A test device for measuring shear viscosity of sand under confined stress state

Abstract

The invention discloses a test device for measuring shear viscosity of sand under confined stress state, including a soil sample confined torsion deformation sample tube, a vertical pressure / displacement application system, and a torsion deformation / torque application system. The soil sample confined torsion deformation sample tube is an inner and outer three-layer structure, including an outer rigid tube, a middle annular friction control stacked ring bearing, an inner vertical friction control stacked ring sleeve, and inner stacked ring inter-ring balls, and the inner vertical friction control stacked ring and the inner ring of the middle stacked ring bearing are processed as a whole; the vertical pressure / displacement application system includes a frame with a guide rail, a loading hydraulic cylinder, a loading arm, a mobile loading beam clamped on both sides on the guide rail, a vertical force sensor, a vertical displacement sensor, a sample upper pressure plate, and a sample lower support plate, and the contact surface between the sample upper pressure plate and the lower support plate and the soil sample is engraved with radial protrusions; the torsion deformation / torque application system includes a servo motor, a reducer, a rotating shaft, a torque sensor, and a coupler connected to the lower support plate.

Description

Technical Field

[0001] The invention relates to a test device for measuring the shear viscosity of sand under a lateral limit stress state, which is used for testing foundation soil and filling soil materials. Background Art

[0002] With the construction of a modern infrastructure system, the number of backfill projects using sand as a building material is increasing day by day, and roads, bridges, earth-rock dams, offshore oil and gas projects built on sand foundations are widely appearing. The mechanical properties of foundation sand directly affect the safety and stability of the superstructure, and the rheological properties of foundation sand significantly affect the later safety of the building structure, especially for deep sand foundations. Even if the sand undergoes small stress-strain changes, the cumulative effect may still cause a large deformation of the foundation surface, increasing the risk of engineering failure. On the contrary, good plastic flow characteristics are more desired in the excavation of sand. However, no matter what the application scenario, it is extremely important to accurately grasp the rheological properties of sand.

[0003] Sand is a typical material with density and stress state correlation, that is, the shear viscosity (the ratio of shear stress to shear strain rate) changes with the change of dry density and the change of stress state. In order to ensure the long-term safety of sand foundation projects, it is necessary to accurately measure the shear viscosity of sand under various density and stress states.

[0004] Rotational shear rheometer is an important tool for testing shear viscosity. It can be divided into double-plate type, cross-plate blade type, concentric cone cylinder type, and cone-plate type according to the rotating parts. However, existing rotational rheometers are only suitable for thin-layer fluids or pastes. When measuring the shear viscosity of sand, there are the following problems: (1) It can only achieve shear but cannot control pressure and density; (2) It cannot distinguish between equipment friction and material friction; (3) The shear state is poorly controlled; (4) The viscosity measurement range is small and the value is low; (5) The sample is small and cannot meet the size requirements.

[0005] Taking the double-plate rotational shear rheometer as an example, the sample is placed between two parallel plates of the same size. By rotating one parallel plate, the sample between the plates is driven to rotate, forming a rotational shear gradient between the rotating plate and the fixed plate. If the sample is subjected to vertical pressure, a large amount of the sample will be extruded from the side, changing the sample density. Therefore, if the shear viscosity under pressure is measured, lateral constraints need to be imposed on the sample between the two plates. However, while the lateral constraints can avoid extrusion, the friction between the lateral constraints and the contact surface of the sample causes a resisting torque, which will cause serious tangential interference to the rotation of the sample. The larger the distance between the two plates, the more serious the lateral constraints will interfere with the tangential rotation, which is the fundamental reason why the sample size of the existing double-plate rotational shear rheometer is too small. The maximum particle size of gravel-containing sand involved in actual filling projects and foundation projects is up to 20 mm. In order to meet the principle of diameter-to-diameter ratio greater than 5 required by the size effect, the parallel plate diameter and the distance between the plates must be no less than 100 mm.

[0006] In summary, in order to measure the shear viscosity of sand under confined stress state, it is necessary to overcome the tangential interference of the confinement constraint on the rotation on the basis of the double-plate rotational shear rheometer. In other words, a large-scale shear viscosity measuring device is urgently needed to avoid the tangential interference of the confinement constraint on the rotation. Summary of the invention

[0007] The purpose of the present invention is to provide a test device for measuring the shear viscosity of sand under the lateral confinement stress state. On the basis of a double-plate rotational shear rheometer, a bearing stacked ring side wall and ring sleeve structure are adopted to avoid lateral extrusion of the sample while also avoiding the tangential interference of the lateral confinement constraint on the rotation, thereby realizing the measurement of the shear viscosity of sand under the lateral confinement stress state.

[0008] In order to achieve the above object, the scheme of the present invention is:

[0009] A test device for measuring shear viscosity of sand under a lateral confined stress state comprises a vertical pressure / displacement applying system, a torsional deformation / torque applying system, and a soil sample lateral confined torsional deformation sample tube arranged on a frame, wherein the vertical pressure / displacement applying system applies a vertical pressure of a controllable stress or strain state to the soil sample in the sample tube, and measures the vertical strain while controlling the vertical stress, or measures the vertical stress while controlling the vertical strain; the torsional deformation / torque applying system applies a controllable rotation angle and rotation speed to the bottom of the soil sample in the sample tube, and measures the torque while applying the controllable rotation angle and rotation speed, or measures the rotation angle while applying the controllable torque and torque speed change; the soil sample lateral confined torsional deformation sample tube provides a torsional deformation test condition for constraining the overall lateral deformation of the soil sample and controlling the vertical stress or strain, and constrains the overall rotation of the soil sample in the same plane around the central axis under the joint action of the vertical pressure / displacement applying system and the torsional deformation / torque applying system.

[0010] The scheme is further as follows: the soil sample lateral torsion deformation sample tube is placed on the rack platform, the soil sample lateral torsion deformation sample tube includes an outer rigid tube and an inner multi-layer bearing stacked vertically, the outer ring of the bearing is connected and fixed to the outer rigid tube, the inner ring of the bearing rotates under force and constrains the soil sample, an upper pressure plate is arranged at the upper end of the soil sample, the upper pressure plate is used to apply vertical pressure to the soil sample by the vertical pressure / displacement application system, and a lower support plate is arranged at the lower end of the soil sample, the lower support plate is used to apply a controllable angle and rotation speed to the bottom of the soil sample by the torsion deformation / torque application system; the stacked multi-layer bearing inner ring provides the soil sample with torsion deformation test conditions that limit the overall lateral deformation and control the vertical stress or strain, and the central axis rotation power is provided at the bottom of the soil sample by the lower support plate, and the stacked multi-layer bearing inner ring realizes the constraint of the overall rotation of the soil sample in the same plane around the central axis.

[0011] The scheme is further as follows: the bearings of the multi-layer bearings are separated and stacked by spacer rings, the spacer rings are pads between the stacked outer rings of the bearings, a ring sleeve is connected to the inner side of the inner ring of each layer of the bearing, the ring sleeve is connected to the inner ring of the bearing as a whole and rotates with the inner ring of the bearing to form an inner ring assembly, the inner ring assemblies of adjacent bearings close the gaps formed by the spacer rings between the bearings, and the upper and lower adjacent inner ring assemblies are connected by ball relative rolling seals, and the ball relative rolling seal connection converts the rotational contact of the end faces between the inner rings of adjacent layers of bearings into rotational contact of the ball points between the inner ring assemblies of adjacent layers of bearings.

[0012] A further solution is that a barrier curtain is arranged at one end of the outer side of the bearing inner ring assembly, and the barrier curtain covers the gap between the inner ring assemblies.

[0013] The solution is further as follows: the vertical pressure / displacement application system includes a loading movable beam arranged on the frame, and the loading movable beam is pushed by a loading arm to move vertically up and down along a guide rail to apply pressure to an upper pressure plate arranged at the upper end of the soil sample, and a vertical loading force sensor is arranged between the loading arm and the loading movable beam to achieve vertical pressure in a controllable stress or strain state applied to the soil sample in the sample tube.

[0014] The solution is further as follows: the torsional deformation / torque application system includes a torsional reducer arranged under the platform, the upward shaft of the torsional reducer is connected to a driving shaft through a torque sensor, the driving shaft is positioned in a through hole arranged in the middle of the platform, the lower support plate is connected to the driving shaft, and the driving shaft drives the rotation to apply a controllable angle and speed to the bottom of the soil sample.

[0015] The solution is further that the driving shaft and the platform transmit power through the thrust bearing, so that the downward pressure of the loading moving beam acts on the thrust bearing through the upper pressure plate, the soil sample, the lower support plate, and the driving shaft.

[0016] A further solution is that the contact surfaces of the upper pressing plate and the lower supporting plate with the soil sample are respectively provided with raised radial ribs, and the radial ribs are embedded in the upper and lower end surfaces of the soil sample to prevent the upper pressing plate and the lower supporting plate from sliding relative to the soil sample.

[0017] The beneficial effects of the present invention are as follows: the stacked ring side wall is adopted to solve the tangential interference problem of rotation caused by the lateral limit constraint while avoiding lateral extrusion, and the shear viscosity of sand under lateral limit stress can be measured.

[0018] The invention is described in detail below with reference to the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the present invention;

[0020] Figure 2It is a schematic structural diagram of the side-limited torsion deformation sample cylinder assembly of the present invention;

[0021] Figure 3 This is a schematic diagram of the structure of the bearing inner ring assembly of the present invention. Figure 2 A magnified view of part A;

[0022] Figure 4 It is a schematic diagram of the structure of the contact surface between the sample upper pressing plate and the sample lower supporting plate and the soil sample of the present invention. DETAILED DESCRIPTION

[0023] A test device for measuring the shear viscosity of sand under lateral confining stress state, suitable for measuring the shear viscosity of foundation sand and fill sand, such as Figures 1 to 4 As shown, the test device includes a vertical pressure / displacement application system, a torsional deformation / torque application system, and a soil sample lateral torsional deformation sample tube 8 arranged on a frame 1; the vertical pressure / displacement application system applies a vertical pressure of a controllable stress or strain state to the soil sample in the sample tube, and measures the vertical strain while controlling the vertical stress, or measures the vertical stress while controlling the vertical strain, and the system also avoids circumferential deformation of the top of the soil sample; the torsional deformation / torque application system applies a controllable rotation angle and rotation speed to the bottom of the soil sample in the sample tube, and measures the torque while applying the controllable rotation angle and rotation speed, or measures the rotation angle while applying the controllable torque and torque speed change; the soil sample lateral torsional deformation sample tube, under the joint action of the vertical pressure / displacement application system and the torsional deformation / torque application system, provides a torsional deformation test condition for the soil sample to constrain the overall lateral deformation of the soil sample and control the vertical stress or strain, and constrains the overall rotation of the soil sample in the same plane around the central axis.

[0024] in:

[0025] The vertical pressure / displacement application system, such as Figure 1 As shown, the frame 1 includes a vertical guide rail 101 disposed inside the columns on both sides, a loading arm 2, such as a loading electric cylinder, disposed at the upper end of the frame, a loading moving beam 3 disposed between the columns on both sides, the two ends of the loading moving beam 3 are slidably connected to the vertical guide rails 101 disposed inside the columns on both sides, the upper end of the loading moving beam 3 is connected to the telescopic arm of the loading arm 2, the loading moving beam 3 is pushed by the loading arm 2 to move vertically up and down along the guide rail, and pressure is applied to the upper pressure plate disposed at the upper end of the soil sample, a vertical loading force sensor 4 is disposed between the loading arm 2 and the loading moving beam 3, and the loading electric cylinder is controlled by the above structure to thereby realize the vertical pressure of the controllable stress or strain state applied to the soil sample, and the vertical strain is measured while the vertical stress is controlled, or the vertical stress is measured while the vertical strain is controlled. The frame 1 is provided with a platform 102 under the loading moving beam 3.

[0026] The torsional deformation / torque application system includes a torsional reducer 5 arranged under the platform 102 , and the upward shaft 501 of the torsional reducer 5 is connected to a driving shaft 7 through a torque sensor 6 , and the driving shaft 7 is positioned in a through hole arranged in the middle of the positioning platform 102 .

[0027] The soil sample lateral torsion deformation sample tube 8 is placed on the rack platform 102. The soil sample lateral torsion deformation sample tube 8 includes an outer rigid tube 801 and an inner multi-layer bearing 9 vertically stacked. The outer ring of the bearing is connected and fixed to the outer rigid tube 801. The inner ring of the bearing rotates under force around the constrained soil sample 10. An upper pressure plate 11 is arranged at the upper end of the soil sample. The upper pressure plate 11 is pressed on the soil sample 10 for applying vertical pressure to the soil sample by the vertical pressure / displacement application system. There is a lower support plate 12, which supports the soil sample 10. The lower support plate 12 is connected to the driving shaft 7 through a toggle connector (coupler) 13 and is driven to rotate by the driving shaft 7. The lower support plate 12 is used to apply a controllable angle and rotation speed to the bottom of the soil sample by the torsional deformation / torque application system; during measurement, the upper pressure plate 11 is pressed and immobilized by the loading moving beam 3 through the retaining connector 14, and the lower support plate 12 grasps the bottom surface of the soil sample and is driven to rotate by the driving shaft 7 to drive the bottom of the soil sample to twist.

[0028] The above-mentioned soil sample lateral torsion deformation specimen tube 8 structure provides torsion deformation test conditions for limiting overall lateral deformation and controlling vertical stress or strain for the soil sample under the joint action of the vertical pressure / displacement application system and the torsion deformation / torque application system. The lower support plate 12 provides central axis rotation power at the bottom of the soil sample 10, and the stacked multi-layer bearing inner rings realize the constraint of the rotation of the soil sample as a whole around the central axis in the same plane.

[0029] The torsional deformation / torque application system can be used to apply a controllable angle and rotation speed to the bottom of the soil sample in the sample tube, measure the torque while applying the controllable angle and rotation speed, or measure the angle while applying the controllable torque and torque speed change (the angle can be measured by an angle sensor (not shown in the figure) provided on the driving shaft 7), and control the torsional reducer 5 through the signal of the torque sensor 6, so that the angle is maximum at the bottom of the soil sample and gradually decreases vertically until there is no torsion angle at the top of the soil sample.

[0030] Among them: the toggle connecting member 13 is fixedly connected to the lower supporting plate 12 by bolts, the lower end of the toggle connecting member 13 is provided with a prism, and the upper end surface of the driving shaft 7 is provided with a corresponding prism hole, and the toggle connecting member 13 is connected to the driving shaft 7 by inserting the prism into the prism hole, so that the driving shaft 7 can stably drive the lower supporting plate 12 to rotate, and at the same time, the driving shaft 7 is connected to the platform 102 through the thrust bearing 15, and the thrust bearing 15 transmits power, so that the downward pressure of the loading moving beam 3 is directly applied to the thrust bearing 15 by the driving shaft 7 through the upper pressure plate 11, the lower supporting plate 12, and the tested sample, so that the driving shaft 7 can rotate smoothly.

[0031] In order to prevent the upper pressing plate and the lower supporting plate from sliding relative to the soil sample to be tested, the contact surfaces of the upper pressing plate 11 and the lower supporting plate 12 with the soil sample to be tested are respectively provided with raised radial ribs or radial arc bars 11-1, 12-1, the radial ribs or radial arc bars are high in the middle and low on the outer edges, and the radial ribs or radial arc bars are used to embed into the upper and lower end surfaces of the soil sample to be tested.

[0032] The multi-layer bearing realizes layered rotation of the soil sample to form a rotation gradient. The number of bearing layers is set according to needs. In this embodiment, 17 layers are set.

[0033] During the test: the rotation of the soil sample 10 drives the inner ring of the bearing to rotate as the side limit ring. The side limit ring only limits the lateral extrusion of the soil sample. While ensuring that the soil sample is not extruded, it must not affect the free rotation of the soil sample (no additional friction resistance torque is provided for the free rotation of the soil sample). Since the overlapping of the bearings is the friction contact between the end faces, if the side limit rings are just stacked together, although the problem of side limit constraints to avoid lateral extrusion is solved and improved, and the detection accuracy has been greatly improved, the sliding friction between the rings will lead to inaccurate measurements, that is, the torque that makes the sample rotate is much smaller than the torque measured by the torque sensor. The surface friction is changed to rolling line or point friction, and the rotational torque will not be lost. It is equivalent to the rotation of the sample under the torque measured by the torque sensor.

[0034] For this reason, Figure 2 , 3As shown, the bearings 9 are separated and stacked by spacer rings 16, and the spacer rings 16 are padded between the bearing outer rings 901. A ring sleeve 17 is provided on the inner side of each layer of the bearing, close to the inner ring 902, and the ring sleeve 17 is connected to the bearing inner ring 902 as a whole and rotates with the bearing inner ring 902 to form an inner ring assembly 902-1. The adjacent inner ring assemblies 902-1 close the gap formed by the spacer rings between the bearings 9 and the bearings 9. The upper and lower adjacent inner ring assemblies 902-1 are connected by relative rolling seals with balls 18. The relative rolling seal connection of the balls converts the rotational contact of the end faces between the inner rings of adjacent layers of bearings 9 into rotational contact of the ball points between the inner ring assemblies 902-1 of adjacent layers of bearings 9.

[0035] In order to prevent soil samples from entering through the gap between the inner ring assembly 902-1 and the inner ring assembly 902-1 to increase friction, a barrier curtain 1705 is provided (pasted) at one end of the outer side of the bearing inner ring assembly 902-1, and the barrier curtain 1705 covers the gap between the inner ring assembly 902-1 and the inner ring assembly 902-1; for example, a rubber sheet is used as the barrier curtain.

[0036] Further description of the inner ring assembly 902-1 is as follows: Figure 2 and Figure 3 As shown, the cross section of the ring sleeve 17 is in a horizontally lying "T" shape, and the vertical "1" 1701 of the "T" shape divides the horizontal "1" of the "T" shape into unequal parts of the short side 1702 and the long side 1703 of the horizontal "1", and the vertical "1" 1701 of the ring sleeve is placed between the bearings 9 and the bearings 9 separated by the spacer ring 16, wherein: the vertical "1" 1701 of the ring sleeve "T" shape and the adjacent surface of the long side 1703 of the horizontal "1" of the stacked lower bearing 9 are tightly fixed (bolted or welded) to the inner ring 902 of the lower bearing 9 to form an inner ring assembly 902-1 (the figure is connected as a whole with a section line, Figure 3 The figure further illustrates the structure of the inner ring assembly 902-1 in which the ring sleeve 17 and the inner ring 902 are integrated. It can even be said that the bearing has been improved. The inner ring assembly 902-1 formed by the ring sleeve 17 and the inner ring 902 can be processed separately). A gap is left between the adjacent surfaces of the vertical "1" 1701 and the short side 1702 of the horizontal "1" of the "T"-shaped cross-section of the ring sleeve and the opposite surfaces surrounded by the inner ring 902 of the stacked upper bearing 9, and a gap 1704 of no more than 0.2 mm is left between the opposite end faces of the ring sleeves of adjacent bearings (between the opposite end faces of the short side 1702 and the long side 1703 of the horizontal "1" of adjacent ring sleeves). Relative arc grooves are respectively arranged on the end faces of the opposite ends of the adjacent ring sleeves, and balls 18 are placed in the grooves. The adjacent ring sleeves rotate relative to each other through the balls 18, thereby converting the rotational contact of the end faces between the inner rings of adjacent layers of bearings into rotational contact of the ball points between adjacent layers of bearings.

[0037] Through the above measures, the rotational friction of the instrument itself is greatly reduced, and the combined structure 902-1 composed of the inner layer vertical friction control stack ring and the inner ring of the middle layer annular friction control bearing is realized, and the synchronous layered rotation with the internal soil is achieved.

[0038] Although the width of the gap 1704 between the inner ring sleeves 17 and the inner ring sleeves 17 is less than 0.2 mm, (that is: the width of the gap between the inner ring assembly 902-1 and the inner ring assembly 902-1 is less than 0.2 mm), in order to prevent small soil particles from entering through the gap and affecting the free rotation of the ball 18 and increasing the friction, a curtain 1705 is set (glued) at the outer end of the inner stacked ring sleeves 17 close to the soil body, that is, it is set (glued) at the outer end of the long side 1703 of the "T"-shaped horizontal "one" of each ring sleeve, and the curtain 1705 covers the gap between the ring sleeves, for example, a rubber sheet is used as the curtain.

[0039] The above-mentioned test device embodiment for measuring the shear viscosity of sand under the lateral confinement stress state adopts a bearing stacked ring side wall and ring sleeve structure, which solves the problem of lateral confinement constraint avoiding lateral extrusion and tangential interference of lateral confinement constraint on rotation, thereby realizing the measurement of shear viscosity of sand under the lateral confinement stress state.

Claims

1. A test device for measuring shear viscosity of sand under a lateral limit stress state, comprising a vertical pressure / displacement application system, a torsional deformation / torque application system, and a soil sample lateral limit torsional deformation sample tube arranged on a frame, wherein the vertical pressure / displacement application system applies a vertical pressure in a controllable stress or strain state to the soil sample in the sample tube, and measures the vertical strain while controlling the vertical stress, or measures the vertical stress while controlling the vertical strain; the torsional deformation / torque application system applies a controllable rotation angle and rotation speed to the bottom of the soil sample in the sample tube, and measures the torque while applying the controllable rotation angle and rotation speed, or measures the rotation angle while applying the controllable torque and torque speed change; characterized in that: The soil sample lateral torsion deformation sample tube provides a torsion deformation test condition for constraining the overall lateral deformation of the soil sample and controlling the vertical stress or strain under the joint action of the vertical pressure / displacement application system and the torsion deformation / torque application system, and constrains the overall rotation of the soil sample in the same plane around the central axis; the soil sample lateral torsion deformation sample tube is placed on the rack platform, and the soil sample lateral torsion deformation sample tube includes an outer rigid tube and an inner multi-layer bearing vertically stacked, the outer ring of the bearing is connected and fixed to the outer rigid tube, and the inner ring of the bearing rotates around about The soil sample is restrained, an upper pressure plate is arranged at the upper end of the soil sample, and the upper pressure plate is used for applying vertical pressure to the soil sample by the vertical pressure / displacement applying system, and a lower supporting plate is arranged at the lower end of the soil sample, and the lower supporting plate is used for applying a controllable rotation angle and rotation speed to the bottom of the soil sample by the torsional deformation / torque applying system; the stacked multi-layer bearing inner ring provides the soil sample with torsional deformation test conditions for limiting the overall lateral deformation and controlling the vertical stress or strain, and the central axis rotation power is provided at the bottom of the soil sample by the lower supporting plate, and the stacked multi-layer bearing inner ring realizes the constraint of the soil sample in the same plane to rotate around the central axis as a whole.

2. The test device according to claim 1, characterized in that: The bearings of the multi-layer bearings are separated and stacked by spacer rings, and the spacer rings are placed between the outer rings of the stacked bearings. A ring sleeve is connected to the inner side of the inner ring of each layer of the bearings. The ring sleeve is connected to the inner ring of the bearing as a whole and rotates with the inner ring of the bearing to form an inner ring assembly. The inner ring assemblies of adjacent bearings close the gaps formed by the spacer rings between the bearings. The upper and lower adjacent inner ring assemblies are connected by ball relative rolling seals. The ball relative rolling seal connection converts the rotational contact of the end faces between the inner rings of adjacent layers of bearings into rotational contact of the ball points between the inner ring assemblies of adjacent layers of bearings.

3. The test device according to claim 2, characterized in that: A barrier curtain is arranged at one end of the outer side of the bearing inner ring assembly, and the barrier curtain covers the gap between the inner ring assemblies.

4. The test device according to claim 1, characterized in that: The vertical pressure / displacement applying system includes a loading movable beam arranged on a frame. The loading movable beam is pushed by a loading arm to move vertically up and down along a guide rail, and applies pressure to an upper pressure plate arranged at the upper end of the soil sample. A vertical loading force sensor is arranged between the loading arm and the loading movable beam, so as to realize vertical pressure in a controllable stress or strain state being applied to the soil sample in the sample tube.

5. The test device according to claim 1, characterized in that: The torsional deformation / torque application system includes a torsional reducer arranged under the platform. The upward shaft of the torsional reducer is connected to a driving shaft through a torque sensor. The driving shaft is positioned in a through hole arranged in the middle of the platform. The lower support plate is connected to the driving shaft, and the driving shaft drives the rotation to apply a controllable angle and speed to the bottom of the soil sample.

6. The test device according to claim 5, characterized in that: The driving shaft and the platform transmit power through the thrust bearing, so that the downward pressure of the loading moving beam acts on the thrust bearing through the upper pressing plate, the soil sample, the lower supporting plate and the driving shaft.

7. The test device according to claim 1, characterized in that: The contact surfaces of the upper pressing plate and the lower supporting plate with the soil sample are respectively provided with raised radial ribs or radial arc bars, which are embedded in the upper and lower end surfaces of the soil sample to prevent the upper pressing plate and the lower supporting plate from sliding relative to the soil sample.

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