Portable in-situ direct shear apparatus and shear strength index testing method

Abstract

The invention provides a portable in-situ direct shear apparatus. The portable in-situ direct shear apparatus comprises a movement limiting groove formed in a bearing platform, a mechanical arm assembly electrically connected with a monitoring system and a shearing assembly. The moving limiting groove is used for placing soil blocks; the mechanical arm assembly comprises an electric mechanical arm; the electric mechanical arm is fixedly connected with the bearing platform through the center stand column. The electric mechanical arm is connected with a rotary driver, or is connected with a soil sample cutter, or is connected with a shear box cover; a soil sample fixer is arranged on one side, facing the movement limiting groove, of the central stand column; a cutting ring device is arranged at the bottom of the rotary driver; the shearing assembly comprises a first shearing box, a second shearing box, a shearing box cover and a horizontal transmission assembly; the horizontal transmission assembly is connected between the second shear box and the central upright post; the monitoring system comprises a displacement sensor, a host and a display screen. And the displacement sensor is connected with the second shear box. The problems that during field investigation, an existing direct shear apparatus is inconvenient to carry, and the shear strength index of an undisturbed soil sample is difficult to rapidly obtain are solved.

Description

Technical Field

[0001] The present application relates to a portable in-situ direct shear apparatus, and in particular to a portable in-situ direct shear apparatus and a shear strength index testing method, belonging to the field of shear strength index testing. Background Art

[0002] Soil shear strength parameters—cohesion (c) and internal friction angle (φ)—are important indicators for determining soil shear strength. They are used to assess soil stability (slope stability, foundation bearing capacity and stability, and retaining wall earth pressure). They are also essential parameters for studying soil strength properties (stress-strain relationships, peak strength and residual strength, and volume change) and simulating drainage conditions under different engineering conditions (unconsolidated undrained, consolidated undrained, and consolidated drained). They provide key design input data for various stability calculations and analyses involving soil shear failure in geotechnical engineering.

[0003] Existing soil shear tests are mainly carried out indoors, which cannot meet the need to quickly obtain soil shear properties during field surveys. In addition, the existing in-situ direct shear instrument requires a large working surface, and field survey conditions are limited, which cannot provide a sufficiently large working surface for the in-situ direct shear instrument.

[0004] The present invention takes into account the problems that the existing direct shear instrument is inconvenient to carry during field surveys and it is difficult to quickly obtain the shear strength index of the original soil sample, and designs a portable in-situ direct shear instrument and a shear strength index testing method. Summary of the Invention

[0005] In view of this, the present application provides a portable in-situ direct shear apparatus and a shear strength index testing method to solve or alleviate the technical problems existing in the prior art and at least provide a beneficial option.

[0006] The technical solution of the embodiment of the present application is implemented as follows: a portable in-situ direct shear instrument, comprising: a movement limiting groove arranged on a base, a robotic arm assembly and a shearing assembly electrically connected to a monitoring system; the movement limiting groove is used to place soil blocks; the robotic arm assembly comprises: an electric robotic arm; the electric robotic arm is fixedly connected to the base through a central column; the electric robotic arm is connected to a rotary drive, or a soil sample cutter, or a shear box cover; a soil sample holder is provided on the side of the central column facing the movement limiting groove; a ring knife device is provided at the bottom of the rotary drive; the shearing assembly comprises: a first shear box, a second shear box, the shear box cover and a horizontal transmission assembly; the horizontal transmission assembly is connected between the second shear box and the central column; the monitoring system comprises: a displacement sensor, a host and a display screen; the displacement sensor is connected to the second shear box; the host is also connected to the electric robotic arm.

[0007] Further preferably, the inner diameter of the first shear box is 15 to 20 cm, and it is fixedly arranged on the base; the inner diameter of the second shear box is the same as that of the first shear box, and it is connected to the first shear box through a sliding guide rail.

[0008] Further preferably, the support platform is a rectangular aluminum alloy plate with a length and width of 45 cm and a height of 3 cm; the height of the central column is 45 cm.

[0009] Further preferably, the ring knife device has a diameter of 6.18 cm and a height of 2 cm.

[0010] Based on the same concept, the present application also provides a shear strength index testing method applied to the portable in-situ direct shear apparatus as described above, wherein the shear strength index testing method is:

[0011] S1. Soil Sample Preparation: Clean the test site surface, cut a cubic soil block with a length, width, and height of 10 cm, and place it in the movement restriction groove of the foundation.

[0012] S2. Ring knife sampling: Assemble the rotary drive and electric manipulator to the central column. Install the ring knife device in the rotary slot at the end of the electric manipulator. After applying vaseline to the outer wall of the ring knife device, drive the rotary drive to drive the ring knife device to obtain a ring knife soil sample in the cubic soil block.

[0013] S3. Soil sample trimming: Place the ring cutter soil sample into the soil sample holder on the central column, switch the electric manipulator arm to connect the soil sample cutter, and drive the soil sample cutter to trim the end face of the ring cutter soil sample;

[0014] S4. Shearing preparation: Install the shear box cover into the rotating slot of the electric manipulator, place the trimmed ring cutter soil sample into the first shear box and the second shear box, and place permeable stones at the upper and lower ends of the soil sample;

[0015] S5. Stepwise Pressurization: Control the electric manipulator as a vertical pressure device, applying vertical pressure to the shear box cover in three levels: 25 kPa, 50 kPa, and 100 kPa. Maintain each pressure level for 3 minutes, and then record the initial displacement data of the displacement sensor.

[0016] S6. Shear Test: Start the horizontal drive assembly and apply horizontal thrust at a set rate, while simultaneously collecting shear displacement and horizontal thrust data from the displacement sensor. Terminate the test when the shear force reaches a peak and then decreases, or when the shear displacement reaches 15% of the side length of the second shear box, and record the maximum shear force.

[0017] S7. Repeat the test: Replace the soil sample and repeat steps S4-S6 to complete at least three sets of tests under different vertical pressures.

[0018] Further preferably, in S5, the vertical pressure control accuracy is ±1 kPa, and the pressure stability criterion for each level is: the displacement sensor reading change rate does not exceed ±0.01 mm / min for 30 consecutive seconds.

[0019] Further preferably, in S6, the application range of the horizontal thrust is 0.5 to 5 kN, and the thrust control accuracy is ±0.1N.

[0020] Further preferably, in S6, the loading rate of the horizontal thrust is adjusted by the host.

[0021] Further preferably, in S6, the monitoring range of the displacement sensor is 0-50 mm, and the data acquisition accuracy is ±0.01 mm.

[0022] Further preferably, in S6, the shear displacement threshold for terminating the test is 15% of the inner diameter of the second shear box.

[0023] The embodiment of the present application adopts the above technical solution, which has the following advantages:

[0024] A portable in-situ direct shear apparatus and a shear strength index testing method are proposed to solve the problem that the existing direct shear apparatus is inconvenient to carry and difficult to quickly obtain the shear strength index of the original soil sample during field investigation.

[0025] The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present application will be readily apparent by reference to the accompanying drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or technical descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a structural diagram of the portable in-situ direct shear apparatus described in this application.

[0028] Figure 2 This is a structural diagram of the portable in-situ direct shear apparatus described in this application.

[0029] Figure 3 This is a flow chart of the shear strength index testing method described in this application.

[0030] Explanation of the accompanying figures: 1. Electronic funnel; 2. Conduit; 3. Compactor; 4. Compacting cylinder; 5. Lifting cylindrical table; 6. Bottom support; 7. Cylindrical support; 8. First connecting rod; 9. Second connecting rod; 10. Spiral Vaseline box; 11. Cylindrical telescopic arm; 12. Third connecting rod; 13. Controller. DETAILED DESCRIPTION

[0031] Hereinafter, only certain exemplary embodiments are briefly described. As will be appreciated by those skilled in the art, the described embodiments may be modified in various ways without departing from the spirit or scope of the present application. Therefore, the drawings and description are to be regarded as illustrative in nature and not restrictive.

[0032] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0033] like Figure 1-2 As shown, an embodiment of the present application provides a portable in-situ direct shear instrument, comprising: a movement limiting groove 3 arranged on a base 2, a robotic arm assembly and a shearing assembly electrically connected to a monitoring system; the movement limiting groove 3 is used to place a soil block 1; the robotic arm assembly comprises: an electric robotic arm 5; the electric robotic arm 5 is fixedly connected to the base 2 through a central column 6; the electric robotic arm 5 is connected to a rotary driver 4, or is connected to a soil sample cutter 12, or is connected to a shear box cover 15; the central column 6 is provided with a soil sample holder 11 on the side facing the movement limiting groove 3; a ring knife device 8 is provided at the bottom of the rotary driver 4; the shearing assembly comprises: a first shear box 13, a second shear box 14, the shear box cover 15 and a horizontal transmission assembly 16; the horizontal transmission assembly 16 is connected between the second shear box 14 and the central column 6; the monitoring system comprises: a displacement sensor 17, a host 7 and a display screen 18; the displacement sensor 17 is connected to the second shear box 14; the host 7 is also connected to the electric robotic arm 5.

[0034] Further preferably, the first shear box 13 has an inner diameter of 15 to 20 cm and is fixedly mounted on the support 2 ; the second shear box 14 has the same inner diameter as the first shear box 13 and is connected to the first shear box 13 via a sliding guide rail.

[0035] Further preferably, the support platform 2 is a rectangular aluminum alloy plate with a length and width of 45 cm and a height of 3 cm; the central column 6 is 45 cm in height.

[0036] Further preferably, the ring knife device 8 has a diameter of 6.18 cm and a height of 2 cm.

[0037] The specific implementation is as follows:

[0038] Select a field test site, remove weeds and debris using a shovel, soft brush, or other tools, and remove a 10cm long, wide, and high cubic soil block 1. Carefully move the cubic soil block 1 into the movement restriction slot 3 on the foundation 2. Assemble the rotary actuator 4, electric manipulator 5, and circular blade device 8. Apply petroleum jelly to the circular blade device 8. Use the host computer 7 to control the rotary actuator 4, electric manipulator 5, and circular blade device 8 to remove a circular blade soil sample 10 from the cubic soil block 1.

[0039] The prepared ring-type soil sample 10 is placed in the ring-type soil sample holder 11, and the soil sample cutter 12 is taken out and installed on the electric mechanical arm 5. The mechanical arm drives the soil sample cutter 12 to cut the soil sample in the soil sample holder 11 flat. The cut ring-type soil sample 10 can be subjected to the shear test.

[0040] Fix the first shear box 13 on the base 2 and place the permeable stone. Rotate the electric manipulator 5 to the right of the center column 6, connect the shear box cover 15, carefully place the ring cutter soil sample 10 into the shear box, place another piece of permeable stone on top of the soil sample, and move the electric manipulator 5 so that the shear box cover 15 covers the second shear box 14.

[0041] The displacement sensor 17 is installed on the side of the second shear box 14 to record the shear displacement in real time; the display screen 18 collects data in real time.

[0042] After the vertical pressure is set, the vertical pressure device and the horizontal transmission assembly 16 are started simultaneously under the control of the host 7, and the shear test of the soil sample to be tested begins. During the test, the shear force and displacement values ​​under different pressures are read in real time from the data collector, the cohesion and internal friction angle of the soil are calculated, and the shear strength under each vertical pressure is determined.

[0043] It is necessary to obtain test data under three graded vertical pressures of 25kPa, 50kPa, and 100kPa. The initial displacement data should be recorded after each level of pressure is stabilized for 3 minutes. Each group of measuring points should be repeated at least 3 times.

[0044] After the field test of soil sample shear strength is completed, each component is removed in turn and cleaned and maintained.

[0045] like Figure 3 As shown, based on the same concept, the present application also provides a shear strength index testing method applied to the portable in-situ direct shear apparatus as described above, the shear strength index testing method:

[0046] S1. Soil sample preparation: Clean the surface of the test point, cut a cubic soil block 1 with a length, width and height of 10 cm, and

[0047] Place

[0048] In the movement limiting groove 3 of the platform 2;

[0049] S2. Ring knife sampling: Assemble the rotary driver 4 and the electric manipulator 5 on the central column 6.

[0050] The ring knife device 8 is installed in the rotating slot at the end of the arm 5. After applying vaseline on the outer wall of the ring knife device 8, the rotation drive

[0051] Device 4

[0052] The ring knife device 8 is driven to prepare a ring knife soil sample 10 in the cubic soil block 1;

[0053] S3 soil sample trimming: the ring cutter soil sample 10 into the soil sample holder 11 on the center column 6, switch the motor

[0054] Robotic arm 5 connection

[0055] A soil sample cutter 12 is driven to trim the end surface of the ring-cut soil sample 10;

[0056] S4. Shearing preparation: The shear box cover 15 is installed in the rotating slot of the electric manipulator 5, and the trimmed ring

[0057] Knife soil sample 10

[0058] Place the soil sample in the first shear box 13 and the second shear box 14, and place permeable stones at the upper and lower ends of the soil sample;

[0059] S5. Gradual pressurization: Control the electric manipulator 5 as a vertical pressure device, and apply vertical pressure to the shear box cover 15 at three levels of 25kPa, 50kPa, and 100kPa; each level of pressure is maintained stable for 3 minutes and then the displacement sensor is recorded.

[0060] 17 initial displacement data;

[0061] S6. Shear test: Start the horizontal transmission component 16 to apply horizontal thrust at a set rate and simultaneously collect displacement

[0062] Sensing

[0063] The shear displacement data and horizontal thrust data of the device are collected; when the shear force value reaches a peak value and then decreases, or when the shear displacement reaches 15% of the side length of the second shear box 14, the test is terminated and the maximum shear force value is recorded;

[0064] S7. Repeat the test: Replace the soil sample and repeat steps S4-S6 to complete at least three sets of tests under different vertical pressures.

[0065] Further preferably, in S5, the vertical pressure control accuracy is ±1 kPa, and the pressure stability criterion for each level is: the rate of change of the displacement sensor 17 reading does not exceed ±0.01 mm / min for 30 consecutive seconds.

[0066] Further preferably, in S6, the application range of the horizontal thrust is 0.5 to 5 kN, and the thrust control accuracy is ±0.1N.

[0067] Further preferably, in S6 , the loading rate of the horizontal thrust is adjusted by the host 7 .

[0068] Further preferably, in S6, the monitoring range of the displacement sensor 17 is 0 to 50 mm, and the data acquisition accuracy is ±0.01 mm.

[0069] Further preferably, in S6 , the shear displacement threshold for terminating the test is 15% of the inner diameter of the second shear box 14 .

[0070] like Figure 1-3 As shown, the specific implementation is as follows:

[0071] Select a test point, clean off any loose soil and weeds, and use a soil removal tool to remove a cubic soil block 1 (10 cm in length, width, and height). Carefully transfer this block 1 to the movement restriction slot 3 on the micro-in-situ direct shear apparatus's base 2, a rectangular aluminum alloy plate with a length and width of 45 cm and a height of 3 cm.

[0072] The rotary actuator 4 and electric manipulator arm 5 are assembled and mounted on a 45 cm high central column 6. Under the control of the host computer 7, the rotary actuator 4 drives the electric manipulator arm 5 below to rotate and remove soil. The electric manipulator arm 5 can freely extend and rotate. A rotating slot is installed on the electric manipulator arm 5 below the rotary actuator 4. A circular cutter device 8 with a diameter of 6.18 cm and a height of 2 cm is installed in the rotating slot. Vaseline is applied to the circular cutter device 8. The rotary actuator 4 drives the electric manipulator arm 5 and the circular cutter device 8 to remove a circular cutter soil sample 10 from the cubic soil block 1.

[0073] Place the prepared ring knife soil sample 10 into the ring knife soil sample holder 11, take out the soil sample cutter 12 and install it on the electric mechanical arm 5, and use the mechanical arm to drive the soil sample cutter 12 to cut the soil sample in the soil sample holder 11 flat. The cut ring knife soil sample 10 can be subjected to shear test, such as Figure 1 shown.

[0074] like Figure 2As shown, the first shear box 13 is made of high-strength aluminum alloy with an inner diameter of 15 to 20 cm. It is mounted on the base 2 and cannot be moved. The second shear box 14 matches the first shear box 13 and has the same inner diameter. It is linked to the first shear box 13 by a sliding guide rail to ensure that the shearing direction is horizontal. Controlled by the host 7, the electric manipulator 5 can be rotated to the right to act as a vertical pressure device, which can apply a vertical pressure of 0 to 200 kPa, with a pressure display accuracy of ±1 kPa. The horizontal transmission assembly 16 can provide a horizontal thrust of 0.5 to 5 kN, with a thrust accuracy of ±0.1 N, and the loading rate can be adjusted by the host 7. The monitoring system includes a displacement sensor 17 and a display screen 18. The displacement sensor 17 is mounted on the side of the second shear box 14, with a range of 0 to 50 mm and an accuracy of ±0.01 mm. It records the shear displacement in real time, and the display screen 18 can collect data in real time.

[0075] Connect the shear box cover 15 to the rotating slot of the electric manipulator 5, place the ring cutter soil sample 10 into the shear box, and place a permeable stone on each side. Start the vertical pressure device and apply vertical pressure according to the preset levels: 25kPa, 50kPa, and 100kPa. After each pressure level stabilizes for 3 minutes, record the initial displacement data.

[0076] The horizontal transmission assembly 16 is started, and horizontal thrust is applied at a set rate, while horizontal shear force and shear displacement data are collected simultaneously.

[0077] When the shear force reaches its peak and then begins to decrease, or when the shear displacement reaches 15% of the side length of the shear box, stop the test and record the maximum shear force value; follow the above steps to complete the test under different vertical pressures, and repeat each group of measuring points at least 3 times.

[0078] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any person skilled in the art can easily conceive of various modifications or substitutions within the technical scope disclosed in this application, and such modifications or substitutions should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A portable in-situ direct shear apparatus, characterized in that: include: A movement limiting groove (3) provided on the support platform (2), a mechanical arm assembly and a shearing assembly electrically connected to the monitoring system; The movement limiting groove (3) is used to place the soil block (1); the mechanical arm assembly includes: an electric mechanical arm (5); the electric mechanical arm (5) is fixedly connected to the support platform (2) through a central column (6); the electric mechanical arm (5) is connected to a rotary driver (4), or connected to a soil sample cutter (12), or connected to a shear box cover (15); the central column (6) is provided with a soil sample holder (11) on the side facing the movement limiting groove (3); a ring knife device (8) is provided at the bottom of the rotary driver (4); the shearing assembly includes: a first shear box (13), a second shear box (14), the shear box cover (15) and a horizontal transmission assembly (16); the horizontal transmission assembly (16) is connected between the second shear box (14) and the central column (6); the monitoring system includes: a displacement sensor (17), a host (7) and a display screen (18); the displacement sensor (17) is connected to the second shear box (14); the host (7) is also connected to the electric mechanical arm (5).

2. The portable in-situ direct shear apparatus according to claim 1, characterized in that: The first shear box (13) has an inner diameter of 15 to 20 cm and is fixedly mounted on the support platform (2); the second shear box (14) has the same inner diameter as the first shear box (13) and is connected to the first shear box (13) via a sliding guide rail.

3. The portable in-situ direct shear apparatus according to claim 1, characterized in that: The support platform (2) is a rectangular aluminum alloy plate with a length and width of 45 cm and a height of 3 cm; the central column (6) is 45 cm in height.

4. The portable in-situ direct shear apparatus according to claim 1, characterized in that: The ring knife device (8) has a diameter of 6.18 cm and a height of 2 cm.

5. A method for testing shear strength index of a portable in-situ direct shear apparatus according to any one of claims 1 to 4, characterized in that: The shear strength index test method: S1. Soil sample preparation: Clean the surface of the test point, cut a cubic soil block (1) with a length, width and height of 10 cm, and place it in the movement restriction groove (3) of the base (2); S2. Ring knife sampling: Assemble the rotary driver (4) and the electric manipulator (5) on the central column (6), install the ring knife device (8) in the rotary slot at the end of the electric manipulator (5), apply vaseline on the outer wall of the ring knife device (8), drive the rotary driver (4) to drive the ring knife device (8) to prepare a ring knife soil sample (10) in the cubic soil block (1); S3 soil sample trimming: the ring cutter soil sample (10) is placed in the soil sample holder (11) on the center column (6), the electric manipulator (5) is switched to connect the soil sample cutter (12), the soil sample cutter (12) is driven to trim the end face of the ring cutter soil sample (10); S4 shear preparation: the shear box cover (15) is mounted on the rotary slot of the electric manipulator (5), the trimmed ring cutter soil sample (10) is placed in the first shear box (13) and the second shear box (14), and permeable stone is placed at the upper and lower ends of the soil sample; S5. Gradual pressurization: Control the electric manipulator (5) as a vertical pressure device to apply vertical pressure to the shear box cover (15) at three levels of 25 kPa, 50 kPa, and 100 kPa; after each level of pressure is maintained for 3 minutes, the initial displacement data of the displacement sensor (17) is recorded; S6. Shear test: Start the horizontal transmission assembly (16) to apply horizontal thrust at a set rate, and simultaneously collect shear displacement data and horizontal thrust data from the displacement sensor (17); terminate the test when the shear force value reaches a peak value and then decreases, or when the shear displacement reaches 15% of the side length of the second shear box (14), and record the maximum shear force value; S7. Repeat the test: Replace the soil sample and repeat steps S4-S6 to complete at least three sets of tests under different vertical pressures.

6. The shear strength index testing method according to claim 5, characterized in that: In S5, the vertical pressure control accuracy is ±1 kPa, and the pressure stability criterion for each level is: the rate of change of the displacement sensor (17) reading does not exceed ±0.01 mm / min for 30 consecutive seconds.

7. The shear strength index testing method according to claim 5, characterized in that: In S6, the application range of the horizontal thrust is 0.5~5 kN, and the thrust control accuracy is ±0.1 N.

8. The shear strength index testing method according to claim 7, characterized in that: In S6, the loading rate of the horizontal thrust is adjusted by the host (7).

9. The shear strength index testing method according to claim 5, characterized in that: In S6, the monitoring range of the displacement sensor (17) is 0-50 mm, and the data acquisition accuracy is ±0.01 mm.

10. The shear strength index testing method according to claim 5, characterized in that: In S6, the shear displacement threshold for terminating the test is 15% of the inner diameter of the second shear box (14).

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