A single-anchor reaction in-situ soil ring shear test device and its application method

Abstract

This invention discloses a single-anchor reaction-type in-situ soil ring shear test device and its usage method. The device includes a ring shear mechanism comprising a base plate, on which a fixed anchor rod, a shear cover plate, and a driving mechanism are mounted. An opening is provided in the center of the base plate, through which the shear cover plate is inserted into the soil to be tested. Ribs protrude circumferentially from the lower surface of the shear cover plate. The driving mechanism drives the shear cover plate to perform the ring shear test. A reaction force application mechanism is also included to apply thrust to the shear cover plate. This invention features a simple structure and convenient installation, enabling tests that were previously only possible indoors to be conducted outdoors. While maintaining the original structure and mechanical properties of the soil sample, in-situ soil ring shear tests can be performed to obtain more accurate engineering property parameters during large displacement shearing of the soil.

Description

Technical Field

[0001] This invention relates to the field of soil mechanics testing, and in particular to a single-anchor reaction in-situ soil ring shear test device and its usage method. Background Technology

[0002] The shear strength of soil reflects its ability to resist deformation and failure under stress conditions, and is a key analytical and design parameter in geotechnical engineering and soil mechanics.

[0003] Methods for testing soil shear strength include the ring shear test, which measures the engineering mechanical properties of soil under large shear displacement conditions. The basic principle of existing soil ring shear testing equipment is to fabricate a soil sample into a ring of a certain thickness and place the sample inside two shear rings. By fixing the upper shear ring and simultaneously rotating the lower shear ring at a certain speed or torque, the upper and lower parts of the soil rotate relative to each other. By changing the vertical pressure, relative rotation speed, or shear torque between the upper and lower shear rings, the engineering mechanical properties of the soil sample under large displacement conditions can be tested, such as peak strength, residual strength, stress-strain curves, and creep properties.

[0004] Currently, the ring shear apparatus used in practical engineering and scientific research are all laboratory testing instruments, requiring soil samples to be removed from their original location and sent back to the laboratory for testing. However, once the soil sample is removed from its original environment, its structure and stress state change, resulting in alterations to the engineering properties of the soil sample. Therefore, laboratory ring shear tests cannot accurately obtain the actual engineering mechanical properties of in-situ soil. Summary of the Invention

[0005] To address the problem that existing technologies for soil ring shear tests can only be conducted in the laboratory and cannot accurately obtain the actual engineering mechanical properties of in-situ soil, this invention provides a single-anchor reaction type in-situ soil ring shear test device.

[0006] The device includes a ring shearing mechanism, which comprises a base plate on which a fixed anchor rod, a shearing cover plate, and a driving mechanism are mounted. The base plate has an opening in the middle, through which the shearing cover plate is inserted into the soil to be tested. Ribs are circumferentially protruding from the lower surface of the shearing cover plate. The driving mechanism is used to drive the shearing cover plate to perform a ring shearing test. The device also includes a reaction force application mechanism, which is used to apply a thrust to the shearing cover plate.

[0007] Furthermore, the drive mechanism is connected to the shear cover plate via a gear set, and the gear set meshes with the outer edge of the shear cover plate.

[0008] Furthermore, the reaction force application mechanism includes a reaction force anchor rod and a hollow jack sleeved on the reaction force anchor rod. One end of the reaction force anchor rod passing through the hollow jack is threaded with an anchor head to prevent the hollow jack from detaching from the reaction force anchor rod. A pressure plate is fixed to the bottom of the hollow jack. The lower surface of the pressure plate is in contact with the upper surface of the shear cover plate. The shear cover plate and the pressure plate are provided with through holes for the reaction force anchor rod to pass through.

[0009] Furthermore, the upper surface of the shear cover plate is provided with a groove for the pressure plate to be embedded, and a ball ring is provided between the groove and the mating surface of the pressure plate.

[0010] Furthermore, the bottom of the reaction anchor is also provided with an expansion shell, which is used to expand after being inserted into the soil to be tested.

[0011] Furthermore, a shear ring assembly is provided below the shear cover plate. The shear ring assembly includes a limiting shaft sleeved on the reaction anchor rod, an inner shear ring sleeved on the limiting shaft, and an outer shear ring coaxially disposed outside the inner shear ring. The space between the inner shear ring and the outer shear ring allows the rib to pass through.

[0012] Furthermore, a lubricant is provided between the limiting shaft and the inner shear ring.

[0013] Furthermore, the inner shear ring is a stacked inner lower shear ring and an inner upper shear ring, and the outer shear ring is a stacked outer lower shear ring and an outer upper shear ring.

[0014] This application also provides a method for using a single-anchor reaction in-situ soil circumferential shear test device, comprising the following steps:

[0015] S1. Insert the reaction anchor into the soil to be tested, and install the inner shear ring and the outer shear ring coaxially on the bottom of the reaction anchor;

[0016] Then, from bottom to top, the pressure plate and the hollow jack are coaxially sleeved on the reaction anchor rod, and the anchor head is installed at the top of the reaction anchor rod;

[0017] The hollow jack is controlled by a computer to apply thrust, pressing the inner and outer shear rings of the shear ring assembly into the soil to be tested.

[0018] The anchor head, the hollow jack, the pressure plate and the shear cover are removed in sequence, the soil inside the inner shear ring is excavated, and soil samples are taken for testing.

[0019] S2. The limiting shaft is coaxially sleeved on the reaction anchor rod and placed inside the inner shear ring; the bottom plate is placed on the surface of the soil to be tested through the reaction anchor rod, and the bottom plate is fixed on the soil to be tested by the fixing anchor rod.

[0020] S3. Install the drive mechanism on the fixed bracket, and then install the shear cover plate through the reaction anchor rod onto the base plate. The drive mechanism and the shear cover plate are connected by the gear set.

[0021] S4. The pressure plate and the hollow jack are sequentially fitted onto the reaction anchor rod, and the anchor head is fixed to the top of the reaction anchor rod by threaded connection;

[0022] S5. The hollow jack is controlled by a computer to apply a normal thrust to the shear cover plate, and the drive mechanism is controlled to drive the shear cover plate so that the soil to be tested between the inner shear ring and the outer shear ring undergoes a ring shear test under normal pressure conditions through the ribs on the shear cover plate.

[0023] Furthermore, step S1 also includes excavating the soil within a preset distance range outside the outer shear ring.

[0024] Compared with the prior art, the advantages of the present invention are as follows:

[0025] The device of this invention is simple and convenient to install, and can move the tests that could originally only be carried out indoors to the outdoors. Under the condition of maintaining the original structure and mechanical properties of the soil sample, in-situ soil ring shear tests can be carried out to obtain more accurate engineering property parameters of soil during large displacement shear process. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the structure of the single-anchor reaction in-situ soil ring shear test device of the present invention;

[0027] Figure 2 This is a schematic diagram of the base plate structure;

[0028] Figure 3 This is a schematic diagram showing the connection between the shear cover and the drive mechanism;

[0029] Figure 4 This is a schematic diagram of the reaction force application mechanism;

[0030] Figure 5 This is a schematic diagram of the structure of the shear ring assembly;

[0031] In the diagram: 1. Base plate; 2. Fixed anchor bolt; 3. Fixed bracket; 4. Hollow jack; 5. Pressure plate; 6. Anchor head; 7. Reaction anchor bolt; 8. Shear cover plate; 9. Ball ring; 10. Drive mechanism; 11. Gear set; 12. Outer upper shear ring; 13. Inner upper shear ring; 14. Outer lower shear ring; 15. Inner lower shear ring; 16. Limiting shaft. Detailed Implementation

[0032] This application provides a single-anchor reaction in-situ soil ring shear test device, which includes:

[0033] The annular shearing mechanism includes a U-shaped base plate 1 with multiple pre-drilled holes for anchor bolts 2 to pass through. A circular shearing cover plate 8 passes through the center of the base plate 1. A fixing bracket 3 is fixed to the center of each long side of the base plate 1, and a drive mechanism 10 is fixed to each fixing bracket 3. The output end of the drive mechanism 10 is connected to the shearing cover plate 8 via a gear set 11. The outer edge of the shearing cover plate 8 has teeth for meshing with the gear set 11. The bottom of the shearing cover plate 8 is annular and has ribs protruding from its lower surface for insertion into the soil to be measured. The drive mechanism 10 is a servo motor.

[0034] The base plate 1 is fixed to the soil to be tested by the fixed anchor rod 2, so that the base plate 1 will not move during the ring shear test, thereby avoiding errors in the sampling results of the soil to be tested; the four gear sets 11 mesh with the shear cover plate 8, which can restrict the planar degree of freedom of the shear cover plate 8 during the ring shear test, and prevent the shear cover plate 8 from moving; at the same time, multiple drive mechanisms 10 can achieve a wider range of output torque changes under the control of the computer.

[0035] A reaction force application mechanism is installed above the shear cover plate 8, which includes a reaction anchor rod 7 and a hollow jack 4 sleeved on the reaction anchor rod 7. One end of the reaction anchor rod 7 passing through the hollow jack 4 is threaded with an anchor head 6, and the other end is provided with an expansion shell. The end of the hollow jack 4 away from the reaction anchor rod 7 is fixed with a pressure plate 5 for the reaction anchor rod 7 to pass through. The shear cover plate 8 is provided with a groove for the pressure plate 5 to be embedded and a through hole for the reaction anchor rod 7 to pass through. The end of the reaction anchor rod 7 with the expansion shell passes through the shear cover plate 8 and is inserted into the soil to be tested.

[0036] During the ring shear test, the hollow jack 4 can output thrust through computer control, and the top of the shear cover plate 8 is completely fixed by the pressure plate 5 to prevent vertical displacement of the shear cover plate 8, thereby improving the accuracy of the test results. At the same time, it can apply different pressures to the soil surface to adapt to different geological environments. The bottom of the reaction anchor 7 is equipped with an expansion shell, which provides pull-out resistance to the reaction anchor 7 after it is inserted into the soil to be tested, so that it can be fixed in the soil to be tested.

[0037] The upper surface of the groove is provided with a ball ring 9, and the lower surface of the pressure plate 5 is in contact with the ball ring 9. The ball ring 9 enables the shear cover plate 8 to rotate relative to the reaction anchor rod 7 without friction.

[0038] It also includes a shear ring assembly, which includes a limiting shaft 16 sleeved on the reaction anchor rod 7, an inner shear ring sleeved on the limiting shaft 16, an outer shear ring coaxially arranged outside the inner shear ring, the ribs at the bottom of the shear cover plate 8 can pass through the space between the inner and outer shear rings, and the bottom of the inner shear ring is also provided with an annular blade.

[0039] A lubricant is provided between the limiting shaft 16 and the inner shear ring, so that the inner shear ring sleeved on the limiting shaft 16 can rotate without friction; the bottom of the inner shear ring is provided with an annular blade, so that the inner lower shear ring 15 can easily enter the soil to be tested.

[0040] The inner shear ring is divided into an inner lower shear ring 15 and an inner upper shear ring 13, and the outer shear ring is divided into an outer lower shear ring 14 and an outer upper shear ring 12. By stacking them, the depth of the shear ring group inserted into the soil to be tested can be controlled.

[0041] In addition, this application also provides a method for using a single-anchor reaction in-situ soil circumferential shear test device, including the following steps:

[0042] S1. Insert the reaction anchor 7 into the soil to be tested, and install the inner shear ring and the outer shear ring coaxially on the bottom of the reaction anchor 7;

[0043] Then, from bottom to top, the pressure plate 5 and the hollow jack 4 are coaxially fitted onto the reaction anchor rod 7, and the anchor head 6 is installed on the top of the reaction anchor rod 7;

[0044] The hollow jack 4 is controlled by computer to apply thrust, pressing the inner and outer shear rings of the shear ring assembly into the soil to be tested.

[0045] The anchor head 6, hollow jack 4, pressure plate 5 and shear cover plate 8 were removed in sequence, the soil inside the inner shear ring was excavated, and soil samples were taken for testing.

[0046] S2. Coaxially sleeve the limiting shaft 16 onto the reaction anchor 7 and place it inside the inner shear ring; place the bottom plate 1 through the reaction anchor 7 onto the surface of the soil to be tested, and fix the bottom plate 1 onto the soil to be tested by fixing the anchor 2;

[0047] S3. Install the drive mechanism 10 on the fixed bracket 3, and then install the shear cover plate 8 through the reaction anchor rod 7 onto the base plate 1. The drive mechanism 10 and the shear cover plate 8 are connected through the gear set 11.

[0048] S4. The pressure plate 5 and the hollow jack 4 are sequentially placed on the reaction anchor rod 7, and the anchor head 6 is fixed to the top of the reaction anchor rod 7 by threaded connection.

[0049] S5. The hollow jack 4 is controlled by computer to apply normal thrust to the shear cover plate 8, and the drive mechanism 10 is controlled to drive the shear cover plate 8, so that the soil to be tested between the inner shear ring and the outer shear ring can undergo a ring shear test under normal pressure conditions through the ribs on the shear cover plate 8.

[0050] Using the above-described method, researchers can now perform single-anchor reaction in-situ soil ring shear tests, which are currently only possible indoors. By assembling the device and placing it in the original location of the soil to be tested, the test site is moved from indoors to the actual location of the soil. Then, the hollow jack 4 is controlled by a computer to apply thrust to the soil to be tested, and the output torque of the servo motor is controlled to make the soil between the outer and inner shear rings follow the shear cover plate 8 under the set normal pressure conditions for ring shearing. This allows researchers to obtain the engineering property parameters of the soil under the original structure and mechanical properties, thereby improving the accuracy of the test results.

[0051] Furthermore, step S1 also includes excavating the soil within a preset distance range outside the shear ring to prevent the lower part of the shear cover plate 8 (excluding the ribs) from sinking into the soil to be tested. The preset distance is 5 cm.

[0052] In this document, the directional terms such as front, back, top, and bottom are defined based on the location of the components in the accompanying drawings and their relative positions to each other, solely for the purpose of clarity and convenience in expressing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed in this application.

[0053] Where there is no conflict, the above embodiments and features described herein can be combined with each other.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A single-anchor reaction in-situ soil circumferential shear test device, characterized in that: The device includes a ring shearing mechanism, which includes a base plate (1), a fixed anchor rod (2), a shearing cover plate (8) and a driving mechanism (10) installed on the base plate (1). The base plate (1) has an opening in the middle, and the shearing cover plate (8) is inserted into the soil to be tested through the opening. The lower surface of the shearing cover plate (8) is provided with ribs protruding in the circumferential direction. The driving mechanism (10) is used to drive the shear cover plate (8) to perform a ring shear test; It also includes a reaction force application mechanism for applying a thrust to the shear cover plate (8); The reaction force application mechanism includes a reaction force anchor rod (7) and a hollow jack (4) sleeved on the reaction force anchor rod (7). An anchor head (6) is threaded to one end of the reaction force anchor rod (7) that passes through the hollow jack (4) to restrict the hollow jack from detaching from the reaction force anchor rod (7). A pressure plate (5) is fixed to the bottom of the hollow jack (4). The lower surface of the pressure plate (5) is attached to the upper surface of the shear cover plate (8), and the shear cover plate (8) and the pressure plate (5) are provided with through holes for the reaction anchor rod (7) to pass through.

2. The single-anchor reaction type in-situ soil ring shear test device as described in claim 1, characterized in that: The drive mechanism (10) is connected to the shear cover plate (8) via a gear set (11), and the gear set (11) meshes with the outer edge of the shear cover plate (8).

3. The single-anchor reaction type in-situ soil ring shear test device as described in claim 1, characterized in that: The upper surface of the shear cover plate (8) is provided with a groove for the pressure plate (5) to be embedded, and a ball ring (9) is provided between the groove and the mating surface of the pressure plate (5).

4. The single-anchor reaction type in-situ soil ring shear test device as described in claim 1, characterized in that: The bottom of the reaction anchor (7) is also provided with an expansion shell, which is used to expand after being inserted into the soil to be tested.

5. The single-anchor reaction type in-situ soil ring shear test device as described in claim 2, characterized in that: Below the shear cover plate (8), a shear ring assembly is also provided. The shear ring assembly includes a limiting shaft (16) sleeved on the reaction anchor rod (7). An inner shear ring is sleeved on the limiting shaft (16), and an outer shear ring is coaxially arranged outside the inner shear ring. The space between the inner shear ring and the outer shear ring allows the rib to pass through.

6. The single-anchor reaction type in-situ soil ring shear test device as described in claim 5, characterized in that: A lubricant is provided between the limiting shaft (16) and the inner shear ring.

7. The single-anchor reaction type in-situ soil ring shear test device as described in claim 5, characterized in that: The inner shear ring consists of an inner lower shear ring (15) and an inner upper shear ring (13) stacked together, and the outer shear ring consists of an outer lower shear ring (14) and an outer upper shear ring (12) stacked together.

8. A method for using a single-anchor reaction type in-situ soil circumferential shear test device, employing the single-anchor reaction type in-situ soil circumferential shear test device as described in claims 5-7, characterized in that: S1. Insert the reaction anchor (7) into the soil to be tested, and install the inner shear ring and the outer shear ring coaxially on the bottom of the reaction anchor (7); Then, from bottom to top, the pressure plate (5) and the hollow jack (4) are coaxially sleeved on the reaction anchor rod (7), and the anchor head (6) is installed on the top of the reaction anchor rod (7); The hollow jack (4) is controlled by computer to apply thrust, pressing the inner shear ring and outer shear ring in the shear ring group into the soil to be tested; Remove the anchor head (6), the hollow jack (4), the pressure plate (5) and the shear cover plate (8) in sequence, excavate the soil inside the inner shear ring, and take soil samples to be tested. S2. The limiting shaft (16) is coaxially sleeved on the reaction anchor (7) and placed inside the inner shear ring; the bottom plate (1) is placed on the surface of the soil to be tested through the reaction anchor (7), and the bottom plate (1) is fixed on the soil to be tested by the fixing anchor (2); S3. Install the drive mechanism (10) on the fixed bracket (3), and then install the shear cover plate (8) through the reaction anchor rod (7) on the base plate (1). The drive mechanism (10) and the shear cover plate (8) are connected by the gear set (11). S4. The pressure plate (5) and the hollow jack (4) are sequentially fitted onto the reaction anchor rod (7), and the anchor head (6) is fixed to the top of the reaction anchor rod (7) by threaded connection; S5. The hollow jack (4) is controlled by computer to apply normal thrust to the shear cover plate (8), and the drive mechanism (10) is controlled to drive the shear cover plate (8) so that the soil to be tested between the inner shear ring and the outer shear ring undergoes a ring shear test under normal pressure conditions through the ribs on the shear cover plate (8).

9. The method of using the single-anchor reaction type in-situ soil circumferential shear test device as described in claim 8, characterized in that: Step S1 also includes excavating the soil within a predetermined range outside the outer shear ring.

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