Soil body visual seepage direct shear test device and method

Abstract

The invention provides a soil body visual seepage direct shear test device and method, and relates to the technical field of material performance testing. The shear boxes are communicated with one another and stacked in an overlapped manner; a water injection tank; the shearing mechanism is respectively connected with the test base and each shearing box; wherein each shear box is prepared from a transparent material and is used for observing the evolution rule of a test soil body under the action of seepage; wherein two adjacent shearing boxes are combined to form a shearing unit; the plurality of shearing units with different placement heights are used for placing test soil bodies with different sampling depths, and the placement heights are matched with the sampling depths, so that the permeability coefficient and the shearing strength of the test soil bodies with the corresponding sampling depths are obtained. The device provided by the invention solves the problems that the existing indoor direct shear test equipment cannot master the evolution rule of fine particles in waste residue soil and cannot obtain the permeability coefficients of soil bodies with different depths.

Description

Technical Field

[0001] The present application relates to the technical field of material performance testing, and in particular to a soil visualization seepage direct shear test device and method. Background Art

[0002] The shear property of soil is one of the mechanical properties that must be considered in the stability analysis of actual projects. In the evaluation of foundation bearing capacity, slope and roadbed stability, the shear strength index of soil is the most important mechanical parameter, which is usually determined by indoor direct shear test, triaxial test or in-situ test. However, due to the large particle size, wide gradation and high looseness of the large amount of waste soil generated during the construction process, it is difficult for conventional indoor direct shear test equipment to obtain its accurate parameters. At the same time, since coarse-grained soil such as waste soil is often affected by its large pore characteristics, under the action of water infiltration, the fine particles in the soil are easy to migrate, deposit and clog between the skeleton pores composed of coarse particles, and change the soil structure, reduce the stability of the soil, and thus cause geological disasters such as collapse, landslide and mud-rock flow. At the same time, with the migration of fine particles, the permeability and shear strength characteristics of the soil at different depths will also change accordingly.

[0003] However, the existing shear strength testing technology can only obtain the shear strength parameters of the soil at the solid depth after seepage destruction, but it is also unable to obtain the permeability coefficient of the soil at different depths, nor can it grasp the dynamic process of fine particle migration and loss in the abandoned soil. Summary of the invention

[0004] In view of the above problems, one of the purposes of the present invention is to provide a soil visualization seepage direct shear test device to solve the problem that the existing indoor direct shear test equipment cannot grasp the evolution law of fine particles in the abandoned soil, and cannot obtain the permeability coefficient and shear strength of soil at different depths under seepage conditions. The second purpose of the present invention is to provide a soil visualization seepage direct shear test method.

[0005] In order to achieve one of the objectives, the first aspect of the present invention provides a soil visualization seepage direct shear test device, the technical solution adopted is: A soil visualized seepage direct shear test device, the device comprising: The test base is hollow inside and has two openings on opposite sides as observation ends; A plurality of interconnected shear boxes are located in the cavity of the test base, and the plurality of shear boxes are stacked from the bottom to the top of the test base; a water injection box, connected to the shear box near the top of the test base, for establishing seepage conditions; A shear mechanism, connected to the test base and each of the shear boxes, respectively, for applying a shear force to the shear boxes; Wherein, two adjacent shear boxes are combined to form a shear unit, and the multiple shear units do not overlap; and the multiple shear units at different placement heights are used to place test soils at different sampling depths, and the placement heights match the size of the sampling depths to obtain the permeability coefficient and shear strength of the test soils at each corresponding sampling depth; Wherein, each of the shear boxes is made of transparent material and is used to observe the evolution law of the test soil under the action of seepage.

[0006] Optionally, the device further comprises: a sedimentation tank, connected to the shear box near the bottom of the test base, for receiving water and particulate matter flowing out of the shear box under seepage conditions; A measuring cup is communicated with the sedimentation tank and is used for receiving water overflowing from the sedimentation tank.

[0007] Optionally, a first filtering structure is provided between the shear box and the sedimentation tank; and a second filtering structure is provided between the sedimentation tank and the measuring cup.

[0008] Optionally, at least one load-bearing column is provided in the sedimentation tank, and the load-bearing column abuts against the shear box.

[0009] Optionally, the test base includes an upper movable structure and a lower supporting structure, wherein the upper movable structure is telescopically arranged on the top of the lower supporting structure; and at least one supporting column is arranged at the bottom of the lower supporting structure for connection.

[0010] Optionally, the shear mechanism includes a first jack and a plurality of second jacks; wherein the first jack is arranged on the top wall of the test base and opposite to the top of the shear box, for applying a vertical load; and the plurality of second jacks are arranged on the side walls of the test base and respectively opposite to the opposite sides of each of the shear boxes, for applying a horizontal load.

[0011] Optionally, a water inlet and an overflow port are respectively provided on opposite sides of the water injection box, and the water inlet and the overflow port are opposite to the opening of the test base; wherein each of the shear units is connected to a transparent pressure measuring tube.

[0012] Optionally, the device further comprises a camera, wherein the camera is located opposite to the opening of the test base.

[0013] Optionally, waterstop tape is wrapped between two adjacent shear boxes and between the shear box near the top of the test base and the water injection box; and a non-woven geotextile is also arranged between the shear box and the water injection box.

[0014] To achieve the second purpose, the second aspect of the present invention provides a soil visualized seepage direct shear test method, the technical solution adopted is: A soil visualization seepage direct shear test method, relying on the soil visualization seepage direct shear test device provided by the first aspect of the present invention to conduct the test, the test method comprising: Sampling to obtain test soil at different depths on the slope of the waste dump; Multiple shear units are stacked in sequence from the bottom to the top of the test base, and the test soil is stacked in sequence from the deepest to the shallowest sampling depth into each of the shear units from the lowest to the highest; the shear unit is composed of two transparent shear boxes; Opening the water injection box, so that the water in the water injection box seeps from the shear box near the top of the test base into the shear box near the bottom of the test base; Observe and record the evolution of the test soil under the action of seepage; Calculate the permeability coefficient of the test soil at different sampling depths; The water injection box is closed and removed, and a shear force is applied to each shear unit individually through a shear mechanism to obtain the shear strength of the test soil at different sampling depths.

[0015] Compared with the prior art, this application has the following significant improvements: The device provided by an embodiment of the present invention includes: a test base with openings on two opposite sides as observation ends and a hollow interior; a plurality of interconnected shear boxes located in the cavity of the test base, wherein the plurality of shear boxes are stacked overlappingly from the bottom to the top of the test base; a water injection box connected to the shear box near the top of the test base for establishing seepage conditions; a shear mechanism connected to the test base and each shear box, respectively, for applying shear force to the shear box; wherein each shear box is made of transparent material and is used to observe the evolution law of the test soil under the action of seepage; wherein two adjacent shear boxes are combined to form a shear unit, and the plurality of shear units do not overlap; and a plurality of shear units at different placement heights are used to place test soils of different sampling depths, and the placement height matches the sampling depth to obtain the permeability coefficient and shear strength of the test soils of each corresponding sampling depth.

[0016] By adopting the technical solution of the present invention, a transparent shear box can be used to directly observe the migration, deposition, and blockage of soil particles during the seepage process, as well as the evolution of the pore structure of coarse-grained soil under the action of seepage force. By stacking multiple shear boxes in an overlapping manner and dividing them into shear units with different placement heights, it is possible to perform multi-level tests on the shear characteristics and permeability characteristics of test soils at different depths, providing more comprehensive and accurate physical and mechanical parameters of the soil. The device simulates the water seepage environment through a water injection tank, and the shear mechanism applies different shear forces. It can study the shear strength characteristics of soils at different depths under seepage damage or natural seepage force, and provide more realistic engineering data. Therefore, the present application solves the problems of large particle size of traditional coarse-grained soil, the difficulty in ignoring the sample size effect, and the difficulty in measuring the migration and deposition effects of fine particles during the direct shear of seepage. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the description of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0018] Figure 1 It is a front view structural schematic diagram of a soil visual seepage direct shear test device according to an embodiment of the present application; Figure 2 It is a side view structural schematic diagram of a soil visual seepage direct shear test device according to an embodiment of the present application; Figure 3 It is a schematic diagram of the top view of the structure of the soil visualization seepage direct shear test device according to one embodiment of the present application; Figure 4 is a front view of a test base according to an embodiment of the present application; Figure 5 is a side view of a test base according to an embodiment of the present application; Figure 6 is a top view of a test base according to an embodiment of the present application; Figure 7 It is a flow chart of the steps of a soil visualization seepage direct shear test method described in one embodiment of the present application.

[0019] Description of reference numerals: 1. Test soil; 2. Shear box; 3. Water injection box; 31. Overflow port; 32. Water injection port; 4. Test base; 5. Sedimentation tank; 51. Overflow pipe; 52. Overflow hole; 6. Measuring cup; 7. First jack; 8. Second jack; 9. Screw; 10. High-strength bolt; 11. Load-bearing column; 12. Support column; 13. Pad; 14. Transparent pressure measuring tube; 15. Porous filter plate; 16. Non-woven geotextile; 17. Waterstop tape; 18. Pressure cover plate. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] It is known that a large amount of waste soil and rock mixed granular bodies will be generated during the construction process, which have the characteristics of looseness and large pores. After the waste soil is filled to form a waste dump, the fine particles in the soil will migrate to the deep part of the slope under the action of rainfall infiltration and gravity driving. The migration of fine particles in the waste soil is often one of the main reasons for changing the mechanical properties of the soil and causing geological disasters in the waste dump.

[0022] The existing seepage direct shear test device can only obtain the shear strength parameters of the soil after seepage damage, but cannot obtain the dynamic process of fine particle migration and loss in the abandoned soil; at the same time, with the migration of fine particles, the permeability and shear strength characteristics of the soil at different depths have changed accordingly, and the existing seepage direct shear test device cannot obtain the permeability coefficient of the soil at different depths and the shear strength under seepage conditions. Finally, the existing seepage direct shear test device only solves the strength test problem of the soil at a certain sampling depth after seepage damage, and cannot obtain the loss value of fine particles in the soil.

[0023] In view of this, the present invention proposes a multi-performance parameter testing device suitable for waste soil under seepage state, and in particular relates to the dynamic evaluation of soil structure changes under water seepage. Figure 1-Figure 3 As shown, Figure 1 , Figure 2 and Figure 3The front view, side view and top view of a soil visualization seepage direct shear test device are shown respectively. A soil visualization seepage direct shear test device, the device comprises: a test base 4, which is open on two opposite sides as observation ends and is hollow inside; a plurality of interconnected shear boxes 2, which are located in the cavity of the test base 4, and the plurality of shear boxes 2 are stacked from the bottom to the top of the test base 4; a water injection box 3, which is connected to the shear box 2 near the top of the test base 4, and is used to establish seepage conditions; a shear mechanism, which is respectively connected to the test base 4 and each shear box 2, and is used to apply shear force to the shear box 2; wherein each shear box 2 is made of transparent material, and is used to observe the evolution law of the test soil 1 under the action of seepage; wherein two adjacent shear boxes 2 are combined to form a shear unit, and the plurality of shear units do not overlap; and a plurality of shear units at different placement heights are used to place test soils 1 of different sampling depths, and the placement height matches the size of the sampling depth, so as to obtain the permeability coefficient and shear strength of the test soil 1 of each corresponding sampling depth.

[0024] Specifically, the test base 4 is the bearing part of the device, and the interior is a hollow structure to form a receiving cavity, which can accommodate other components (such as the shear box 2, the water injection box 3, etc.). The test base 4 has an opening to form an observation end, so that the experimenter can grasp the test conditions of each component in the cavity in real time through the observation end, such as the seepage process and shear process of the soil, and it is convenient for the experimenter to assemble or disassemble the components in the cavity through the observation end.

[0025] In this embodiment, the test base 4 is a reaction steel plate, the front and rear sides of the test base 4 are open, and the top plate is connected to the left and right side plates to form an inverted U-shaped cavity. In some embodiments, a plurality of support columns 12 connecting the left and right side plates are arranged at the bottom, and a pad 13 is arranged below the support columns 12.

[0026] A plurality of shear boxes 2 are arranged in the inverted U-shaped cavity, and each shear box 2 is hollowed out at the top and bottom, so each shear box 2 is interconnected with the adjacent boxes, and a plurality of shear boxes 2 are stacked from bottom to top along the central axis direction of the test base 4, and the topmost shear box 2 has a distance from the top plate of the test base 4, and the bottommost shear box 2 has a distance from the bottom of the test base 4, and a water injection tank 3 and a sedimentation tank 5 are respectively arranged in the distance space.

[0027] The water injection tank 3 is located directly above the top shear box 2, and a test soil 1 is placed in each shear box 2. The multiple shear boxes 2 are interconnected through the upper and lower hollow structures. Therefore, water is injected into the top shear box 2 through the water injection tank 3, and the water gradually seeps into each shear box 2 below until it flows out from the bottom shear box 2, thereby simulating the seepage conditions in the actual environment.

[0028] Wherein, the shear box 2 is made of transparent material, so when conducting a water seepage test, the experimenter can directly observe the evolution of the migration, deposition and changes in the soil structure of fine particles of the test soil 1 under the action of seepage. Preferably, the transparent material may include transparent plastic or glass, etc. Wherein, each shear box 2 is made of steel plate and plexiglass to take into account the strength and visualization function of the structure. Wherein, the position of the plexiglass-formed plate is opposite to the position of the observation end, and the experimenter can observe the rotation, migration, blockage and other processes of soil particles under the action of seepage and shear during the test through the plexiglass plates on both sides from the observation end.

[0029] Furthermore, a camera can be set at a position opposite to the opening of the test base 4, and the camera can directly capture and record the entire process of migration, blockage and loss of soil particles in the shear box 2 under the influence of water seepage, helping experimenters to capture tiny changes that are difficult to detect with the naked eye in real time, thereby helping experimenters to conduct subsequent in-depth analysis.

[0030] Among the stacked multiple split transparent shear boxes, the number of shear boxes 2 can be determined according to the actual soil depth. The size of the shear box 2 can be customized according to the particle size of the soil particles. According to the "Geotechnical Test Regulations", the diameter of the shear box 2 should be greater than 5 times the maximum particle size of the particles.

[0031] In this embodiment, a shear mechanism is installed on the top plate and the left and right side plates of the test base 4, and the shear mechanism is connected to each shear box 2 to simulate the shear strength of the test soil 1 under different shear loads. The shear force applied by the shear mechanism generally includes vertical load and horizontal load.

[0032] As an explanation of this embodiment, a plurality of axially superimposed shear boxes 2 are divided into a plurality of shear units, each of which is composed of two shear boxes 2 stacked up and down, and a test soil body 1 corresponding to the sampling depth is placed in each shear unit. Among them, the fact that the multiple shear units do not overlap can be understood as the shear boxes 2 in each shear unit are not shared, that is, each shear box 2 can only form one shear unit. Therefore, each shear unit can represent a soil layer, and each shear unit is independently tested by the shear mechanism, which helps to obtain the shear strength of soil layers of different depths after seepage damage, thereby avoiding mutual interference between different shear areas and improving the accuracy of the experiment.

[0033] It can be known that the placement height of each shear unit is different, and the height of the shear unit closer to the top of the test base 4 is always greater than the height of the shear unit closer to the bottom of the test base 4. Therefore, according to the sampling depth of the test soil 1, the soil with a deeper sampling depth can be piled in the shear unit with a lower placement height, and the soil with a shallower sampling depth can be piled in the shear unit with a higher placement height. Therefore, shear units of different heights are piled with test soils 1 of different depths according to the matching relationship of low to deep and high to shallow, so as to simulate the permeability coefficient and shear strength of soils of different depths, thereby more comprehensively evaluating the mechanical properties of the soil.

[0034] For example, Figure 2 As shown, there are six shear boxes 2, which are the first shear box, the second shear box, the third shear box, the fourth shear box, the fifth shear box and the sixth shear box from top to bottom. The first shear box and the second shear box form a first shear unit, the third shear box and the fourth shear box form a second shear unit, and the fifth shear box and the sixth shear box form a third shear unit. In the process of stacking the shear boxes 2, they are stacked layer by layer from the bottom shear box 2 (sixth shear box) to the top shear box 2 (first shear box) according to the soil layer sampling depth from deep to shallow, and a test soil sample corresponding to the sampling depth is filled into a shear unit corresponding to the placement height. As shown Figure 1 The samples filled in the first and second shear boxes are the waste soil at the upper part of the waste slope, the samples filled in the third and fourth shear boxes are the waste soil in the middle of the waste field, and the samples filled in the fifth and sixth shear boxes are the waste soil at the lower part of the slope.

[0035] In summary, the device uses a transparent shear box 2, which can directly observe the migration, deposition, and blockage of soil particles during the seepage process, as well as the evolution of the pore structure of coarse-grained soil under the action of seepage force. By stacking multiple shear boxes 2 and designing them into shear units with different placement heights, the shear characteristics and permeability characteristics of the test soil 1 at different depths can be tested at multiple levels, providing more comprehensive and accurate soil physical and mechanical parameters. The device simulates the water seepage environment through the water injection box 3, and the shear mechanism applies different shear forces. The shear strength characteristics of soil at different depths under seepage damage or natural seepage force can be studied, providing more realistic engineering data. Therefore, the problems of large particle size of traditional coarse-grained soil, difficult to ignore the sample size effect, and difficult to measure the migration and deposition effects of fine particles during the seepage direct shear process are solved. It can be applied to the fields of soil stability analysis, slope design, foundation bearing capacity assessment in engineering projects, and will have important application value for projects such as soil and water conservation, slope management, and landslide prevention.

[0036] In a further technical solution, the device also includes: a sedimentation tank 5, which is connected to the shear box 2 near the bottom of the test base 4, and is used to receive water and particulate matter flowing out of the shear box 2 under seepage conditions; a measuring cup 6, which is connected to the sedimentation tank 5, and is used to receive water overflowing from the sedimentation tank 5.

[0037] In this embodiment, the sedimentation tank 5 is located between the bottom shear box 2 and the support column 12 of the test base 4, and is connected to the bottom shear box 2 to receive water flowing from multiple shear boxes 2 from top to bottom and fine particles lost from the soil. Under the action of gravity, the fine particles gradually settle in the sedimentation tank 5 for centralized collection. An overflow hole 52 is opened on the side wall of the sedimentation tank 5, and the overflow hole 52 and the measuring cup 6 are connected through the overflow pipe 51, so that the measuring cup 6 receives the water overflowing from the sedimentation tank 5, so that the water and the fine particles are separated. Therefore, the seeping water is collected by the measuring cup 6, and the lost fine particles are collected by the sedimentation tank. By drying the sedimentation tank 5 and performing particle size analysis regularly, the loss of fine particles can be quantified.

[0038] Specifically, by measuring the amount of water seeping through the measuring cup 6, the water seepage state can be evaluated, and the permeability coefficient of the test soil 1 during the experiment can be calculated. In the specific test process, the outflow rate of water in the sedimentation tank 5 can be calculated based on the amount of water added in the measuring cup 6 per unit time. When the rate of increase of the amount of water per unit time in the measuring cup 6 is constant, it can be considered that the seepage has reached a stable state. In some embodiments, a flow monitor can be installed at the overflow pipe 51 to determine the stable state of the seepage through the flow monitor.

[0039] The water injection box 3 and the test base 4 are provided with water injection ports 32 and overflow ports 31 on the same two sides as the opening side; each shear unit is connected to a transparent pressure measuring tube 14. The water injection ports 32 and overflow ports 31 are also provided on the front and rear sides of the water injection box 3, and are opposite to the position of the opening, so as to facilitate water injection and water recovery. The water injection port 32 is used to introduce water into the water injection box 3, and overflows when the water level in the water injection box 3 reaches the height of the overflow port 31. Therefore, the water injection box 3 can keep the seepage water pressure unchanged through the water injection port 32 and the overflow port 31, that is, realize the constant head seepage test.

[0040] Each shear box 2 is provided with a transparent hose as a pressure measuring tube at the front or rear side. The permeability coefficient of the soil at the corresponding sampling depth in each shear box 2 is measured by a transparent pressure measuring tube 14. Shear units at different heights are connected to a transparent pressure measuring tube 14 to obtain the permeability pressure corresponding to the soil at different depths or positions. The water injection pipe connected to the water injection port 32, the water outlet pipe connected to the overflow port 31, and the above-mentioned overflow pipe 51 are all provided with valves.

[0041] Exemplarily, taking three shear units as an example, during the test, the valve at the water injection port 32 is opened, and the high-definition camera is turned on to record the entire process of migration, blockage, and loss of soil particles in the shear box 2 under the influence of water seepage; water is injected from the water injection port 32, and when the water level reaches the height of the overflow port 31, it overflows, so that the water level in the water tank always remains at a constant value h. When the water head of the transparent pressure measuring tube 14 corresponding to each shear unit is stable, the water head height is measured and recorded as h1, h2, and h3. When the overflow hole 52 of the sedimentation tank 5 overflows water at a constant flow rate, the seepage amount Q within time t is recorded. The permeability coefficient value k of the soil layer in the i-th shear box 2 from the bottom up can be calculated by the following formula i : (1); Where L is the height of shear box 2, A is the bottom area of ​​shear box 2, ∆h i is the water head height h in the pressure measuring tube corresponding to the i-th shear box 2 i The difference between the water head height h in the water injection tank 3, that is, ∆h i =hh i .

[0042] When the seepage is stopped, close the valve at the water injection port 32, and when no water seeps out of the overflow pipe 51 of the sedimentation tank at the bottom, remove the water injection box 3 and continue the shear strength test.

[0043] Preferably, the water inlet 32 ​​faces the front side, the overflow port 31 faces the rear side, and the transparent pressure measuring tube 14 also faces the front side, and all three are opposite to the opening side of the test base 4, so that the experimenter can inject water from the observation end, observe the overflow of water flow, and the water head height in the pressure measuring tube. Among them, the water inlet 32 ​​can be set higher than the overflow port 31. The transparent pressure measuring tube 14 is also set as a hose, which is convenient for extending from the opening and assembling on the bracket.

[0044] Preferably, a first filter structure is provided between the shear box 2 and the sedimentation tank 5; and a second filter structure is provided between the sedimentation tank 5 and the measuring cup 6. The shear box 2 at the bottom is connected to the sedimentation tank 5 through the first filter structure, and the water and particulate matter flowing out of the shear box 2 are filtered through the first filter structure to prevent larger particles or impurities in the waste soil from flowing out. The sedimentation tank 5 specifically collects the seepage water and the fine particulate matter that migrates during the seepage process. The sedimentation tank 5 is connected to the measuring cup 6 through the second filter structure to further filter the water overflowing from the sedimentation tank 5 to prevent fine particulate matter from entering the measuring cup 6 and affecting the accuracy of the water measurement.

[0045] The first filter structure may be a porous filter plate 15, which is used to allow fine particles migrating during the seepage process to flow out and prevent other particles from passing through. The pore size of the porous filter plate may be determined according to the particle gradation of the waste soil body.

[0046] The second filtering structure may be a filter screen installed at the overflow port 31 of the sedimentation tank 5 to prevent fine particles from overflowing from the overflow port 31 .

[0047] Furthermore, at least one load-bearing column 11 is provided in the sedimentation tank 5, and the load-bearing column 11 is in contact with the shear box 2. In this embodiment, a plurality of vertically extending load-bearing columns 11 are provided in the sedimentation tank 5, and both ends of the load-bearing columns 11 are in contact with the bottommost shear box 2 and the bottom of the sedimentation tank 5, respectively, to support the weight of the plurality of shear boxes 2 at the top.

[0048] Exemplarily, one load-bearing column 11 may be provided, located in the center of the sedimentation tank 5. Exemplarily, two load-bearing columns 11 may be provided, spaced apart on the left and right sides of the sedimentation tank 5. Exemplarily, multiple load-bearing columns 11 may be provided, distributed in the four corners or different positions of the sedimentation tank 5.

[0049] The position of the load-bearing column 11 avoids the hollow part of the shear box 2 to avoid affecting the water seepage process.

[0050] In another embodiment, if Figure 4 , Figure 5 and Figure 6 The front view, side view and top view of the test base are shown respectively. The test base 4 comprises an upper movable structure and a lower support structure, wherein the upper movable structure can be telescopically arranged on the top of the lower support structure; the bottom of the lower support structure is connected to the two sides adjacent to the opening through at least one support column 12.

[0051] In combination with the above embodiments, the test base 4 is specifically an inverted U-shaped reaction steel plate composed of a top plate and left and right side plates, the inverted U-shaped reaction steel plate is divided into an upper movable structure and a lower support structure, and a plurality of support columns 12 connecting the left and right side plates are arranged at the bottom of the lower support structure. The upper movable structure is composed of the top plate and the upper parts of the left and right side plates, and the lower support structure is composed of the lower parts of the left and right side plates. The upper movable structure can be movable and retracted relative to the lower support structure, thereby changing the overall height of the test base 4.

[0052] Among them, the support columns 12 can be four transverse rigid support columns, which are fixed to the lower support structure by high-strength bolts 10. Pads 13 are arranged under the four transverse rigid support columns to ensure that the entire test base 4 remains stable under the action of various forces such as water penetration, shear load and particle deposition, especially to prevent the reaction steel plate from being squeezed and deformed during the pressure application of the shear mechanism.

[0053] The upper movable structure is movably embedded in the lower support structure and is adjusted by a detachable screw rod 9. Exemplarily, six screw rods 9 are provided, three of which are symmetrically connected to the left and right side plates of the lower support structure. When the height needs to be adjusted, the operator slides the upper movable structure upward or downward into the lower support structure, and tightens the screw rod 9 again after sliding to the appropriate height, so that the test base 4 can adjust the height as needed, so that the top plate is close to or away from the top shear box 2 during each test, supporting soil tests at different depths.

[0054] Therefore, the upper movable structure and the lower support structure provide the dual functions of adjustable height and stable support. The scalability of the upper structure can adjust the height according to the experimental requirements, while the lower structure provides the necessary bearing capacity and stability through the support column 12, so that the device always remains stable when conducting seepage, shear and other experiments.

[0055] This embodiment is used to illustrate the shear mechanism. The shear mechanism includes a first jack 7 and a plurality of second jacks 8; wherein the first jack 7 is arranged on the top wall of the test base 4 and is opposite to the top of the topmost shear box 2 during each test process, for applying a vertical load; and the plurality of second jacks 8 are arranged on the side walls of the test base 4 and are respectively opposite to the opposite sides of each shear box 2, for applying a horizontal load.

[0056] In combination with the above embodiments, a first jack 7 is provided on the top plate, facing the topmost shear box 2, and a vertical load is applied to the topmost shear box 2. A plurality of second jacks 8 are provided on the left and right side plates from top to bottom, and the left and right sides of each shear box 2 face two second jacks 8 at the same height. When the number of shear boxes 2 in the test base 4 decreases, the first jack 7 on the top plate is again made to face the topmost shear box 2 among the latest number of shear boxes 2 by moving the upper movable structure, and the test is performed in the same steps.

[0057] Among them, the first jack 7 is a hydraulic jack; the second jack 8 is a pressure pump jack.

[0058] Exemplarily, taking three shear units as an example, during the test, the height of the upper movable structure is adjusted to a suitable position, a hydraulic jack is installed on the top plate, and a vertical load is applied. After the vertical load is stable, a pump jack is placed on the left and right sides of each shear box 2, so that one end of the pump jack is just pressed against the reaction steel plate, and the other end is pressed against the shear box 2, and it will not fall under the action of gravity. Remove the pump jack on one side of the second shear box, and apply a horizontal shear load through the jack on the other side. During the shearing process, keep the jacks on the left and right sides of the other shear boxes 2 stationary, place a displacement sensor or a dial indicator at the load application position of the second shear box, and record the shear displacement, so as to obtain the load-displacement curve of the upper soil layer under shear action.

[0059] When the shearing of the upper soil layer is completed, stop the lateral loading, remove the top positive load, and remove the first shear box, the second shear box and the specimen. Adjust the height of the reaction steel plate to a suitable position, apply vertical and horizontal loads again, and use the same method as above to obtain the load-displacement curves of the middle and lower soil layers under shearing, and finally obtain the shear characteristics of the upper, middle and lower soil layers at different depths under a certain positive pressure condition.

[0060] Among them, by changing the normal stress condition and repeating the above steps again, the shear strength index of the waste soil body under different normal stresses and different soil layer depths can be obtained.

[0061] Each time a load is applied by means of a hydraulic jack, a pressure-bearing cover plate 18 is placed between the hydraulic jack and the topmost shear box 2 .

[0062] As a further illustration of the above embodiment, a waterstop tape 17 is wrapped between two adjacent shear boxes 2; and a non-woven geotextile 16 and a waterstop tape 17 are provided between the shear box 2 and the water injection tank 3. The waterstop tape 17 is a transparent waterstop tape 17 with high pressure resistance, high viscosity and leak-proof functions. The waterstop tape 17 is wrapped at the contact position of the two shear boxes 2, and at the contact position of the top shear box 2 and the water injection tank 3, to prevent water from leaking from the contact gap of each shear box 2. A layer of non-woven geotextile 16 is placed above the top shear box 2 and between the bottom of the water injection tank 3 to evenly disperse the water flow input from the water injection tank 3.

[0063] In summary, the seepage direct shear test device provided by the present invention has the properties of being disassembled, easy to assemble, and highly operable, and can meet the requirements for studying the shear strength characteristics of abandoned soil under seepage.

[0064] See also Figure 7 , Figure 7The flowchart of the soil visualization seepage direct shear test method of the present invention is shown. The method relies on a soil visualization seepage direct shear test device provided by the present invention to perform the test. The test method includes the following steps: S1. Sampling to obtain test soil 1 at different depths on the slope of the waste dump; S2. Multiple shear units are stacked in sequence from the bottom to the top of the test base 4, and the test soil 1 is stacked in sequence from the deepest to the shallowest sampling depth into each shear unit from the lowest to the highest; the shear unit is composed of two transparent shear boxes 2; S3, opening the water injection box 3, so that the water in the water injection box 3 infiltrates from the shear box 2 near the top of the test base 4 into the shear box 2 near the bottom of the test base 4, forming a seepage condition; S4. Observe and record the evolution of the test soil 1 under the action of seepage; S5, calculating the permeability coefficient of the test soil 1 at different sampling depths; S6. Close and remove the water injection box 3, and apply shear force to each shear unit individually through the shear mechanism to obtain the shear strength of the test soil 1 at different sampling depths.

[0065] As for the method embodiment, since it is basically similar to the device embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the device embodiment.

[0066] In combination with the above embodiments, taking a specific device embodiment as an example, the method embodiment provided by the present invention is further described: A soil visualization seepage direct shear test method, the method comprises the following steps: 1. Obtain soil samples at different depths of the slope of the waste dump through on-site sampling; 2. Stack the sixth shear box onto the sedimentation tank 5 with the load-bearing column 11. The shear box 2 is transparent and hollowed out at the top and bottom. A porous filter plate is placed between the sixth shear box and the sedimentation tank 5 to filter the fine particles migrating during the seepage process. 3. Pile the test soil sample into the sixth shear box, compact it slightly after it is full, and then stack the fifth shear box. The sixth and fifth shear boxes are filled with the waste soil at the bottom of the waste field; Then, the fourth shear box and the third shear box are stacked, and the waste soil in the middle of the waste field is filled in the fourth shear box and the third shear box; Finally, the second shear box and the first shear box are stacked, and the waste soil on the upper part of the waste field is filled in the second shear box and the first shear box; 4. After the shear boxes 2 are completely filled with the sample, a layer of water-stop tape 17 is wrapped around the contact position of each layer of shear boxes 2 to prevent water from flowing out from the gap between the two shear boxes 2 during the seepage process; 5. Place a layer of non-woven geotextile 16 on top of the shear box 2 assembled from bottom to top to evenly disperse the water flow; 6. Install the water injection box 3 on the top of the assembled shear box 2, and fix the water injection box 3 and the top shear box 2 with the water stop tape 17; 7. Open the valve at the water injection port 32, and turn on the high-definition camera to record the entire process of soil particles in the shear box 2 being migrated, blocked, and lost under the influence of water seepage; record the water head height in the water injection tank 3; 8. When the water head in the transparent pressure measuring tube 14 connected to each shear box 2 is stable, measure the water head height corresponding to each transparent pressure measuring tube 14; 9. When the overflow pipe 51 of the sedimentation tank 5 overflows water at a constant flow rate, record the volume of the measuring cup 6 and the amount of water seepage within the set time; 10. Calculate the permeability coefficient k of the soil layer in the i-th shear box 2 from the bottom using the above formula (1): i ; 11. After the seepage is stopped, close the valve of the water injection port 32. When no water seeps out of the overflow port 31 of the bottom sedimentation tank, remove the water stop tape 17 between the top water injection box 3 and the shear box 2, remove the water injection box 3, and place the pressure cover plate 18 on the top of the first shear box; 12. Adjust the height of the reaction plate to a suitable position, install a hydraulic jack between the pressure cover plate 18 and the reaction plate, and apply a vertical load; 13. After the vertical load is stable, place a pressure pump jack on both sides of the six shear boxes 2, so that one end of the jack is just pressed against the reaction plate and the other end is pressed against the shear box 2, and will not fall under the action of gravity; 14. Remove the jack on one side of the second shear box, apply horizontal shear load through the jack on the other side, keep the jacks on the other side of the shear box 2 stationary during the shearing process, place a displacement sensor or dial indicator at the load application position of the second shear box, record the shear displacement, and obtain the load-displacement curve under the shear action of the upper soil layer.

[0067] 15. After the shearing of the upper soil layer is completed, stop the lateral loading, remove the top positive load, and remove the first shear box, the second shear box and the specimen; 16. Place the pressure cover plate 18 on the top of the third shear box, adjust the height of the reaction plate to a suitable position, and apply the same vertical load again using the vertical jack; 17. After the vertical load stabilizes, remove the jack on the side of the fourth shear box, and apply the horizontal shear load through the jack on the other side. During the shearing process, keep the jacks on the sides of the other shear boxes 2 stationary. Place a displacement sensor or dial indicator at the load application position of the fourth shear box to record the shear displacement, thereby obtaining the load-displacement curve under the shear action of the middle soil layer.

[0068] 18. The same method as above is used to obtain the load-displacement curve diagram under the shear action of the lower soil layer, and finally the shear characteristics of the upper, middle and lower soil layers at three different depths under a certain positive pressure can be obtained.

[0069] 19. By changing the normal stress conditions and repeating the above steps, the shear strength index of the waste soil body at different soil depths under different normal stresses can be obtained.

[0070] 20. During the entire test, a high-definition camera was used to record the structural change characteristics of the waste soil particles under seepage and direct shear conditions, as well as the migration and blockage laws of fine particles.

[0071] It should be noted that, for the method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the embodiments of the present application are not limited by the described order of actions, because according to the embodiments of the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present application.

[0072] As for the method embodiment, since it is basically similar to the system embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0073] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0074] It should also be noted that, in this article, the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations, nor can they be understood as indicating or implying relative importance. Moreover, the term "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device.

[0075] The above is a detailed introduction to a soil visualization seepage direct shear test device and method provided by the present application. This article uses specific examples to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the present application, and the content of this specification should not be understood as a limitation on the present application. At the same time, for those of ordinary skill in the art, according to the present application, there will be different forms of changes in the specific implementation methods and application scopes. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived from this are still within the scope of protection of the present application.

Claims

1. A soil visualization seepage direct shear test device, characterized in that: The device includes: The test base is hollow inside and has two openings on opposite sides as observation ends; A plurality of interconnected shear boxes are located in the cavity of the test base, and the plurality of shear boxes are stacked from the bottom to the top of the test base; a water injection box, connected to the shear box near the top of the test base, for establishing seepage conditions; A shear mechanism, connected to the test base and each of the shear boxes, respectively, for applying a shear force to the shear boxes; Wherein, two adjacent shear boxes are combined to form a shear unit, and the multiple shear units do not overlap; and the multiple shear units at different placement heights are used to place test soils at different sampling depths, and the placement heights match the size of the sampling depths to obtain the permeability coefficient and shear strength of the test soils at each corresponding sampling depth; Wherein, each of the shear boxes is made of transparent material and is used to observe the evolution law of the test soil under the action of seepage.

2. A soil visual seepage direct shear test device according to claim 1, characterized in that: The device also includes: a sedimentation tank, connected to the shear box near the bottom of the test base, for receiving water and particulate matter flowing out of the shear box under seepage conditions; A measuring cup is connected to the sedimentation tank and is used to receive water overflowing from the sedimentation tank.

3. A soil visual seepage direct shear test device according to claim 2, characterized in that: A first filtering structure is arranged between the shear box and the sedimentation tank; and a second filtering structure is arranged between the sedimentation tank and the measuring cup.

4. The soil visualization seepage direct shear test device according to claim 2 is characterized in that: At least one load-bearing column is arranged in the sedimentation tank, and the load-bearing column abuts against the shear box.

5. The soil visualized seepage direct shear test device according to claim 1 is characterized in that: The test base comprises an upper movable structure and a lower supporting structure. The upper movable structure is telescopically arranged on the top of the lower supporting structure. The bottom of the lower supporting structure is provided with at least one supporting column for connection.

6. The soil visualization seepage direct shear test device according to claim 1 is characterized in that: The shear mechanism includes a first jack and a plurality of second jacks; wherein the first jack is arranged on the top wall of the test base and opposite to the top of the shear box, for applying a vertical load; and the plurality of second jacks are arranged on the side walls of the test base and opposite to the opposite sides of each of the shear boxes, for applying a horizontal load.

7. The soil visualization seepage direct shear test device according to claim 1 is characterized in that: The water injection box is provided with a water injection port and a water overflow port on opposite sides thereof, and the water injection port and the water overflow port are opposite to the opening of the test base; wherein each of the shearing units is connected to a transparent pressure measuring tube.

8. The soil visualization seepage direct shear test device according to claim 1 is characterized in that: The device further comprises a camera, which is located opposite to the opening of the test base.

9. A soil visual seepage direct shear test device according to any one of claims 1 to 8, characterized in that: Waterstop tape is wrapped between two adjacent shear boxes and between the shear box near the top of the test base and the water injection box; and a non-woven geotextile is also arranged between the shear box and the water injection box.

10. A soil visualized seepage direct shear test method, characterized in that: The test is carried out by relying on the soil visualization seepage direct shear test device as described in any one of claims 1 to 9, and the test method includes: Sampling to obtain test soil at different depths on the slope of the waste dump; Multiple shear units are stacked in sequence from the bottom to the top of the test base, and the test soil is stacked in sequence from the deepest to the shallowest sampling depth into each of the shear units from the lowest to the highest; the shear unit is composed of two transparent shear boxes; Opening the water injection box, so that the water in the water injection box seeps from the shear box near the top of the test base into the shear box near the bottom of the test base; Observe and record the evolution of the test soil under the action of seepage; Calculate the permeability coefficient of the test soil at different sampling depths; The water injection box is closed and removed, and a shear force is applied to each shear unit individually through a shear mechanism to obtain the shear strength of the test soil at different sampling depths.

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