Soil rheological test device based on single gravity application

Abstract

The invention discloses a soil rheological test device based on single gravity application, which comprises a bracket, an angle-adjustable platform, a sample preparation platform, an oil cylinder riding wheel, a multilayer shear box and a loading cover plate, one end of the angle-adjustable platform is hinged with the top of the bracket, the oil cylinder riding wheel is arranged on the bracket, and the loading cover plate is arranged on the bottom of the bracket. The other side of the angle-adjustable platform is lifted by an angle through an oil cylinder riding wheel, the oil cylinder riding wheel vertically ascends to enable the angle-adjustable platform to reach a target angle, and the sample preparation platform is detachably connected with the angle-adjustable platform. The device is reasonable in structural design, normal force and tangential force can be simultaneously applied to a sample by only one group of gravity applying devices in a mode of inclining the shear boxes, meanwhile, the mode of loading by gravity is more stable, the influence of stress fluctuation on a rheological test is effectively avoided, and by adopting the mode of multiple layers of shear boxes, the test efficiency is improved. The stress field on the sheared sample is more uniform, and the test result is more accurate.

Description

Technical Field

[0001] The invention relates to the technical field of sand rheological property test and testing, and in particular to a soil rheological test device based on single gravity application. Background Art

[0002] The rheological properties of sand have always been an important influencing factor of the long-term deformation of earth-rock dams on thick sandy overburden. Clarifying the influence mechanism of sand rheology on the subsequent stress-strain development can provide an innovative method for accurately calculating the real stress-strain state and evolution law of anti-seepage structures such as anti-seepage walls and panels, effectively supporting the reinforcement of deep sandy dam foundations, the optimal design of anti-seepage walls and panels, and providing important support for guiding engineering design, demonstration and decision-making. Generally speaking, rheological tests usually use instruments such as triaxial instruments, but traditional macroscopic rheological tests do not involve their microscopic mechanisms. In order to further study the mechanism of the time effect on the evolution of stress-strain relationship in granular materials such as sand, Rubinstein et al. proposed to study the rheological properties of sand from the perspective of the change of microscopic particle contact over time, that is, by observing the change of contact between two polished glass bricks during relative motion to analyze the change process of particle contact during sand rheology. Many scholars (Pengyi Tian et al., 2016; Dillavou et al., 2018; Pilvelait et al., 2020; Cebry et al., 2022; Stelnhardt et al., 2019) have proposed this. et al., 2023) conducted research on this basis, and continuously improved the test equipment and gradually replaced the test material with sand itself. However, there are still some difficult problems to solve. For example, a stable load needs to be applied during rheological tests, while the current loading methods often use hydraulics, motors, etc., which will fluctuate near the target value. It is difficult to ensure the stability of the applied load, which has a certain impact on the test results.

[0003] At present, the equipment used in related tests often applies normal force through motors or hydraulic rods and tangential force through stepper motors. This way of applying load cannot remain constant after reaching the target stress value, but will fluctuate around the target value, especially under low confining pressure conditions, where the fluctuation value exceeds the 10% required in the specification, which will have a certain impact on the test results. In addition, the conventional direct shear instrument artificially stipulates the shear surface, which is quite different from the actual situation. For this reason, we designed a soil rheology test device based on single gravity application to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to solve the problems existing in the prior art of how to apply a constant load during a long-term rheological test and how to avoid the sand test from being damaged along the artificially specified shear surface during the shear process and make the stress field it is subjected to more uniform, and to propose a soil rheological test device based on single gravity application.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A soil rheology test device based on single gravity application, including a bracket, an adjustable angle platform, a sample preparation platform, a cylinder support wheel, a multi-layer shear box and a loading cover plate, wherein one end of the adjustable angle platform is hinged to the top of the bracket, the cylinder support wheel is arranged on the bracket, the other side of the adjustable angle platform is lifted by the cylinder support wheel, the cylinder support wheel rises vertically to make the adjustable angle platform reach the target angle, the sample preparation platform is detachably connected to the adjustable angle platform, the multi-layer shear box is located on the sample preparation platform, the loading cover plate covers the multi-layer shear box and applies load to the sample in the multi-layer shear box through a loading device.

[0007] Preferably, the bracket is composed of a leg frame welded from "A"-shaped hollow square steel and a solid platform on the top, the solid platform has a fixed hole reserved for installing the cylinder support wheel, and the adjustable angle platform is hinged to the solid platform.

[0008] Preferably, the cylinder supporting wheel comprises a roller, a connecting head, a hydraulic rod and a cylinder body. The roller is hinged to the adjustable angle platform. The roller and the hydraulic rod are connected via a connecting head. The hydraulic rod and the cylinder body form a hydraulic cylinder. The hydraulic cylinder can be disassembled from the roller via the connecting head.

[0009] Preferably, a positioning plate is welded on the bracket, a plurality of holes are formed through the positioning plate at equal intervals, and corresponding positions on the adjustable angle platform are provided with slots for fixing the positioning plate.

[0010] Preferably, the angle adjustment range of the adjustable angle platform is 0°-30°.

[0011] Preferably, the side of the loading cover plate in contact with the sample has a protrusion that is consistent with the cross-sectional size of the sample.

[0012] Preferably, the loading device is connected to the bottom of the loading cover plate through a plurality of connecting pieces, and the loading device is composed of a force transmission rod, a tray and a weight, and a groove is provided on one side of the weight for mounting the weight on the tray.

[0013] Preferably, the connecting member includes a connecting block with a threaded hole at the bottom, the force transmission rod is threadedly connected to the threaded hole at the bottom of the connecting block, the upper part of the connecting block is U-shaped and has a sliding opening therethrough, the bottom of the loading cover plate has a plurality of connecting holes therethrough, and the sliding opening on the connecting member is connected to the corresponding connecting holes by connecting bolts.

[0014] Preferably, the multilayer shear box is divided into ten layers, each layer is circular on one side in contact with the sample and is a regular hexadecagon on the outside, and a tetrafluoroethylene coating is applied between the multilayer shear boxes and on the inner wall of the multilayer shear box to reduce friction, and the displacement of the bottom and top layers of the multilayer shear box is measured by a laser displacement sensor.

[0015] Preferably, the sample preparation platform is provided with a fixing device for fixing the multi-layer shear box during the molding stage, and the fixing device is divided into two left and right fixing plates, both of which are penetrated with mounting holes, and both of the fixing plates are fixed to the sample preparation platform by fixing bolts, and the inner walls of the two fixing plates are both arc-shaped and adapted to the multi-layer shear box.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. This soil rheology test device based on single gravity application can achieve the application of normal force and tangential force to the sample at the same time by only one set of gravity application devices by tilting the shear box. At the same time, the gravity loading method is more stable, which effectively avoids the influence of stress fluctuation on the rheological test.

[0018] 2. This soil rheology test device based on single gravity application adopts a multi-layer shear box to make the stress field of the sheared sample more uniform and the test results more accurate.

[0019] 3. This soil rheology test device based on single gravity application can greatly reduce the requirements of rheology test on equipment through gravity loading to achieve long-term rheology test. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic diagram of the structure of a soil rheology test device based on single gravity application proposed by the present invention;

[0021] Figure 2 is a schematic diagram of the support structure;

[0022] Figure 3 This is a schematic diagram of the connection between the adjustable angle platform at 0° and the bracket and the cylinder support wheel;

[0023] Figure 4 It is a schematic diagram of the adjustable angle platform of 30° and the connection with the bracket and the cylinder supporting wheel in the evacuated state of the hydraulic rod;

[0024] Figure 5 This is a schematic diagram of the oil cylinder supporting wheel structure;

[0025] Figure 6 It is a schematic diagram of the connection between the multi-layer shear box, the loading cover plate, and the loading device;

[0026] Figure 7 It is a schematic diagram of the connection between the loading cover plate, the force transmission rod and the connecting parts;

[0027] Figure 8 It is a schematic diagram of the top view of the loading cover and tray connection structure;

[0028] Fig. 9 It is a schematic diagram of the connection between the weight and the groove;

[0029] Fig.10 It is a schematic diagram of the connection between the loading cover plate, the protrusion and the connection hole;

[0030] Fig.11 It is a schematic diagram of the multi-layer shear box structure;

[0031] Fig.12 This is a schematic diagram of the connection between the sample preparation platform, fixed plate, and fixed holes.

[0032] In the figure: 1, bracket; 101, leg frame; 102, solid platform; 103, fixing hole; 2, adjustable angle platform; 3, sample preparation platform; 4, cylinder supporting wheel; 401, roller; 402, connector; 403, hydraulic rod; 404, cylinder body; 5, multi-layer shear box; 6, loading cover plate; 601, protrusion; 602, connecting hole; 7, loading device; 701, force transmission rod; 702, tray; 703, weight; 704, groove; 8, positioning plate; 801, hole position; 9, connector; 901, connecting block; 902, slide; 903, connecting bolt; 10, fixing plate; 1001, mounting hole. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0034] Reference Figure 1-Figure 12A soil rheology test device based on single gravity application includes a bracket 1, an adjustable angle platform 2, a sample preparation platform 3, a cylinder support wheel 4, a multi-layer shear box 5 and a loading cover plate 6. One end of the adjustable angle platform 2 is hinged to the top of the bracket 1, and the cylinder support wheel 4 is arranged on the bracket 1. The other side of the adjustable angle platform 2 is lifted by the cylinder support wheel 4. The cylinder support wheel 4 rises vertically to make the adjustable angle platform 2 reach the target angle. The sample preparation platform 3 is detachably connected to the adjustable angle platform 2. The multi-layer shear box 5 is located on the sample preparation platform 3. The loading cover plate 6 covers the multi-layer shear box 5 and applies load to the sample in the multi-layer shear box 5 through the loading device 7;

[0035] Reference Figure 2 The bracket 1 is composed of a leg frame 101 welded from an "A"-shaped hollow square steel and a top solid platform 102. There are two leg frames 101, which are respectively located on both sides of the bottom of the solid platform 102 to provide stable support for the solid platform 102. The solid platform 102 has a fixed hole 103 reserved for installing the cylinder support wheel 4. One end of the adjustable angle platform 2 is hinged to the solid platform 102, so that the adjustable angle platform 2 can rotate around the hinge point.

[0036] Reference Figure 3-Figure 5 The oil cylinder roller 4 includes a roller 401, a connector 402, a hydraulic rod 403 and a cylinder body 404. The roller 401 is hinged with the adjustable angle platform 2. The roller 401 is composed of a roller frame, a roller and a bearing. The roller is connected to the bottom of the adjustable angle platform 2. The roller rotates in the roller frame through the bearing. A connecting shaft is hinged between the bottom of the roller frame and the connector 402, so that the adjustable angle platform 2 can rotate around the hinge point with the solid platform 102. The roller 401 is connected to the hydraulic rod 403 through the connector 402. The hydraulic rod 403 and the cylinder body 404 form a hydraulic cylinder. The hydraulic cylinder can be disassembled from the roller 401 through the connector 402. The hydraulic cylinder adopts the YGX series micro hydraulic cylinder-LB type;

[0037] A positioning plate 8 is welded on the bracket 1, and a plurality of holes 801 are formed on the positioning plate 8 at equal intervals. A slot for fixing the positioning plate 8 is formed on the side wall of the adjustable angle platform 2. After the oil cylinder supporting wheel 4 rises vertically to make the adjustable angle platform 2 reach the target angle, the adjustable angle platform 2 is fixed in the corresponding hole 801 and the slot by means of a rod. After the adjustable angle platform 2 is fixed, the hydraulic cylinder can be disassembled through the connector 402. The angle adjustment range of the adjustable angle platform 2 is 0°-30°.

[0038] Reference Figure 6-Figure 10The side of the loading cover 6 in contact with the sample has a protrusion 601 that is consistent with the cross-sectional size of the sample, which is convenient for applying pressure to the sample. The loading device 7 is connected to the bottom of the loading cover 6 through multiple connecting pieces 9. The loading device 7 consists of a force transmission rod 701, a tray 702 and a weight 703. A groove 704 is provided on one side of the weight 703 for mounting the weight 703 on the tray 702. The load on the sample is applied by the loading device 7 through the loading cover 6. The left and right parts of the weight 703 do not contact each other during the angle adjustment process of the adjustable angle platform 2. The connection method between the two sides of the loading cover 6 and the force transmission rod 701 is as follows Figure 7 As shown, the force transmission rod 701 always remains vertical during the process of the adjustable angle platform 2 rising, and the loading point position is consistent with the center height of the sample. The purpose of this design is to ensure that the stress field shown by the sample is uniform during the test and to ensure accurate test results;

[0039] The connecting member 9 includes a connecting block 901 with a threaded hole at the bottom, and the force transmission rod 701 is threadedly connected to the threaded hole at the bottom of the connecting block 901. The upper part of the connecting block 901 is U-shaped and has a sliding opening 902 extending therethrough. The bottom of the loading cover plate 6 has a plurality of connecting holes 602 extending therethrough. The sliding opening 902 on the connecting member 9 is connected to the corresponding connecting holes 602 via a connecting bolt 903. The sliding opening 902 and the connecting hole 602 are connected via the connecting bolt 903. The connecting bolt 903 can rotate in the sliding opening 902, so that the connecting block 901 can rotate relative to the loading cover plate 6, so that the force transmission rod 701 always remains vertical during the process of the angle of the adjustable angle platform 2 rising.

[0040] Reference Fig.11 The multilayer shear box 5 is divided into ten layers, each layer is circular on one side in contact with the sample, and is a regular hexadecagon on the outside. The multilayer shear boxes 5 and the inner wall of the multilayer shear box 5 are coated with a tetrafluoroethylene coating to reduce friction. The multilayer shear boxes 5 do not need additional connections. The design of the multilayer shear box 5 can effectively improve the problem that the sample can only be destroyed from the artificially specified shear surface, making the sample deformation more free and the sample result closer to the actual situation.

[0041] The displacement of the bottom and top layers of the multilayer shear box 5 is measured by a laser displacement sensor. When the adjustable angle platform 2 is 0°, the maximum load is 500 kPa. As the angle of the adjustable angle platform 2 is raised, it is possible to simultaneously apply normal force and tangential force to the sample by a single gravity load. Compared with other load application methods, the advantages of applying load by gravity are stability, sufficient loading time, and the hydraulic rod 403 lifts the adjustable angle platform 2 to the target angle and then removes it, and then fixes it by a through rod, which can effectively solve the problems of load fluctuation and limited test time in the current sand rheology test. In addition, by setting the target value, speed, and staged lifting of the angle, sand rheology tests under different stress paths can be achieved;

[0042] The sample preparation platform 3 is provided with a fixing device for fixing the multi-layer shear box 5 during the molding stage. The fixing device is divided into two left and right fixing plates 10. The two fixing plates 10 are penetrated with mounting holes 1001. The two fixing plates 10 are fixed to the sample preparation platform 3 by fixing bolts. The inner walls of the two fixing plates 10 are both arc-shaped and matched with the multi-layer shear box 5. The fixing device is used to fix the multi-layer shear box 5 during the molding stage. After the molding is completed, the sample preparation platform 3 together with the fixing device and the sample are transferred to the sample device, that is, after the sample preparation platform 3 is fixed on the adjustable angle platform 2, the loading cover plate 6 and the loading device 7 are placed. After the arrangement is completed, the fixing device is removed and the test officially begins.

[0043] The present invention can be explained by the following operation mode:

[0044] In the present invention, the soil rheology test device based on single gravity application can be divided into the following steps when used:

[0045] 1. Preparation of test soil samples: The soil samples are prepared by layered compaction method using a multi-layer shear box 5 (the sample preparation is not carried out on the equipment);

[0046] The multilayer shear box 5 is fixed on the sample preparation platform 3 through the sample fixing device;

[0047] 2. After the sample preparation is completed, the sample preparation platform 3 together with the multi-layer shear box 5 and the sample fixing device fixed thereon are transferred to the adjustable angle platform 2 for fixing. At this time, the adjustable angle platform 2 is 0°;

[0048] 3. After the fixation is completed, the protrusion 601 below the loading cover plate 6 is aligned with the sample to arrange the loading cover plate 6, and then the loading device 7 is connected to both sides of the loading cover plate 6 by connecting bolts 903;

[0049] 4. After the above operations are completed, a weight 703 is applied to the tray 702 of the loading device 7 to a target value, and then the sample fixing device is removed and a laser displacement sensor is arranged;

[0050] 5. Then, the adjustable angle platform 2 is lifted to the target value by the oil cylinder support wheel 4, and the adjustable angle platform 2 is fixed by the positioning plate 8. Different loading paths can be achieved by adjusting the lifting speed, etc. After loading, the sample will be subjected to uniform and constant stress during the rheological process, where the normal stress is: σ1=Ggcosθ / A

[0051] Shear stress is: σ3=Ggsinθ / A

[0052] Where G: weight of the weight A: sample area g: gravitational acceleration

[0053] θ: Adjustable angle platform 2 lifting angle

[0054] 6. The axial flow rate at time t is:

[0055] Where ε1: rheological deformation of the sample h: height of the sample.

[0056] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A soil rheology test device based on single gravity application, comprising a bracket (1), an adjustable angle platform (2), a sample preparation platform (3), a cylinder support wheel (4), a multi-layer shear box (5) and a loading cover plate (6), characterized in that: One end of the adjustable angle platform (2) is hinged to the top of the bracket (1), the cylinder support wheel (4) is arranged on the bracket (1), the other side of the adjustable angle platform (2) is lifted by the cylinder support wheel (4), the cylinder support wheel (4) rises vertically to make the adjustable angle platform (2) reach the target angle, the sample preparation platform (3) is detachably connected to the adjustable angle platform (2), the multi-layer shear box (5) is located on the sample preparation platform (3), the loading cover plate (6) covers the multi-layer shear box (5) and applies load to the sample in the multi-layer shear box (5) through the loading device (7).

2. A soil rheology test device based on single gravity application according to claim 1, characterized in that: The support (1) is composed of a leg frame (101) welded from "A"-shaped hollow square steel and a top solid platform (102); the solid platform (102) is provided with a fixing hole (103) for installing a cylinder support wheel (4); and the adjustable angle platform (2) is hinged to the solid platform (102).

3. The soil rheology test device based on single gravity application according to claim 2, characterized in that: The oil cylinder supporting wheel (4) comprises a supporting roller (401), a connecting head (402), a hydraulic rod (403) and a cylinder body (404); the supporting roller (401) is hinged to the adjustable angle platform (2); the supporting roller (401) and the hydraulic rod (403) are connected via the connecting head (402); the hydraulic rod (403) and the cylinder body (404) form a hydraulic cylinder; and the hydraulic cylinder can be disassembled from the supporting roller (401) via the connecting head (402).

4. The soil rheology test device based on single gravity application according to claim 1, characterized in that: A positioning plate (8) is welded on the bracket (1), a plurality of holes (801) are formed through the positioning plate (8) at equal intervals, and a slot for fixing the positioning plate (8) is provided at a corresponding position on the adjustable angle platform (2).

5. The soil rheology test device based on single gravity application according to claim 1, characterized in that: The angle adjustment range of the adjustable angle platform (2) is 0°-30°.

6. The soil rheology test device based on single gravity application according to claim 1, characterized in that: The side of the loading cover plate (6) in contact with the sample has a protrusion (601) that is consistent with the cross-sectional size of the sample.

7. The soil rheology test device based on single gravity application according to claim 1, characterized in that: The loading device (7) is connected to the bottom of the loading cover plate (6) via a plurality of connecting pieces (9); the loading device (7) is composed of a force transmission rod (701), a tray (702) and a weight (703); a groove (704) is provided on one side of the weight (703) for mounting the weight (703) on the tray (702).

8. The soil rheology test device based on single gravity application according to claim 7, characterized in that: The connecting member (9) comprises a connecting block (901) with a threaded hole at the bottom, the force transmission rod (701) is threadedly connected to the threaded hole at the bottom of the connecting block (901), the upper part of the connecting block (901) is U-shaped and has a sliding opening (902) extending therethrough, the bottom of the loading cover plate (6) has a plurality of connecting holes (602) extending therethrough, and the sliding openings (902) on the connecting member (9) are connected to the corresponding connecting holes (602) via connecting bolts (903).

9. The soil rheology test device based on single gravity application according to claim 1, characterized in that: The multilayer shear box (5) is divided into ten layers in total, and the side of each layer in contact with the sample is circular, and the outer side is a regular hexadecagon. The multilayer shear boxes (5) and the inner wall of the multilayer shear box (5) are coated with a tetrafluoroethylene coating to reduce friction resistance, and the displacement of the bottom layer and the top layer of the multilayer shear box (5) is measured by a laser displacement sensor.

10. The soil rheology test device based on single gravity application according to claim 1, characterized in that: The sample preparation platform (3) is provided with a fixing device for fixing the multi-layer shear box (5) during the molding stage, and the fixing device is divided into two left and right fixing plates (10), and the two fixing plates (10) are both penetrated with mounting holes (1001). The two fixing plates (10) are fixed to the sample preparation platform (3) by fixing bolts, and the inner walls of the two fixing plates (10) are both arranged in an arc shape that is compatible with the multi-layer shear box (5).

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