Shear method and single shear apparatus with uniform distribution of shear strain

Abstract

This invention proposes a single-shear apparatus and shearing method for uniform shear strain distribution. The shearing method includes installing a shearing assembly, loading the sample into the stack of plates of the shearing assembly, installing a vertical loading device and a shear force loading device, applying a vertical load to the sample to consolidate the sample, installing a left-side sliding limit device, and applying a horizontal load to the consolidated sample for shearing. This invention can precisely control the shearing direction, solve the problem of shear force direction deflection in the prior art, and enable uniform shearing of the sample, ensuring uniform vertical shear strain distribution.

Description

Technical Field

[0001] This invention relates to a single shear apparatus and shearing method with uniform shear strain distribution, belonging to the field of geotechnical testing in geotechnical engineering, and is applicable to the determination of mechanical properties such as stress, strain and strength of fine-grained soils. Background Technology

[0002] Accurately understanding the mechanical properties of soil is of great significance for the safe operation of engineering projects. Currently, the main testing instruments used by scholars at home and abroad to study the mechanical properties of soil are direct shear apparatus, single shear apparatus, and triaxial apparatus. Due to the advantages of the single shear apparatus, such as a constant shear surface area and an unfixed shear failure surface during the shearing process, it can better simulate on-site working conditions and is more suitable for the study of the mechanical properties of soil.

[0003] Chinese Patent (Publication No.: 102269676A) discloses a high-precision geotechnical single shear apparatus and its usage method. The single shear apparatus is equipped with multiple horizontal displacement sensors connected to the lower shear box and the upper shear stacked ring group, which can measure the displacement of each stacked ring. This utility model has a simple structure and is easy to implement. It can measure the shear deformation characteristics of soil with high precision. However, when using this structure, the stacked rings are prone to shaking, and the vertical force and shear force are prone to deflection. In addition, the cylindrical sample causes uneven distribution of shear stress and shear strain. Summary of the Invention

[0004] The purpose of this invention is to provide a single shear apparatus and shearing method with uniform shear strain distribution, which can accurately control the shearing direction, solve the problem of shear force direction deflection in the prior art, enable uniform shearing of the sample, and ensure uniform vertical shear strain distribution.

[0005] A shearing method with uniform shear strain distribution includes the following steps:

[0006] Step 1: Install the shear assembly 20 and load the sample into the stack 24 of the shear assembly 20;

[0007] The shearing component 20 includes a trolley 22, a stacking limit frame 23, and a stacking assembly 24, and specifically includes the following steps:

[0008] Step 1A: Assemble the stack 24, which provides shear space for the consolidated sample. It includes n layers of stacked sheets 241 stacked along the Z-axis, specifically including the following steps:

[0009] Step 1A1: Along the Z direction, stack the n layers of laminate 241 sequentially;

[0010] Step 1A2: Insert the same pin 242 into the corresponding waist hole in each layer of laminate 241 and the adjacent layer of laminate 241. A shear deformation space is formed between the pin 242 and each layer of laminate 241.

[0011] Each layer of laminate 241 has several waist holes arranged along the Y direction;

[0012] Step 1A3: Insert a connecting rod for the pin 242 to rotate into the through hole along the Y direction on the topmost lamination 241, and make the connecting rod pass through each pin 242 in sequence along the Y direction.

[0013] Step 1B: Fix the base plate 231 of the stacking limit frame 23 to the trolley 22, and install the stacking limit frame 23 around the stacking assembly 24. This includes the following steps:

[0014] Step 1B1: Fix the bottommost stacked piece 241 closest to the trolley 22 to the base plate 231 so that the bottommost stacked piece 241 can move along the X direction with the trolley 22;

[0015] Before consolidation in step 3, the uppermost stacked piece 241 is detachably fixed to the top surface of the stacked piece limiting frame 23 using limiting screws to prevent the stacked piece group 24 from moving along the Z direction during the sample consolidation process in step 3. The stacked piece limiting frame 23 is a detachable structure, used in two ways: first, during the sample preparation process in step 1C, to prevent the stacked piece group 24 from slipping and reduce soil sample disturbance; second, during the sample consolidation process in step 3, to provide limiting space for the sample and prevent the sample from being squeezed between the stacked pieces. Before the shearing in step 4, the limiting component located in the X direction is removed from the foundation plate 231.

[0016] Step 1C: Place the sample into the sample preparation cavity formed by the stacked plates 24;

[0017] Step 2: Install the vertical loading device 31 and the shear loading device 33; wherein, the vertical loading device 31 includes a pressure cover plate 311, a vertical load loading lever 312, and a loading rod 313; the shear loading device 33 includes a roller assembly and a wire rope;

[0018] Specifically, the following steps are included:

[0019] Step 2A: Install the vertical loading device 31: Fix the upper end of the vertical load loading lever 312 along the Z direction to a lever structure. The lever structure is hinged to a support frame. The lower end of the lever along the Z direction has a ball connector. Place the ball connector into the upper semi-circular groove of the loading rod 313 along the Z direction. Finally, thread the lower end of the loading rod 313 to the pressure cover plate 311, so that the pressure cover plate 311 fits with the sample preparation cavity formed by the uppermost stacked pieces 241.

[0020] Step 2B: Install the shear loading device 33, which specifically includes the following steps:

[0021] Step 2B1: Secure the mounting base containing the roller assembly;

[0022] Step 2B2: Wrap the wire rope around the roller assembly, pass it through the concave block 321, and connect it to the trolley 22;

[0023] Step 3: Apply a vertical load to the specimen to solidify it, specifically including the following steps:

[0024] By configuring the weights at both ends of the vertical load loading lever 312, the vertical load loading lever 312 is tilted toward the sample side, so that the vertical load is applied to the sample through the pressure cover plate 311, so that the water in the sample is discharged to compress the sample, and finally a solidified sample is obtained.

[0025] After consolidation, the pressure cover plate 311 is pressed firmly onto the upper surface of the consolidated sample; at the same time, the lower end face of the pressure cover plate 311 along the Z direction is located in the uppermost stacked sheet 241 to prevent the pressure cover plate 311 from restricting the pin 242 from rotating around the connecting rod during the shearing process in step 4; at the same time, during the consolidation process, the pressure cover plate 311 moves downward along the Z direction with the loading rod 313.

[0026] Step 4: Install the left sliding limit device 32, which includes a concave block 321 and a top rod support 322, specifically including the following steps:

[0027] The concave block 321 is fixed between the trolley and the roller assembly, and the top rod support 322 is fixed to the side of the concave block 321 facing the trolley; the pressure cover plate 311 and the top rod support 322 are slidably connected in the Z direction to prevent the uppermost stacked piece 241 from moving along the X direction with the trolley 22 during shearing, and at the same time eliminate the friction force of the top rod support 322 on the pressure cover plate 311 and the bending moment generated by the loading rod 313;

[0028] Step 5: Apply a horizontal load to the consolidated specimen to perform shearing, specifically including the following steps:

[0029] Step 5A: Keep the vertical consolidation pressure constant so that a portion of the consolidated sample in contact with it remains stationary under the pressure applied by the pressure plate 311;

[0030] Step 5B: Remove the limiting component of the stacking limit frame 23 in the X direction, and separate the uppermost stacking piece 241 from the stacking limit frame 23;

[0031] Step 5C: Pull the steel wire rope so that the lowest layer 241 connected to the trolley 22 is subjected to the tension transmitted by the shear loading device 33; since the pin 242 is rigid, the top of the pin 242 is limited to the uppermost layer 241, and the bottom of the pin 242 is located at the lowest layer 241. When the lowest layer 241 is pulled, the pin 242 tilts, causing the remaining layers 241 to undergo uniform displacement.

[0032] Preferably, when the shear loading device 33 is not used, step 5 further includes a step of shearing based on the horizontal loading device 34, which includes a linear motor 341 and a force sensor 342, specifically including the following steps:

[0033] First, fix the base of the linear motor 341, connect the housing of the force sensor 342 to the output end of the linear motor 341, and make the sensing end of the force sensor 342 face the trolley 22.

[0034] Then, the linear motor 341 is started. When the sensing end of the force sensor 342 contacts the trolley 22, the linear motor 341 is started and then turned off to zero the force sensor 342.

[0035] Then, the linear motor 341 is started again, and the bottom layer 241 connected to the trolley 22 is subjected to the thrust transmitted by the horizontal loading device 34.

[0036] Since the pin 242 is rigid, the top of the pin 242 is located at the uppermost lamination 241, and the bottom of the pin 242 is located at the lowermost lamination 241. When the lowermost lamination 241 is pushed, the pin 242 tilts, causing the remaining laminations 241 to undergo uniform displacement.

[0037] Preferably, the stacked limiting frame 23 further includes: two fixing plates 232 and two guide plates 233.

[0038] Two guide plates 233 are arranged opposite each other in the Y direction and fixed to the base plate 231, which can limit the Y direction of the stacked assembly 24;

[0039] Each guide plate 233 is provided with a limiting flange 234 at its top. The limiting flange 234 extends toward the sample preparation cavity and is located above the uppermost stacked plate 241. The limiting flange 234 and the uppermost stacked plate 241 are detachably connected by a limiting screw 235.

[0040] Two fixing plates 232 are arranged opposite each other in the X direction and fixed to the base plate 231, which can limit the X direction of the stacked plate group 24.

[0041] Preferably, the limiting flange 234 and the uppermost stack 241 have a gap in the Z direction to prevent the guide plate 233 from rubbing against the stack 24 during shearing.

[0042] Preferably, there is a gap of 0.05mm-0.1mm between the stacked sheet group 24 and each guide plate 233, which prevents the guide plate 233 from generating lateral friction on the stacked sheet group 24 during shearing.

[0043] Preferably, each stack 241 has a U-shaped structure, which makes the tendency to overturn and rotate after shear deformation smaller than that of a cube or cylindrical specimen.

[0044] Compared with the prior art, the advantages of the present invention are:

[0045] 1. It can achieve uniform shearing. The design of the pin and the waist-shaped hole ensures that the relative displacement of each layer of stacked sheets is the same during shearing, preventing the stacked sheets from swaying left and right during shearing, ensuring that the shearing force is in the same direction, and at the same time ensuring that the shearing surface area remains unchanged, thereby making the vertical shear strain uniformly distributed.

[0046] 2. It can control the shearing direction. The two guide plates and pins restrict the width direction of the stacked plate group, ensuring the directionality of the sample during shearing and preventing lateral deviation. At the same time, the two guide plates and the stacked plate group are spaced apart, avoiding friction on the stacked plate group, resulting in more accurate test results.

[0047] 3. It can prevent soil from squeezing out of the stacked pieces during consolidation, fix the stacked pieces, and restrict the stacked pieces by the stacked piece limiting frame. It does not slip when placing the sample. The structure is simple and stable, avoids soil sample disturbance, and the setting of the limiting screw can prevent soil from squeezing out of the stacked pieces during consolidation.

[0048] 4. The top of the loading rod is hinged and has a ball groove. It is connected to the vertical load loading lever by a ball head, which can adapt to different angles of the vertical load loading lever and keep the horizontal position of the ball head unchanged. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the single-shear device.

[0050] Figure 2 This is a schematic diagram of the shearing component.

[0051] Figure 3 This is a cross-sectional view of the method for fixing the stacked plate limiting frame.

[0052] Figure 4 This is a schematic diagram showing the position of the pin in the oblong hole of the laminate.

[0053] Figure 5 This is a schematic diagram of the position of the pin in the oblong hole of the laminate.

[0054] Figure 6 This is a schematic diagram of the position of the pin in the oblong hole of the laminate after the trolley has been displaced.

[0055] Figure 7 A schematic diagram showing the connection between the lever and the loading rod for vertical load application.

[0056] Figure 8 This is a schematic diagram of a top rod support;

[0057] Figure 9 Force analysis diagram for laminated assemblies without pins;

[0058] Figure 10 Shear strain distribution diagram of a laminated assembly without pins.

[0059] Among them, 10. Base; 20. Shear assembly; 21. Guide rail; 22. Trolley; 23. Stacked plate limiting frame; 231. Foundation plate; 232. Fixing plate; 233. Guide plate; 234. Limiting flange; 235. Limiting screw; 24. Stacked plate group; 241. Stacked plate; 242. Pin; 30. Loading device; 31. Vertical loading device; 311. Pressure cover plate; 312. Vertical load loading lever; 313. Loading rod; 32. Left side sliding limiting device; 321. Concave block; 322. Top rod support; 33. Shear loading device; 34. Horizontal loading device; 341. Linear motor; 342. Force sensor; 40. Data acquisition box; 50. Digital display controller. Detailed Implementation

[0060] The single-shear apparatus and shearing method for uniform shear strain distribution of the present invention will be described in more detail below with reference to schematic diagrams, which illustrate preferred embodiments of the invention. It should be understood that those skilled in the art can modify the invention described herein while still achieving the advantageous effects of the invention. Therefore, the following description should be understood as being of general knowledge to those skilled in the art and is not intended to limit the invention.

[0061] like Figures 1 to 8 As shown, a single shearing device includes a base 10, a shearing assembly 20, a loading device 30, a data acquisition box 40, and a digital display controller 50.

[0062] The shearing assembly 20 includes a guide rail 21, a trolley 22, a stacking limit frame 23, and a stacking assembly 24.

[0063] The guide rail 21 is arranged in the middle of the base 10 along the length direction (X direction). Steel balls are laid on the guide rail 21. The trolley 22 is slidably connected to the guide rail 21 through the steel balls, and the trolley 22 can slide freely along the guide rail 21.

[0064] The stacked limiting frame 23 is arranged inside the body of the trolley 22, and includes a base plate 231, two fixing plates 232 and two guide plates 233. The base plate 231 is fixedly installed on the bottom surface of the trolley 22 and can move synchronously with the trolley 22.

[0065] Preferably, a permeable plate is provided between the bottommost laminate 241 and the base plate 231.

[0066] Two guide plates 233 are arranged opposite each other in the Y direction and fixed to the base plate 231, which can limit the Y direction of the stacked assembly 24;

[0067] Each guide plate 233 is provided with a limiting flange 234 at its top. The limiting flange 234 extends toward the sample preparation cavity and is located above the uppermost stacked plate 241. The limiting flange 234 and the uppermost stacked plate 241 are detachably connected by a limiting screw 235.

[0068] Two fixing plates 232 are arranged opposite each other in the X direction and fixed to the base plate 231, which can limit the X direction of the stacked plate group 24.

[0069] The limiting flange 234 and the uppermost stack 241 have a gap in the Z direction, preferably 0.5 mm, to prevent the guide plate 233 from rubbing against the stack 24 during shearing.

[0070] The limiting flange 234 has a through hole running vertically through it. The limiting flange 234 is connected to the uppermost stacked piece 241 by limiting screws 235. Preferably, there are 8 limiting screws 235, which are evenly distributed along the Y direction on the top of the limiting flange 234 of the two guide plates 233. The limiting screws 235 can be screwed into the limiting flange 234 and press down on the uppermost stacked piece 241, restricting the vertical upward movement of the stacked piece 241 (along the Z direction) to prevent the soil from being squeezed out of the stacked piece 241 during sample preparation and consolidation. The limiting screws 235 are detachable and can be removed during shearing without affecting the shearing process.

[0071] Preferably, there is a gap of 0.05mm-0.1mm between the stacked sheet group 24 and each guide plate 233, so that there is no friction between the side of the guide plate 233 and the side of the stacked sheet group 24 during shearing.

[0072] The stacked piece group 24 is arranged within the stacked piece limiting frame 23, including n stacked pieces 241 and pins 242, where n is a positive integer greater than or equal to 3; the n stacked pieces 241 include, from top to bottom, the topmost stacked piece 241, n-2 middle stacked pieces 241 of equal thickness and the bottommost stacked piece 241.

[0073] The bottom layer stack 241 is directly or indirectly installed on the top of the base plate 231 and its position is fixed so that the bottom layer stack 241 moves together with the trolley 22 during shearing.

[0074] Each stack 241 has a U-shaped structure and is preferably made of stainless steel, thus enabling the stack 24 to have a rectangular sample preparation cavity. The length-to-width ratio of the sample preparation cavity is 2.5:1. The sample preparation cavity can be filled with clay to form a sample, thus the length-to-width ratio of the sample is also 2.5:1. The rectangular cross-section of the sample makes the tendency of the sample to overturn and rotate after shear deformation much smaller than that of a cube or cylindrical sample, and the shear stress on the plane is more uniform.

[0075] In this embodiment, the thickness of the uppermost stacked sheet 241, the lowermost stacked sheet 241, and the middle stacked sheets 241 gradually decrease. Further, the thickness of the uppermost stacked sheet 241 is preferably 5 mm, the thickness of the lowermost stacked sheet 241 is preferably 4 mm, and the thickness of each middle stacked sheet 241 is preferably 2 mm. The stacked sheet group 24 in this invention is applicable to the preparation and shearing of fine-grained soil samples such as clay.

[0076] Each layer of laminate 241 has at least two waist-shaped holes on its left side. Let the waist-shaped hole in the uppermost laminate 241 be the upper layer waist-shaped hole, the waist-shaped hole in the middle laminate 241 be the middle layer waist-shaped hole, and the waist-shaped hole in the lowermost laminate 241 be the lower layer waist-shaped hole. Preferably, the major axis dimensions of the upper layer waist-shaped hole and the lower layer waist-shaped hole are the same, and the major axis dimension of the middle layer waist-shaped hole is smaller than that of the upper layer waist-shaped hole.

[0077] A pin 242 is inserted into each oblong hole of the stacked plates 24. The pin 242 slides against the wall surface corresponding to the short axis of the oblong hole. When the trolley 22 moves to the left (towards the shear loading device 33), the bottommost stacked plate 241 moves to the left, allowing the pin 242 to move along the long axis of the oblong hole with the stacked plate 241, limiting the displacement of the short axis of the oblong hole and further preventing the stacked plate 241 from swaying back and forth during shearing, thus ensuring the directionality of the shear force. The top of each pin 242 is rotatably connected to the connecting rod in the topmost stacked plate 241 (the connecting rod passes through the pin 242). There is a vertical gap between the bottom of each pin 242 and the bottom surface (the bottom surface along the Z direction) of the bottommost stacked plate 241, and a vertical gap between the top of each pin 242 and the top surface of the topmost stacked plate 241. In this embodiment, the vertical gap is preferably 1.5 mm. Preferably, there are three pins 242, which are evenly distributed on the left side of the stacked plate group 24 (X direction is left) along the width direction of the stacked plate group 24; the uppermost stacked plate 241 is provided with a through hole, and a thin straight rod is inserted into the through hole, and the three pins 242 can rotate around the thin straight rod.

[0078] Preferably, when all the stacked pieces 241 in the stacked piece group 24 overlap (i.e., there is no shear displacement), the pin 242 contacts the right side of the corresponding lower layer waist-shaped hole, leaves a gap with the left side of the corresponding lower layer waist-shaped hole, contacts the left side of the corresponding middle layer waist-shaped hole, leaves a gap with the right side of the corresponding middle layer waist-shaped hole, and leaves gaps on both the left and right sides of the corresponding upper layer waist-shaped hole.

[0079] Specifically, when designing the waist-shaped hole, relevant literature was consulted and combined with laboratory tests. The shear strain γ at soil failure was specified as 20%. If the sample height is H, according to the shear strain formula: γ = ΔL / H, where ΔL is the total shear deformation of the soil, the shear deformation at soil failure is 0.2H. This means the displacement difference between the uppermost and lowermost stacked rings is 0.2H. The size of the waist-shaped hole is set based on this displacement difference. For a conservative design, the uppermost stacked ring is fixed, and the major axis dimension of the waist-shaped hole is designed based on the lowermost stacked ring being able to move a distance of 0.3H. The 0.3H displacement is proportionally distributed to each stacked ring according to its height, and the largest calculated result is used for design. Let the height of the highest stacked ring be h. Then the 0.3H displacement distributed to this stacked ring should be 0.3H*h / H = 0.3h. Therefore, the distance between the pin and the rightmost edge of the waist-shaped hole should be slightly greater than 0.3h (except for the bottommost stacked ring). The size of the waist-shaped hole in the top and bottom stacked rings should be designed to ensure that the rotation of the pin is not affected.

[0080] The reason for designing the pins is that the soil will undergo compressive deformation after being subjected to vertical pressure. Although Vaseline is applied to the inside of the stacked ring, the sidewall friction force generated by the inner wall of the stacked ring on the soil can only decrease, not disappear. Therefore, as the vertical pressure is transmitted from top to bottom, the total vertical force will gradually decrease along the stacked ring due to the influence of the sidewall friction force.

[0081] Further explanation: Let the vertical pressure applied by the lever be p, and the sidewall friction force of the i-th layer of the stacked ring be f. ci ,like Figure 9 Then, the total vertical pressure F on the soil body surrounded by the i-th layer of stacked rings (i.e., the soil body at the same height as the i-th layer of stacked rings) is... i for: (where n is the number of stacked rings), thus the vertical stress on the soil enclosed by the i-th stacked ring can be calculated as: σ i =F i / A (where A is the cross-sectional area of ​​the sample), i.e., σ i It gradually decreases from top to bottom.

[0082] according to Soil strength parameters: cohesion (c) and angle of internal friction. When all remain constant, the vertical stress σ i The shear strength τ gradually decreases from top to bottom, resulting in a lower shear strength τ for each layer. fiThe shear strength of the soil gradually decreases from top to bottom, resulting in an uneven distribution of shear strength for each layer of the stacked rings, with the strength decreasing towards the bottom. When a horizontal shear stress τ is applied to the soil, this stress overcomes the soil's own strength, causing shear deformation and horizontal displacement of the stacked rings. Since the applied horizontal shear stress is consistent, and the strength decreases towards the bottom, the lower the stacked rings, the easier they are to slide, leading to uneven shear strain distribution. Macroscopically, this manifests as unequal relative displacements between adjacent stacked rings. Figure 10 .

[0083] During shearing, the trolley 22 is pushed or pulled to slide to the left along the guide rail 21. The lowest layer of the stacked sheet assembly 24, 241, moves to the left, while the highest layer remains stationary. The pin 242 tilts. To prevent the top and bottom of the tilted pin 242 from hitting the upper and lower permeable plates, causing the stacked sheet assembly 24 to detach from them, a corresponding vertical gap is provided. After the pin 242 tilts, as... Figure 6 As shown, except for the topmost lamination 241 which did not displace, all other laminations 241 displaced. Since the thickness of the middle laminations 241 is the same, the displacement difference Δx between adjacent laminations 241 is equal. The shear strain γ = Δx / 2 of each lamination 241 is equal. When Δx is equal, the shear strain of each lamination 241 is equal, which can ensure that the shear strain distribution is uniform in the vertical plane perpendicular to the shear force, so that the laminations 241 are sheared uniformly and the shear strain is uniformly distributed along the vertical direction.

[0084] The loading device 30 includes a vertical loading device 31, a left-side sliding limit device 32, a shear loading device 33, and a horizontal loading device 34.

[0085] The vertical loading device 31 is positioned above the specimen and can apply a vertical load to the specimen. The vertical loading device 31 includes a pressure cover plate 311, a vertical load lever 312, a loading rod 313, and a vertical displacement monitoring meter.

[0086] The pressure cover plate 311 is the same length and width as the sample preparation cavity and is in contact with the top surface of the sample. After a vertical load is applied to the sample and the sample is solidified, the bottom of the pressure cover plate 311 is located in the uppermost stack 241 of the stack 24.

[0087] The vertical load applying lever 312 is horizontally positioned directly above the stacked plate assembly 24, with weights placed at both ends. Since the fulcrum is on the right, before the test, in order to keep the vertical load applying lever 312 horizontal, the weight on the left end is less than the weight on the right end. During the test, the weight on the left end is increased to make the vertical load applying lever 312 apply a downward force. A ball head is connected to the bottom middle of the vertical load applying lever 312.

[0088] The top of the loading rod 313 has a ball groove and is connected to the vertical load loading lever 312 by a ball head. The position of the loading rod 313 in the X direction remains unchanged. After the weight is added, the lever will rotate in the direction of the heavier weight, the sample will settle, and the ball head will rotate in the ball groove at the top of the loading rod 313, which does not affect the position of the loading rod 313 in the Y direction.

[0089] A vertical displacement monitoring meter is installed on loading rod 313 to measure vertical displacement (during the consolidation process). During the consolidation period, when the change in vertical displacement within 24 hours is less than 0.01 mm, it indicates that consolidation is complete.

[0090] The left-side sliding limit device 32 restricts the uppermost stacked piece 241 from moving to the left. It includes a concave block 321 and a top rod support 322. The concave block 321, with its notch facing downwards, is mounted on the base 10 on the left side of the trolley 22. The top rod support 322 is horizontally mounted on the concave block 321 and contacts the pressure cover plate 311. The top rod support 322 is designed to hold the pressure cover plate 311 in place. Before shearing, the top rod support 322 contacts the left side of the pressure cover plate 311 and holds it in place. The head of the top rod support 322 that contacts the pressure cover plate 311 uses a rotatable steel ball that can roll up and down. That is, the top rod support 322 and the pressure cover plate 311 are slidably connected. This is to ensure that there is virtually no friction when the pressure cover plate 311 is lowered due to the application of vertical load.

[0091] The horizontal displacement monitoring meter is set on the trolley 22 to measure the horizontal displacement of the trolley, which is the horizontal shear of the soil.

[0092] The shear loading device 33 includes a wire rope, a weight, and a pulley. The weight is applied to the lower end of the wire rope, and the pulley applies shear force to the trolley.

[0093] The horizontal loading device 34 includes a horizontal loading rod, a linear motor 341, and a force sensor 342, which can push the trolley 22 to move to the left. The horizontal displacement of the motor shaft and the reading of the force sensor can be displayed through a digital display controller or a computer interface.

[0094] The data acquisition box 40 is connected to the vertical displacement monitoring meter and the horizontal displacement monitoring meter to collect the vertical and horizontal displacement of the soil.

[0095] The digital display controller 50 is connected to the force sensor 342 and the linear motor 341. It is used to control the horizontal servo motor 341 to apply a set speed to the sample and to collect the data and horizontal displacement of the force sensor 342.

[0096] Strain-controlled test: The digital display controller 50 controls the linear motor 341, which can apply different shear rates to the trolley 22. Through the feedback of the force sensor 342, the force transmitted by the horizontal linear motor 341 to the bottommost laminate 241 connected to the trolley 22 is measured.

[0097] In this process, the strain rate can be controlled and the shear strength of the soil can be determined: First, adjust the axis of the linear motor 341 so that the force sensor 342 just contacts the trolley 22, and stop the motor rotation to correct the zero point of the force sensor 342; then set different slow loading rates to perform shearing, and collect the shear stress (monitored by the force sensor 342) and shear displacement (monitored and displayed by the digital display controller).

[0098] Stress-controlled test: The shear loading device 33 pulls the trolley 22 so that the bottommost lamination 241 of the lamination group 24 connected to the trolley 22 is subjected to the force transmitted by the shear loading device 33.

[0099] During this process, stress can be controlled and soil creep tests can be conducted. Since pin 242 is rigid, the top of pin 242 is limited to the top of the stacked plate group 24, and the bottom of pin 242 is located at the bottom of the stacked plate group 24. If the bottommost stacked plate 241 is pulled, pin 242 will tilt, causing the remaining stacked plates 241 to produce uniform displacement. The horizontal displacement monitoring table obtains the displacement of the trolley 22 through the data acquisition box 40.

[0100] The strain-controlled test allows for different strain rate tests by setting different shear rates, enabling the determination of various soil strength parameters (consolidated fast shear test, consolidated slow shear test, long-term strength test), and stress relaxation tests, thus integrating multiple functions. The stress-controlled test allows for shear creep tests of soil by setting different stress levels (0.2, 0.4, 0.6, 0.8), with a test accuracy of 0.001 mm. The test results are of significant reference value for slope landslides, roadbed lateral displacement, and the long-term shear behavior of soils in coastal areas.

[0101] The shearing method based on the uniform shear strain distribution of this single shear apparatus includes the following steps:

[0102] Step 1: Install the shear assembly 20 and load the sample into the stack 24 of the shear assembly 20.

[0103] The shearing component 20 includes a trolley 22, a stacking limit frame 23, and a stacking assembly 24, and specifically includes the following steps:

[0104] Step 1A: Assemble the stack 24, which provides shear space for the consolidated sample. It includes n layers of stacked sheets 241 stacked along the Z-axis, specifically including the following steps:

[0105] Step 1A1: Along the Z direction, stack the n layers of laminate 241 sequentially;

[0106] Step 1A2: Insert the same pin 242 into the corresponding waist hole in each layer of laminate 241 and the adjacent layer of laminate 241. A shear deformation space is formed between the pin 242 and each layer of laminate 241.

[0107] Each layer of laminate 241 has several waist holes arranged along the Y direction;

[0108] Step 1A3: Insert a connecting rod for the pin 242 to rotate into the through hole along the Y direction on the topmost lamination 241, and make the connecting rod pass through each pin 242 in sequence along the Y direction.

[0109] Step 1B: Fix the base plate 231 of the stacking limit frame 23 to the trolley 22, and install the stacking limit frame 23 around the stacking assembly 24. This includes the following steps:

[0110] Step 1B1: Fix the bottommost stacked piece 241 closest to the trolley 22 to the base plate 231 so that the bottommost stacked piece 241 can move along the X direction with the trolley 22;

[0111] Before consolidation in step 3, the uppermost stacked piece 241 is detachably fixed to the top surface of the stacked piece limiting frame 23 using limiting screws to prevent the stacked piece group 24 from moving along the Z direction during the sample consolidation process in step 3. The stacked piece limiting frame 23 is a detachable structure, used in two ways: first, during the sample preparation process in step 1C, to prevent the stacked piece group 24 from slipping and reduce soil sample disturbance; second, during the sample consolidation process in step 3, to provide limiting space for the sample and prevent the sample from being squeezed between the stacked pieces. Before the shearing in step 4, the limiting component located in the X direction is removed from the foundation plate 231.

[0112] Step 1C: Place the sample into the sample preparation cavity formed by the stacked plates 24;

[0113] Step 2: Install the vertical loading device 31 and the shear loading device 33; wherein, the vertical loading device 31 includes a pressure cover plate 311, a vertical load loading lever 312, and a loading rod 313; the shear loading device 33 includes a roller assembly and a wire rope;

[0114] Specifically, the following steps are included:

[0115] Step 2A: Install the vertical loading device 31: Fix the upper end of the vertical load loading lever 312 along the Z direction to a lever structure. The lever structure is hinged to a support frame. The lower end of the lever along the Z direction is a ball. Place the lower end of the lever into the semi-circular groove at the upper end of the loading rod 313 along the Z direction. Finally, thread the lower end of the loading rod 313 to the pressure cover plate 311, so that the pressure cover plate 311 fits into the sample preparation cavity formed by the uppermost stacked pieces 241.

[0116] Step 2B: Install the shear loading device 33, which specifically includes the following steps:

[0117] Step 2B1: Install the mounting base with the roller assembly at the front end of the trolley in the X direction, 50cm away from the trolley (a distance that does not affect the shearing process).

[0118] Step 2B2: Wrap the wire rope around the roller assembly, pass it through the concave block 321, and connect it to the trolley;

[0119] Step 3: Apply a vertical load to the specimen to solidify it, specifically including the following steps:

[0120] By configuring the weights at both ends of the vertical load loading lever 312, the vertical load loading lever 312 is tilted toward the sample side, so that the vertical load is applied to the sample through the pressure cover plate 311, so that the water in the sample is discharged to compress the sample, and finally a solidified sample is obtained.

[0121] After consolidation, the pressure plate 311 is compacted onto the upper surface of the consolidated sample; simultaneously, the lower end face of the pressure plate 311 along the Z direction is located in the uppermost stack 241 to prevent the pressure plate 311 from restricting the pin 242 from rotating around the connecting rod during the shearing process in step 4; at the same time,

[0122] During the consolidation process, the pressure cover plate 311 moves downward along the Z direction along with the loading rod 313;

[0123] Step 4: Install the left sliding limit device 32, which includes a concave block 321 and a top rod support 322, specifically including the following steps:

[0124] The concave block 321 is fixed between the trolley and the roller assembly, and the top rod support 322 is fixed on the side of the concave block 321 facing the trolley; the pressure cover plate 311 and the top rod support 322 are slidably connected in the Z direction to prevent the uppermost stacked piece 241 from moving along the X direction with the trolley 22 during shearing.

[0125] Step 5: Apply a horizontal load to the consolidated specimen to perform shearing, specifically including the following steps:

[0126] Step 5A: Keep the vertical consolidation pressure constant so that a portion of the consolidated sample in contact with it remains stationary under the pressure applied by the pressure plate 311;

[0127] Step 5B: Remove the limiting component of the stacking limit frame 23 in the X direction, and separate the uppermost stacking piece 241 from the stacking limit frame 23;

[0128] Step 5C: Pull the steel wire rope so that the lowest layer 241 connected to the trolley 22 is subjected to the tension transmitted by the shear loading device 33; since the pin 242 is rigid, the top of the pin 242 is limited to the uppermost layer 241, and the bottom of the pin 242 is located at the lowest layer 241. When the lowest layer 241 is pulled, the pin 242 tilts, causing the remaining layers 241 to undergo uniform displacement.

[0129] Furthermore, when the shear loading device 33 is not used, step 5 also includes a step of shearing based on the horizontal loading device 34, which includes a linear motor 341 and a force sensor 342, specifically including the following steps:

[0130] First, fix the base of the linear motor 341, connect the housing of the force sensor 342 to the output end of the linear motor 341, and make the sensing end of the force sensor 342 face the trolley 22.

[0131] Then, the linear motor 341 is started. When the sensing end of the force sensor 342 contacts the trolley 22, the linear motor 341 is started and then turned off to zero the force sensor 342.

[0132] Then, the linear motor 341 is started again, and the bottom layer 241 connected to the trolley 22 is subjected to the thrust transmitted by the horizontal loading device 34.

[0133] Since the pin 242 is rigid, the top of the pin 242 is located at the uppermost lamination 241, and the bottom of the pin 242 is located at the lowermost lamination 241. When the lowermost lamination 241 is pushed, the pin 242 tilts, causing the remaining laminations 241 to undergo uniform displacement.

[0134] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.

Claims

1. A shearing method with uniform shear strain distribution, characterized in that, Includes the following steps: Step 1: Install the shear assembly (20) and load the sample into the stack (24) of the shear assembly (20). The shearing component (20) includes a trolley (22), a stacking limit frame (23), and a stacking assembly (24), and specifically includes the following steps: Step 1A: Assemble the stacked sheet group (24), which is used to provide shear space for the consolidated sample, comprising n layers of stacked sheets (241) along the Z direction, specifically including the following steps: Step 1A1: Along the Z direction, stack the n layers of laminate (241) sequentially; Step 1A2: Insert the same pin (242) into the corresponding waist hole of each layer of lamination (241) and the adjacent layer of lamination (241). A shear deformation space is formed between the pin (242) and each layer of lamination (241). Among them, each layer of laminations (241) has several waist holes arranged along the Y direction; Step 1A3: Insert a connecting rod for the pin (242) to rotate into the through hole along the Y direction on the topmost lamination (241), and make the connecting rod pass through each pin (242) in sequence along the Y direction. Step 1B: Fix the base plate (231) of the stacking limit frame (23) to the trolley (22), and install the stacking limit frame (23) around the stacking assembly (24). Specifically, this includes the following steps: Step 1B1: Fix the bottommost stacked piece (241) closest to the trolley (22) to the base plate (231) so that the bottommost stacked piece (241) can move along the X direction with the trolley (22); Before the consolidation in step 3, the uppermost stacked piece (241) is detachably fixed to the top surface of the stacked piece limiting frame (23) with limiting screws to prevent the stacked piece group (24) from moving along the Z direction during the sample consolidation process in step 3. The stacked piece limiting frame (23) is a detachable structure. First, it is used in the sample preparation process in step 1C to prevent the stacked piece group (24) from slipping and reduce soil sample disturbance. Second, it is used in the sample consolidation process in step 3 to provide limiting space for the sample and prevent the sample from being squeezed between the stacked pieces. Before the shearing in step 4, the limiting component located in the X direction is removed from the foundation plate (231). Step 1 C, Place the sample: Place the sample into the sample preparation cavity enclosed by the stacked pieces (24); Step 2: Install the vertical loading device (31) and the shear loading device (33); wherein, the vertical loading device (31) includes a pressure cover plate (311), a vertical load loading lever (312), and a loading rod (313); the shear loading device (33) includes a roller assembly and a wire rope; Specifically, the following steps are included: Step 2A, Install the vertical loading device (31): Fix the upper end of the vertical load loading lever (312) along the Z direction to a lever structure. The lever structure is hinged to a support frame. The lower end of the lever along the Z direction has a ball connector. Place the ball connector into the upper semi-circular groove of the loading rod (313) along the Z direction. Finally, thread the lower end of the loading rod (313) to the pressure cover plate (311) so that the pressure cover plate (311) fits with the sample preparation cavity formed by the uppermost stacked pieces (241). Step 2B, Install the shear loading device (33), which specifically includes the following steps: Step 2B1: Secure the mounting base containing the roller assembly; Step 2B2: Wrap the wire rope around the roller assembly, pass it through the concave block (321), and connect it to the trolley; Step 3: Apply a vertical load to the specimen to solidify it, specifically including the following steps: By configuring the weights at both ends of the vertical load loading lever (312), the vertical load loading lever (312) is tilted toward the sample side, so that the vertical load is applied to the sample through the pressure cover plate (311), so that the water in the sample is discharged to compress the sample, and finally a solidified sample is obtained. After consolidation, the pressure cover plate (311) is pressed firmly onto the upper surface of the consolidated sample; at the same time, the lower end face of the pressure cover plate (311) along the Z direction is located in the uppermost stack (241) to prevent the pressure cover plate (311) from restricting the pin (242) from rotating around the connecting rod during the shearing process in step 4; at the same time, during the consolidation process, the pressure cover plate (311) moves downward along the Z direction with the loading rod (313); Step 4: Install the left sliding limit device (32), which includes a concave block (321) and a top rod support (322), specifically including the following steps: The concave block (321) is fixed between the trolley and the roller assembly, and the top rod support (322) is fixed to the side of the concave block (321) facing the trolley; the pressure cover plate (311) and the top rod support (322) are slidably connected in the Z direction to prevent the uppermost stacked piece (241) from moving along the X direction with the trolley (22) during shearing, while eliminating the friction of the top rod support (322) on the pressure cover plate (311) and the bending moment generated by the loading rod (313); Step 5: Apply a horizontal load to the consolidated specimen to perform shearing, specifically including the following steps: Step 5A: Keep the vertical consolidation pressure constant so that a portion of the consolidated sample in contact with it remains stationary under the pressure applied by the pressure plate (311); Step 5B: Remove the limiting component of the stacking limit frame (23) in the X direction, and separate the uppermost stacking piece (241) from the stacking limit frame (23); Step 5C: Pull the wire rope so that the bottommost laminate (241) connected to the trolley (22) is subjected to the tension transmitted by the shear loading device (33); since the pin (242) is rigid, the top of the pin (242) is limited to the topmost laminate (241), and the bottom of the pin (242) is located at the bottommost laminate (241). When the bottommost laminate (241) is pulled, the pin (242) tilts, causing the remaining laminates (241) to produce uniform displacement.

2. The shearing method for uniform shear strain distribution according to claim 1, characterized in that, When the shear loading device (33) is not in use, step 5 also includes a step of shearing based on the horizontal loading device (34), which includes a linear motor (341) and a force sensor (342), specifically including the following steps: First, fix the base of the linear motor (341), connect the housing of the force sensor (342) to the output end of the linear motor (341), and make the sensing end of the force sensor (342) face the trolley (22). Then the linear motor (341) is started. When the sensing end of the force sensor (342) touches the trolley (22), the linear motor (341) is turned off to achieve zeroing of the force sensor (342). Then, the linear motor (341) is started again, and the bottommost stack (241) connected to the trolley (22) is subjected to the thrust transmitted by the horizontal loading device (34); Since the pin (242) is rigid, the top of the pin (242) is located at the uppermost lamination (241), and the bottom of the pin (242) is located at the lowermost lamination (241). When the lowermost lamination (241) is pushed, the pin (242) tilts, causing the remaining laminations (241) to undergo uniform displacement.

3. The shearing method for uniform shear strain distribution according to claim 1, characterized in that, The stacked plate limiting frame (23) also includes: two fixing plates (232) and two guide plates (233): Two guide plates (233) are arranged opposite each other in the Y direction and fixed to the base plate (231), which can limit the Y direction of the stacked piece group (24); Each guide plate (233) is provided with a limiting flange (234) at its top. The limiting flange (234) extends toward the sample preparation cavity and is located above the uppermost stack (241). The limiting flange (234) and the uppermost stack (241) are detachably connected by a limiting screw (235). Two fixing plates (232) are arranged opposite each other in the X direction and fixed to the base plate (231), which can limit the X direction of the stacked pieces (24).

4. The shearing method for uniform shear strain distribution according to claim 3, characterized in that, The limiting flange (234) and the uppermost lamination (241) have a gap in the Z direction to prevent the guide plate (233) from rubbing against the lamination group (24) during shearing.

5. The shearing method for uniform shear strain distribution according to claim 3, characterized in that, There is a gap of 0.05mm-0.1mm between the stacked plate group (24) and each guide plate (233), which prevents the guide plate (233) from generating lateral friction on the stacked plate group (24) during shearing.

6. The shearing method for uniform shear strain distribution according to claim 1, characterized in that, Each stack (241) has a U-shaped structure, which makes the tendency to overturn and rotate after shear deformation smaller than that of a cube or cylindrical specimen.

7. A single shear apparatus with uniform shear strain distribution, based on the shearing method with uniform shear strain distribution according to any one of claims 1 to 6, characterized in that, It includes the shearing assembly (20), the vertical loading device (31), the shear loading device (33), and the left sliding limit device (32).

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