Circulating simple shear instrument with uniform strain and test method thereof

Abstract

The invention discloses a uniform-strain circulating single shear instrument and a test method thereof.The instrument comprises a movable base, a first stacking ring and a second stacking ring, the first stacking ring is provided with a trapezoidal cross section drill hole, the second stacking ring is provided with a circular drill hole and connected with a rigid rod, one end of the rigid rod is rotatably connected with the movable base, and the other end of the rigid rod is connected with a clamping device; the rigid rod is connected with the first stacking ring and the second stacking ring, so that the displacement directions of all layers of positions are consistent in the moving process of the test soil sample, the displacement amounts are also basically consistent, and the position of the outermost layer of the stacking ring is linearly changed. The cyclic single shear apparatus can improve the test precision and uniformity of the whole apparatus, can simplify the whole structure, has the advantages of high strength, good durability, good repeatability, wide adaptability, and excellent and convenient practical performance, and especially has a good application prospect under the working conditions of multiple tests and large-range strain amplitude tests. And the accuracy of measuring the mechanical parameters of the soil body can be greatly improved.

Description

Technical Field

[0001] The present invention relates to the fields of geotechnical testing and earthquake technology, and in particular to a cyclic simple shear instrument with uniform strain and a test method thereof, which is suitable for detecting the mechanical properties of soil samples in geotechnical engineering in earthquake and tsunami disasters. Background Art

[0002] Earthquakes are frequent, and foundation failure caused by liquefaction of saturated sand during strong earthquakes is particularly prominent. Traditional geotechnical testing methods (such as direct shear and triaxial instruments) have significant limitations when simulating seismic loads. The boundary constraints of direct shear instruments lead to localized shear bands in the specimen (strain differences exceeding 30%), failing to reflect true uniform deformation of the soil. While triaxial instruments can control confining pressure, the complex loading path makes it difficult to match the spectral characteristics of seismic waves (1-20 Hz), and the limited specimen size (≤10 cm in diameter) makes it difficult to meet the testing requirements for coarse-grained soils. This is particularly true for liquefiable soils such as southern alluvial sands and the fine sands of the Yangtze River Delta. Traditional equipment cannot accurately quantify the pore water pressure accumulation pattern and critical cyclic stress ratio under cyclic loading, leading to inaccurate liquefaction risk assessments.

[0003] Early cyclic simple shear instruments relied on imported equipment. Their rigid shear box exhibited significant friction effects at the boundaries, leading to severe strain concentration at the specimen edges and errors of 15%-25% in the measured shear modulus. A flexible boundary design (silicone-Teflon composite film), combined with hydraulic servo closed-loop control, has reduced strain dispersion from 30% to less than 5%. In recent years, major national projects such as the Sichuan-Tibet Railway and coastal nuclear power plants have placed increasing demands on the accuracy of soil dynamic parameters. The "Cyclic Simple Shear Test" procedure has been added to the "Standard for Geotechnical Test Methods" (GB / T 50123-2019), further promoting technological advancements in domestically produced instruments.

[0004] Based on the above-mentioned existing device, the present invention upgrades and improves the test device to improve the accuracy and scientificity of the geotechnical test. Summary of the Invention

[0005] The purpose of the present invention is to address the problems existing in the prior art and provide a cyclic single shear instrument with uniform strain and a test method thereof, so that the strain of the soil sample to be tested at different depths during the shearing process of the cyclic single shear instrument is uniform, thereby improving the repeatability of the test and the accuracy of the mechanical properties of the soil sample to be tested.

[0006] To achieve the above object, the technical solution adopted by the present invention is: On the one hand, a cyclic simple shear instrument with uniform strain is provided, comprising a movable base, wherein the movable base is provided with multiple layers of stacked rings, the multiple layers of stacked rings enclose a sample filling area, and a top pressure device is provided above the sample filling area; the multiple layers of stacked rings include multiple layers of first stacked rings and multiple layers of second stacked rings, the first stacked rings are provided with trapezoidal cross-section drilled holes, and the second stacked rings are provided with circular drilled holes, the trapezoidal cross-section drilled holes and the circular drilled holes on the same side are stacked layer by layer and connected with a rigid rod, one end of the rigid rod is rotatably connected to the movable base, and the other end extends from above the multiple layers of stacked rings, the rigid rod involves the first stacked ring and the second stacked ring so that the displacement direction of each layer of the test soil sample is consistent during the movement, the displacement amount is also basically consistent, and the position of the outermost layer of the stacked rings shows linear change.

[0007] The cyclic single shear instrument has a simple structure and is easy to use and operate. By improving the movement mode and force-bearing mode of the multiple layers of stacked rings, it can not only improve the test accuracy and uniformity of the entire instrument, but also simplify the overall structure. There is no need for complex force-applying mechanisms and limit mechanisms to act on the stacked rings. In addition, it has high strength, good durability, good repeatability, and wide adaptability. It has excellent and convenient practical performance. Especially under the working conditions of multiple tests and tests with a large range of strain amplitudes, the instrument can greatly improve the accuracy of measuring soil mechanical parameters.

[0008] This cyclic simple shear instrument innovatively connects multiple stacked rings with the swingable rigid rod, and uses the mobile base and the rigid rod to synchronously drive the movement of multiple layers of stacked rings, which can greatly improve the accuracy and repeatability of the cyclic simple shear test, make the strain of the specimen more uniform when sheared, and make the detection of soil mechanical properties more reliable.

[0009] By combining a stacked ring design with holes of different geometric sizes, the strain of the soil sample to be tested at different depths during the shearing process of the cyclic single shear instrument is uniform, thereby improving the repeatability of the test and the accuracy of the mechanical properties of the soil sample to be tested.

[0010] Furthermore, a rubber membrane is provided on the inner periphery of the sample filling area, and the rubber membrane is closely attached to the inner periphery of the stacked ring and extends to the interior of the movable base.

[0011] Furthermore, the movable base includes a movable slide, a boss is provided above the slide, a sample supporting base is provided on the boss, a ring seat is provided on the periphery of the boss, the stacking ring is provided above the ring seat, and the rigid rod is rotatably connected to the ring seat.

[0012] Furthermore, the ring seat is fixedly connected to the slide seat by a number of bolts, the upper surface of the ring seat is arranged flush with the upper surface of the sample support base plate, and a clamping gap is provided between the inner periphery of the ring seat and the outer periphery of the sample support base plate and the boss; a seal is also provided between the ring seat and the slide seat.

[0013] Furthermore, the boss is provided with a plurality of drainage grooves, and the slide is provided with a discharge channel; and the sample support bottom plate is provided with a plurality of striped protrusions.

[0014] Preferably, the rigid rods are a pair, mounting grooves are respectively provided on both sides of the movable base, connecting ear plates are respectively provided in the mounting grooves, and the ends of the rigid rods are rotatably connected to the connecting ear plates through hinge shafts.

[0015] Preferably, the first stacked rings and the second stacked rings are both low-friction rigid rings, the second stacked rings are arranged above the first stacked rings, and the second stacked rings are arranged in 1 to 3 layers.

[0016] Preferably, the large hole of the trapezoidal cross-section drilled hole is arranged downward, the inner diameter of the circular drilled hole is larger than the inner diameter of the small hole of the trapezoidal cross-section drilled hole, and the inclination of the hole wall of the trapezoidal cross-section drilled hole is 60-70°.

[0017] In another aspect, a test method for a cyclic single shear instrument with uniform strain is provided, the test method comprising the following steps: Preparing the cyclic single shearing instrument and preheating the cyclic single shearing instrument; Apply an interface agent to the bottom of the mobile base and prepare a rubber film; Stacking a plurality of first stacking rings and a plurality of second stacking rings on the movable base in sequence, with the rigid rod passing through the trapezoidal cross-section drilled hole and the circular drilled hole; installing the stacking rings to form the sample filling area, and placing the rubber membrane in the sample filling area so that the rubber membrane wraps and fits around the inner circumference of the first stacking rings and the second stacking rings; The test soil sample is loaded according to the test requirements, and the rubber membrane is always kept in close contact with the stacking ring during the loading process; Lowering the top pressure device to make the top of the test soil sample fit into the top pressure device; moving the movable base, and the stacking ring moves linearly under the drive of the rigid rod; At the same time, set the target working conditions, input the test parameters of the loading control, and carry out the loading and unloading process according to the test sequence; During the loading process, regularly observe the working status of the test to confirm whether the test is stable; After the preset test target is reached, the top pressure device is raised, and the second stacking ring, the first stacking ring and the rubber membrane are disassembled; after the disassembly is completed, the mobile base is checked to ensure that no soil sample remains.

[0018] Furthermore, one way to install the rubber membrane is as follows: One end of the rubber film is sleeved and clamped on the movable base. After the stacking rings are installed, the rubber film is spread out and turned upward and outward so that the rubber film is wrapped around the inner circumference of the first stacking ring and the second stacking ring; a vacuum pump is used to extract the rubber film so that the rubber film is tightly fitted to the inner circumference of the first stacking ring and the second stacking ring.

[0019] Compared with the prior art, the beneficial effects of the present invention are: 1. The cyclic single shear instrument has a simple structure and is easy to use and operate. By improving the movement mode and force mode of the multiple layers of stacked rings, it can not only improve the test accuracy and uniformity of the entire instrument, but also simplify the overall structure. There is no need for complex force-applying mechanisms and limiting mechanisms to act on the stacked rings. Moreover, it has high strength, good durability, good repeatability, and wide adaptability, and has excellent and convenient practical performance. Especially under the working conditions of multiple tests and large-scale strain amplitude tests, the instrument can greatly improve the accuracy of measuring soil mechanical parameters; 2. The cyclic single shear instrument innovatively connects the multiple stacked rings with the swingable rigid rod, and uses the mobile base and the rigid rod to synchronously drive the multiple layers of stacked rings to move, which can greatly improve the accuracy and repeatability of the cyclic single shear test. The invention can make the strain of the sample more uniform when it is sheared, and make the detection of the mechanical properties of the soil more reliable; 3. The setting of the rigid rod can also improve the integrity and rigidity of the stacking rings, so that the stacking rings can be neatly stacked layer by layer from bottom to top on top of the mobile base, and the stacking rings will not detach or shake on their own; 4. The trapezoidal cross-section boreholes of the first stacking rings and the circular boreholes of the second stacking rings can not only be used in conjunction with the rigid rods, but also can play different roles respectively. The inclined hole wall can limit the maximum swing range of the rigid rod, so that each layer of stacking rings reaches the preset shear position, and the two complement each other and work together; 5. By combining the design of drilled holes and stacking rings with different geometric sizes, the strain of the soil samples to be tested at different depths during the shearing process of the cyclic single shear instrument is uniform, thereby improving the repeatability of the test and the accuracy of the mechanical properties of the soil samples to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the overall structure of a cyclic single shear instrument with uniform strain according to the present invention; Figure 2 This is a schematic diagram of the partial structure of a cyclic single shear instrument with uniform strain according to the present invention; Figure 3 Schematic diagram of the structure of the first stacked ring of the present invention; Figure 4 Schematic diagram of the structure of the second stacked ring of the present invention; Figure 5 This is a schematic diagram of a shearing state in which the rigid rod swings to the left when the movable base of the present invention moves; Figure 6 This is a schematic diagram of a shearing state in which the rigid rod swings to the right when the movable base moves according to the present invention; Figure 7 Schematic diagram of the maximum swing state of the rigid rod of the present invention; Figure 8 This is a schematic diagram of the test of the cyclic single shear instrument of the present invention. Figure 1 ; Figure 9 This is a schematic diagram of the test of the cyclic single shear instrument of the present invention. Figure 2 ; In the figure: 1. Mobile base; 101. Sliding seat; 102. Boss; 103. Sample support base plate; 104. Ring seat; 2. Stacked rings; 201. First stacked ring; 202. Second stacked ring; 3. Test soil sample; 4. Rigid rod; 5. Top pressure device; 6. Rubber membrane; 7. Trapezoidal cross-section drill hole; 8. Circular drill hole; 9. Seal; 10. Connecting ear plate. DETAILED DESCRIPTION

[0021] The following will clearly and completely describe the technical solution of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," etc., etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Example 1

[0023] like Figures 1 to 7As shown, a cyclic simple shear instrument with uniform strain includes a mobile base 1, on which are provided multiple layers of stacked rings 2, the multiple layers of stacked rings 2 enclose a sample filling area, the sample filling area is filled with a test soil sample 3 to be tested, and a top pressure device 5 is provided above the sample filling area; the multiple layers of stacked rings 2 include multiple layers of first stacked rings 201 and multiple layers of second stacked rings 202, the first stacked rings 201 are provided with trapezoidal cross-section drilled holes 7, the second stacked rings 202 are provided with circular drilled holes 8, the trapezoidal cross-section drilled holes 7 and the circular drilled holes 8 on the same side are stacked layer by layer and connected with a rigid rod 4, one end of the rigid rod 4 is rotatably connected to the mobile base 1, and the other end extends from above the multiple layers of stacked rings 2, the rigid rod 4 involves the first stacked rings 201 and the second stacked rings 202 so that the displacement of each position of the test soil sample 3 is consistent during the movement, and the position of the outermost layer of the stacked rings shows linear change.

[0024] The cyclic single shear instrument has a simple structure and is easy to use and operate. By improving the movement mode and force-bearing mode of the multiple layers of stacked rings, it can not only improve the test accuracy and uniformity of the entire instrument, but also simplify the overall structure. There is no need for complex force-applying mechanisms and limit mechanisms to act on the stacked rings. In addition, it has high strength, good durability, good repeatability, and wide adaptability. It has excellent and convenient practical performance. Especially under the working conditions of multiple tests and tests with a large range of strain amplitudes, the instrument can greatly improve the accuracy of measuring soil mechanical parameters.

[0025] This cyclic simple shear instrument innovatively connects multiple stacked rings 2 with the swingable rigid rod 4, and uses the mobile base 1 and the rigid rod 4 to synchronously drive the movement of multiple layers of stacked rings 2, which can greatly improve the accuracy and repeatability of the cyclic simple shear test, make the strain of the specimen more uniform when sheared, and make the detection of the mechanical properties of the soil more reliable.

[0026] The provision of the rigid rod 4 can also improve the integrity and rigidity of these stacking rings, so that these stacking rings can be neatly stacked layer by layer from bottom to top on top of the mobile base. Although the ends of the rigid rod 4 are not locked, these stacking rings will not detach or shake on their own. It is precisely because the upper ends of the rigid rods are not locked that they can drive each layer of stacking rings to move; under the pressure of the top pressure device 5 and the horizontal movement of the mobile base 1, these stacking rings 2 can be horizontally displaced from bottom to top, thereby achieving shearing of the soil; if there is no top pressure device, when the mobile base moves, these stacking rings will be moved at the same time, and will not be able to produce a shearing effect on the soil; if there is no rigid rod, even if the top pressure device is applied above, when the mobile base moves, these stacking rings will have irregular displacement, the stacking rings cannot play a good shearing role in each layer, and the displacement of the stacking rings is uncontrollable.

[0027] This strain-uniform cyclic single shear instrument drills holes on these stacking rings 2 and passes the rigid rods 4 through these holes, so that these stacking rings 2 can be connected in series. When the top is subjected to vertical pressure from the top pressure device 5, the mobile base 1 moves horizontally, and cooperates with the rotation connection of the rigid rod 4, so that the rigid rod 4 can apply horizontal force to each layer of the stacking rings 2 during the deflection process, so that each layer of the stacking rings 2 can exert a shear effect on the soil, thereby realizing the detection test of the soil performance.

[0028] The stacking ring 2 is provided with two types of boreholes, namely the trapezoidal cross-section borehole 7 of the first stacking ring 201 and the circular borehole 8 of the second stacking ring 202. These two types of boreholes can not only be used in conjunction with the rigid rod, but can also each play a different role. The inclined hole wall of the trapezoidal cross-section borehole 7 can limit the maximum swing range of the rigid rod 4. The rigid rod 4 uses the trapezoidal cross-section borehole 7 and the circular borehole 8 to drive the movement of each stacking ring, but is also limited by the trapezoidal cross-section borehole 7. When the first stacking ring 201 moves to the point where the hole wall inclination of the trapezoidal cross-section borehole 7 of each layer is straight and on the same oblique line, the rigid rod 4 also reaches the maximum swing amplitude, forming a limit for the rigid rod and allowing each layer of stacking rings to reach the preset shear position. The two complement each other and work together.

[0029] By combining a stacked ring design with holes of different geometric sizes, the strain of the soil sample to be tested at different depths during the shearing process of the cyclic single shear instrument is uniform, thereby improving the repeatability of the test and the accuracy of the mechanical properties of the soil sample to be tested.

[0030] Furthermore, the top pressure device 5 is capable of completely covering the test soil sample, and its orthographic projection dimensions are substantially the same as those of the sample support base 103 on the mobile base 1. The top pressure device 5 can only move vertically up and down and is fixed and cannot move horizontally. The mobile base 1 can only move horizontally and is fixed and cannot move vertically.

[0031] Furthermore, a rubber membrane 6 is provided on the inner periphery of the sample filling area. The rubber membrane 6 is in close contact with the inner periphery of the stacking ring 2 and extends to the interior of the movable base 1, that is, between the sample supporting bottom plate and the ring seat.

[0032] The first stacking ring 201, the second stacking ring 202, the test soil sample 3 and the rubber membrane 6 are tightly fitted together. On the one hand, this can prevent the soil sample from penetrating into the gaps between adjacent stacking rings, especially preventing the soil from soaking into the stacking ring 2 during the moving shear process. This not only reduces the difficulty of cleaning after the test, but also facilitates the accuracy of the shear test; on the other hand, it can prevent water in the soil from seeping out of the gaps between the stacking rings 2.

[0033] Furthermore, the mobile base 1 includes a movable slide 101, with a boss 102 disposed above the slide 101, a sample support base 103 disposed on the boss 102, a ring seat 104 disposed on the periphery of the boss 102, the stacking ring 2 disposed above the ring seat 104, and the rigid rod 4 rotatably connected to the ring seat 104. The slide 101 is disposed above a slide rail or a slide plate and can be moved along the slide rail under external drive.

[0034] The sample support base plate 103 is configured to support the test soil sample and, in its initial state, is positioned opposite the top pressure device 5 above. The ring seat 104 facilitates connection to the rigid rod 4 and supports the stacked rings 2. A clamping gap is defined between the inner periphery of the ring seat 104 and the outer peripheries of the sample support base plate 103 and the boss 102. This gap allows for connection to the rubber membrane 6, allowing it to extend from the lowest ring seat 104 all the way to the uppermost stacked ring 2, forming a membrane structure around the entire inner periphery of the sample filling area.

[0035] Furthermore, the ring seat 104 is fixedly connected to the slide 101 by a number of bolts, and the upper surface of the ring seat 104 is arranged flush with the upper surface of the sample support base 103. Such an arrangement can avoid the first stacked rings 201 of the bottom layer from causing motion interference with the sample support base 103 when the mobile base 1 moves, which is conducive to the first stacked rings 201 of the bottom layer sliding smoothly on the ring seat and the sample support base.

[0036] The inner lower edge of the ring seat 104 is provided with a chamfer, and a sealing member 9, such as a rubber sealing ring, is provided between the chamfer and the sliding seat 101 to form a sealing structure therebetween to prevent water seepage therein.

[0037] Furthermore, the boss 102 is provided with a plurality of drainage grooves, and the slide 101 is provided with a discharge channel. Water flowing into the soil from the bottom can be discharged through the drainage grooves and the discharge channel; the sample support base plate 103 is provided with a plurality of striped protrusions, which can increase the friction and bonding force of the sample support base plate, which is conducive to the adhesion of the soil sample at the bottom to the sample support base plate.

[0038] Preferably, the rigid rods 4 are a pair of symmetrically arranged bilaterally. Mounting slots are provided on either side of the ring base 104. Connecting lugs 10 are provided in the mounting slots. The ends of the rigid rods 4 are rotatably connected to the connecting lugs 10 via hinges. This connection allows the rigid rods 4 to rotate relative to the ring base 104, i.e., the mobile base 1.

[0039] Preferably, both the first stacked rings 201 and the second stacked rings 202 are low-friction rigid rings, and the second stacked rings 202 are disposed above the first stacked rings 201. The second stacked rings 202 are provided in two layers, and the number of the first stacked rings 201 is much greater than the number of the second stacked rings 202. Placing the second stacked rings 202 at the top, that is, the circular bore 8 at the top, can avoid interference with the end of the rigid rod 4 during its swinging.

[0040] Preferably, the large holes of the trapezoidal cross-section drillings 7 are arranged downward, and the initial arrangement direction of all the first stacking rings 201 is the same, that is, the large holes of the trapezoidal cross-section drillings are all facing upward and the small holes are located above. The trapezoidal cross-section is a positive structure. This regular arrangement is conducive to the movement of the first stacking rings in the same direction and avoids interference in the movement of adjacent layers. At the same time, since the first stacking rings 201 in the bottom layer are provided with large holes at the bottom, the rigid rods have a higher degree of freedom at the lower end surface of the first stacking rings, which is conducive to swinging, avoiding long-term contact of the rigid steel with this location, reducing wear on the hole opening, and extending the service life of the first stacking rings.

[0041] The trapezoidal cross-section drill hole 7 can be a trapezoidal through hole or a truncated cone through hole. The large hole size of the trapezoidal cross-section drill hole 7 is larger than the outer diameter of the rigid rod. The inner diameter of the circular drill hole 8 is larger than the inner diameter of the small hole of the trapezoidal cross-section drill hole 7 and not larger than the inner diameter of the large hole. The inclination of the hole wall of the trapezoidal cross-section drill hole 7 is 60 to 70°, so that the rigid rod can swing to a maximum inclination angle of 60 to 70°.

[0042] In this embodiment, the rigid rod 4 is a rigid cylindrical straight rod with a diameter of 5 mm and a height of 22 mm. The rigid rod hardly deforms during the shearing process and can swing freely left and right with the end hinge or shaft as the center of gravity.

[0043] The second stacked ring 202 has a thickness of 2 mm, an inner radius of 35.5 mm, an outer radius of 43.5 mm, and a circular hole with a radius of 3.5 mm at the center of the radial line of the inner and outer rings. During the test, it can move linearly with the rigid rod.

[0044] The thickness of the first stacked ring 201 is 2 mm, the inner radius is 35.5 mm, the outer radius is 43.5 mm, and a trapezoidal hole is opened in the center of the radial line of the inner and outer rings, with the upper part (small hole) having a radius of 2.5 mm and the lower part (large hole) having a radius of 3.5 mm. During the test, it can move linearly with the rigid straight rod. Example 2

[0045] This embodiment provides a test method for the cyclic single shear instrument with uniform strain in Example 1, combined with Figure 8 and Figure 9 As shown, the test method includes the following steps: (1) Confirm that the test device is placed in a stable, well-ventilated environment with no flammable materials around it; pay special attention to the power switch being away from water sources.

[0046] (2) Check whether there is any residual soil sample in the cyclic single shear instrument to ensure that the interior is clean.

[0047] (3) Check whether there are twisted wires or rubber shedding between the conductors of the cyclic single shear instrument.

[0048] (4) After the cyclic single shearing instrument is prepared, preheat the cyclic single shearing instrument for 10 to 15 minutes.

[0049] (5) According to the experimental requirements, the ambient temperature of the cyclic single shear instrument should be close to the room temperature, with 20±5℃ being the best, and should not be too high or too low; the humidity of the environment in which the cyclic single shear instrument is located should not be too high to avoid poor contact or short circuit of the wires.

[0050] (6) Clean the mobile base 1, apply an interface agent, such as industrial vaseline, to the bottom of the mobile base 1, and then select a rubber film of uniform length and thickness.

[0051] (7) Stacking a plurality of first stacking rings 201 and second stacking rings 202 in sequence on the ring seat 103 on the mobile base 1, the rigid rod 4 passes through the trapezoidal cross-section bore 7 and the circular bore 8; installing the stacking rings 2 to form the sample filling area, and setting the rubber membrane 6 in the sample filling area so that the rubber membrane 6 wraps and fits around the inner periphery of the first stacking rings 201 and the second stacking rings 202.

[0052] (8) The test soil sample 3 is loaded according to the test requirements, and the rubber membrane 6 is always kept in close contact with the stacking ring 2 during the loading process.

[0053] (9) Lower the top pressure device 5 so that the top of the test soil sample 3 fits into the top pressure device 5; move the movable base 1, and the stacking ring 2 moves linearly under the drive of the rigid rod 4.

[0054] (10) Set the target working conditions, input the test parameters of loading control (such as stiffness, confining pressure, waveform, loading amplitude frequency, etc.), and perform the loading and unloading process according to the test sequence.

[0055] (11) During the loading process, regularly observe the working status of the test to confirm whether the test is stable; (12) After reaching the preset test target, the top pressure device is raised, and the second stacking ring, the first stacking ring and the rubber membrane are removed.

[0056] (13) After disassembly, check the mobile base to ensure that no soil sample remains.

[0057] (14) Turn off the main power.

[0058] In this embodiment, the rigid rod 4 extends through the first stacking ring 201 and the second stacking ring 202, creating minimal friction between the stacking rings. Driven by the rigid rod 4, the stacking rings 2 are arranged linearly from top to bottom. As the mobile base moves left and right, the rigid rod 4 translates with it, driving the stacking rings 2 in linear motion. After the base moves, the low-friction stacking rings assume a linear distribution and adhere tightly to the rubber membrane.

[0059] This test method has good integrity of the entire unit test, especially when facing multiple tests and test conditions with large deformation, the strain is uniform from top to bottom, the test repeatability is high, and the test device can greatly improve the accuracy of measuring soil mechanical parameters.

[0060] Furthermore, one way to install the rubber membrane is as follows: One end of the rubber membrane 6 is sleeved and clamped on the mobile base 1. After the stacking ring 2 is installed, the rubber membrane 6 is spread out and flipped upward and outward so that the rubber membrane 6 is wrapped around the inner periphery of the first stacking ring 201 and the second stacking ring 202; a vacuum pump is used to extract the rubber membrane 6 so that the rubber membrane 6 is tightly fitted to the inner periphery of the first stacking ring 201 and the second stacking ring 202.

[0061] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A cyclic single shear instrument with uniform strain, characterized in that: It includes a movable base, on which are provided multiple layers of stacked rings, which enclose a sample filling area, and a top pressure device is provided above the sample filling area; the multiple layers of stacked rings include multiple layers of first stacked rings and multiple layers of second stacked rings, the first stacked rings are provided with trapezoidal cross-section drilled holes, and the second stacked rings are provided with circular drilled holes, the trapezoidal cross-section drilled holes and the circular drilled holes on the same side are stacked layer by layer and connected with a rigid rod, one end of the rigid rod is rotatably connected to the movable base, and the other end extends from above the multiple layers of stacked rings.

2. The cyclic single shear instrument with uniform strain according to claim 1, characterized in that: A rubber membrane is further provided on the inner periphery of the sample filling area. The rubber membrane is closely attached to the inner periphery of the stacking ring and extends to the interior of the movable base.

3. The cyclic single shear instrument with uniform strain according to claim 1, characterized in that: The movable base includes a movable slide, a boss is provided above the slide, a sample supporting base plate is provided on the boss, a ring seat is provided on the periphery of the boss, the stacking ring is provided above the ring seat, and the rigid rod is rotatably connected to the ring seat.

4. The cyclic single shear instrument with uniform strain according to claim 3, characterized in that: The ring seat is fixedly connected to the slide seat by a plurality of bolts. The upper surface of the ring seat is arranged flush with the upper surface of the sample support base plate. A clamping gap is provided between the inner periphery of the ring seat and the outer peripheries of the sample support base plate and the boss. A seal is also provided between the ring seat and the slide seat.

5. The cyclic single shear instrument with uniform strain according to claim 3, characterized in that: The boss is provided with a plurality of drainage grooves, and the slide is provided with a discharge channel; the sample support bottom plate is provided with a plurality of striped protrusions.

6. The cyclic single shear instrument with uniform strain according to claim 1, characterized in that: The rigid rods are a pair, and mounting grooves are respectively provided on both sides of the movable base. Connecting ear plates are respectively provided in the mounting grooves, and the ends of the rigid rods are rotatably connected to the connecting ear plates through hinge shafts.

7. The cyclic single shear instrument with uniform strain according to claim 1, characterized in that: The first stacked rings and the second stacked rings are both low-friction rigid rings. The second stacked rings are arranged above the first stacked rings. The second stacked rings are arranged in 1 to 3 layers.

8. The cyclic single shear instrument with uniform strain according to claim 1, characterized in that: The large hole of the trapezoidal cross-section drilled hole is arranged downward, the inner diameter of the circular drilled hole is larger than the inner diameter of the small hole of the trapezoidal cross-section drilled hole, and the inclination of the hole wall of the trapezoidal cross-section drilled hole is 60-70°.

9. A test method for a cyclic simple shear instrument with uniform strain according to any one of claims 1 to 8, characterized in that: The test method comprises the following steps: Preparing the cyclic single shearing instrument and preheating the cyclic single shearing instrument; Apply an interface agent to the bottom of the mobile base and prepare a rubber film; stacking a plurality of first stacking rings and a second stacking ring on the movable base in sequence, and passing the rigid rod through the trapezoidal cross-section borehole and the circular borehole; Install the stacking rings to form the sample filling area, and arrange the rubber film in the sample filling area so that the rubber film wraps and fits around the inner circumferences of the first stacking ring and the second stacking ring; The test soil sample is loaded according to the test requirements, and the rubber membrane is always kept in close contact with the stacking ring during the loading process; Lowering the top pressure device so that the top of the test soil sample fits into the top pressure device; The movable base is moved, and the stacking ring moves linearly driven by the rigid rod; At the same time, set the target working conditions, input the test parameters of the loading control, and carry out the loading and unloading process according to the test sequence; During the loading process, regularly observe the working status of the test to confirm whether the test is stable; After the preset test target is reached, the top pressure device is raised, and the second stacking ring, the first stacking ring and the rubber membrane are removed; After disassembly, the mobile base is inspected to ensure that no soil sample remains.

10. The testing method of the cyclic simple shear instrument with uniform strain according to claim 9, characterized in that: One way to install the rubber membrane is as follows: One end of the rubber film is sleeved and clamped on the movable base. After the stacking rings are installed, the rubber film is spread out and turned upward and outward so that the rubber film is wrapped around the inner circumference of the first stacking ring and the second stacking ring; a vacuum pump is used to extract the rubber film so that the rubber film is tightly fitted to the inner circumference of the first stacking ring and the second stacking ring.

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