Full-transparent soil triaxial internal erosion test system and test method thereof

Abstract

The invention discloses a full-transparent soil triaxial internal erosion test system and a test method thereof. The system comprises a transparent loading system, a seepage control system, a laser imaging system, a water-sand separation system, a water pressure control system and an axial loading system. The transparent loading system comprises a base, a transparent pressure chamber is mounted on the base, and a sample table, a porous filter plate, a transparent soil sample, a porous stone and a sample cap are sequentially placed on the base from bottom to top in the transparent pressure chamber. And five L-shaped pipelines, namely a pipeline I, a pipeline II, a pipeline III, a pipeline IV and a pipeline V, are arranged in the base. The pipeline I is connected with the seepage control system, the pipeline II is connected with the water pressure control system, and the pipeline III is connected with the water-sand separation system and the water pressure control system. According to the device disclosed by the invention, a transparent soil sample can be monitored by combining a particle image velocity measurement technology, so that the displacement change of the multi-section soil body in the three-axis internal erosion process of the soil body can be obtained, and the internal structure of the soil body can be reproduced.

Description

Technical Field

[0001] This invention relates to the field of indoor soil mechanics-hydraulic coupling performance testing technology in the field of geotechnical and geological engineering, specifically a fully transparent triaxial internal erosion test system for soil and its test method. Background Technology

[0002] In a discontinuously graded, cohesive-free soil under certain hydraulic conditions, fine particles migrate and are lost through the pore channels between coarse particles, a process known as internal erosion of the soil. This process is a complex multiphase and multi-field coupling involving pore water seepage, erosion and migration of movable fine particles, deformation of porous media, and redistribution of soil stress.

[0003] A triaxial testing apparatus for soil can be used to determine the mechanical properties of soil under different stress states and drainage conditions. By applying axial and radial stress to the soil sample and monitoring the deformation response of the soil sample, the triaxial testing apparatus can calculate important parameters of the soil such as shear strength and compression modulus.

[0004] To further control the stress state of the soil and more realistically simulate actual erosion effects, the base plate of the conventional triaxial testing apparatus was modified into a mesh screen structure, allowing fine particles to pass through and detach from the original sample, thus achieving the erosion effect. Based on the microscopic distribution characteristics and variations of coarse and fine particles within the soil, the mechanism of erosion within the soil can be intuitively analyzed and explained. However, these characteristics are not visible in real soil or in conventional triaxial instruments.

[0005] Therefore, developing a fully transparent triaxial internal erosion testing system for soil is of great significance. Summary of the Invention

[0006] The purpose of this invention is to provide a fully transparent triaxial internal erosion testing system for soil.

[0007] It includes a transparent loading system, a seepage control system, a laser imaging system, a water-sand separation system, a water pressure control system, and an axial loading system.

[0008] The transparent loading system includes a base, a transparent pressure chamber, a sample stage, a porous filter plate, a permeable stone, and a sample cap.

[0009] A transparent pressure chamber is installed on the base. Inside the transparent pressure chamber and on the base, a sample stage, a porous filter plate, a transparent soil sample, a permeable stone, and a sample cap are placed sequentially from bottom to top. The outer walls of the sample stage, the porous filter plate, the transparent soil sample, the permeable stone, and the sample cap are wrapped with a transparent rubber membrane.

[0010] The base has five L-shaped pipes inside, namely pipe I, pipe II, pipe III, pipe IV and pipe V.

[0011] The vertical sections of pipes I and II pass through the top surface of the base and communicate with the inner cavity of the transparent pressure chamber. The horizontal sections pass through the side wall of the base and are connected to the seepage control system and the water pressure control system, respectively. The seepage control system is used to provide pressurized water head to the top of the transparent soil sample. The water pressure control system is used to regulate the lateral pressure and pore water pressure on the transparent soil sample.

[0012] The vertical section of pipe III passes through the top surface of the sample stage and contacts the porous filter plate, while the horizontal section passes through the side wall of the base and connects to the water-sand separation system and the water pressure control system. The water-sand separation system is used to collect the transparent sand particles separated under seepage and to measure their mass.

[0013] The vertical sections of pipes IV and V pass through the top surface of the sample stage and contact the porous filter plate, while the horizontal sections pass through the side wall of the base and communicate with the outside. Pipes IV and V are arranged opposite to each other.

[0014] The sample cap is equipped with an L-shaped pipe VI. The vertical section of the pipe VI passes through the bottom of the sample cap and contacts the permeable stone, while the horizontal section passes through the side wall of the sample cap and is connected to the pipe I through a rigid pipe.

[0015] The axial loading system includes a loading rod and a loading column. The transparent loading system is installed above the loading column. One end of the loading rod passes through the top plate of the transparent pressure chamber and rests against the top of the specimen cap, used to apply an axial load to the transparent soil specimen.

[0016] The laser imaging system includes a rotating disk, laser I, laser II, camera I, camera II, rotating rod I, rotating rod II, rotating rod III, hinge interface, rotating rod IV, and rotating rod V.

[0017] The rotating disk has a ring-shaped structure, with the inner ring sleeved on the outer wall of the loading column, and rotating rods I, II, and III installed at intervals on the outer ring.

[0018] Laser I and laser II are respectively installed on rotating rod I and rotating rod II, and laser I and laser II are set at 180° on the same horizontal plane.

[0019] The end of the rotating rod III away from the rotating disk is connected to the rotating rods IV and V through a hinge interface. Camera I and camera II are respectively mounted on the rotating rods IV and V.

[0020] The imaging planes of camera I and camera II are perpendicular to the light sheet planes of laser I and laser II.

[0021] Furthermore, the transparent soil sample comprises a framework material and a pore fluid. The framework material is fused silica sand. The pore fluid is a mixture of white oil and n-dodecane.

[0022] Furthermore, the diameter of pipe III is greater than that of pipes IV and V, and at least reaches the median value of the particle size range of the skeleton material sand.

[0023] Furthermore, the two ends of the transparent rubber membrane are fixed to the sample cap and the sample stage by rubber rings.

[0024] Furthermore, the rotating disk can be electrically rotated in a horizontal plane.

[0025] The rotating rods I, II, III, IV, and V can be adjusted in angle and height at will.

[0026] Furthermore, the transparent pressure chamber includes a glass cover and a top plate. One end of the glass cover is fixedly connected to the base, and the other end is fixedly connected to the top plate. Water-stopping gaskets are provided at the connection points between the glass cover and the base and top plate.

[0027] Furthermore, the axial loading system also includes a load cell, support rods, and a reverse crossbeam.

[0028] The loading column is fixed to the load cell. Two support rods are installed at intervals around the loading column on the load cell. A reverse crossbeam is vertically mounted on the support rod. A loading rod is vertically mounted on the middle of the reverse crossbeam. The loading rod passes through the top plate and connects to the curved surface of the top of the sample cap.

[0029] A water-stop sleeve is provided at the contact position between the loading rod and the top plate.

[0030] Furthermore, the seepage control system includes an outer pipe I, a seepage liquid tank, a seepage pressure controller, and a seepage pressure channel.

[0031] The seepage liquid tank is filled with pore liquid. The seepage liquid tank is connected to the horizontal section of pipe I via outer pipe I. The seepage liquid tank is connected to the seepage pressure controller via a seepage pressure channel.

[0032] The water pressure control system includes outer pipe II, outer pipe III, confining pressure controller, and back pressure controller.

[0033] The confining pressure controller is connected to the horizontal section of pipe II via outer pipe III. The back pressure controller is connected to the horizontal section of pipe III via outer pipe II.

[0034] The water-sand separation system includes a sand container, a weight sensor, a liquid container, outer pipe IV, outer pipe V, and a filter screen.

[0035] One end of the outer tube IV is connected to the outer tube II, and the other end extends into the sand container. A weight sensor is provided at the bottom of the sand container.

[0036] The bottom of the sand container is connected to the outer tube V, and a filter screen is provided at the connection point. The other end of the outer tube V is connected to the liquid container.

[0037] Furthermore, a porous liquid is injected into the transparent rubber membrane through pipe IV. A valve is installed at the end of pipes IV and V that connects to the outside.

[0038] Another objective of this invention is to provide a test method based on a fully transparent soil triaxial erosion test system, comprising the following steps:

[0039] S1. Install a triaxial internal erosion test system, including a transparent loading system, a seepage control system, a laser imaging system, a water-sand separation system, a water pressure control system, and an axial loading system, and prepare and install transparent soil samples in a transparent pressure chamber;

[0040] S2. Porous liquid is introduced into the transparent pressure chamber and the transparent rubber membrane through pipes III and IV, respectively, and then the confining pressure controller and the back pressure controller are used to control the pressure for consolidation.

[0041] S3. After consolidation is complete, turn on laser I and laser II and adjust the angles to make the entire vertical laser plane appear in the transparent soil sample. Then adjust the power to make the transparent soil sample show a clear high-brightness speckle field.

[0042] S4. After turning on Camera I and Camera II and adjusting the angle, adjust the exposure to make the photo have bright bokeh, and set the rotation speed of the dial.

[0043] S5. A hydraulic gradient is applied using a pressure controller to control the flow of liquid in the seepage tank toward the transparent soil sample; the set pressure of the pressure controller is higher than the set pressure value of the back pressure controller.

[0044] S6. During the erosion process, the eroded soil flows along pipe III into outer pipe II and outer pipe IV. The seepage control stops when the value on the weight sensor reaches the set soil loss value.

[0045] S7. Set the loading rate of the load cell and the rotation rate of the rotating disk so that the rotating disk can rotate exactly 180° within one loading level time.

[0046] S8. Begin vertical loading until the sample fails;

[0047] Cameras I and II take real-time photos of the transparent soil sample during the application of seepage pressure and loading. After the test, particle image velocimetry is used to monitor the displacement changes of the soil sample in multiple sections during the triaxial erosion process, thereby reproducing the internal structure of the soil.

[0048] The technical effects of this invention are undeniable, and its beneficial effects are as follows:

[0049] 1. This invention proposes a fully transparent triaxial internal erosion test instrument for soil. The device has a simple structure, high integration, strong applicability, and convenient operation, which greatly improves the test efficiency.

[0050] 2. This device, combined with particle image velocimetry technology, can fully visualize the erosion process inside a transparent soil sample and the deformation and failure under triaxial stress after erosion. It can also intuitively observe the microscopic mechanism of erosion development in the soil and the shear band development process during the deformation and failure of the soil after erosion.

[0051] 3. The laser imaging system of this device can monitor the displacement changes of soil in multiple sections during the triaxial erosion process, providing a data source for reconstructing the three-dimensional digital model of the soil, thereby reproducing the internal microstructure of the soil.

[0052] 4. The refractive index of the solid particles, pore liquid, glass cover, and polyurethane materials such as transparent rubber membrane, water-stopping gasket, and water-stopping rubber ring of the transparent soil sample is around 1.4584, which greatly reduces the error caused by light refraction.

[0053] 5. Using two cameras and two lasers for image acquisition can effectively solve the limitations of image distortion and laser irradiation range inside the glass cover. The hinged frame can be adjusted at any angle, providing a wide range of options. Attached Figure Description

[0054] Figure 1 This is a three-dimensional structural schematic diagram of a fully transparent triaxial internal erosion testing instrument for soil, as described in an embodiment of the present invention.

[0055] Figure 2 This is a cross-sectional view of the transparent pressure chamber.

[0056] Figure 3 This is a schematic diagram of the imaging system.

[0057] In the diagram: 1-Transparent loading system; 2-Seepage control system; 3-Laser imaging system; 4-Water-sand separation system; 5-Water pressure control system; 6-Loading rod; 7-Bolt; 8-Glass cover; 9-Sample cap; 10-Permeable stone; 11-Transparent soil sample; 12-Waterstop sleeve; 13-Pipe I; 14-Pipe II; 15-Pipe III; 16-Pipe IV; 17-Pipe V; 18-Rigid pipe; 19-Transparent rubber membrane; 20-Porous filter plate; 21-Sample stage; 22-Base; 23-Outer pipe I; 24-Seepage liquid tank; 25-Outer pipe II; 26-Outer pipe III; 27-Rotating disk; 28-Laser I ; 29-Laser II; 30-Camera I; 31-Camera II; 32-Rotating rod I; 33-Rotating rod II; 34-Rotating rod III; 35-Hinge interface; 36-Rotating rod IV; 37-Rotating rod V; 38-Reverse crossbeam; 39-Support rod; 40-Loading housing; 41-Pressure seepage controller; 42-Pressure seepage channel; 43-Sand container; 44-Weight sensor; 45-Liquid container; 46-Outer pipe IV; 47-Outer pipe V; 48-Confining pressure controller; 49-Back pressure controller; 50-Transparent pressure chamber; 51-Water-stop gasket; 52-Pipe VI; 53-Loading column; 54-Rubber ring; 55-Filter screen. Detailed Implementation

[0058] The present invention will be further described below with reference to embodiments, but it should not be construed that the scope of the present invention is limited to the following embodiments. Various substitutions and modifications made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention should be included within the scope of protection of the present invention.

[0059] Example 1:

[0060] A fully transparent triaxial internal erosion test system for soil includes a transparent loading system 1, a seepage control system 2, a laser imaging system 3, a water-sand separation system 4, a water pressure control system 5, and an axial loading system.

[0061] The transparent loading system 1 includes a base 22, a transparent pressure chamber 50, a sample stage 21, a porous filter plate 20, a permeable stone 10, and a sample cap 9.

[0062] A transparent pressure chamber 50 is installed on the base 22. Inside the transparent pressure chamber 50 and on the base 22, a sample stage 21, a porous filter plate 20, a transparent soil sample 11, a permeable stone 10, and a sample cap 9 are placed sequentially from bottom to top. The outer walls of the sample stage 21, the porous filter plate 20, the transparent soil sample 11, the permeable stone 10, and the sample cap 9 are wrapped with a transparent rubber membrane 19.

[0063] The base 22 has five L-shaped pipes inside, namely pipe I 13, pipe II 14, pipe III 15, pipe IV 16 and pipe V 17.

[0064] The vertical sections of pipes I13 and II14 pass through the top surface of the base 22 and communicate with the inner cavity of the transparent pressure chamber 50. The horizontal sections pass through the side wall of the base 22 and are connected to the seepage control system 2 and the water pressure control system 5, respectively. The seepage control system 2 is used to provide pressurized water head to the top of the transparent soil sample. The water pressure control system 5 is used to regulate the lateral pressure and pore water pressure on the transparent soil sample 11.

[0065] The vertical section of pipe Ⅲ15 passes through the top surface of the sample stage 21 and contacts the porous filter plate 20, while the horizontal section passes through the side wall of the base 22 and connects to the water-sand separation system 4 and the water pressure control system 5. The water-sand separation system 4 is used to collect the transparent sand particles separated under seepage and to measure their mass.

[0066] The vertical sections of pipes IV16 and V17 pass through the top surface of the sample stage 21 and contact the porous filter plate 20, while the horizontal sections pass through the side wall of the base 22 and communicate with the outside. Pipes IV16 and V17 are arranged opposite to each other.

[0067] The sample cap 9 is provided with an L-shaped pipe VI52. The vertical section of the pipe VI52 passes through the bottom of the sample cap 9 and contacts the permeable stone 10, while the horizontal section passes through the side wall of the sample cap 9 and is connected to the pipe I13 through the rigid pipe 18.

[0068] The axial loading system includes a loading rod 6 and a loading column 53. The transparent loading system 1 is installed above the loading column 53. One end of the loading rod 6 passes through the top plate of the transparent pressure chamber 50 and rests against the top of the sample cap 9, and is used to apply an axial load to the transparent soil sample 11.

[0069] The laser imaging system 3 includes a rotating disk 27, laser I 28, laser II 29, camera I 30, camera II 31, rotating rod I 32, rotating rod II 33, rotating rod III 34, hinge interface 35, rotating rod IV 36, and rotating rod V 37.

[0070] The rotating disk 27 has a ring-shaped structure, with the inner ring sleeved on the outer wall of the loading column 53, and rotating rods I 32, II 33, and III 34 installed at intervals on the outer ring.

[0071] Laser I28 and laser II29 are respectively installed on the rotating rod I32 and rotating rod II33, and the laser I28 and laser II29 are set at 180° on the same horizontal plane.

[0072] The end of the rotating rod III 34 away from the rotating disk 27 is connected to the rotating rod IV 36 and the rotating rod V 37 through the hinge interface 35. Camera I 30 and camera II 31 are respectively mounted on the rotating rod IV 36 and the rotating rod V 37.

[0073] The imaging planes of cameras I 30 and II 31 are perpendicular to the light sheet planes of lasers I 28 and II 29.

[0074] Example 2:

[0075] The main structure of this embodiment is the same as that of Embodiment 1. Furthermore, the transparent soil sample 11 includes a framework material and a pore fluid. The framework material is fused silica sand. The pore fluid is a mixture of white oil and n-dodecane.

[0076] Example 3:

[0077] The main structure of this embodiment is the same as any one of embodiments 1 to 2. Furthermore, the diameter of pipe Ⅲ15 is greater than that of pipe Ⅳ16 and pipe Ⅴ17, and at least reaches the median value of the particle size range of the skeleton material sand.

[0078] Example 4:

[0079] The main structure of this embodiment is the same as any one of embodiments 1 to 3. Furthermore, the two ends of the transparent rubber membrane 19 are fixed to the sample cap 9 and the sample stage 21 by rubber rings 54. The material of the rubber rings 54 is synthetic rubber.

[0080] Example 5:

[0081] The main structure of this embodiment is the same as any one of embodiments 1 to 4. Furthermore, the rotating disk 27 can rotate electrically in the horizontal plane.

[0082] The rotating rods I 32, II 33, III 34, IV 36 and V 37 can be adjusted in angle and height at will.

[0083] Example 6:

[0084] The main structure of this embodiment is the same as any one of embodiments 1 to 5. Further, the transparent pressure chamber 50 includes a glass cover 8 and a top plate. One end of the glass cover 8 is fixedly connected to the base 22, and the other end is fixedly connected to the top plate. A water-stopping washer 51 is provided at the connection point between the glass cover 8 and the base 22 and the top plate. The material of the water-stopping washer 51 is synthetic rubber.

[0085] Example 7:

[0086] The main structure of this embodiment is the same as any one of embodiments 1 to 6. Furthermore, the axial loading system also includes a load cell 40, a support rod 39, and a reverse crossbeam 38.

[0087] The loading column 53 is fixed to the load cell 40. Two support rods 39 are installed at intervals around the loading column 53 on the load cell 40. A reverse crossbeam 38 is vertically installed on the support rod 39. A loading rod 6 is vertically installed in the middle of the reverse crossbeam 38. The loading rod 6 passes through the top plate and connects with the curved top surface of the sample cap 9.

[0088] A water-stop sleeve 12 is provided at the contact position between the loading rod 6 and the top plate. The water-stop sleeve 12 is made of synthetic rubber.

[0089] Example 8:

[0090] The main structure of this embodiment is the same as any one of embodiments 1 to 7. Furthermore, the seepage control system 2 includes an outer pipe I 23, a seepage liquid tank 24, a seepage pressure controller 41, and a seepage pressure channel 42.

[0091] The seepage liquid tank 24 is filled with pore liquid. The seepage liquid tank 24 is connected to the horizontal section of pipe I13 via outer pipe I23. The seepage liquid tank 24 is connected to the seepage pressure controller 41 via seepage pressure channel 42.

[0092] The water pressure control system 5 includes outer pipe II 25, outer pipe III 26, confining pressure controller 48, and back pressure controller 49.

[0093] The confining pressure controller 48 is connected to the horizontal section of pipe II14 via outer pipe III26, and is mainly used to apply and control a constant fluid pressure acting on the side of the cylindrical soil sample.

[0094] The back pressure controller 49 is connected to the horizontal section of pipe Ⅲ15 via outer pipe Ⅱ25, and is mainly used to apply and control the pressure acting on the pore water inside the soil sample.

[0095] The water-sand separation system 4 includes a sand container 43, a weight sensor 44, a liquid container 45, an outer pipe IV 46, an outer pipe V 47, and a filter screen 55.

[0096] One end of the outer tube IV 46 is connected to the outer tube II 25, and the other end extends into the sand container 43. A weight sensor 44 is provided at the bottom of the sand container 43. The weight sensor 44 has an accuracy of 0.01g.

[0097] The bottom of the sand container 43 is connected to the outer tube V 47, and a filter screen 55 is provided at the connection point. The other end of the outer tube V 47 is connected to the liquid container 45.

[0098] Example 9:

[0099] The main structure of this embodiment is the same as any one of embodiments 1 to 8. Furthermore, the transparent rubber membrane 19 is injected with pore liquid through pipe IV 15.

[0100] When back pressure is applied, the liquid is injected directly into the pores through the back pressure controller 49 via the outer pipe II 25 and then through the inner pipe IV 15 of the base 22, without passing through the transparent pressure chamber 50. When the seepage control system 2 provides a high head, the liquid is injected into the pores between the transparent pressure chamber 50 and the transparent rubber membrane 19 through the seepage liquid tank 24, the outer pipe I 23, the inner pipe I 13 of the base 22, and then through the rigid pipe 18.

[0101] Valves are installed at the ends of pipes IV16 and V17 that connect to the outside.

[0102] Pipe IV16 or pipe V17 can be connected to an external pore water pressure gauge.

[0103] Water or carbon dioxide is introduced into pipe IV16 or pipe V17 to achieve head saturation or carbon dioxide saturation.

[0104] Example 10:

[0105] The main structure of this embodiment is the same as any one of embodiments 1 to 9. Further, a fully transparent triaxial internal erosion test system for soil includes a transparent loading system 1, a seepage control system 2, a laser imaging system 3, a water-sand separation system 4, a water pressure control system 5, and an axial loading system.

[0106] The transparent loading system 1 includes a base 22, a transparent pressure chamber 50, a sample stage 21, a porous filter plate 20, a permeable stone 10, and a sample cap 9.

[0107] A transparent pressure chamber 50 is installed on the base 22.

[0108] The transparent pressure chamber 50 includes a glass cover 8 and a top plate. One end of the glass cover 8 is fixedly connected to the base 22, and the other end is fixedly connected to the top plate. A water-stopping gasket 51 is provided at the connection position between the glass cover 8 and the base 22 and the top plate. The water-stopping gasket 51 is made of synthetic rubber.

[0109] Inside the transparent pressure chamber 50, on the base 22, a sample stage 21, a porous filter plate 20, a transparent soil sample 11, a permeable stone 10, and a sample cap 9 are placed sequentially from bottom to top. A transparent rubber membrane 19 is wrapped around the outer walls of the sample stage 21, the porous filter plate 20, the transparent soil sample 11, the permeable stone 10, and the sample cap 9. The two ends of the transparent rubber membrane 19 are fixed to the sample cap 9 and the sample stage 21 by rubber rings 54. The transparent rubber membrane 19 and the rubber rings 54 are made of synthetic rubber.

[0110] The base 22 has five L-shaped pipes inside, namely pipe I 13, pipe II 14, pipe III 15, pipe IV 16 and pipe V 17.

[0111] The vertical sections of pipes I13 and II14 pass through the top surface of the base 22 and communicate with the inner cavity of the transparent pressure chamber 50. The horizontal sections pass through the side wall of the base 22 and are connected to the seepage control system 2 and the water pressure control system 5, respectively.

[0112] The seepage control system 2 is used to control the fluid velocity and flow rate inside the transparent soil sample. The seepage control system 2 includes an outer pipe I 23, a seepage liquid tank 24, a seepage pressure controller 41, and a seepage pressure channel 42. The seepage liquid tank 24 is filled with pore liquid. The seepage liquid tank 24 is connected to the horizontal section of pipe I 13 via the outer pipe I 23. The seepage liquid tank 24 is connected to the seepage pressure controller 41 via the seepage pressure channel 42.

[0113] The water pressure control system 5 is used to regulate the pore water pressure on the transparent soil sample 11. The water pressure control system 5 includes an outer pipe II 25, an outer pipe III 26, a confining pressure controller 48, and a back pressure controller 49. The confining pressure controller 48 is connected to the horizontal section of pipe II 14 via the outer pipe III 26. The back pressure controller 49 is connected to the horizontal section of pipe III 15 via the outer pipe II 25.

[0114] The vertical section of the pipe Ⅲ15 passes through the top surface of the sample stage 21 and contacts the porous filter plate 20, while the horizontal section passes through the side wall of the base 22 and connects to the water-sand separation system 4 and the water pressure control system 5.

[0115] The water-sand separation system 4 is used to separate the water flowing out with the seepage during the experiment from the transparent soil particles. The water-sand separation system 4 includes a sand container 43, a weight sensor 44, a liquid container 45, an outer tube IV 46, an outer tube V 47, and a filter screen 55. One end of the outer tube IV 46 is connected to the outer tube II 25, and the other end extends into the sand container 43. The weight sensor 44 is located at the bottom of the sand container 43. The weight sensor 44 has an accuracy of 0.01g. The side wall of the sand container 43 is connected to the outer tube V 47, and a filter screen 55 is located at the connection point. The other end of the outer tube V 47 is connected to the liquid container 45.

[0116] The vertical sections of pipes IV16 and V17 pass through the top surface of the sample stage 21 and contact the porous filter plate 20, while the horizontal sections pass through the side wall of the base 22 and communicate with the outside. Pipes IV16 and V17 are arranged opposite to each other.

[0117] The sample cap 9 is provided with an L-shaped pipe VI52. The vertical section of the pipe VI52 passes through the bottom of the sample cap 9 and contacts the permeable stone 10, while the horizontal section passes through the side wall of the sample cap 9 and is connected to the pipe I13 through the rigid pipe 18.

[0118] The transparent soil sample 11 comprises a framework material and a pore fluid. The framework material is fused silica sand. The pore fluid is a mixture of white oil and n-dodecane. The diameter of pipe III 15 is greater than that of pipes IV 16 and V 17, and at least reaches the median of the particle size range of the framework material sand.

[0119] The axial loading system also includes a load cell 40, a support rod 39, a reverse crossbeam 38, a loading rod 6, and a loading column 53.

[0120] The transparent loading system 1 is installed above the loading column 53. The loading column 53 is fixed to the load chamber 40. Two support rods 39 are installed at intervals around the loading column 53 on the load chamber 40. A reverse crossbeam 38 is vertically installed on the support rod 39. A loading rod 6 is vertically installed in the middle of the reverse crossbeam 38. The loading rod 6 passes through the top plate and connects with the top curved surface of the sample cap 9, and is used to apply axial load to the transparent soil sample 11.

[0121] A water-stop sleeve 12 is provided at the contact position between the loading rod 6 and the top plate. The water-stop sleeve 12 is made of synthetic rubber.

[0122] The laser imaging system 3 includes a rotating disk 27, laser I 28, laser II 29, camera I 30, camera II 31, rotating rod I 32, rotating rod II 33, rotating rod III 34, hinge interface 35, rotating rod IV 36, and rotating rod V 37.

[0123] The rotating disk 27 has a ring-shaped structure and can rotate electrically in a horizontal plane. The inner ring of the rotating disk 27 is sleeved on the outer wall of the loading column 53, and rotating rods I 32, II 33, and III 34 are installed at intervals on the outer ring.

[0124] The rotating rods I 32, II 33, III 34, IV 36 and V 37 can be adjusted in angle and height at will.

[0125] Laser I28 and laser II29 are respectively installed on the rotating rod I32 and rotating rod II33, and the laser I28 and laser II29 are set at 180° on the same horizontal plane.

[0126] The end of the rotating rod III 34 away from the rotating disk 27 is connected to the rotating rod IV 36 and the rotating rod V 37 through the hinge interface 35. Camera I 30 and camera II 31 are respectively mounted on the rotating rod IV 36 and the rotating rod V 37.

[0127] The imaging planes of cameras I 30 and II 31 are perpendicular to the light sheet planes of lasers I 28 and II 29.

[0128] Example 11:

[0129] The main structure of this embodiment is the same as any one of embodiments 1 to 10. Furthermore, a fully transparent triaxial internal erosion test system for soil includes a transparent loading system 1, a seepage control system 2, a laser imaging system 3, a water-sand separation system 4, and a water pressure control system 5.

[0130] The transparent loading system 1 includes a loading rod 6, a transparent pressure chamber 50, a water-stopping washer 51, a bolt 7, a glass cover 8, a sample cap 9, a permeable stone 10, a transparent soil sample 11, a water-stopping sleeve 12, pipe I 13, pipe II 14, pipe III 15, pipe IV 16, pipe V 17, a rigid pipe 18, a transparent rubber membrane 19, a porous filter plate 20, a sample stage 21, a base 22, a water-stopping washer 51, a pipe VI 52, a loading column 53, and a rubber ring 54.

[0131] The sample stage 21 is located at the center of the top surface of the base 22.

[0132] The transparent soil sample 11 is a cylinder and is placed on the sample stage 21.

[0133] A permeable stone 10 is placed above the transparent soil sample 11, and a porous filter plate 20 is placed below it. A sample cap 9 is placed on top of the permeable stone 10.

[0134] The loading rod 6 passes through the middle of the transparent pressure chamber 50, and two water-stop sleeves 12 are provided at the contact point. The bottom of the loading rod 6 is connected to the sample cap 9 with a curved surface.

[0135] The outer walls of the transparent soil sample 11, sample stage 21, porous filter plate 20, sample cap 9, and permeable stone 10 are wrapped with a transparent rubber membrane 19.

[0136] The upper end of the transparent rubber membrane 19 is fixed to the sample cap 9 by a rubber ring 54. The lower end of the transparent rubber membrane 19 is fixed to the sample stage 21 by a rubber ring 54.

[0137] The glass cover 8 is connected to the transparent pressure chamber 50 at the top and placed on the base 22 at the bottom. A water-stopping gasket 51 is provided at the contact point between the two.

[0138] Five L-shaped pipes are provided on the base 22. One end of pipes I13 and II14 is connected to the top surface of the base 22, and the other end is connected to the side wall of the base 22. One end of pipes III15, IV16 and V17 is connected to the sample stage 21 on the top surface of the base 22, and the other end is connected to the side wall of the base 22. Pipes IV16 and V17 are arranged symmetrically.

[0139] Pipe Ⅳ16 is connected to an external pore water pressure gauge.

[0140] Pipeline Ⅳ16 is connected to an external valve.

[0141] The sample cap 9 is provided with a pipe VI52.

[0142] Pipeline VI52 is connected to pipe I13 via rigid pipe 18.

[0143] The base 22 and the glass cover 8 are connected and fixed by four bolts 7.

[0144] The transparent loading system 1 is mounted on the load cell 40 below. A reverse crossbeam 38 is provided above the load cell 40 via a support rod 39. The loading rod 6 in the transparent loading system 1 is connected to the middle of the lower end of the reverse crossbeam 38.

[0145] The seepage control system 2 includes an outer pipe I 23, a seepage liquid tank 24, a seepage pressure channel 42, and a seepage pressure controller 41.

[0146] One end of the outer pipe I23 is connected to the pipe I13, and the other end is connected to the seepage liquid tank 24.

[0147] One end of the osmotic pressure channel 42 is connected to the seepage liquid tank 24, and the other end is connected to the osmotic pressure controller 41.

[0148] The laser imaging system 3 includes a rotating disk 27, laser I 28, laser II 29, camera I 30, camera II 31, rotating rod I 32, rotating rod II 33, rotating rod III 34, hinge interface 35, rotating rod IV 36, and rotating rod V 37.

[0149] The rotating disk 27 is mounted on the loading column 53. The rotating disk 27 can rotate electrically in the horizontal plane.

[0150] One end of the rotating rod I32 is connected to the laser I28, and the other end is connected to the rotating disk 27.

[0151] One end of the rotating rod II 33 is connected to the laser II 29, and the other end is connected to the rotating disk 27.

[0152] One end of the rotating rod Ⅲ34 is connected to the hinge interface 35, and the other end is connected to the rotating disk 27.

[0153] One end of the rotating rod IV36 is connected to the camera I30, and the other end is connected to the hinge interface 35.

[0154] One end of the rotating rod V37 is connected to the camera II31, and the other end is connected to the hinge interface 35.

[0155] The rotating rods I 32, II 33, III 34, IV 36 and V 37 can be adjusted in angle and height at will.

[0156] Laser I 28 and laser II 29 are at 180° to each other on the same horizontal plane. Laser I 28 and laser II 29 are perpendicular to the axis of symmetry of camera I 30 and camera II 31.

[0157] The water-sand separation system 4 includes a sand container 43, a weight sensor 44, a liquid container 45, and a filter screen 55. The weight sensor 44 is placed below the sand container 43.

[0158] The filter screen 55 is located at the end where the outer tube V47 connects to the sand container 43.

[0159] One end of the outer tube IV 46 is connected to the outer tube II 25, and the other end is connected to the sand container 43. One end of the outer tube V 47 is connected to the sand container 43, and the other end is connected to the liquid container 45.

[0160] The water pressure control system 5 includes a confining pressure controller 48 and a back pressure controller 49.

[0161] One end of the outer pipe III26 is connected to the confining pressure controller 48, and the other end is connected to the pipe II14. One end of the outer pipe II25 is connected to the back pressure controller 49, and the other end is connected to the pipe III15.

[0162] Furthermore, the transparent soil sample 11 comprises a framework material and a pore fluid. The framework material is fused silica sand. The pore fluid is a mixture of white oil and n-dodecane.

[0163] Furthermore, the diameter of pipe Ⅲ15 must be larger than that of pipe Ⅳ16 and pipe Ⅴ17, at least reaching the median value of the fused silica sand particle size range.

[0164] Furthermore, the seepage liquid tank 24 is filled with a porous liquid, namely a mixed solution of white oil and n-dodecane.

[0165] Furthermore, a porous liquid is injected between the transparent pressure chamber 50 and the transparent rubber membrane 19 via pipe III 15. Porous liquid is also injected into the interior of the transparent rubber membrane 19 via pipe IV 16.

[0166] Furthermore, the materials of the water-stop sleeve 12, transparent rubber membrane 19, water-stop washer 51, and rubber ring 54 are all synthetic rubber.

[0167] Furthermore, the rotating disk 27 is controlled by a motor, and the rotation speed can be freely adjusted.

[0168] Furthermore, lasers I28 and II29 are fixed to rotating rods I32 and II33 by telescopic clamps, and lasers I28 and II29 can emit diffused laser planes through the front emission port. Lasers I28 and II29 are at 180° to each other on the same horizontal plane, forming complete laser coverage inside the transparent soil sample 11. Cameras I30 and II31 are high-resolution industrial cameras that capture the laser plane at a certain angle, obtaining cross-sections from multiple angles.

[0169] Furthermore, the weight sensor 44 has an accuracy of up to 0.01g.

[0170] Furthermore, the seepage direction of the transparent soil sample 11 is vertically downward.

[0171] Example 12:

[0172] The main structure of this embodiment is the same as any one of embodiments 1 to 11. Furthermore, a test method based on a fully transparent soil triaxial erosion test system includes the following steps:

[0173] S1. Install a triaxial internal erosion test system, including a transparent loading system 1, a seepage control system 2, a laser imaging system 3, a water-sand separation system 4, a water pressure control system 5, and an axial loading system, and prepare and install a transparent soil sample 11 in a transparent pressure chamber 50.

[0174] S2. Porous liquid is introduced into the transparent pressure chamber 50 and the transparent rubber membrane 19 through pipes Ⅲ15 and Ⅳ16 respectively, and then the pressure is controlled by confining pressure controller 48 and back pressure controller 49 respectively to achieve solidification.

[0175] S3. After consolidation is complete, turn on laser I 28 and laser II 29, and adjust the angles to make the entire vertical laser plane appear in the transparent soil sample 11. Then adjust the power to make the transparent soil sample 11 show a clear high-brightness speckle field.

[0176] S4. After turning on Camera I 30 and Camera II 31 and adjusting the angle, adjust the exposure to make the photo show bright speckle, and set the rotation speed of the dial 27.

[0177] S5. Apply a hydraulic gradient using the seepage pressure controller 41 to control the flow of liquid in the seepage liquid tank 24 toward the transparent soil sample 11; the set pressure of the seepage pressure controller 41 is higher than the set pressure value of the back pressure controller 49.

[0178] S6. During the erosion process, the eroded soil flows along pipe Ⅲ15 into outer pipe Ⅱ25 and outer pipe Ⅳ46. When the value on the weight sensor 44 reaches the set soil loss value, the seepage control 41 stops.

[0179] S7. Set the loading rate of the load cell 40 and the rotation rate of the rotating disk 27 so that the rotating disk 27 can rotate exactly 180° within one loading level time.

[0180] S8. Begin vertical loading until the sample fails;

[0181] Cameras I 30 and II 31 take real-time photos of the transparent soil sample 11 during the application of seepage pressure and loading. After the test, particle image velocimetry technology is used to monitor the displacement changes of the soil in multiple sections during the triaxial erosion process of the transparent soil sample, and the internal structure of the soil is reproduced.

[0182] Example 13:

[0183] The main structure of this embodiment is the same as any one of embodiments 1 to 12. Furthermore, a test method based on a fully transparent soil triaxial internal erosion test system includes the following steps:

[0184] 1) Prepare and install a transparent soil sample 11 in a transparent pressure chamber 50. Introduce pore liquid into the transparent pressure chamber 50 and the transparent rubber membrane 19 through pipes III 15 and IV 16 respectively, and use confining pressure controller 48 and back pressure controller 49 to control the pressure for consolidation.

[0185] 2) After consolidation, turn on laser I28 and laser II29 and adjust the angle to make the entire vertical laser plane appear in the transparent soil sample 11, and adjust the power to make the transparent soil sample 11 show a clear high-brightness speckle field; turn on camera I30 and camera II31, adjust the angle and adjust the exposure to make the photograph show high-brightness speckle.

[0186] 3) Set the rotation speed of the rotating disk 27 so that it can rotate slowly and uniformly during the seepage of the transparent soil sample 11.

[0187] 4) A hydraulic gradient is applied using a seepage pressure controller 41 to control the flow of liquid in the seepage liquid tank 24 toward the transparent soil sample 11. The set pressure of the seepage pressure controller 41 should be higher than the set pressure value of the back pressure controller 49.

[0188] 5) The eroded soil flows along pipe Ⅲ15 into outer pipe Ⅱ25 and outer pipe Ⅳ46. When the value on the weight sensor 44 reaches the set soil loss value, the seepage control 41 stops.

[0189] 6) Set the loading rate of the load cell 40 and the rotation rate of the rotating disk 27 so that the rotating disk 27 can rotate exactly 180° within one loading level time.

[0190] 7) Start vertical loading until the sample fails. During the application of seepage pressure and loading, cameras I30 and II31 take continuous pictures. The particle image velocimetry technology is used to monitor the transparent soil sample and obtain the displacement changes of the soil in multiple sections during the triaxial erosion process, thus reproducing the internal structure of the soil.

Claims

1. A fully transparent triaxial erosion testing system for soil, characterized in that: It includes a transparent loading system (1), a seepage control system (2), a laser imaging system (3), a water-sand separation system (4), a water pressure control system (5), and an axial loading system; The transparent loading system (1) includes a base (22), a transparent pressure chamber (50), a sample stage (21), a porous filter plate (20), a permeable stone (10), and a sample cap (9); A transparent pressure chamber (50) is installed on the base (22). Inside the transparent pressure chamber (50) and on the base (22), a sample platform (21), a porous filter plate (20), a transparent soil sample (11), a permeable stone (10), and a sample cap (9) are placed sequentially from bottom to top. The outer walls of the sample platform (21), the porous filter plate (20), the transparent soil sample (11), the permeable stone (10), and the sample cap (9) are wrapped with a transparent rubber membrane (19). The base (22) is equipped with five L-shaped pipes, namely pipe I (13), pipe II (14), pipe III (15), pipe IV (16) and pipe V (17); The vertical sections of pipe I (13) and pipe II (14) pass through the top surface of the base (22) and are connected to the inner cavity of the transparent pressure chamber (50). The horizontal sections pass through the side wall of the base (22) and are connected to the seepage control system (2) and the water pressure control system (5) respectively. The seepage control system (2) is used to provide pressurized water head to the top of the transparent soil sample. The water pressure control system (5) is used to regulate the lateral pressure and pore water pressure on the transparent soil sample (11). The vertical section of the pipe Ⅲ (15) passes through the top surface of the sample platform (21) and contacts the porous filter plate (20), while the horizontal section passes through the side wall of the base (22) and connects to the water-sand separation system (4) and the water pressure control system (5). The water-sand separation system (4) is used to collect the transparent sand particles separated under the seepage action and to measure their mass. The vertical sections of pipes IV (16) and V (17) pass through the top surface of the sample stage (21) and contact the porous filter plate (20), while the horizontal sections pass through the side wall of the base (22) and communicate with the outside. Pipes IV (16) and V (17) are arranged opposite to each other. The sample cap (9) is provided with an L-shaped pipe VI (52). The vertical section of the pipe VI (52) passes through the bottom of the sample cap (9) and contacts the permeable stone (10). The horizontal section passes through the side wall of the sample cap (9) and is connected to the pipe I (13) through a rigid pipe (18). The axial loading system includes a loading rod (6) and a loading column (53); the transparent loading system (1) is installed above the loading column (53); one end of the loading rod (6) passes through the top plate of the transparent pressure chamber (50) and rests against the top of the sample cap (9) to apply axial load to the transparent soil sample (11); The laser imaging system (3) includes a rotating disk (27), laser I (28), laser II (29), camera I (30), camera II (31), rotating rod I (32), rotating rod II (33), rotating rod III (34), hinge interface (35), rotating rod IV (36) and rotating rod V (37); The rotating disk (27) has a ring structure, with the inner ring sleeved on the outer wall of the loading column (53), and rotating rods I (32), II (33), and III (34) installed at intervals on the outer ring; Laser I (28) and laser II (29) are respectively installed on the rotating rod I (32) and rotating rod II (33), and the laser I (28) and laser II (29) are set at 180° on the same horizontal plane; The end of the rotating rod III (34) away from the rotating disk (27) is connected to the rotating rod IV (36) and the rotating rod V (37) through a hinge interface (35). Camera I (30) and camera II (31) are respectively mounted on the rotating rod IV (36) and the rotating rod V (37). The imaging planes of cameras I (30) and II (31) are perpendicular to the light sheet planes of lasers I (28) and II (29).

2. The fully transparent triaxial erosion testing system for soil according to claim 1, characterized in that: The transparent soil sample (11) includes a framework material and a pore liquid; the framework material is fused silica sand; the pore liquid is a mixture of white oil and n-dodecane.

3. The fully transparent triaxial erosion testing system for soil according to claim 1, characterized in that: The diameter of pipe Ⅲ (15) is greater than that of pipe Ⅳ (16) and pipe Ⅴ (17), and at least reaches the median value of the particle size range of the skeleton material sand.

4. The fully transparent triaxial erosion testing system for soil according to claim 1, characterized in that: The two ends of the transparent rubber membrane (19) are fixed to the sample cap (9) and the sample stage (21) by rubber rings (54).

5. The fully transparent triaxial erosion testing system for soil according to claim 1, characterized in that: The rotating disk (27) can rotate electrically in the horizontal plane; The rotating rods I (32), II (33), III (34), IV (36) and V (37) can be adjusted in angle and height at will.

6. The fully transparent triaxial erosion testing system for soil according to claim 1, characterized in that: The transparent pressure chamber (50) includes a glass cover (8) and a top plate; one end of the glass cover (8) is fixedly connected to the base (22), and the other end is fixedly connected to the top plate; a water-stopping gasket (51) is provided at the connection position between the glass cover (8) and the base (22) and the top plate.

7. The fully transparent triaxial erosion testing system for soil according to claim 1, characterized in that: The axial loading system also includes a load cell (40), a support rod (39), and a reverse crossbeam (38); The loading column (53) is fixed on the load chamber (40); two support rods (39) are installed at intervals around the loading column (53) on the load chamber (40); a reverse crossbeam (38) is vertically installed on the support rod (39); a loading rod (6) is vertically installed in the middle of the reverse crossbeam (38); the loading rod (6) passes through the top plate and connects with the top curved surface of the sample cap (9). The water-stop sleeve (12) is provided at the contact position between the loading rod (6) and the top plate.

8. The fully transparent triaxial erosion testing system for soil according to claim 1, characterized in that: The seepage control system (2) includes an outer pipe I (23), a seepage liquid tank (24), a seepage pressure controller (41), and a seepage pressure channel (42); The seepage liquid tank (24) is filled with pore liquid; the seepage liquid tank (24) is connected to the horizontal section of pipe I (13) through outer pipe I (23); the seepage liquid tank (24) is connected to the seepage pressure controller (41) through seepage pressure channel (42). The water pressure control system (5) includes outer pipe II (25), outer pipe III (26), confining pressure controller (48) and back pressure controller (49); The confining pressure controller (48) is connected to the horizontal section of pipe II (14) via outer pipe III (26); the back pressure controller (49) is connected to the horizontal section of pipe III (15) via outer pipe II (25); The water-sand separation system (4) includes a sand container (43), a weight sensor (44), a liquid container (45), an outer pipe IV (46), an outer pipe V (47), and a filter screen (55); One end of the outer tube IV (46) is connected to the outer tube II (25), and the other end extends into the sand container (43). The weight sensor (44) is provided at the bottom of the sand container (43). The bottom of the sand container (43) is connected to the outer tube V (47), and a filter screen (55) is provided at the connection point; the other end of the outer tube V (47) is connected to the liquid container (45).

9. The fully transparent triaxial erosion testing system for soil according to claim 1, characterized in that: The transparent rubber membrane (19) is filled with pore liquid through pipe IV (15); the ends of pipe IV (16) and pipe V (16) that connect to the outside are equipped with valves.

10. A test method based on the fully transparent soil triaxial erosion test system described in claims 1-10, characterized in that, Includes the following steps: S1. Install a triaxial internal erosion test system, including a transparent loading system (1), a seepage control system (2), a laser imaging system (3), a water-sand separation system (4), a water pressure control system (5), and an axial loading system, and prepare and install transparent soil samples (11) in a transparent pressure chamber (50); S2. Pore fluid is introduced into the transparent rubber membrane (19) through pipe III (15), and then the pressure is controlled by confining pressure controller (48) and back pressure controller (49) respectively to solidify the membrane. S3. After consolidation is completed, turn on laser I (28) and laser II (29) and adjust the angle so that the entire vertical laser plane appears in the transparent soil sample (11). Then adjust the power so that the transparent soil sample (11) presents a clear high-brightness speckle field. S4. Open camera I (30) and camera II (31), adjust the angle and then adjust the exposure to make the photo show bright speckle, and set the rotation speed of the dial (27); S5. Apply a hydraulic gradient using a pressure controller (41) to control the flow of liquid in the seepage liquid tank (24) toward the transparent soil sample (11); the set pressure of the pressure controller (41) is higher than the set pressure value of the back pressure controller (49). S6. During the erosion process, the eroded soil flows into the outer pipe II (25) and the outer pipe IV (46) along the pipe III (15). When the value on the weight sensor (44) reaches the set soil loss value, the seepage control (41) stops. S7. Set the loading rate of the load cell (40) and the rotation rate of the rotating disk (27) so that the rotating disk (27) can rotate 180° within one loading level time. S8. Begin vertical loading until the sample fails; Camera I (30) and Camera II (31) take real-time photos of the transparent soil sample (11) during the application of seepage pressure and loading. After the test, the particle image velocimetry technology is used to monitor the displacement changes of the soil in multiple sections during the triaxial erosion process of the transparent soil sample, and reproduce the internal structure of the soil.

Images