A device and method for determining the soil shear strength of a root-containing soil

Abstract

The application belongs to the technical field of soil detection, and particularly relates to a device and method for determining the shear strength of soil containing root systems. The device for determining the shear strength of soil containing root systems comprises a sample module, a loading module and a measuring module. The sample module comprises a sample box and a shearing box. The sample box is of a segmented structure and comprises an upper box and a lower box. A top plate is arranged on the top of the upper box. Limiting blocks are arranged in the gap between the lower box and the shearing box. The loading module comprises a normal pressure driver and a horizontal pressure driver. The normal pressure driver is arranged above the top plate, and the horizontal pressure driver is arranged on the side of the shearing box. The measuring module comprises a normal displacement sensor, a horizontal displacement sensor and a tension meter. The present application reflects the interaction between the root systems and the soil through the shearing experiment of the upper box and the lower box. The design is simple and convenient to operate. The underwater soil containing root systems, the saturated soil containing root systems, the soil containing root systems with specific moisture content and other different working conditions can be considered. The indoor experimental requirements of the root and stem plants can be met.

Description

Technical Field

[0001] This invention belongs to the field of soil testing technology, and specifically relates to a device and method for measuring the shear strength of soil containing roots. Background Technology

[0002] Plant roots have a certain soil-fixing function, which is reflected in the fact that the combination of plant roots and soil has better mechanical properties than soil alone. The soil-fixing capacity of plant roots is mainly measured by the shear strength value of the soil containing the roots, which is generally obtained through shear tests. The shearing methods mainly include direct shear tests, triaxial tests, and in-situ shear tests in the field.

[0003] Direct shear tests offer good repeatability and are easy to operate; however, existing direct shear testing apparatuses typically have small shear boxes, and some tests utilize fibers instead of roots, which does not accurately reflect the interaction between roots and soil. Triaxial testing apparatuses suffer from cumbersome and time-consuming operation, and improper application of confining pressure. In-situ field shear tests require precise control of site selection, soil moisture content, and other conditions. Therefore, existing testing methods cannot adequately measure the shear strength of root-containing soils. A large-scale indoor direct shear testing device is needed to measure the shear strength of root-containing soils. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a device and method for measuring the shear strength of root-containing soil. The device reflects the interaction between roots and soil through shear experiments in the upper and lower boxes. The design is simple and easy to operate, and it can take into account different working conditions such as underwater root-containing soil, saturated drainage, and natural root-containing soil, thus meeting the indoor experimental needs of root and rhizomatous plants.

[0005] The technical solution of the present invention is as follows: a device for determining the shear strength of soil containing roots, comprising a sample module, a loading module, and a measurement module. The sample module includes a sample box and a shear box. The sample box is located in the middle of the shear box. The sample box has a segmented structure, including an upper box and a lower box. The upper box has a top plate. A limiting block is provided in the gap between the lower box and the shear box. The loading module includes a normal pressure actuator and a horizontal pressure actuator. The normal pressure actuator is located above the top plate. The output end of the normal pressure actuator is connected to a normal driving rod. The lower end of the normal driving rod is fixedly connected to the top plate. The horizontal pressure actuator is located on the side of the shear box. The output end of the horizontal pressure actuator is connected to a horizontal driving rod. The end of the horizontal driving rod is fixedly connected to the outside of the shear box. The measurement module includes a normal displacement sensor, a horizontal displacement sensor, and a tension meter. The normal displacement sensor is located above the top plate. The horizontal displacement sensor is located on the side of the shear box near the fixed column. The tension meter is located directly above the shear surface between the upper and lower boxes.

[0006] The top side of the upper box is provided with a connecting plate, a fixing rod is connected to the connecting plate, and a fixing post is connected to the end of the fixing rod.

[0007] The bottom of the shear box is equipped with multiple rollers.

[0008] The bottom of the lower box is provided with a water outlet hole, and the bottom of the shear box is provided with a drain hole.

[0009] The bottom side of the upper box and the top side of the lower box are respectively provided with limiting holes, and fastening bolts are provided in the limiting holes.

[0010] The outer side of the sample box is a steel plate, and the inner surface of the steel plate is provided with a synthetic wood board, the surface of which is provided with an anti-stick coating.

[0011] The sample box has internal dimensions of 500mm*500mm and a depth of 400mm, while the shear box has internal dimensions of 700mm*700mm.

[0012] A flexible membrane is provided between the top plate and the root-containing soil sample in the upper box. The flexible membrane is made of PVC cloth or HDPE cloth and has a thickness of 2mm.

[0013] A method for determining the shear strength of root-containing soil, using the root-containing soil shear strength determination device as described above, includes the following steps:

[0014] S1: Soil preparation, the specific process is as follows: take soil from the field area of ​​the test target, remove boulders and other debris, dry it and backfill it into the sample box. The backfilling of the upper and lower boxes of the sample box is carried out in layers, and the layers are roughened to ensure good connection between the layers. Place the sample box in an open area.

[0015] S2: Transplanting plants. The specific process is as follows: Based on the characteristics of the plants, select seedlings and insert them into the soil of the sample box. Place the sample box in an open area and water it regularly and in measured amounts.

[0016] S3: Conduct a shearing experiment, the specific process is as follows:

[0017] 1. Underwater soil failure test: After the plant above the sample box was cut and leveled, it was placed in the shearing box. The water outlet of the sample box was opened and the drainage hole of the shearing box was closed. The outer wall of the upper box was fixed to the fixed column by the fixing rod. The shearing box was filled with water and left to stand for 24 hours. Then, the normal pressure actuator was started to apply vertical pressure. When the vertical displacement stabilized and no longer increased, the horizontal pressure actuator was started to perform horizontal shearing. The shearing box was kept full of water throughout the shearing process and the shearing surface was below the water level. During the experiment, the normal pressure actuator was set with three normal stresses of 5 kPa, 10 kPa and 15 kPa respectively. The horizontal pressure actuator drove the horizontal drive rod to drive the shearing box to start shearing at a constant displacement rate of 0.2 mm / min. The measurement module recorded the corresponding data, so as to obtain the mechanical property parameters of the soil containing roots under the underwater soil failure condition.

[0018] 2. Saturated Drainage Test: After leveling the plant material at the top of the sample box, place it inside the shearing box. Open the water outlet of the sample box and close the drain hole of the shearing box. Fix the outer wall of the upper box to the fixing column using fixing rods. Fill the shearing box with water and let it stand for 24 hours. Then open the drain hole of the shearing box and start the normal pressure actuator to apply vertical pressure. When the vertical displacement stabilizes and no longer increases, start the horizontal pressure actuator to perform horizontal shearing at a saturated density of 25 kN / m³. 3 In the calculation and experiment, the normal pressure actuator was set with three normal stresses: 15 kPa, 30 kPa and 50 kPa. The horizontal pressure actuator drove the horizontal drive rod to drive the shear box to start shearing at a constant displacement rate of 0.2 mm / min. The measurement module recorded the corresponding data, thereby obtaining the mechanical property parameters of the soil containing roots under saturated drainage conditions.

[0019] The technical advantages of this invention are as follows: 1. This invention reflects the interaction between roots and soil through shearing experiments in the upper and lower boxes. The design is simple and easy to operate; 2. This invention, through nested shearing boxes and sample boxes, can consider different working conditions such as underwater soil containing roots, saturated soil containing roots at specific moisture contents, etc., and can meet the indoor experimental needs of root and stem plants.

[0020] The following will provide further explanation in conjunction with the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of a device for measuring the shear strength of soil containing roots, according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram showing the positional relationship between the sample box and the shear box in an embodiment of the present invention.

[0023] Reference numerals: 1-Sample box, 2-Shear box, 3-Connecting plate, 4-Water outlet, 5-Limiting block, 6-Limiting hole, 7-Roller, 8-Fixing rod, 9-Fixing column, 10-Top plate, 11-Normal pressure actuator, 12-Horizontal pressure actuator, 13-Horizontal drive rod, 14-Normal displacement sensor, 15-Normal drive rod, 16-Horizontal displacement sensor, 17-Tensile gauge. Detailed Implementation Example 1

[0024] like Figure 1 , Figure 2 As shown, a device for determining the shear strength of soil containing roots includes a sample module, a loading module, and a measurement module. The sample module includes a sample box 1 and a shear box 2. The sample box 1 is located in the middle of the shear box 2. The sample box 1 has a segmented structure, including an upper box and a lower box. The upper box has a top plate 10, and a limiting block 5 is provided in the gap between the lower box and the shear box 2. The loading module includes a normal pressure actuator 11 and a horizontal pressure actuator 12. The normal pressure actuator 11 is located above the top plate 10, and the output end of the normal pressure actuator 11 is connected to a normal drive rod 15. The lower end of the normal drive rod 15 is fixedly connected to the top plate 10. The horizontal pressure actuator 12 is located on the side of the shear box 2. The output end of the horizontal pressure actuator 12 is connected to the horizontal drive rod 13. The end of the horizontal drive rod 13 is fixedly connected to the outside of the shear box 2. The measurement module includes a normal displacement sensor 14, a horizontal displacement sensor 16, and a tension meter 17. The normal displacement sensor 14 is located above the top plate 10. The horizontal displacement sensor 16 is located on the side of the shear box 2 near the fixed column 9. The tension meter 17 is located directly above the shearing surface between the upper and lower boxes.

[0025] In practical use, after the plant on the upper part of the sample box 1 is cut and leveled, it is placed in the shear box 2. Then, the normal pressure actuator 11 is activated to apply vertical pressure. When the vertical displacement stabilizes and no longer increases, the horizontal pressure actuator 12 is activated to perform horizontal shearing. The measurement module records the corresponding data, thereby obtaining the mechanical property parameters of the soil containing the root system. This invention reflects the interaction between the root system and the soil through the shearing experiment of the upper and lower boxes. It is simple in design and easy to operate. Example 2

[0026] Preferably, based on Embodiment 1, in this embodiment, a connecting plate 3 is provided on the top side of the upper box, a fixing rod 8 is connected to the connecting plate 3, and a fixing post 9 is connected to the end of the fixing rod 8.

[0027] In actual use, the upper box of the present invention is provided with a connecting plate 3 on the top side, and a fixing rod 8 is connected to the connecting plate 3. The fixing rod 8 is connected to a fixing column 9 at its end. During the shearing experiment, the horizontal pressure driver 12 pushes the lower box to move, and the fixing rod 8 fixes the upper box, thereby realizing the shearing process of the sample box 1. Example 3

[0028] Preferably, based on Embodiment 1 or Embodiment 2, in this embodiment, the bottom of the shearing box 2 is provided with multiple rollers 7.

[0029] In actual use, the shear box 2 of the present invention is provided with multiple rollers 7 at the bottom, which facilitates the horizontal pressure driver 12 to push the lower box to move. Example 4

[0030] Preferably, based on Embodiment 1 or Embodiment 3, in this embodiment, the bottom of the lower box is provided with a water outlet 4, and the bottom of the shearing box 2 is provided with a drainage hole.

[0031] In actual use, the bottom of the lower box of the present invention is provided with a water outlet 4, and the bottom of the shear box 2 is provided with a drainage hole, so as to realize the storage and drainage of the sample box 1. It is used for different working conditions such as underwater soil containing roots, saturated soil containing roots with specific moisture content, etc., and can meet the indoor experimental needs of root and stem plants. Example 5

[0032] Preferably, based on Embodiment 1 or Embodiment 4, in this embodiment, the bottom side of the upper box and the top side of the lower box are respectively provided with limiting holes 6, and fastening bolts are provided in the limiting holes 6.

[0033] In actual use, the upper box and the lower box are respectively provided with limiting holes 6 around the bottom side and the top side of the lower box. The limiting holes 6 are provided with fastening bolts for connecting and disassembling the upper box and the lower box. Example 6

[0034] Preferably, based on Example 1 or Example 5, in this example, the outer side of the sample box 1 is a steel plate, the inner surface of the steel plate is provided with a synthetic wood board, and the surface of the synthetic wood board is provided with an anti-stick coating.

[0035] In actual use, the surface of the synthetic wood board of the present invention is provided with an anti-stick coating, which facilitates the cleaning of soil in the sample box 1 after the test. Example 7

[0036] Preferably, based on Example 1 or Example 6, in this example, the internal dimensions of the sample box 1 are 500mm*500mm and the depth is 400mm, and the internal dimensions of the shear box 2 are 700mm*700mm.

[0037] In actual use, the sample box 1 of the present invention has an internal size of 500mm*500mm and a depth of 400mm, while the shear box 2 has an internal size of 700mm*700mm. The internal size of the shear box 2 is larger than that of the sample box 1. Through the nested shear box and sample box, different working conditions such as underwater soil containing roots, saturated soil containing roots with specific moisture content, etc. can be considered, which can meet the indoor experimental needs of root and stem plants. Example 8

[0038] Preferably, based on Embodiment 1 or Embodiment 7, in this embodiment, a flexible membrane is provided between the top plate 10 and the root-containing soil sample in the upper box. The flexible membrane is made of PVC cloth or HDPE cloth, and the thickness of the PVC cloth or HDPE cloth is 2mm.

[0039] In actual use, a flexible membrane is provided between the top plate 10 and the root-containing soil sample in the upper box to avoid uneven application of normal pressure due to root residues or uneven surface soil. Example 9

[0040] A method for determining the shear strength of root-containing soil, using the root-containing soil shear strength determination device as described above, includes the following steps:

[0041] S1: Soil preparation, the specific process is as follows: take soil from the field area of ​​the test target, remove boulders and other debris, dry it and backfill it into sample box 1. The backfilling of the upper and lower boxes of sample box 1 is carried out in layers, and the layers are roughened to ensure good connection between the layers. Place sample box 1 in an open area.

[0042] S2: Transplanting plants. The specific process is as follows: Based on the characteristics of the plants, select seedlings and insert them into the soil of sample box 1. Place sample box 1 in an open area and water it regularly and quantitatively.

[0043] S3: Conduct a shearing experiment, the specific process is as follows:

[0044] 1. Underwater soil failure test: After the plant on the upper part of the sample box 1 was cut and leveled, it was placed in the shearing box 2. The water outlet 4 of the sample box 1 was opened and the drainage hole of the shearing box 2 was closed. The outer wall of the upper box was fixed to the fixed column 9 by the fixing rod 8. The shearing box 2 was filled with water and left to stand for 24 hours. Then, the normal pressure actuator 11 was started to apply vertical pressure. When the vertical displacement stabilized and no longer increased, the horizontal pressure actuator 12 was started to perform horizontal shearing. Throughout the shearing process, the shearing box 2 was filled with water and the shearing surface was below the water level. During the experiment, the normal pressure actuator 11 was set with three normal stresses: 5 kPa, 10 kPa and 15 kPa. The horizontal pressure actuator 12 drove the horizontal drive rod 13 to drive the shearing box 2 to start shearing at a constant displacement rate of 0.2 mm / min. The measurement module recorded the corresponding data, thereby obtaining the mechanical property parameters of the soil containing roots under the underwater soil failure condition.

[0045] 2. Saturated Drainage Test: After leveling the plant material at the top of sample box 1, place it into shear box 2. Open the water outlet 4 of sample box 1 and close the drainage hole of shear box 2. Fix the outer wall of the upper box to the fixing column 9 using fixing rod 8. Fill shear box 2 with water and let it stand for 24 hours. Then open the drainage hole of shear box 2 and start the normal pressure actuator 11 to apply vertical pressure. When the vertical displacement stabilizes and no longer increases, start the horizontal pressure actuator 12 to perform horizontal shearing, based on a saturated density of 25 kN / m³. 3 During the calculation and experiment, the normal pressure actuator 11 was set with three normal stresses: 15 kPa, 30 kPa and 50 kPa. The horizontal pressure actuator 12 drove the horizontal drive rod 13 to drive the shear box 2 to start shearing at a constant displacement rate of 0.2 mm / min. The measurement module recorded the corresponding data, thereby obtaining the mechanical performance parameters of the soil containing roots under saturated drainage conditions.

[0046] 3. Natural Moisture Content Test: After trimming and leveling the upper part of the plant in sample box 1, place it into shear box 2. Open the water outlet 4 of sample box 1 and the drainage hole of shear box 2. Fix the outer wall of the upper box to the fixing column 9 using fixing rod 8. Start the normal pressure actuator 11 to apply vertical pressure. When the vertical displacement stabilizes and no longer increases, start the horizontal pressure actuator 12 to perform horizontal shearing, based on a natural density of 17 kN / m³. 3 In the calculation and experiment, the normal pressure actuator was set with three normal stresses: 10 kPa, 20 kPa and 30 kPa. The horizontal pressure actuator 12 drove the horizontal drive rod 13 to drive the shear box to start shearing at a constant displacement rate of 0.2 mm / min. The measurement module recorded the corresponding data, thereby obtaining the mechanical property parameters of the soil containing roots under the natural moisture content condition.

[0047] In step S1, the soil preparation involves placing the soil in sample box 1 for 1 year or 0.5 years.

[0048] In step S2, 8-week-old seedlings can be selected and inserted into the sample box.

[0049] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A device for measuring the shear strength of soil containing roots, characterized in that: The system includes a sample module, a loading module, and a measurement module. The sample module includes a sample box (1) and a shear box (2). The sample box (1) is located in the middle of the shear box (2). The sample box (1) has a segmented structure, including an upper box and a lower box. The upper box has a top plate (10) on top, and a limiting block (5) is provided in the gap between the lower box and the shear box (2). The loading module includes a normal pressure actuator (11) and a horizontal pressure actuator (12). The normal pressure actuator (11) is located above the top plate (10). The output end of the normal pressure actuator (11) is connected to a normal driving rod (15). The lower end of the normal driving rod (15) is fixedly connected to the top plate (10). The horizontal pressure actuator (12) is located on the side of the shear box (2). The output end of the horizontal pressure actuator (12) is connected to a horizontal driving rod (13). The end of the horizontal drive rod (13) is fixedly connected to the outside of the shear box (2). The measuring module includes a normal displacement sensor (14), a horizontal displacement sensor (16), and a tension meter (17). The normal displacement sensor (14) is located above the top plate (10). The horizontal displacement sensor (16) is located on the side of the shear box (2) near the fixed column (9). The tension meter (17) is located directly above the shearing surface between the upper box and the lower box. The top side of the upper box is provided with a connecting plate (3). A fixed rod (8) is connected to the connecting plate (3). The end of the fixed rod (8) is connected to the fixed column (9). The bottom of the lower box is provided with a water outlet (4). The bottom of the shear box (2) is provided with a drainage hole. The bottom side of the upper box and the top side of the lower box are respectively provided with limiting holes (6). The limiting holes (6) are provided with fastening bolts.

2. The device for determining the shear strength of soil containing roots according to claim 1, characterized in that: The bottom of the shear box (2) is provided with multiple rollers (7).

3. The device for measuring the shear strength of soil containing roots according to claim 1, characterized in that: The outer side of the sample box (1) is a steel plate, and the inner surface of the steel plate is provided with a synthetic wood board, and the surface of the synthetic wood board is provided with an anti-stick coating.

4. The device for determining the shear strength of soil containing roots according to claim 1, characterized in that: The sample box (1) has an internal size of 500mm*500mm and a depth of 400mm, and the shear box (2) has an internal size of 700mm*700mm.

5. The device for determining the shear strength of soil containing roots according to claim 1, characterized in that: A flexible membrane is provided between the top plate (10) and the root-containing soil sample in the upper box. The flexible membrane is made of PVC cloth or HDPE cloth and the thickness of the PVC cloth or HDPE cloth is 2mm.

6. A method for determining the shear strength of root-containing soil, using the shear strength determination device for root-containing soil as described in any one of claims 1 to 5, characterized in that: Includes the following steps: S1: Soil preparation, the specific process is as follows: take soil from the field area of ​​the test target, remove boulders and other debris, dry it and backfill it into the sample box (1). The backfilling of the upper and lower boxes of the sample box (1) is carried out in layers. The layers are roughened to ensure good connection between the layers. Place the sample box (1) in an open area. S2: Transplanting plants, the specific process is as follows: according to the characteristics of the plants, select seedlings and insert them into the soil of the sample box (1), place the sample box (1) in an open area, and water them regularly and quantitatively. S3: Conduct a shearing experiment, the specific process is as follows:

1. Underwater soil failure test: After the upper part of the plant in the sample box (1) is cut and leveled, it is placed in the shear box (2). The water outlet (4) of the sample box (1) is opened and the drainage hole of the shear box (2) is closed. The outer wall of the upper box is fixed to the fixed column (9) by the fixing rod (8). The shear box (2) is filled with water and left to stand for 24 hours. Then the normal pressure actuator (11) is started to apply vertical pressure. When the vertical displacement is stable and no longer increases, the horizontal pressure actuator (12) is started to perform horizontal shearing. The shear box (2) is always filled with water throughout the shearing process. The shearing surface is below the water level. During the experiment, the normal pressure actuator (11) is set with three normal stresses, 5 kPa, 10 kPa and 15 kPa respectively. The horizontal pressure actuator (12) drives the horizontal drive rod (13) to drive the shear box (2) to start shearing at a constant displacement rate of 0.2 mm / min. The measurement module records the corresponding data, so as to obtain the mechanical performance parameters of the soil containing roots under the underwater soil failure condition.

2. Saturated drainage test: After cutting and leveling the plant on the upper part of the sample box (1), place it into the shear box (2), open the water outlet (4) of the sample box (1), close the drainage hole of the shear box (2), fix the outer wall of the upper box to the fixed column (9) through the fixing rod (8), fill the shear box (2) with water, let it stand for 24 hours, then open the drainage hole of the shear box (2), start the normal pressure actuator (11) to apply vertical pressure, when the vertical displacement stabilizes and no longer increases, start the horizontal pressure actuator (12) to perform horizontal shearing, according to the saturated unit weight of 25kN / m 3 During the experiment, the normal pressure actuator (11) was set with three normal stresses: 15 kPa, 30 kPa and 50 kPa. The horizontal pressure actuator (12) drove the horizontal drive rod (13) to drive the shear box (2) to start shearing at a constant displacement rate of 0.2 mm / min. The measurement module recorded the corresponding data, thereby obtaining the mechanical performance parameters of the root-containing soil under saturated drainage conditions.

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