Sample preparation mold and method for loess high fill interfacial effect research test
By using a combination mold of square ring cutter and layered compaction pad, the initial state of the loess high fill interface was simulated, which solved the problem of sample damage and improved the accuracy and repeatability of the test.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-20
- Publication Date
- 2026-03-27
AI Technical Summary
Existing technologies cannot effectively simulate the initial state of loess high fill interfaces, and traditional sample preparation methods are prone to sample damage, affecting the accuracy of the test.
A combined mold consisting of a square ring cutter, protective components, multiple layered compaction pads, and a sample cap was used to prepare a combined sample of compacted loess and undisturbed loess by inverting and compacting in layers, ensuring initial bond strength and sample integrity.
It significantly reduces the gap between the simulated interface and the actual interface, improves the accuracy and repeatability of the experiment, and reduces the dispersion and systematic error of the test results.
Smart Images
Figure CN121740564A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of geotechnical engineering technology, and in particular to a sample preparation mold and method for studying the interface effect of loess high fill. Background Technology
[0002] In the Loess Plateau region, soil from loess ridges and hilltops with higher elevations is excavated and filled into valleys with lower elevations to achieve on-site equilibrium of soil potential energy. However, such high-fill loess structures disrupt the original geological balance of the region, resulting in significant deformation and stability issues in the newly created sites. The large scale of these filling projects, with substantial volumes and heights, leads to a large thickness of deformable media, and the pressure on the filling units can reach megapascal levels. Compacted loess is a fine-grained fill material with a high degree of underconsolidation, making it prone to significant creep deformation under long-term stress. Under high pressure, the underlying undisturbed loess also exhibits creep.
[0003] The interface of loess high fills has unique characteristics: First, the interface shape follows the undulations of the original surface and is inclined, with drastic variations in the thickness of the fill medium within the slope area. Second, the two sides of the interface are undisturbed loess and compacted loess, respectively. Although both belong to the loess category, the compacted loess, after being remolded and compacted, has a fundamentally different microstructure and solid-liquid-gas three-phase interaction compared to undisturbed loess. It is a homogeneous heterogeneous material with significantly different strength and deformation properties. Under the pressure of the fill's own weight, the fill body and the underlying undisturbed loess layer need to achieve coordinated deformation through interface interaction. Third, the interface is an artificially created interruption of the stratigraphic continuity for the entire geological body, representing a weak surface. When the differential deformation of the soil on both sides exceeds the coordination limit of the interface strength, it is prone to triggering landslides. Unlike landslides in general geological bodies, loess high fills are constrained by the mountain on both sides, and landslides are not triggered rapidly but occur slowly with the creep settlement of the fill, essentially a low-speed shear rheology (creep). Therefore, the interface interaction of loess high fills is extremely complex and is one of the key factors affecting the overall stability of the fill body.
[0004] Currently, research on the interface effect of two-phase soil and rock materials mainly focuses on two scenarios: first, the contact problem between sand (clay) and concrete, steel, and wood structures in underground engineering; and second, geological hazards such as landslides caused by the contact between soil and bedrock. These studies involve interfaces between two-phase materials with significantly different stiffnesses, and the experimental methods used mainly include direct shear tests, single shear tests, and circumferential shear tests. However, the stiffness of the materials on both sides of the interface in loess high fills is similar, belonging to the contact problem of two-phase soft soil and rock materials, and related research is relatively scarce. Existing sporadic studies mostly borrow research methods from the contact problems of two-phase materials with significantly different stiffnesses, mainly using direct shear tests (including conventional direct shear and large-scale direct shear). Considering that small-scale direct shear tests are significantly affected by size effects, large-scale direct shear tests are more suitable for this type of research.
[0005] The traditional large-scale direct shear test sample preparation and installation process involves first cutting a half-height undisturbed loess sample and placing it in the lower shear box, then pressing a half-height compacted loess sample and placing it in the upper shear box. The two shear boxes are then combined and placed on a direct shear apparatus, where vertical pressure is applied for shearing. This method essentially simulates the direct contact friction between two phases of materials, which deviates significantly from the actual formation process of the interface in high loess embankments. The actual interface is formed by the compaction of loose remolded soil onto the undisturbed soil bed, resulting in a tight bond. Compacted soil particles are embedded and adsorbed onto the surface of the undisturbed soil at the interface, meaning the two sides of the interface are not completely separated and possess initial cohesion. This state is between that of continuous and discontinuous materials, which does not match the contact friction state without initial cohesion in the traditional method. Furthermore, the traditional method of placing the sample upright by hand is prone to localized damage when placing it into the shear box without bottom support due to the large size and weight of the soil sample, affecting the accuracy of the test.
[0006] In summary, there is an urgent need to design a technical solution that can simulate the initial state of the actual filling interface and avoid sample damage during the sample loading process. Summary of the Invention
[0007] The purpose of this invention is to provide a sample preparation mold and method for studying the interface effect of loess high fill, so as to solve the problems existing in the prior art, simulate the initial state of the actual fill interface, and avoid sample damage during the sample loading process.
[0008] To achieve the above objectives, the present invention provides the following solution: This invention provides a sample preparation mold for studying the interface effect of loess high fill, comprising: A square ring cutter with a square cross-section and a cutting edge on the outer side wall at one end is used to cut undisturbed loess samples. A protective component with an opening at one end, wherein the square ring cutter can be inserted into the protective component through the opening end of the protective component, and the outer side wall of the square ring cutter abuts against the inner side wall of the protective component; Multiple layered compaction pads can be stacked sequentially on top of the opening end of the protective component; and The top of the sampling cap can pass through the layered compaction pad and abut against the compacted loess sample inside the square ring cutter. The top of the sampling cap has an outer edge that can overlap with the top of the uppermost layered compaction pad.
[0009] In one embodiment, the protective assembly includes a sample pressing base and a side wall sleeve; the sample pressing base is closed at one end and open at the other end, the side wall sleeve is open at both ends, and the side wall sleeve is fixedly abutted against the open end of the sample pressing base.
[0010] In one embodiment, the sum of the depth dimension of the sample pressing base and the height dimension of the side wall casing is the same as the height dimension of the square ring cutter.
[0011] In one embodiment, the depth dimension of the sample pressing base is less than half the height dimension of the square ring cutter.
[0012] In one embodiment, the sample ejection mold is further included. One end of the sample ejection mold can extend into the square ring cutter, and the other end has a flange on its side wall, which can abut against one end of the square ring cutter.
[0013] In one embodiment, the outer side of the sidewall sleeve away from the sample pressing base is provided with a groove; the outer edge of the sample pressing cap is provided with a protrusion that can abut against the groove.
[0014] In one embodiment, the layered compaction pad has a square ring structure, with the slot on the outer side of its top and the protrusion on the outer side of its bottom. The protrusion of the layered pad can abut against the slot of the adjacent layered pad or the slot of the sidewall sleeve. The protrusion on the outer edge of the sample top cap can abut against the slot of the sidewall sleeve or the slot of the uppermost layered compaction pad.
[0015] In one embodiment, there are a total of 5 layered compaction pads, each with a height of 2cm.
[0016] This invention also provides a sample preparation method for studying the interface effect of loess high fill, comprising the following steps: A complete undisturbed loess sample is cut using a square ring cutter. The square ring cutter containing the complete undisturbed loess sample is rotated 180° and inverted, and placed on a similarly inverted sample ejection mold. Force is applied evenly downwards on the side wall of the square ring cutter to eject the complete undisturbed loess sample out of the square ring cutter by half its height. The ejected part is then cut off with a soil cutting knife to obtain a undisturbed loess sample that is half the height inside the square ring cutter. The sample is then flipped and placed back on its original position simultaneously with the square ring cutter. Place the square ring cutter and half the height of the original loess sample in the sample pressing base, and install the side wall casing; Install a layered compaction pad using a slot, and fill the empty space above the undisturbed loess sample with the mass of premixed loose soil material with the target moisture content required for the target compaction degree and one-tenth of the height of the square ring cutter. Compact the sample with the top cap until the top cap can no longer descend, obtaining one-fifth of the height of the target compacted loess sample. Roughen its surface and repeat this step until the last layer is compacted to be flush with the top of the square ring cutter, forming a combined sample of compacted loess sample and undisturbed loess sample. Remove the square ring cutter along with the assembled sample.
[0017] In one embodiment, a sample loading step is further included, the sample loading step comprising: Invert the sample ejection mold on a horizontal surface, and simultaneously invert the combined sample with the square ring cutter, and place it on the top of the sample ejection mold. Keep the side wall of the sample ejection mold flush with the inner wall of the square ring cutter, and apply downward force around the square ring cutter to separate the square ring cutter from the combined sample. Assemble the upper and lower shear boxes of the straight shear machine and fix them together with fixing bolts; After the upper and lower shear boxes are inverted and connected, they slide synchronously from top to bottom to load the demolded composite sample into them, and then the shear boxes are flipped over.
[0018] The present invention achieves the following technical effects compared to the prior art: This invention overcomes the shortcomings of traditional sample preparation methods that fail to form effective initial bonding at the interface, significantly reducing the gap between the simulated interface and the actual interface. Using a sample preparation mold, a undisturbed loess sample is first prepared at the bottom. Then, compacted loose soil is combined with the undisturbed loess to form a composite sample of the compacted and undisturbed loess samples. Some loose soil particles penetrate the surface of the undisturbed loess, forming effective adsorption bonds. This results in an interface that not only has initial bond strength but also exhibits a higher internal friction angle during shearing compared to traditional sample preparation methods. This fundamentally reduces testing system errors.
[0019] The mold and sample preparation method of this invention make the sample preparation process more controllable, the prepared samples more accurate and uniform, reduce the dispersion of test results, and ensure repeatability. First, a square ring cutter cuts out a complete undisturbed loess sample and then pushes out half of it, making the preparation of the undisturbed soil portion precise and controllable. Second, the compacted soil portion is statically pressed by the mold, which is less affected by human factors compared to compaction sampling. The compacted loess is evenly distributed in the plane, and the layered roughening and compaction also ensures uniformity in the height direction, maximizing the consistency of parallel samples from different batches. The sample loading method of this invention overcomes the problem of soil fragments falling off under gravity due to the lack of support at the bottom when loading in the traditional forward direction, or the need to apply greater hand force to prevent sudden drop into the shear box and breakage, resulting in localized damage to the sample. The inverted demolding and loading method of this invention allows the sample to slowly enter the shear box from bottom to top with bottom support at all times. After being fully loaded, it forms a uniform and effective frictional force with the side wall of the shear box, avoiding localized detachment during subsequent movement.
[0020] The various processes in this invention are cleverly connected, ensuring both the accuracy of sample preparation and simplifying operation for easy application. First, the method involves multiple flipping and inversion of the sample and mold, ensuring that the undisturbed soil is at the bottom and the compacted soil is on top in the final combined sample, while the loading positions of the two parts correspond to the upper and lower shear boxes. Second, the combination of various simple molds can realize sample preparation and loading, which has the significance of promotion and transformation. Attached Figure Description
[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0022] Figure 1 This is a schematic diagram of the sample preparation mold structure for the study of the interface effect of loess high fill in one or more embodiments of the present invention. Figure 2 This is a front view of the square ring cutter of the present invention; Figure 3 for Figure 2 Top view; Figure 4 This is a front view of the sample pressing base of the present invention; Figure 5 for Figure 4 Top view; Figure 6 This is a front view of the sidewall casing of the present invention; Figure 7 for Figure 6 Top view; Figure 8 This is a front view of the layered compaction pad of the present invention; Figure 9 for Figure 8 Top view; Figure 10 This is a front view of the top cap of the sample pressing device of the present invention; Figure 11 for Figure 10 Top view; Figure 12 This is a front view of the ejection mold for the first sample of the present invention; Figure 13 for Figure 12 Top view; Figure 14 This is a front view of the ejection mold for the second sample of the present invention; Figure 15 for Figure 14 Top view; Figure 16 This is a schematic diagram of the sample preparation method for the experimental study of the interface effect of loess high fill in this invention.
[0023] In the figure: 1-Sampling cap; 2-Side wall casing; 3-Square ring cutter; 4-Sampling base; 5-Layered compaction pad; 6-Compacted loess sample; 7-Simulated interface between compacted loess and undisturbed loess; 8-Undisturbed loess sample; 9-First sample ejection mold; 10-Second sample ejection mold; 11-Lower shear box; 12-Upper shear box; 13-Loose soil; 14-Fixing bolt. Detailed Implementation
[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0025] The purpose of this invention is to provide a sample preparation mold and method for studying the interface effect of loess high fill, so as to solve the problems existing in the prior art, simulate the initial state of the actual fill interface, and avoid sample damage during the sample loading process.
[0026] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.
[0027] Traditional large-scale direct shear tests use existing equipment. This invention employs the ShearTracIII direct shear apparatus. The sample preparation and installation process involves first cutting a half-height undisturbed loess sample and placing it in the lower shear box, then pressing a half-height compacted loess sample and placing it in the upper shear box. The two shear boxes are then combined and placed on the direct shear apparatus, and vertical pressure is applied for shearing. This method essentially simulates the direct contact friction between two phases of materials, which deviates significantly from the actual formation process of the interface in high loess embankments. The actual interface is formed by the compaction of loose remolded soil onto the undisturbed soil bed, resulting in a tight bond. Compacted soil particles are embedded and adsorbed onto the surface of the undisturbed soil at the interface, meaning the two sides of the interface are not completely separated and possess initial cohesion. This state is between that of continuous and discontinuous materials, which differs from the contact friction state without initial cohesion in traditional methods. To address this issue, this invention provides a sample preparation mold for studying the interface effect in high loess embankments, referencing... Figures 1-15As shown, the device includes a square ring cutter 3, a sample ejection mold, a protective component sample pressing cap 1, and multiple layered compaction pads 5. The square ring cutter 3 has a U-shaped cross-section, and its outer side wall at one end is provided with a cutting edge to cut the undisturbed loess sample 8. The protective component is open at one end, allowing the square ring cutter 3 to be inserted into the protective component through the open end, and the outer side wall of the square ring cutter 3 abuts against the inner side wall of the protective component. In one embodiment, the protective component includes a sample pressing base 4 and a side wall protective sleeve 2. The sample pressing base 4 is closed at one end and open at the other end, and the side wall... The protective sleeve 2 is open at both ends, and the side wall of the protective sleeve 2 is fixedly abutted against the open end of the sample pressing base 4; multiple layered compaction pads 5 can be stacked sequentially on the top of the open end of the protective component; the bottom of the sample pressing cap 1 can pass through the layered compaction pads 5 and abut against the compacted loess sample 6 inside the square ring cutter 3; the top of the sample pressing cap 1 is provided with an outer edge, which can overlap with the top of the uppermost layered compaction pad 5; one end of the sample ejection mold can extend into the square ring cutter 3, and the other end of the side wall is provided with a flange, which can abut against one end of the square ring cutter 3.
[0028] The square ring cutter 3 of this invention is customized to fit a direct shear apparatus. One side is flat and the other side has a cutting edge. It can cut samples according to the undisturbed soil sample preparation method in the "Standard for Geotechnical Testing" (GB / T 50123-2019). The sample pressing base 4 is adapted to the size of the square ring cutter 3 and is a support component at the bottom of the sample. The side protrusion height is lower than half the height line of the square ring cutter 3, which can restrict the lateral movement of the square ring cutter 3. The side wall sleeve 2 is adapted to the size of the square ring cutter 3 and provides four-sided restriction for the square ring cutter 3. Together with the sample pressing base 4, it can just accommodate the square ring cutter 3. The top outer side is reserved with a groove, which can be mechanically connected to the layered compaction pad 5 and the sample pressing top cap 1 to restrict lateral movement. The layered compaction pad 5 is a square ring structure. There are 5 of them, each with a height of 2cm, which can compact the 10cm high loess sample 6 in five layers. The transverse wall thickness of the layered compaction pad 5 is the sum of the wall thicknesses of the side wall casing 2 and the square ring cutter 3, ensuring that the inner wall is flush with the inner wall of the square ring cutter 3 and the outer wall is flush with the outer wall of the side wall casing 2. There are protrusions and grooves near the upper and lower surfaces of the outer wall, which fit with the other layered compaction pad 5 below it (or the side wall casing 2) and the other layered compaction pad 5 above it (or the sampling cap 1). The sampling cap 1 can compact the loose soil material 13 to the preset thickness with the help of the reaction force of the jack, and its size is compatible with the sampling pad. In this embodiment, there are two sample ejection molds: a first sample ejection mold 9 and a second sample ejection mold 10. The first sample ejection mold 9 is adapted to the size of the square ring cutter 3, and its usable height is half the height of the square ring cutter 3. It can eject half of a complete undisturbed loess sample 8 from the square ring cutter 3, leaving half of the space for compacting loess samples on the other side of the interface. The second sample ejection mold 10 is adapted to the size of the square ring cutter 3, and its usable height is the height of the square ring cutter 3. It is used to demold the combined sample and load it into the shearing box of a large direct shear apparatus.
[0029] This invention also provides a sample preparation method for studying the interface effect of loess high fill, referring to... Figure 16 As shown, it includes the following steps: Use a square ring cutter 3 to cut a complete undisturbed loess sample 8; rotate the square ring cutter 3 containing the complete undisturbed loess sample 8 180° and invert it, place it on the inverted sample ejection mold and align it, apply force evenly downward on the side wall of the square ring cutter 3 to eject the complete undisturbed loess sample 8 out of the square ring cutter 3 by half the height, use a soil cutting knife to cut off the ejected part, thus obtaining the undisturbed loess sample 8 at half the height inside the square ring cutter 3, and then flip it and place it upright synchronously with the square ring cutter 3. Place the square ring cutter 3 and the loess sample 8 at half its height in the sample pressing base 4, and install the side wall protective sleeve 2; A layered compaction pad 5 is installed using a slot, and pre-mixed loose soil material 13 with the target moisture content is placed in the empty space above the undisturbed loess sample 8. The required mass of the pre-mixed loose soil material 13 with the target compaction degree and one-tenth the height of the square ring cutter 3 is filled in. The compaction is carried out using the top cap 1 until the top cap 1 can no longer descend, thus obtaining one-fifth the height of the target compacted loess sample 6. The surface of the sample is roughened, and this step is repeated until the last layer is compacted to be flush with the top of the square ring cutter 3, forming a combined sample of compacted loess sample 6 and undisturbed loess sample 8. The particles of compacted loess sample 6 will be embedded and adsorbed on the surface of undisturbed loess sample 8 at the interface 7 between compacted loess and undisturbed loess. This means that the two sides of the interface 7 between compacted loess and undisturbed loess are not completely separated, and have initial cohesion. Its state is between continuous and discontinuous materials. Remove the square ring cutter 3 along with the combined sample, and then load the sample.
[0030] The sample loading steps include: inverting the sample ejection mold on a horizontal surface, inverting the combined sample with the square ring cutter 3, and placing it on top of the sample ejection mold, keeping the side wall of the sample ejection mold flush with the inner wall of the square ring cutter 3, and applying downward force around the square ring cutter 3 to separate the square ring cutter 3 from the combined sample. Assemble the upper shear box 12 and lower shear box 11 of the straight shearing machine, and fix the upper shear box 12 and lower shear box 11 together with fixing bolts 14; After the upper shear box 12 and lower shear box 11 are connected in reverse, they slide synchronously from top to bottom to load the demolded combined sample into them, and then the shear box is flipped.
[0031] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.
Claims
1. A sample preparation mold for loess high fill interface effect research test, characterized in that: The utility model relates to a kind of original state loess sample preparation device, including: Square ring cutter, its cross section is mouth-shaped, and the outside wall of one end is provided with cutting edge, to cut original loess sample; Protective assembly, one end is open, the square ring cutter can be inserted into the protective assembly through the open end of the protective assembly, and the outer side wall of the square ring cutter is in abutment with the inner side wall of the protective assembly; Multiple layered compaction pads, which can be stacked in the protective assembly sequentially; Sample pressing top cap, the bottom of the sample pressing top cap can pass through the layered compaction pad and abut with the compacted loess sample in the square ring cutter, and the top of the sample pressing top cap is provided with an outer edge, which can be overlapped with the top of the uppermost layered compaction pad.
2. The sample preparation mold for studying the interface effect of high loess fill according to claim 1, characterized in that: The protective assembly includes a sample pressing base and a side wall protection cylinder; one end of the sample pressing base is closed, and the other end is open; the side wall protection cylinder is open at both ends, and is fixedly abutted with the open end of the sample pressing base.
3. The sample preparation mold for studying the interface effect of high loess fill according to claim 2, characterized in that: The depth of the sample pressing base and the height of the side wall protection cylinder are equal to the height of the square ring cutter.
4. The sample preparation mold for studying the interface effect of high loess fill according to claim 3, characterized in that: The depth of the sample pressing base is less than half of the height of the square ring cutter.
5. The sample preparation mold for studying the interface effect of high loess fill according to claim 1, characterized in that: The utility model further includes a sample ejection mold, one end of which can extend into the square ring cutter, and the other end is provided with a flange, which can abut with one end of the square ring cutter.
6. The sample preparation mold for studying the interface effect of high loess fill according to claim 2, characterized in that: The outer side of the side wall protection cylinder away from the sample pressing base is provided with a clamping groove; the end of the outer edge of the sample pressing top cap is provided with a protrusion, which can be abutted in the clamping groove.
7. The sample preparation mold for studying the interface effect of high loess fill according to claim 6, characterized in that: The layered compaction pad is a square ring structure, and the top outer side is provided with the clamping groove, and the bottom outer side is provided with the protrusion; the protrusion of the layered pad can be abutted in the clamping groove of the adjacent layered pad or the clamping groove of the side wall protection cylinder; the protrusion on the outer edge of the sample pressing top cap can be abutted in the clamping groove of the side wall protection cylinder or the clamping groove of the uppermost layered compaction pad.
8. The sample preparation mold for studying the interface effect of high loess fill according to claim 7, characterized in that: There are five layered compaction pads, each with a height of 2 cm.
9. A method for preparing a sample for a loess high fill interface effect research test, characterized in that: The utility model includes the following steps: Use the square ring cutter to cut the complete original loess sample; invert the square ring cutter with the complete original loess sample by 180°, place it on the inverted sample ejection mold, align, apply force evenly to the side wall of the square ring cutter, eject the complete original loess sample from the square ring cutter by half the height, cut off the ejected part with the cutter, realize the preparation of the original loess sample in the square ring cutter by half the height, and flip it over synchronously with the square ring cutter; Place the square ring cutter and the original loess sample by half the height in the sample pressing base, and install the side wall protection cylinder; Install a layered compaction pad with the help of the clamping groove, and fill the corresponding target compaction degree, the required mass of the pre-mixed target moisture content loose soil in the space above the original loess sample, compact it with the sample pressing top cap until the sample pressing top cap cannot go down, obtain one-fifth of the height of the target compacted loess sample, shave the surface, and repeat the step until the last layer is compacted to the top of the square ring cutter, forming a combined sample of the compacted loess sample and the original loess sample; Take out the square ring cutter together with the combined sample.
10. The method according to claim 9, wherein the method is characterized in that: The utility model further includes a sample loading step, which includes: The sample ejection mold is inverted on a horizontal plane, the combined sample with the square ring cutter is inverted, and the combined sample is placed on the top of the sample ejection mold, the side wall of the sample ejection mold is kept flush with the inner wall of the square ring cutter, force is applied downward around the square ring cutter to separate the square ring cutter from the combined sample; The upper shear box and the lower shear box of the straight shear instrument are assembled, and the upper shear box and the lower shear box are fixedly connected through fixing bolts; The connected upper shear box and lower shear box are inverted, and the upper shear box and the lower shear box are synchronously slid from top to bottom, the demolded combined sample is loaded into the upper shear box and the lower shear box, and the shear box is turned over.