipeline to move in the radial and axial directions, maximizing the simulation of the real existence environment of the pipeline. It realizes the full-condition simulation of the radial and axial pipe-soil interaction that may occur during pipeline operation. The matrix suction measuring device can accurately obtain the matrix suction, making the soil suction controllable. The data acquisition unit acquires relevant data to establish relevant calculation theories.

[0042] 2) The particle capture component in the data acquisition unit of this invention acquires the displacement of soil particles in the soil; the matrix suction distribution measurement component effectively acquires the matrix suction distribution in the soil; the pipeline displacement measurement component can acquire the radial and axial displacement of the pipeline, and the stress measurement component can acquire the pipeline resistance under the radial and axial displacement modes; the strain gauge is used to calculate the axial stress distribution on the pipeline surface, thereby comprehensively capturing the stress and deformation data during the pipe-soil interaction process, and more realistically acquiring the soil displacement and progressive failure mechanism of the rupture surface during the pipe-soil interaction process, providing a basic reference for constructing the calculation theory.

[0043] 3) The matrix suction control unit of the present invention forms a suspended water supply source by setting up a first water tank and a second water tank, and sets up a matrix suction measuring device to realize high-precision simulation and control of matrix suction in unsaturated soil, and simulates the real existence environment of the pipeline to the greatest extent; at the same time, it has the characteristics of simple operation, economy and efficiency.

[0044] 4) By setting up the loading unit, the present invention can drive the pipeline to move in the radial and axial directions. The whole can realize the full-condition simulation of the pipe-soil interaction of shallow buried pipeline in unsaturated soil under the action of internal and external forces, and restore the whole process of pipeline-soil interaction to the greatest extent, providing real data support for the establishment of calculation theory. Attached Figure Description

[0045] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0046] Figure 1 This is a front view of a test apparatus for the stability of buried pipelines in unsaturated soil according to one or more embodiments of the present invention.

[0047] Figure 2 This is a top view of a test apparatus for the stability of buried pipelines in unsaturated soil according to one or more embodiments of the present invention.

[0048] Figure 3This is a front view of the first element in a test apparatus for the stability of buried pipelines in unsaturated soil according to one or more embodiments of the present invention.

[0049] The diagram exaggerates the spacing or dimensions between parts to show their positions; the diagram is for illustrative purposes only.

[0050] The components include: 1. Reducer, 2. Reaction beam, 3. Upper water tank, 4. Positioning and displacement measurement mechanism, 5. Tension sensor, 6. Rigid chain, 7. U-shaped water pressure gauge, 8. Water level gauge, 9. Tension gauge, 10. Visual model box, 11. Pipe, 12. Water level, 13. Horizontal reading tube, 14. First pulley, 15. Vacuum section, 16. Support beam, 17. Inlet and outlet pipes, 18. Lower water tank, 19. Transparent hose, 20. Lift, 21. Mounting frame, 22. Crushed stone cushion layer, 23. Geotextile, 24. Fixed shaft, 25. Strain gauge, 26. Joint, 27. Wheel spoke sensor, 28. Axial displacement sensor, 29. Seepage hole. Detailed Implementation

[0051] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0052] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is also intended to include the plural form. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0053] As described in the background section, the existing technology lacks experimental research on the stability of buried pipelines in unsaturated soil. To address this technical problem, the present invention proposes an experimental device for the stability of buried pipelines in unsaturated soil.

[0054] Example 1

[0055] In a typical embodiment of the present invention, reference is made to Figure 1 , Figure 2 and Figure 3 As shown, a test apparatus for the stability of buried pipelines in unsaturated soil includes:

[0056] The bracket supports the reaction beam.

[0057] The visualization model box is supported by a bracket. The inlet and outlet pipes 17 are connected to the visualization model box. The inlet and outlet pipes 17 have seepage holes 29. The outside of the seepage holes is covered with a seepage layer. The visualization model box is filled with soil on one side of the seepage layer. Pipes are buried in the soil and are set close to the side wall of the visualization model box.

[0058] The matrix suction control unit includes a first water tank and a second water tank connected together. The height of the first water tank is higher than the pipe and the second water tank. The height of the second water tank is adjustable. The inlet and outlet pipe 17 is connected to the first water tank. The matrix suction measuring device is connected to the first water tank to obtain the soil suction.

[0059] The loading unit includes a radial loading component and an axial loading component that are respectively connected to the pipe 11. The radial loading component drives the pipe to move arbitrarily within a radially set range, and the axial loading component drives the pipe to move axially.

[0060] The data acquisition unit includes a particle capture component located outside the visualization model box to acquire the displacement of soil particles in the soil during loading; it also includes a matrix suction distribution measurement component, a pipe displacement measurement component, and a stress measurement component. The matrix suction distribution measurement component is embedded in the soil, the pipe displacement measurement component acquires the radial and axial displacement of the pipe, and the stress measurement component acquires the pipe resistance under the radial and axial displacement modes.

[0061] The data acquisition unit, matrix suction control unit, and loading unit are respectively connected to the control unit.

[0062] Specifically, the control unit uses an existing computer with a storage unit capable of storing data; the matrix suction distribution measurement component is a tension meter 9, which is vertically embedded in the visualization model 10 above the pipe, and the tension meter 9 is used to measure the matrix suction distribution in the soil; the particle capture component is an existing Geo-PIV (particle image velocimetry) particle capture component.

[0063] In addition, the data acquisition unit also includes a strain gauge 25, which is fixed to the pipe surface to measure the radial strain of the pipe and calculate the axial stress distribution on the pipe surface based on the longitudinal cross-sectional area of ​​the pipe.

[0064] Specifically, the stress measurement component includes a tension sensor 5 and a spoke sensor 27. The tension sensor 5 is connected to the pipe and the positioning and displacement measurement mechanism 4. The tension sensor 5 is located at the lower part of the reducer 1 and is used to obtain the tension measurement of the pipe 11 in the radial displacement mode.

[0065] The bracket has a set height, the top of the bracket supports the reaction beam 2, and the bottom is equipped with a support beam 16, which is parallel to the reaction beam 2.

[0066] Understandably, the visualization model box 10 is made of transparent glass, such as tempered glass, forming a sealed system. It is installed on the support beam 16. The size of the visualization model box 10 is determined according to the size of the pipe 11 and the burial depth ratio, and the width in the front and rear directions does not exceed 0.5m. A water level gauge 8 is installed on one side of the visualization model box 10 to read the changes in the internal water level 12. A gravel cushion layer 22 is arranged at the bottom, with a thickness of 0.1-0.2m. 3-4 inlet and outlet pipes 17 are installed inside the gravel cushion layer 22. The inlet and outlet pipes 17 are connected to the matrix suction control device. Valves are installed on the inlet and outlet pipes 17, and the valves are connected to the control unit, which controls the opening and closing of the valves.

[0067] The permeable layer is geotextile 23, specifically a permeable high-toughness geotextile.

[0068] In this embodiment, the first water tank is the upper water tank 3, and the second water tank is the lower water tank 18. The upper water tank 3 and the lower water tank 18 are connected by a transparent flexible tube 19. The upper water tank 3 is installed on one side of the mounting frame 21 near the top and at a fixed height. The mounting frame is located on the side of the bracket. The lower water tank 18 is supported by a platform with rollers. The mounting frame 21 is a portal frame with guide rails on both sides. The rollers move along the guide rails. Vertical frames are installed on both sides of the platform. The vertical frames are connected to a lifting mechanism to enable the lower water tank to move up and down in the vertical direction. The lifting mechanism is a lift 20. The elevation of the lower water tank 18 is read by the scale on the mounting frame 21.

[0069] Specifically, the matrix suction measuring device is a U-shaped water pressure gauge 7. The upper water tank 3 is connected to the U-shaped water pressure gauge 7 to read the real-time matrix suction. The other end of the U-shaped water pressure gauge 7 is connected to the horizontal reading tube 13. The horizontal reading tube 13 is connected to the inlet and outlet pipes 17 and the horizontal reading tube is connected to the visualization model box.

[0070] In this embodiment, for the pipe that needs to be moved axially, in order to ensure the axial movement of the pipe, the pipe includes a conduit and a connector 26 installed in the visualization model box. One end of the conduit is inserted into the connector 26, and a sealing ring is set at one end of the connector to prevent water and soil particles from entering the conduit. The other end of the conduit is connected to the visualization model box 10 through a fixed shaft 24. The fixed shaft 24 supports the visualization model box 10. During the loading process, the model pipe 11 is kept close to the tempered glass surface to prevent soil particles from entering the gap between the pipe 11 and the tempered glass and affecting the observation effect.

[0071] To support the pipeline, both ends of the pipeline are sealed. The joint 16 is a ring joint that fixes the pipeline's position and ensures the axial movement space of the pipeline. A spoke sensor is installed at one end of the pipeline to obtain the pipeline resistance in the axial displacement mode. At the same time, an axial displacement sensor 28 is also installed at this end of the pipeline. The axial displacement sensor is supported by the side of the bracket and obtains the axial displacement of the pipeline.

[0072] In some examples, the axial displacement sensor is specifically an LVDT displacement sensor.

[0073] For pipes with radial movement, joints and fixed shafts are not required.

[0074] Pipeline displacement measurement components include a positioning and displacement measurement mechanism and an axial displacement measurement mechanism;

[0075] In addition, the radial loading component includes a power mechanism fixed to the reaction beam. The power mechanism is specifically a reducer 1. The power mechanism is detachably connected to one end of the pipe via a first pulley mounted on the bracket, thereby driving the pipe to rotate within a radially set range of 0-180°. The pipe is also connected to a positioning and displacement measuring mechanism. The first pulley is movable relative to the bracket, and the positioning and displacement measuring mechanism is movable relative to the reaction beam, so as to determine the positions of the first pulley and the positioning and displacement measuring mechanism according to the position of the pipe.

[0076] The first pulley includes two pulleys, which are installed on the lower surface of the support beam 16 at a set distance. The reducer 1 is connected to a rigid chain, which passes around the two first pulleys 14 and is connected to one end of the pipe. The other end of the pipe is then connected to the positioning and displacement measuring mechanism 4 through the rigid chain. By adjusting the relative positions of the reducer 1, the positioning and displacement measuring mechanism 4 and the multiple movable first pulleys, the pipe 11 can move at any angle within the radial range of 0-180°.

[0077] Specifically, the positioning and displacement measuring mechanism 4 has damping and displacement measuring functions, and can measure the radial displacement of the pipeline. The positioning and displacement measuring mechanism 4 is a damper with displacement measuring function. Since the positioning and displacement measuring mechanism is connected to the pipeline, it has a certain positioning effect on the pipeline. The damper is installed on the upper part of the reaction beam. While measuring the displacement according to the damper stroke, the resistance data can also be obtained. The pipeline pull-out force is obtained by subtracting the resistance data of the damper from the tension data measured by the tension sensor. And it works with the first pulley 14 to ensure that the pipeline moves in a straight line in a certain direction.

[0078] The axial loading component includes a second pulley, which is mounted on the bracket. The reducer 1 is connected to another rigid chain. The rigid chain passes around the second pulley and is detachably connected to one end of the pipe. The reducer drives the pipe to move axially. There are two second pulleys, one on the reaction beam 2 and the other on the side wall of the bracket.

[0079] It should be explained that the radial loading component and the axial loading component have two reducers, which are placed at different positions on the reaction beam.

[0080] The experimental apparatus provided in this embodiment connects the first water tank to the second water tank, with the first water tank suspended to form a suspended water column. Combined with a water pressure gauge and a tensiometer, it can achieve precise control and monitoring of the matrix suction in the depth direction of unsaturated soil, maximizing the simulation of the actual pipeline environment. It can also achieve full-condition simulation of radial and axial pipe-soil interactions that may occur during pipeline operation. The visualized experimental apparatus design, combined with PIV technology, enables continuous displacement measurement of soil particles during pipe-soil interactions, extracting the main geometric elements of the soil failure mechanism at the moment of failure. Combined with other experimental data, it is used to establish relevant calculation theories.

[0081] Example 2

[0082] This embodiment provides a method for installing a test device for the stability of buried pipelines in unsaturated soil, including the following:

[0083] Install the bracket, visualization model slot 10, loading unit and matrix suction control unit, and debug the test equipment;

[0084] Install pipe 11, conduct a preload test, and measure the resistance of pipe 11 under radial and axial displacement modes, which is recorded as the frictional force between pipe 11 and the tempered glass interface.

[0085] Remove pipe 11, close the control valves of inlet and outlet pipes 17, connect horizontal reading pipe 13, U-shaped water pressure gauge 7, upper water tank 3, lower water tank 18, etc., install and debug the substrate suction control unit so that the lower water tank 18 can move up and down smoothly;

[0086] Fill the bottom crushed stone cushion layer 22 to the preset height, lay high-toughness geotextile 23, fill the soil to the bottom elevation of the model pipe 11 according to the preset density, adjust the position of the reducer 1, rigid chain 6, movable positioning and displacement measuring device 4 and first pulley 14, install the pipe 11, connect the rigid chain 6 and keep the rigid chain in a taut state; among them, for the axially moving pipe 11, first install the fixed shaft 24 and the joint 26;

[0087] Continue filling the soil to the preset height, during which tension gauges 9 are installed and fixed at the set positions;

[0088] Install the sealing element to keep the visualization model box 10 above the designed water surface sealed. Close the left valve of the inlet and outlet pipe 17 and open the right valve to inject water into the visualization model box 10 so that the water level 12 exceeds the filling height and the air bubbles inside the soil are discharged. After standing for a set time, open the right valve of the inlet and outlet pipe 17 to drain the water so that the water level reaches the set height and the horizontal reading pipe 13 and the U-shaped water pressure gauge 7 are in a vacuum state, forming a vacuum section 15.

[0089] Adjust the substrate suction to the preset value by adjusting the height of the lower water tank 18, measure the substrate suction by the U-shaped water pressure gauge 7, and after settling for a set time, prepare for the loading test;

[0090] Install and debug the loading unit and data acquisition unit. After confirming that the device is operating normally, proceed with the formal loading.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A test apparatus for the stability of buried pipelines in unsaturated soil, characterized in that, include: The bracket supports the reaction beam. The visualization model box is supported by a bracket. Inlet and outlet pipes are introduced into the visualization model box. The inlet and outlet pipes have seepage holes. The outside of the seepage holes is covered with a seepage layer. The visualization model box is filled with soil on one side of the seepage layer, and the pipes are buried in the soil. The matrix suction control unit includes a first water tank and a second water tank connected together. The height of the first water tank is higher than the pipe and the second water tank. The height of the second water tank is adjustable. The inlet and outlet pipes are connected to the first water tank. The matrix suction measuring device is connected to the first water tank to obtain the soil suction. The soil suction force is adjusted to a preset value by adjusting the height of the second water tank, and the soil suction force is measured by a water pressure gauge. The loading unit includes a radial loading component and an axial loading component that are respectively connected to the pipeline. The radial loading component drives the pipeline to move arbitrarily within a radially set range, and the axial loading component drives the pipeline to move axially. The radial loading component includes a power mechanism fixed to the reaction beam. The power mechanism is detachably connected to one end of the pipe via a first pulley mounted on the bracket, thereby driving the pipe to rotate within a radially set range. The data acquisition unit includes a particle capture component located outside the visualization model box to acquire the displacement of soil particles in the soil during loading.

2. The test apparatus for the stability of buried pipelines in unsaturated soil according to claim 1, characterized in that, The data acquisition unit also includes a matrix suction distribution measurement component, a pipe displacement measurement component, and a stress measurement component. The matrix suction distribution measurement component is buried in the soil, the pipe displacement measurement component acquires the radial and axial displacements of the pipe, and the stress measurement component acquires the pipe resistance under the radial and axial displacement modes. The data acquisition unit, matrix suction control unit, and loading unit are respectively connected to the control unit.

3. The test apparatus for the stability of buried pipelines in unsaturated soil according to claim 2, characterized in that, The pipeline displacement measuring component includes a positioning and displacement measuring mechanism and an axial displacement measuring mechanism; The radial loading component includes a power mechanism fixed to the reaction beam. The power mechanism is detachably connected to one end of the pipe via a first pulley mounted on the support, and the pipe is connected to a positioning and displacement measuring mechanism. The first pulley is movable relative to the support, and the positioning and displacement measuring mechanism is movable relative to the reaction beam. The axial loading component includes a second pulley, which is mounted on a bracket, and the power mechanism is detachably connected to one end of the pipe via the second pulley.

4. The test apparatus for the stability of buried pipelines in unsaturated soil according to claim 3, characterized in that, The axial displacement measuring mechanism includes a displacement sensor, which is supported by the bracket, and the measuring end of the displacement sensor is connected to the pipe. The positioning and displacement measuring mechanism is installed on the reaction beam to obtain the radial displacement of the pipeline, and the measuring end of the positioning and displacement measuring mechanism is set towards the radial direction of the pipeline. The positioning and displacement measuring mechanism is a damper that enables displacement measurement.

5. The test apparatus for the stability of buried pipelines in unsaturated soil according to claim 3, characterized in that, The stress measurement component includes a tension sensor and a spoke sensor, with the tension sensor connected to a pipe and a power mechanism. A spoke sensor is installed at the end of the pipe to obtain the pipe resistance in axial displacement mode, and the spoke sensor is connected to the power mechanism.

6. The test apparatus for the stability of buried pipelines in unsaturated soil according to claim 2, characterized in that, The matrix suction distribution measuring component is a tension meter.

7. The test apparatus for the stability of buried pipelines in unsaturated soil according to claim 2, characterized in that, The data acquisition unit also includes strain gauges, which are fixed to the surface of the pipe to measure the radial strain of the pipe.

8. The test apparatus for the stability of buried pipelines in unsaturated soil according to claim 1, characterized in that, The pipeline includes a pipe and a connector installed in the visualization model box. One end of the pipe is inserted into the connector, and a sealing ring is provided at one end of the connector. The other end of the pipe is connected to the visualization model box through a fixed shaft. The pipe can move relative to the connector and the fixed shaft. The pipes are positioned close to the side wall of the visualization model box.

9. The test apparatus for the stability of buried pipelines in unsaturated soil according to claim 1, characterized in that, The second water tank is placed on the platform, which is connected to the lifting mechanism. The lifting mechanism is fixed to the mounting frame, and the mounting frame is set with scale lines in the vertical direction to read the displacement of the second water tank. The matrix suction measuring device is a U-shaped water pressure gauge, which is connected to a horizontal reading tube, and the horizontal reading tube is connected to the visualization model box.

10. A method for installing a test apparatus for the stability of buried pipelines in unsaturated soil according to any one of claims 1-9, characterized in that, Includes the following: The visualization model box is supported by a bracket, and pipes are installed inside the visualization model box. The pipes are connected to the loading unit to conduct a pre-loading test. Remove the pipes and install inlet and outlet pipes inside the visualization model box. The inlet and outlet pipes are connected to the first water tank through a water pressure gauge. The first water tank is connected to the second water tank. A permeable layer is laid on one side of the inlet and outlet pipes, and soil is filled on the other side of the permeable layer opposite the inlet and outlet pipes to the set first height. Adjust the position of the loading unit and reinstall the pipes; Continue filling the soil to the second height; A closed visualization model box is filled with water through inlet and outlet pipes until the water level exceeds the filling height, thus expelling air bubbles from the soil and allowing it to stand for a set time. The soil suction force is adjusted to a preset value by adjusting the height of the second water tank, and the soil suction force is measured by a water pressure gauge. Install the data acquisition unit and conduct a loading test using the loading unit.

Images