A shear box mechanism, soil shear strength testing device and method

Abstract

This invention provides a shear box mechanism, a root-soil shear strength testing device and method, belonging to the field of shear strength testing technology. It includes: an upper shear box, a lower shear box, and a top cover; the upper shear box contains an upper volute limiting ring, an upper pressurized airbag, a first steel coil, and a first fixing steel ring, with the upper pressurized airbag located between the upper volute limiting ring and the first steel coil, and the first fixing steel ring inserted between the first steel coil and the upper pressurized airbag; the lower shear box contains a lower volute limiting ring, a lower pressurized airbag, a second steel coil, and a second fixing steel ring, with the lower pressurized airbag located between the lower volute limiting ring and the second steel coil, and the second fixing steel ring inserted between the second steel coil and the lower pressurized airbag; this device realistically simulates the temperature and stress environment of the root-soil composite, thereby measuring the shear strength of the root-soil composite that conforms to actual conditions, and accurately measuring the cross-sectional area of ​​the root-soil composite after consolidation.

Description

Technical Field

[0001] This invention belongs to the field of shear strength testing technology, specifically relating to a shear box mechanism, a root soil shear strength testing device and method. Background Technology

[0002] In the remediation scheme system proposed by the International Working Group on Landslides in Geosciences, the use of plant root systems to reinforce slopes has been recommended as one of the means of strengthening the internal structure of slopes, and is an important slope reinforcement method. A key indicator for measuring the effectiveness of plant root systems in soil stabilization and slope protection is the shear strength of the root-soil composite, which is crucial for understanding the effect of plant roots on soil strength enhancement. Currently, there are many achievements in root-based slope protection both domestically and internationally, but research lacks consideration of the effects of confining pressure and freezing on root-soil composites. Furthermore, in cold and arid regions, root-soil composites on slopes inevitably bear confining pressure and experience sub-zero temperatures. When the root-soil composite consolidates under confining pressure, its axial force changes, causing the surface soil of the root-soil composite to bulge or loosen, making the slope soil more prone to sliding under thrust, thus easily triggering geological disasters such as landslides, collapses, and debris flows.

[0003] Current testing devices for determining the shear strength of root-soil composites all involve consolidation of the composite under axial force. These devices cannot accurately measure the cross-sectional area of ​​the consolidated composite, cannot simulate the actual soil confining pressure, and can only be used at room temperature. Therefore, there is a lack of testing devices that can accurately measure the cross-sectional area of ​​the consolidated root-soil composite and determine its shear strength under actual soil confining pressure in a sub-zero temperature environment. Summary of the Invention

[0004] To address the aforementioned technical issues, this invention provides a shear box mechanism, a root-soil shear strength testing device and method. This device realistically simulates the temperature and stress environment of the root-soil composite, thereby measuring the shear strength of the root-soil composite that conforms to actual conditions, and accurately measuring the cross-sectional area of ​​the root-soil composite after consolidation.

[0005] The specific technical solution is as follows:

[0006] A shearing box mechanism includes: an upper shearing box, a lower shearing box, and a top cover; the upper shearing box contains an upper volute limiting ring, an upper pressurizing airbag, a first steel coil, and a first fixing steel ring, the upper pressurizing airbag being located between the upper volute limiting ring and the first steel coil, and the first fixing steel ring being inserted between the first steel coil and the upper pressurizing airbag; the lower shearing box contains a lower volute limiting ring, a lower pressurizing airbag, a second steel coil, and a second fixing steel ring, the lower pressurizing airbag being located between the lower volute limiting ring and the second steel coil, and the second fixing steel ring being inserted between the second steel coil and the lower pressurizing airbag; the top cover is a transparent plexiglass plate with dimensional scale lines, the top cover is installed on the top of the upper shearing box by two first fixing pins, and a limiting groove is provided at the center of the top cover.

[0007] In addition, the shear box mechanism in the above-mentioned technical solution provided by the present invention may also have the following additional technical features:

[0008] The above technical solution also includes: a first thrust plate and a second thrust plate; the first thrust plate is fixed on the right side of the upper shear box, and the right side of the first thrust plate is provided with a first groove; the second thrust plate is fixed on the left side of the lower shear box, and the left side of the second thrust plate is provided with a second groove.

[0009] A root soil shear strength testing device under confining pressure includes: the shear box mechanism of claim 2, a temperature control system, a gas supply system, a loading system, a data acquisition and control system, and an assembly mechanism; the temperature control system includes a constant temperature chamber and a constant temperature bath, the shear box mechanism is disposed inside the constant temperature chamber, and the constant temperature bath is located on one side of the constant temperature chamber; the gas supply system includes a supply cylinder and a gas supply station, the supply cylinder passes through the constant temperature bath via a third gas transmission pipe and is connected to the gas supply station, and the gas supply station is connected to the upper pressure airbag and the lower pressure airbag respectively via a first gas transmission pipe and a second gas transmission pipe; the loading system is disposed on the constant temperature chamber, and the loading system is respectively opposite to the first groove of the first thrust plate and the second groove of the second thrust plate; the data acquisition and control system includes a sensor group, a data acquisition box, and a workstation, and the data acquisition box is used to acquire data monitored by the sensor group; the assembly mechanism is disposed inside the constant temperature chamber and is connected to the shear box mechanism.

[0010] In addition, the root soil shear strength testing device under confining pressure provided by the present invention may also have the following additional technical features:

[0011] In the above technical solution, the assembly mechanism includes: a base plate, a shear box support column, and a slide assembly; the base plate is located at the bottom of the lower shear box; the shear box support column is located on the bottom surface of the base plate; the slide assembly includes an upper slide, a lower slide, and pressure rollers, the upper slide is connected to the bottom of the shear box support column, the lower slide is fixed in the constant temperature chamber, and both the upper slide and the lower slide are provided with concave rails that allow the pressure rollers to roll.

[0012] In the above technical solution, the loading system includes: an axial pressure loading device, a lateral load loading device, and a lateral stop bar; the axial pressure loading device passes through the top center of the constant temperature chamber and is in contact with the top cover; the lateral load loading device passes through one side of the constant temperature chamber, and the top of the force transmission rod at the right end of the lateral load loading device is opposite to the second groove; the lateral stop bar passes through the other side of the constant temperature chamber and is opposite to the first groove.

[0013] The above technical solution also includes: a frame; the frame includes a support beam, two pillars and a test platform cabinet, the two pillars are fixed on both sides of the test platform cabinet respectively, the support beam is located above the test platform cabinet, and the constant temperature chamber is set on the test platform cabinet, and the constant temperature chamber is located between the two pillars and the support beam.

[0014] The above technical solution also includes: a pressure-bearing mandrel; the pressure-bearing mandrel is connected to the bottom of the axial pressure measuring and loading device, the bottom diameter of the pressure-bearing mandrel is smaller than the cross-sectional diameter of the limiting groove, and the pressure-bearing mandrel is opposite to the limiting groove.

[0015] In the above technical solution, the transverse stop is a threaded screw, and a handwheel is provided at the right end of the transverse stop.

[0016] In the above technical solution, the contact points between the axial pressure loading device, the transverse load loading device, and the transverse stop bar and the constant temperature chamber are all sealed and heat-insulated by a sealed piston sleeve.

[0017] The above technical solution includes the following steps in its application:

[0018] S1: Sample loading, open the door of the constant temperature chamber, remove the upper shear box, use vernier calipers to measure the inner diameter D0 of the bottom surface of the upper volute limiting ring and the top surface of the lower volute limiting ring, apply a thin layer of Vaseline to the inner wall of the first steel coil and the inner wall of the second steel coil, adjust the second steel coil to be in the middle of the lower shear box, then fill the second steel coil with the pre-prepared root-soil composite with a cross-sectional diameter of 10.0cm and a height equal to the sum of the heights of the first and second steel coils, and adjust the first steel coil to be in the middle of the upper shear box. Slowly lower the upper shear box from the top of the root-soil composite until it is placed on the lower shear box, insert the two second fixing pins from the top cover of the upper shear box into the lower shear box and tighten them to temporarily fix the upper shear box on the lower shear box;

[0019] S2: Start the data acquisition and control system, start collecting temperature and shear displacement information of the root-soil composite, collect axial pressure and lateral thrust information generated after the root-soil composite is consolidated under confining pressure, collect upper and lower limit positions of the axial pressure measuring and loading device and front and rear limit positions of the lateral load loading device, and collect loading and unloading information of the axial pressure measuring and loading device and the lateral load loading device.

[0020] S3: Determine the position of the shear box mechanism, push the lower shear box so that the limiting groove on the top cover is just below the pressure head, manually operate the handwheel so that the protruding part on the left end of the transverse stop bar is just in contact with the first groove, thereby fixing the upper shear box laterally, start the loading system, and set the working parameters of the axial servo control console through the workstation to control the axial pressure loading device to move slowly downward at a constant rate until the bottom surface of the pressure head is in no pressure contact with the bottom surface of the limiting groove of the top cover. Set the working parameters of the transverse servo control console through the workstation to control the transverse load loading device to move slowly to the right at a constant rate until the top end of the force transmission rod of the transverse load loading device is in no pressure contact with the second groove. Rotate and pull out the two second fixing pins from the top cover, upper shear box and lower shear box, and close the door of the constant temperature chamber.

[0021] S4: Turn on the gas supply system and consolidate the root-soil composite according to the test confining pressure to be simulated in the design. Adjust the gas supply pressure of the gas supply station through the first precision regulating valve, the second precision regulating valve and the third precision regulating valve until the pressure value in the first gas transmission pipe displayed by the pressure gauge on the first precision regulating valve and the pressure value in the second gas transmission pipe displayed by the pressure gauge on the second precision regulating valve both reach the set value and stabilize. That is, the gas pressure values ​​in the upper and lower pressurized air bladders both reach the design value and stabilize. Observe and record the stable axial pressure F1 displayed by the workstation. F1 is the axial load generated by the root-soil composite after consolidation under the confining pressure.

[0022] S5: Turn on the temperature control system. According to the negative temperature environment to be simulated, set the working temperature of the constant temperature chamber to be consistent with the design temperature through the first control panel arranged on the constant temperature chamber. Wait for the temperature of the root soil composite displayed on the workstation to reach the set value and stabilize. At this time, the root soil composite is in a frozen state. Set the working temperature of the constant temperature bath to be consistent with the design temperature through the second control panel arranged on the constant temperature bath. Wait for the constant temperature bath to reach the design temperature and stabilize. During this process, the first precision regulating valve and the second precision regulating valve will adjust in real time and maintain the gas pressure in the upper and lower pressurizing air bags to the design value. The temperature control system is always in working state in the following steps.

[0023] S6: Select a suitable fixing steel ring, open the door of the constant temperature chamber, measure the cross-sectional diameter D1 of the root-soil composite after consolidation under confining pressure through the size scale line on the top cover, calculate the cross-sectional area A1 of the root-soil composite after consolidation, input and store A1 in the data processing software of the workstation, and calculate the required inner diameter of the fixing steel ring based on the fact that the difference between the initial cross-sectional diameter 10.0cm of the root-soil composite and the cross-sectional diameter D1 after consolidation is equal to the difference between the outer diameter and inner diameter of the required fixing steel ring, and select a set of fixing steel rings that meet the requirements.

[0024] S7: Install the second fixing steel ring for the lower shear box. Set the working parameters of the axial servo control console via the workstation to control the axial pressure loading device to slowly move upwards at a constant rate for an appropriate distance, making it easier to remove the upper shear box from the top of the root-soil composite. Adjust the first precision regulating valve to stop the gas supply station from supplying gas to the upper pressurized airbag, releasing the pressure around the root-soil composite in the upper shear box. Slowly remove the upper shear box while ensuring the root-soil composite is not damaged, and take any one of the fixing steel rings selected in S6. The second fixing steel ring is inserted between the lower volute limiting ring and the second steel coil along the outer side wall of the second steel coil. The insertion process of the second fixing steel ring is as follows: first, insert a part of it. When the second fixing steel ring contacts the lower pressurization airbag, adjust the second precision regulating valve to stop the gas supply station from supplying gas to the lower pressurization airbag, that is, release the air pressure in the lower pressurization airbag. Then, insert the remaining part of the second fixing steel ring between the lower volute limiting ring and the second steel coil. Finally, the bottom surface of the second fixing steel ring contacts the bottom plate and the top surface is flush with the top surface of the second steel coil.

[0025] S8: Install the first fixing steel ring for the upper shear box. Rotate and pull out the two first fixing pins from the top cover and the upper shear box. Remove the top cover. Adjust the first steel coil to position it in the middle of the upper shear box. Slowly lower the remaining upper shear box from the top of the root-soil composite until it is placed on the lower shear box. Adjust the first precision regulating valve to supply gas to the upper pressurized airbag from the gas supply station until the gas pressure value in the upper pressurized airbag displayed on the pressure gauge of the first precision regulating valve reaches the design value and stabilizes. Take the remaining one of the fixing steel rings selected in S6 as the first fixing steel ring. Insert the first fixing steel ring along the outer side wall of the first steel coil between the upper volute limiting ring and the first steel coil. The insertion process of the first fixing steel ring is as follows: first insert a part of it, when... When the first fixing steel ring contacts the upper pressurized airbag, the first precision regulating valve is adjusted to stop the gas supply station from supplying air to the upper pressurized airbag, thus releasing the air pressure inside the upper pressurized airbag. Then, the remaining part of the first fixing steel ring is inserted between the upper volute limiting ring and the first steel coil, so that the bottom surface of the first fixing steel ring is flush with the bottom surface of the first steel coil and the top surface is flush with the top surface of the first steel coil. At this time, the confining pressure on the root-soil composite is provided by the first fixing steel ring, the second fixing steel ring, the first steel coil and the second steel coil. The top cover is placed on the upper shear box, so that the four holes on the top cover are aligned with the four holes on the upper shear box. Two first fixing pins are inserted into the upper shear box through the two diagonal holes of the top cover and tightened, thereby fixing the top cover to the upper shear box.

[0026] S9: Set the working parameters of the axial servo control console through the workstation, control the axial pressure measuring and loading device to move slowly downward at a constant rate until the workstation displays that the axial pressure applied by the axial pressure measuring and loading device to the root-soil composite is stable at F1, then stop loading, close the door of the constant temperature chamber, and wait for the temperature of the root-soil composite displayed by the workstation to reach the design value and stabilize.

[0027] S10: The shear test begins. The working parameters of the lateral servo control console are set through the workstation, so that the shear box moves to the right at a constant rate under the push of the lateral load loading device. The data acquisition box and the workstation acquire and store the lateral thrust and shear displacement information of the root-soil composite in real time. The data processing software of the workstation calculates, analyzes and images the acquired data. The workstation plots the relationship curve between shear stress (kPa) and shear strain (%). Finally, the shear strength of the root-soil composite under confining pressure in a negative temperature environment is obtained based on the relationship curve between shear stress (kPa) and shear strain (%).

[0028] The shear box mechanism, root soil shear strength testing device and method of the present invention have the following advantages compared with the prior art:

[0029] 1. The upper and lower pressurized airbags expand inward through the air supply system, causing the first and second steel coils to rotate and contract, applying force to the root-soil composite. This allows the root-soil composite to bear uniform confining pressure, thus simulating the actual stress state of the root-soil composite in a soil confining pressure environment. By combining the axial pressure measuring and loading equipment with the top cover, the axial pressure F1 generated by the root-soil composite after consolidation under confining pressure is measured. Furthermore, the cross-sectional diameter of the root-soil composite after consolidation under confining pressure is accurately measured using the dimensional scale lines on the top cover.

[0030] 2. By replacing the gas supply system with a fixed steel ring to apply the design confining pressure to the root-soil composite, the fixed steel ring transmits the lateral thrust during the shear test of the root-soil composite, making the shear resistance of the root-soil composite that the device can measure greater than the designed confining pressure, thereby expanding the range of root-soil composites that the device can test.

[0031] 3. The temperature control system provides a negative temperature environment for the shear test of the root-soil composite. At the same time, the constant temperature chamber serves as the thermal insulation boundary between the shear box mechanism and the test environment, reducing the influence of the test environment temperature on the test data. In addition, the constant temperature bath provides the design temperature for the supplied gas, which makes it easier for the root-soil composite to maintain the test design temperature.

[0032] 4. By combining the gas supply system, temperature control system, fixed steel ring and loading system, the temperature and stress environment of the root-soil composite were realistically simulated, thereby measuring the shear strength of the root-soil composite that conforms to the actual situation. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the shear box mechanism of the present invention;

[0034] Figure 2 This is a cross-sectional view of the upper shear box of the present invention;

[0035] Figure 3 This is a cross-sectional view of the lower shear box of the present invention;

[0036] Figure 4 This is a schematic diagram of the upper shear box of the present invention;

[0037] Figure 5 This is a schematic diagram of the lower shear box of the present invention;

[0038] Figure 6 This is a schematic diagram of the structure of the first fixing steel ring of the present invention;

[0039] in, Figures 1 to 6 The correspondence between the reference numerals and component names in the attached drawings is as follows:

[0040] 1 Upper shear box, 2 Upper volute limiting ring, 3 Upper pressurizing airbag, 4 First steel coil, 5 Top cover, 6 First thrust plate, 6-1 First groove, 7 First gas transmission pipe, 8 Lower shear box, 9 Lower volute limiting ring, 10 Lower pressurizing airbag, 11 Second steel coil, 12 Second thrust plate, 12-1 Second groove, 13 Second gas transmission pipe, 14 Base plate, 15 Temperature sensor, 16 Root-soil composite, 17 Shear box support column, 18 Upper slide rail, 19 First precision regulating valve, 20 Second precision regulating valve, 21 First fixing pin, 22 Second fixing pin, 23 First fixing steel ring. Detailed Implementation

[0041] The following are specific implementation cases and appendices. Figure 1-6 The present invention will be further described, but the present invention is not limited to these embodiments.

[0042] A shear box mechanism, such as Figure 1-6 As shown, the shearing box includes: an upper shearing box 1, a lower shearing box 8, and a top cover 5. The upper shearing box 1 is provided with an upper volute limiting ring 2, an upper pressurizing airbag 3, a first steel coil 4, and a first fixing steel ring 23. The upper pressurizing airbag 3 is located between the upper volute limiting ring 2 and the first steel coil 4, and the first fixing steel ring 23 is inserted between the first steel coil 4 and the upper pressurizing airbag 3. The lower shearing box 8 is provided with a lower volute limiting ring 9, a lower pressurizing airbag 10, a second steel coil 11, and a second fixing steel ring. The lower pressurizing airbag 10 is located between the lower volute limiting ring 9 and the second steel coil 11, and the second fixing steel ring is inserted between the second steel coil 11 and the lower pressurizing airbag 10. The top cover 5 is a transparent organic glass plate with size scale lines. The top cover 5 is installed on the top of the upper shearing box 1 by two first fixing pins 21, and a limiting groove is provided at the center of the top cover 5.

[0043] By filling the root-soil composite 16 into the first steel coil 4 and the second steel coil 11, and controlling the upper pressure airbag 3 and the lower pressure airbag 10 to expand inward, the first steel coil 4 and the second steel coil 11 rotate and contract to apply force to the root-soil composite 16, so that the root-soil composite 16 bears uniform confining pressure, thereby simulating the real stress state of the root-soil composite 16 in the soil confining pressure environment. When the airbag is pressurized and then the first fixed steel ring 23 and the second fixed steel ring are added, when the applied lateral thrust is greater than the pressure inside the airbag, since the upper pressurized airbag 3 and the lower pressurized airbag 10 are filled with gas, the lateral thrust cannot be transmitted to the first steel coil 4 and the second steel coil 11 through the airbag, and therefore cannot be applied to the root-soil composite 16. Therefore, the first fixed steel ring 23 and the second fixed steel ring are used to replace the airbag to apply confining pressure to the root-soil composite 16, thereby realizing that the lateral thrust can be transmitted to the first steel coil 4 and the second steel coil 11 through the first fixed steel ring 23 and the second fixed steel ring, and thus the force can be applied to the root-soil composite 16, expanding the range of testable shear strength of the root-soil composite 16.

[0044] Specifically, the size scale line of the top cover 5 is 7.0~10.0cm, and the size scale line of the top cover 5 is a concentric circle with a diameter difference of 1mm.

[0045] Specifically, the upper shear box 1, the upper volute limiting ring 2, the lower shear box 8, the lower volute limiting ring 9, and the base plate 14 are all made of stainless steel. The upper volute limiting ring 2 and the lower volute limiting ring 9 are the same size and shape. The inner diameter of the upper top surface or the lower bottom surface of the upper volute limiting ring 2 and the lower volute limiting ring 9 is D0. The upper shear box 1 is a cuboid frame with openings at both the upper and lower ends. The lower shear box 8 is a cuboid box with an opening at the upper end and sealed at the lower end by the base plate 14. The upper shear box 1 and the lower shear box 8 have the same cross-sectional area and height.

[0046] Specifically, the upper pressurized airbag 3 and the lower pressurized airbag 10 are respectively bonded and fixed inside the upper volute limiting ring 2 and the lower volute limiting ring 9 with strong sealant, thereby limiting the upper pressurized airbag 3 and the lower pressurized airbag 10 by the upper volute limiting ring 2 and the lower volute limiting ring 9 respectively, preventing them from expanding outward during inflation.

[0047] Specifically, the upper pressure airbag 3 and the lower pressure airbag 10 are identical in size and shape, and both are made of butyl rubber. The first steel coil 4 and the second steel coil 11 are identical in size and shape, and both are made of highly resilient stainless steel. The cross-section between the inner walls of the first steel coil 4 and the second steel coil 11 is a circle with a diameter of 10.0 cm. The height of the first steel coil 4 is the same as the height of the upper shear box 1, and the height of the second steel coil 11 is the same as the height of the lower shear box 8. The inner ends of the first steel coil 4 and the second steel coil 11 are bladed to reduce friction with the root-soil composite 16. In the initial state or when the upper pressure airbag 3 is inflated, the outer side of the first steel coil 4... The inner wall of the upper pressure airbag 3 is always in contact with the outer wall of the first steel coil 4, and the outer wall of the lower pressure airbag 10 is coated with lubricating oil. In the initial state or when the lower pressure airbag 10 is inflated, the outer wall of the second steel coil 11 is always in contact with the inner wall of the lower pressure airbag 10, and the outer wall of the second steel coil 11 is coated with lubricating oil. The inner steel coils of the first steel coil 4 and the second steel coil 11 are in close contact, and lubricating oil is added between the inner steel coils of the first steel coil 4 and the second steel coil 11. When the upper pressure airbag 3 and the lower pressure airbag 10 are inflated, they expand inward, squeezing the first steel coil 4 and the second steel coil 11 to rotate and contract, thereby applying confining pressure to the root-soil composite 16.

[0048] Specifically, to simulate the shear failure of the frozen root-soil composite 16 under high confining pressure, a gas with a low critical temperature and a high critical pressure is required to supply the device. Therefore, safe N2 gas is selected to provide the confining pressure conditions required by the root-soil composite 16. That is, both the upper pressurization bladder 3 and the lower pressurization bladder 10 are N2 pressurization bladders, and the gas supply station supplies N2. To prevent N2 gas liquefaction, the maximum confining pressure provided by the gas supply system to the root-soil composite 16 is 3 MPa.

[0049] It should be understood that the present invention does not limit the gas used to provide the test confining pressure, and can determine it according to actual conditions.

[0050] Specifically, multiple sets of pre-prepared fixing steel rings with a 1mm inner diameter difference are used. Each set contains two identical fixing steel rings. The height of these multiple sets of fixing steel rings is consistent with the height of the first steel coil 4 or the second steel coil 11. The outer diameter of each set is the same as the inner diameter D0 of the top surface of the upper volute limiting ring 2 or the lower volute limiting ring 9. The fixing steel rings are installed between the upper volute limiting ring 2 and the first steel coil 4 and between the lower volute limiting ring 9 and the second steel coil 11 when the confining pressure provided by the air supply system to the root-soil composite 16 reaches the experimental design confining pressure and stabilizes. They are used to fix the first steel coil 4 and the second steel coil 11 and transmit lateral thrust.

[0051] In embodiments of the present invention, such as Figure 1-6As shown, it also includes: a first thrust plate 6 and a second thrust plate 12; the first thrust plate 6 is fixed on the right side of the upper shear box 1, and the right side of the first thrust plate 6 is provided with a first groove 6-1; the second thrust plate 12 is fixed on the left side of the lower shear box 8, and the left side of the second thrust plate 12 is provided with a second groove 12-1.

[0052] By setting the first thrust plate 6 and the second thrust plate 12, it is possible to apply lateral thrust to the upper shear box 1 and the lower shear box 8 in the future.

[0053] Specifically, the first groove 6-1 is used to ensure that the force applied by the transverse stop to the upper shear box 1 is located on the central axis of the upper shear box 1, and to ensure that the transverse stop does not restrict the transmission of axial pressure generated by the upper shear box 1 to the root-soil composite 16 when it is consolidated under confining pressure. Lubricating oil is applied to the first groove 6-1 to reduce the friction between the transverse stop and the first groove 6-1, so that the axial pressure measured by the axial pressure sensor is more accurate.

[0054] Specifically, the second groove 12-1 is used to allow the force applied by the lateral load loading device to the lower shear box 8 to pass through the center of the lower shear box 8.

[0055] A device for testing the shear strength of root soil under confining pressure, such as Figure 1-6 As shown, the system includes: the shear box mechanism of claim 2, a temperature control system, a gas supply system, a loading system, a data acquisition and control system, and an assembly mechanism; the temperature control system includes a constant temperature chamber and a constant temperature bath, the shear box mechanism is disposed inside the constant temperature chamber, and the constant temperature bath is located on one side of the constant temperature chamber; the gas supply system includes an N2 supply cylinder and an N2 gas supply station, the N2 supply cylinder passes through the constant temperature bath via a third gas transmission pipe and is connected to the N2 gas supply station, and the N2 gas supply station is connected to the upper N2 pressurization bladder 3 and the lower N2 pressurization bladder 10 via a first gas transmission pipe 7 and a second gas transmission pipe 13, respectively; the loading system is disposed on the constant temperature chamber, and the loading system is respectively opposite to the first groove 6-1 of the first thrust plate 6 and the second groove 12-1 of the second thrust plate 12; the data acquisition and control system includes a sensor group, a data acquisition box, and a workstation, and the data acquisition box is used to acquire data monitored by the sensor group; the assembly mechanism is disposed inside the constant temperature chamber, and the assembly mechanism is connected to the shear box mechanism.

[0056] The upper N2 pressurization airbag 3 and the lower N2 pressurization airbag 10 are expanded inward by the air supply system, causing the first steel coil 4 and the second steel coil 11 to rotate and contract, applying force to the root-soil composite 16. This allows the root-soil composite 16 to bear uniform confining pressure, thus simulating the actual stress state of the root-soil composite 16 under soil confining pressure. By combining the loading system and the top cover 5, the axial pressure F1 generated by the root-soil composite 16 after consolidation under confining pressure is measured. The cross-sectional diameter of the root-soil composite 16 after consolidation under confining pressure is accurately measured using the dimensional scale lines on the top cover 5. Later, by replacing the air supply system with a fixed steel ring to apply the designed confining pressure to the root-soil composite 16, the fixed steel ring transmits the lateral thrust during the shear test of the root-soil composite 16. This ensures that the shear strength of the root-soil composite 16 that can be measured by this device is greater than the designed confining pressure, thereby expanding the range of root-soil composites that can be tested by this device. The temperature control system provides a negative temperature environment for the shear test of the root-soil composite 16. At the same time, the constant temperature chamber serves as the thermal insulation boundary between the shear box mechanism and the test environment, reducing the influence of the test environment temperature on the test data. The constant temperature bath provides the design temperature for the supplied gas, thus facilitating the root-soil composite 16 to maintain the test design temperature.

[0057] Specifically, by combining the gas supply system, temperature control system, fixed steel ring and loading system, the temperature and stress environment of the root-soil composite 16 were realistically simulated, thereby measuring the shear strength of the root-soil composite 16 that conforms to the actual situation.

[0058] Specifically, the constant temperature chamber is equipped with a first control panel and a temperature probe. The data transmission line of the temperature probe is connected to the first control panel. The first control panel is used to set and display the working temperature of the constant temperature chamber, the temperature probe is used to monitor the temperature inside the constant temperature chamber, and the constant temperature chamber is used to provide the negative temperature environment required for the experimental design of the root-soil composite 16.

[0059] Specifically, the thermostatic bath is equipped with a second control panel, which is used to set and display the working temperature of the thermostatic bath, and the thermostatic bath is used to achieve constant temperature gas supply of the gas supply system.

[0060] Specifically, the sensor group includes an axial pressure sensor, an axial upper limit sensor, an axial lower limit sensor, a lateral pressure sensor, a lateral displacement sensor, a lateral front limit sensor, a lateral rear limit sensor, and a temperature sensor 15. The temperature sensor 15 is installed at the center of the bottom plate 14 of the lower shear box 8 and is used to monitor the temperature of the root-soil composite 16.

[0061] Specifically, the workstation includes an axial servo control console, a lateral servo control console, a microcomputer, and data processing software. The axial servo control console is used to control the operation of the axial pressure loading device, the lateral servo control console is used to control the operation of the lateral load loading device, and the microcomputer and data processing software are used to calculate, analyze, and image the data collected by the data acquisition box and manually input. The data includes the temperature, shear displacement, cross-sectional area after consolidation, lateral thrust, and axial pressure generated after consolidation of the root-soil composite 16 under confining pressure.

[0062] Specifically, the first gas transmission pipe 7 passes through the upper shear box 1 and the upper volute limiting ring 2 and is sealed to the upper N2 pressurizing air bag 3. The first gas transmission pipe 7 is also fixed to the outside of the upper shear box 1 through the first fixing ring. The second gas transmission pipe 13 passes through the lower shear box 8 and the lower volute limiting ring 9 and is sealed to the lower N2 pressurizing air bag 10. The second gas transmission pipe 13 is also fixed to the outside of the lower shear box 8 through the second fixing ring. The first gas transmission pipe 7, the second gas transmission pipe 13, and the third gas transmission pipe located between the constant temperature bath and the N2 gas supply station are all wrapped with heat-insulating pipe material. The first gas transmission pipe 7 and the second gas transmission pipe 13 pass through the side wall of the constant temperature box. The contact points between the first gas transmission pipe 7 and the second gas transmission pipe 13 and the constant temperature box are sealed with sealant. The N2 gas supply station is also wrapped with heat-insulating material.

[0063] Specifically, a first precision regulating valve 19 is installed on the first gas transmission pipe 7, and the first precision regulating valve 19 is equipped with two pressure gauges, one of which is used to display the pressure value in the N2 gas supply station, and the other is used to display the gas pressure value in the first gas transmission pipe 7 regulated by the first precision regulating valve 19; a second precision regulating valve 20 is installed on the second gas transmission pipe 13, and the second precision regulating valve 20 is equipped with two pressure gauges, one of which is used to display the pressure value in the N2 gas supply station, and the other is used to display the gas pressure value in the second gas transmission pipe 13 regulated by the second precision regulating valve 20; a third precision regulating valve is installed on the third gas transmission pipe, and the third precision regulating valve is equipped with two pressure gauges, one of which is used to display the pressure value in the N2 supply cylinder, and the other is used to display the gas pressure value in the third gas transmission pipe regulated by the third precision regulating valve.

[0064] In embodiments of the present invention, such as Figure 1-6 As shown, the assembly mechanism includes: a base plate 14, a shear box support column 17, and a slide assembly; the base plate 14 is located at the bottom of the lower shear box 8; the shear box support column 17 is located on the bottom surface of the base plate 14; the slide assembly includes an upper slide 18, a lower slide, and pressure rollers, the upper slide 18 is connected to the bottom of the shear box support column 17, the lower slide is fixed inside the constant temperature chamber, and both the upper slide 18 and the lower slide are provided with concave rails that allow the pressure rollers to roll.

[0065] By restricting the vertical and horizontal displacement of the bearing rollers by the concave rails, the bearing rollers can only roll in the direction of the lateral thrust applied by the lateral load loading device, thereby causing the lower shear box 8 to only undergo shear displacement in the direction of the lateral thrust applied by the lateral load loading device.

[0066] Specifically, the shear box support 17 is a hollow stainless steel support with circular openings in the front, back, left, and right directions for the data transmission line of the temperature sensor 15 to pass through.

[0067] In embodiments of the present invention, such as Figure 1-6 As shown, the loading system includes: an axial pressure loading device, a lateral load loading device, and a lateral stop bar; the axial pressure loading device passes through the top center of the constant temperature chamber and is in contact with the top cover 5; the lateral load loading device passes through one side of the constant temperature chamber, and the top of the force transmission rod at the right end of the lateral load loading device is opposite to the second groove 12-1; the lateral stop bar passes through the other side of the constant temperature chamber and is opposite to the first groove 6-1.

[0068] Specifically, the axial limiting device is located on one side of the axial pressure loading device, and the lateral limiting device is located on one side of the lateral load loading device.

[0069] An axial pressure sensor is installed inside the axial pressure loading device to monitor the axial load generated after the root-soil composite 16 consolidates under confining pressure. Both an upper and lower axial limit sensor are installed on the axial limiting device. The upper axial limit sensor limits the upper limit position of the axial pressure loading device, and the lower axial limit sensor limits the lower limit position. A lateral pressure sensor and a lateral displacement sensor are installed inside the lateral load loading device. The lateral pressure sensor monitors the lateral thrust on the root-soil composite 16 located in the lower shear box 8, and the lateral displacement sensor monitors the shear displacement of the root-soil composite 16. Both a front and rear lateral limit sensor are installed on the lateral limiting device. The front lateral limit sensor limits the right limit position of the lateral load loading device, and the rear lateral limit sensor limits the left limit position of the lateral load loading device.

[0070] The axial pressure loading device can measure the axial load generated by the root-soil composite 16 after consolidation under confining pressure through its internal axial pressure sensor. The lateral load loading device applies lateral thrust to the root-soil composite 16 by contacting the top of the force transmission rod at its right end with the second thrust plate 12 of the lower shear box 8. The left end of the lateral stop bar contacts the first thrust plate 6 of the upper shear box 1 to fix the upper shear box 1 laterally.

[0071] In an embodiment of the present invention, the invention further includes: a frame; the frame includes a support beam, two pillars and a test platform cabinet, the two pillars are respectively fixed on both sides of the test platform cabinet, the support beam is located above the test platform cabinet, and the constant temperature chamber is installed on the test platform cabinet and located between the two pillars and the support beam.

[0072] The axial compression loading device enters the constant temperature chamber through the top center of the support beam, the lateral load loading device enters the constant temperature chamber through one support column, and the lateral stop bar enters the constant temperature chamber through another support column. An axial limiting device is also installed on the upper wall of the support beam, located on one side of the axial compression loading device. A lateral limiting device is also installed on the left wall of the support column, located on one side of the lateral load loading device. The frame is used to support the loading system, the constant temperature chamber, and the shear box mechanism, and to provide reaction force to the loading system.

[0073] In an embodiment of the present invention, it further includes: a pressure-bearing head; the pressure-bearing head is connected to the bottom of the axial pressure measuring and loading device, the bottom diameter of the pressure-bearing head is smaller than the cross-sectional diameter of the limiting groove, and the pressure-bearing head is opposite to the limiting groove.

[0074] Axial pressure is applied by fitting the pressure-bearing mandrel into the limiting groove.

[0075] Specifically, the shape of the pressure-bearing mandrel is a combination of a frustum-shaped upper part and a cylinder-shaped lower part.

[0076] In an embodiment of the present invention, the transverse stop is a threaded screw, and a handwheel is provided at the right end of the transverse stop.

[0077] The lateral stop lever is controlled by manually operating the handwheel to apply a lateral force to the upper shear box 1 by rotating it in or out.

[0078] In embodiments of the present invention, the contact points between the axial pressure loading device, the transverse load loading device, and the transverse stop bar and the constant temperature chamber are all sealed and heat-insulated by a sealing piston sleeve.

[0079] The temperature during the test was ensured by using a sealed piston sleeve for heat insulation.

[0080] In embodiments of the present invention, the method includes the following steps:

[0081] S1: Sample loading, open the door of the constant temperature chamber, remove the upper shear box 1, use a vernier caliper to measure the inner diameter D0 of the bottom surface of the upper volute limiting ring 2 and the top surface of the lower volute limiting ring 9, apply a thin layer of Vaseline to the inner wall of the first steel coil 4 and the inner wall of the second steel coil 11, adjust the second steel coil 11 so that it is in the middle of the lower shear box 8, then fill the second steel coil 11 with the pre-prepared root-soil composite 16 with a cross-sectional diameter of 10.0cm and a height equal to the sum of the height of the first steel coil 4 and the height of the second steel coil 11, adjust the first steel coil 4 so that it is in the middle of the upper shear box 1, slowly lower the upper shear box 1 from the top of the root-soil composite 16 until it is placed on the lower shear box 8, insert the two second fixing pins 22 from the top cover 5 of the upper shear box 1 into the lower shear box 8 and tighten them, so that the upper shear box 1 is temporarily fixed on the lower shear box 8;

[0082] S2: Start the data acquisition and control system, start collecting temperature and shear displacement information of root-soil composite 16, collect axial pressure and lateral thrust information generated by root-soil composite 16 after consolidation under confining pressure, collect upper and lower limit positions of axial pressure measuring and loading device and front and rear limit positions of lateral load loading device, and collect loading and unloading information of axial pressure measuring and loading device and lateral load loading device.

[0083] S3: Determine the position of the shear box mechanism, push the lower shear box 8 so that the limiting groove on the top cover 5 is just below the pressure head, manually operate the handwheel so that the protruding part of the left end of the transverse stop bar is just in contact with the first groove 6-1, thereby fixing the upper shear box 1 laterally, start the loading system, and set the working parameters of the axial servo control console through the workstation to control the axial pressure loading device to move slowly downward at a constant rate until the bottom surface of the pressure head is in no pressure contact with the bottom surface of the limiting groove of the top cover 5. Set the working parameters of the transverse servo control console through the workstation to control the transverse load loading device to move slowly to the right at a constant rate until the top of the force transmission rod at the right end of the transverse load loading device is in no pressure contact with the second groove 12-1. Rotate and pull out the two second fixing pins 22 from the top cover 5, the upper shear box 1 and the lower shear box 8, and close the door of the constant temperature chamber.

[0084] S4: Turn on the gas supply system and consolidate the root-soil composite 16 according to the test confining pressure to be simulated in the design. Adjust the gas supply pressure of the N2 gas supply station through the first precision regulating valve 19, the second precision regulating valve 20 and the third precision regulating valve until the pressure value in the first gas transmission pipe 7 displayed by the pressure gauge on the first precision regulating valve 19 and the pressure value in the second gas transmission pipe 13 displayed by the pressure gauge on the second precision regulating valve 20 both reach the set value and stabilize. That is, the gas pressure values ​​in the upper N2 pressurizing air bag 3 and the lower N2 pressurizing air bag 10 both reach the design value and stabilize. Observe and record the stable axial pressure F1 displayed by the workstation. F1 is the axial load generated by the root-soil composite 16 after consolidation under the confining pressure.

[0085] S5: Turn on the temperature control system. According to the negative temperature environment to be simulated, set the working temperature of the constant temperature chamber to be consistent with the design temperature through the first control panel arranged on the constant temperature chamber. Wait for the temperature of the root-soil composite 16 displayed on the workstation to reach the set value and stabilize. At this time, the root-soil composite 16 is in a frozen state. Set the working temperature of the constant temperature bath to be consistent with the design temperature through the second control panel arranged on the constant temperature bath. Wait for the constant temperature bath to reach the design temperature and stabilize. During this process, the first precision regulating valve 19 and the second precision regulating valve 20 will adjust in real time and maintain the gas pressure in the upper N2 pressurized air bag 3 and the lower N2 pressurized air bag 10 to the design value. The temperature control system is always in working state in the following steps.

[0086] S6: Select a suitable fixing steel ring, open the door of the constant temperature chamber, measure the cross-sectional diameter D1 of the root-soil composite 16 after consolidation under confining pressure through the size scale line on the top cover 5, calculate the cross-sectional area A1 of the root-soil composite 16 after consolidation, input and store A1 in the data processing software of the workstation, and calculate the inner diameter of the required fixing steel ring based on the fact that the difference between the initial cross-sectional diameter 10.0cm of the root-soil composite 16 and the cross-sectional diameter D1 after consolidation is equal to the difference between the outer diameter and the inner diameter of the required fixing steel ring, and select a set of fixing steel rings that meet the requirements.

[0087] S7: Install the second fixing steel ring for the lower shear box 8. Set the working parameters of the axial servo control console through the workstation to control the axial pressure loading device to move slowly upward at a constant rate for an appropriate distance, making it easy to remove the upper shear box 1 from the top of the root-soil composite 16. Adjust the first precision regulating valve 19 to stop the N2 gas supply station from supplying gas to the upper N2 pressurization airbag 3, and relieve the pressure around the root-soil composite 16 in the upper shear box 1. Slowly remove the upper shear box 1 while ensuring that the root-soil composite 16 is not damaged, and take any one of the fixing steel rings selected in S6 as the second fixing steel ring. The second fixing steel ring is inserted between the lower volute limiting ring 9 and the second steel coil 11 along the outer side wall of the second steel coil 11. The insertion process of the second fixing steel ring is as follows: first, insert a part of it. When the second fixing steel ring contacts the lower N2 pressurization air bag 10, adjust the second precision regulating valve 20 to stop the N2 gas supply station from supplying gas to the lower N2 pressurization air bag 10, that is, release the gas pressure in the lower N2 pressurization air bag 10. Then, insert the remaining part of the second fixing steel ring between the lower volute limiting ring 9 and the second steel coil 11. Finally, the lower bottom surface of the second fixing steel ring contacts the bottom plate 14 and the upper top surface is flush with the top surface of the second steel coil 11.

[0088] S8: Install the first fixing steel ring 23 on the upper shear box 1. Rotate and pull out the two first fixing pins 21 from the top cover 5 and the upper shear box 1. Remove the top cover 5. Adjust the first steel coil 4 to be in the middle of the upper shear box 1. Slowly lower the remaining upper shear box 1 from the top of the root-soil composite 16 until it is placed on the lower shear box 8. Adjust the first precision regulating valve 19 to supply gas to the upper N2 pressurization airbag 3 from the N2 gas supply station until the gas pressure value in the upper N2 pressurization airbag 3 displayed by the pressure gauge on the first precision regulating valve 19 reaches the design value and stabilizes. Take the remaining one of the set of fixing steel rings selected in S6, which is the first fixing steel ring 23. Insert the first fixing steel ring 23 along the outer side wall of the first steel coil 4 between the upper volute limiting ring 2 and the first steel coil 4. The insertion process of the first fixing steel ring 23 is as follows: insert part of it first, when the first When the fixed steel ring 23 contacts the upper N2 pressurized air bag 3, the first precision regulating valve 19 is adjusted to stop the N2 gas supply station from supplying air to the upper N2 pressurized air bag 3, thus releasing the air pressure inside the upper N2 pressurized air bag 3. Then, the remaining part of the first fixed steel ring 23 is inserted between the upper volute limiting ring 2 and the first steel coil 4, so that the bottom surface of the first fixed steel ring 23 is flush with the bottom surface of the first steel coil 4 and the top surface is flush with the top surface of the first steel coil 4. At this time, the confining pressure on the root-soil composite 16 is provided by the first fixed steel ring 23, the second fixed steel ring, the first steel coil 4 and the second steel coil 11. The top cover 5 is placed on the upper shear box 1, so that the four holes on the top cover 5 are aligned with the four holes on the upper shear box 1. Two first fixing pins 21 are inserted into the upper shear box 1 through the two diagonal holes of the top cover 5 and tightened, thereby fixing the top cover 5 to the upper shear box 1.

[0089] S9: Set the working parameters of the axial servo control console through the workstation, control the axial pressure measuring and loading device to move slowly downward at a constant rate until the workstation displays that the axial pressure applied by the axial pressure measuring and loading device to the root-soil composite 16 is stable at F1, then stop loading, close the door of the constant temperature chamber, and wait for the temperature of the root-soil composite 16 displayed by the workstation to reach the design value and stabilize.

[0090] S10: The shear test begins. The working parameters of the lateral servo control console are set through the workstation, so that the shear box 8 moves to the right at a constant rate under the push of the lateral load loading device. The data acquisition box and the workstation acquire and store the lateral thrust and shear displacement information of the root-soil composite 16 in real time. The data processing software of the workstation calculates, analyzes and images the acquired data. The workstation plots the relationship curve between shear stress (kPa) and shear strain (%). When the shear strain (%) increases sharply or the shear deformation reaches 1 / 10 of the specimen size, the root-soil composite 16 is considered to have failed. The corresponding shear stress (kPa) at this time is the shear strength of the root-soil composite 16 under confining pressure in a negative temperature environment.

[0091] It should be understood that when the shear strength of the root-soil composite 16 to be tested is known to be no greater than the pressure applied to the root-soil composite 16 by the air supply system, the process of replacing the air supply system with a fixed steel ring can be omitted, that is, S6, S7, S8 and S9 can be omitted. When the temperature of the root-soil composite 16 reaches the design value and stabilizes, and the gas pressure values ​​in the upper N2 pressurization airbag 3 and the lower N2 pressurization airbag 10 stabilize at the design value, the shear test of the root-soil composite 16 can be carried out directly.

[0092] In the description of this invention, the term "a plurality of" refers to two or more. Unless otherwise explicitly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0093] In the description of this invention, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this invention, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0094] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A shear box mechanism, characterized in that, include: The upper shearing box is provided with an upper volute limiting ring, an upper pressurizing airbag, a first steel coil and a first fixing steel ring, and the upper pressurizing airbag is located between the upper volute limiting ring and the first steel coil. The lower shearing box includes a lower volute limiting ring, a lower pressurizing airbag, a second steel coil, and a second fixing steel ring. The lower pressurizing airbag is located between the lower volute limiting ring and the second steel coil. The top cover is a transparent acrylic sheet with size scale lines. The top cover is installed on the top of the upper shear box by two first fixing pins, and a limiting groove is provided at the center of the top cover. Wherein, the outer diameter of the first fixed steel ring and the second fixed steel ring are the same as the inner diameter of the upper volute limiting ring or the lower volute limiting ring, and the difference between the outer diameter and the inner diameter of the first fixed steel ring and the second fixed steel ring is equal to the difference between the cross-sectional diameter of the root-soil composite in its initial state and the cross-sectional diameter after consolidation under confining pressure. When inflated, the upper and lower pressurized airbags expand inward, squeezing the first and second steel coils to rotate and contract, thereby applying confining pressure to the root-soil composite. The first and second fixing steel rings are installed between the upper volute limiting ring and the first steel coil and between the lower volute limiting ring and the second steel coil, respectively, when the confining pressure provided to the root-soil composite reaches the test design confining pressure and stabilizes. These rings are used to fix the first and second steel coils and transmit lateral thrust.

2. The shearing box mechanism according to claim 1, characterized in that, Also includes: The first thrust plate is fixed to the right side of the upper shear box, and the right side of the first thrust plate is provided with a first groove. The second thrust plate is fixed to the left side of the lower shear box, and the left side of the second thrust plate is provided with a second groove.

3. A device for testing the shear strength of root soil under confining pressure, characterized in that, include: The shear box mechanism as described in claim 2; A temperature control system, comprising a constant temperature chamber and a constant temperature bath, wherein the shear box mechanism is disposed inside the constant temperature chamber and the constant temperature bath is located on one side of the constant temperature chamber; A gas supply system, comprising a supply cylinder and a gas supply station, wherein the supply cylinder passes through the constant temperature bath via a third gas transmission pipe and is connected to the gas supply station, and the gas supply station is connected to the upper pressurization bladder and the lower pressurization bladder via a first gas transmission pipe and a second gas transmission pipe, respectively. A loading system is provided on a constant temperature chamber, and the loading system is respectively opposite to the first groove of the first thrust plate and the second groove of the second thrust plate; A data acquisition and control system, comprising a sensor group, a data acquisition box, and a workstation, wherein the data acquisition box is used to acquire data monitored by the sensor group; An assembly mechanism is disposed inside the constant temperature chamber and is connected to the shearing box mechanism.

4. The root soil shear strength testing device under confining pressure according to claim 3, characterized in that, The assembly mechanism includes: A base plate, wherein the base plate is disposed at the bottom of the lower shear box; A shear box support column is disposed on the bottom surface of the base plate; The slide assembly includes an upper slide, a lower slide, and pressure rollers. The upper slide is connected to the bottom of the shear box support, and the lower slide is fixed inside the constant temperature chamber. Both the upper slide and the lower slide are provided with concave rails that allow the pressure rollers to roll.

5. The root soil shear strength testing device under confining pressure according to claim 4, characterized in that, The loading system includes: An axial pressure loading device is provided, wherein the axial pressure loading device passes through the center of the top of the constant temperature chamber and is in contact with the top cover; A lateral load loading device, wherein the lateral load loading device passes through one side of the constant temperature chamber, and the top of the force transmission rod at the right end of the lateral load loading device is opposite to the second groove; A transverse stop bar passes through the other side of the constant temperature chamber and is opposite to the first groove.

6. The root soil shear strength testing device under confining pressure according to claim 5, characterized in that, Also includes: The frame includes a support beam, two pillars, and a test platform cabinet. The two pillars are fixed on both sides of the test platform cabinet, the support beam is located above the test platform cabinet, and the constant temperature chamber is installed on the test platform cabinet and located between the two pillars and the support beam.

7. The root soil shear strength testing device under confining pressure according to claim 6, characterized in that, Also includes: The pressure-bearing head is connected to the bottom of the axial pressure measuring and loading device. The bottom diameter of the pressure-bearing head is smaller than the cross-sectional diameter of the limiting groove, and the pressure-bearing head is opposite to the limiting groove.

8. The root soil shear strength testing device under confining pressure according to claim 7, characterized in that: The transverse stop is a threaded screw, and a handwheel is provided at the right end of the transverse stop.

9. The root soil shear strength testing device under confining pressure according to claim 8, characterized in that: The axial pressure loading device, the transverse load loading device, and the transverse stop bar are all sealed and heat-insulated at their contact points with the constant temperature chamber using sealed piston sleeves.

10. A method of using a root soil shear strength testing device under confining pressure as described in any one of claims 8-9, characterized in that, The usage method includes the following steps: S1: Sample loading, open the door of the constant temperature chamber, remove the upper shear box, use vernier calipers to measure the inner diameter D0 of the bottom surface of the upper volute limiting ring and the top surface of the lower volute limiting ring, apply a thin layer of Vaseline to the inner wall of the first steel coil and the inner wall of the second steel coil, adjust the second steel coil to be in the middle of the lower shear box, then fill the second steel coil with the pre-prepared root-soil composite with a cross-sectional diameter of 10.0cm and a height equal to the sum of the heights of the first and second steel coils, and adjust the first steel coil to be in the middle of the upper shear box. Slowly lower the upper shear box from the top of the root-soil composite until it is placed on the lower shear box, insert the two second fixing pins from the top cover of the upper shear box into the lower shear box and tighten them to temporarily fix the upper shear box on the lower shear box; S2: Start the data acquisition and control system, start collecting temperature and shear displacement information of the root-soil composite, collect axial pressure and lateral thrust information generated after the root-soil composite is consolidated under confining pressure, collect upper and lower limit positions of the axial pressure measuring and loading device and front and rear limit positions of the lateral load loading device, and collect loading and unloading information of the axial pressure measuring and loading device and the lateral load loading device. S3: Determine the position of the shear box mechanism, push the lower shear box so that the limiting groove on the top cover is just below the pressure head, manually operate the handwheel so that the protruding part on the left end of the transverse stop bar is just in contact with the first groove, thereby fixing the upper shear box laterally, start the loading system, and set the working parameters of the axial servo control console through the workstation to control the axial pressure loading device to move slowly downward at a constant rate until the bottom surface of the pressure head is in no pressure contact with the bottom surface of the limiting groove of the top cover. Set the working parameters of the transverse servo control console through the workstation to control the transverse load loading device to move slowly to the right at a constant rate until the top end of the force transmission rod of the transverse load loading device is in no pressure contact with the second groove. Rotate and pull out the two second fixing pins from the top cover, upper shear box and lower shear box, and close the door of the constant temperature chamber. S4: Turn on the gas supply system and consolidate the root-soil composite according to the test confining pressure to be simulated in the design. Adjust the gas supply pressure of the gas supply station through the first precision regulating valve set in the first gas transmission pipe, the second precision regulating valve set in the second gas transmission pipe, and the third precision regulating valve set in the third gas transmission pipe until the pressure value in the first gas transmission pipe displayed by the pressure gauge on the first precision regulating valve and the pressure value in the second gas transmission pipe displayed by the pressure gauge on the second precision regulating valve both reach the set value and stabilize. That is, the gas pressure values ​​in the upper and lower pressurized air bladders both reach the design value and stabilize. Observe and record the stable axial pressure F1 displayed by the workstation. F1 is the axial load generated by the root-soil composite after consolidation under the confining pressure. S5: Turn on the temperature control system. According to the negative temperature environment to be simulated, set the working temperature of the constant temperature chamber to be consistent with the design temperature through the first control panel arranged on the constant temperature chamber. Wait for the temperature of the root soil composite displayed on the workstation to reach the set value and stabilize. At this time, the root soil composite is in a frozen state. Set the working temperature of the constant temperature bath to be consistent with the design temperature through the second control panel arranged on the constant temperature bath. Wait for the constant temperature bath to reach the design temperature and stabilize. During this process, the first precision regulating valve and the second precision regulating valve will adjust in real time and maintain the gas pressure in the upper and lower pressurizing air bags to the design value. The temperature control system is always in working state in the following steps. S6: Select a suitable fixing steel ring, open the door of the constant temperature chamber, measure the cross-sectional diameter D1 of the root-soil composite after consolidation under confining pressure through the size scale line on the top cover, calculate the cross-sectional area A1 of the root-soil composite after consolidation, input and store A1 in the data processing software of the workstation, and calculate the required inner diameter of the fixing steel ring based on the fact that the difference between the initial cross-sectional diameter 10.0cm of the root-soil composite and the cross-sectional diameter D1 after consolidation is equal to the difference between the outer diameter and inner diameter of the required fixing steel ring, and select a set of fixing steel rings that meet the requirements. S7: Install the second fixing steel ring for the lower shear box. Set the working parameters of the axial servo control console via the workstation to control the axial pressure loading device to slowly move upwards at a constant rate for an appropriate distance, making it easier to remove the upper shear box from the top of the root-soil composite. Adjust the first precision regulating valve to stop the gas supply station from supplying gas to the upper pressurized airbag, releasing the pressure around the root-soil composite in the upper shear box. Slowly remove the upper shear box while ensuring the root-soil composite is not damaged, and take any one of the fixing steel rings selected in S6. The second fixing steel ring is inserted between the lower volute limiting ring and the second steel coil along the outer side wall of the second steel coil. The insertion process of the second fixing steel ring is as follows: first, insert a part of it. When the second fixing steel ring contacts the lower pressurization airbag, adjust the second precision regulating valve to stop the gas supply station from supplying gas to the lower pressurization airbag, that is, release the air pressure in the lower pressurization airbag. Then, insert the remaining part of the second fixing steel ring between the lower volute limiting ring and the second steel coil. Finally, the bottom surface of the second fixing steel ring contacts the bottom plate and the top surface is flush with the top surface of the second steel coil. S8: Install the first fixing steel ring for the upper shear box. Rotate and pull out the two first fixing pins from the top cover and the upper shear box. Remove the top cover. Adjust the first steel coil to position it in the middle of the upper shear box. Slowly lower the remaining upper shear box from the top of the root-soil composite until it is placed on the lower shear box. Adjust the first precision regulating valve to supply gas to the upper pressurized airbag from the gas supply station until the gas pressure value in the upper pressurized airbag displayed on the pressure gauge of the first precision regulating valve reaches the design value and stabilizes. Take the remaining one of the fixing steel rings selected in S6 as the first fixing steel ring. Insert the first fixing steel ring along the outer side wall of the first steel coil between the upper volute limiting ring and the first steel coil. The insertion process of the first fixing steel ring is as follows: first insert a part of it, when... When the first fixing steel ring contacts the upper pressurized airbag, the first precision regulating valve is adjusted to stop the gas supply station from supplying air to the upper pressurized airbag, thus releasing the air pressure inside the upper pressurized airbag. Then, the remaining part of the first fixing steel ring is inserted between the upper volute limiting ring and the first steel coil, so that the bottom surface of the first fixing steel ring is flush with the bottom surface of the first steel coil and the top surface is flush with the top surface of the first steel coil. At this time, the confining pressure on the root-soil composite is provided by the first fixing steel ring, the second fixing steel ring, the first steel coil and the second steel coil. The top cover is placed on the upper shear box, so that the four holes on the top cover are aligned with the four holes on the upper shear box. Two first fixing pins are inserted into the upper shear box through the two diagonal holes of the top cover and tightened, thereby fixing the top cover to the upper shear box. S9: Set the working parameters of the axial servo control console through the workstation, control the axial pressure measuring and loading device to move slowly downward at a constant rate until the workstation displays that the axial pressure applied by the axial pressure measuring and loading device to the root-soil composite is stable at F1, then stop loading, close the door of the constant temperature chamber, and wait for the temperature of the root-soil composite displayed by the workstation to reach the design value and stabilize. S10: The shear test begins. The working parameters of the lateral servo control console are set through the workstation, causing the shear box to move to the right at a constant rate under the push of the lateral load loading device. The data acquisition box and the workstation acquire and store the lateral thrust and shear displacement information of the root-soil composite in real time. The data processing software of the workstation calculates, analyzes and images the acquired data. The workstation plots the relationship curve between shear stress and shear strain. Finally, the shear strength of the root-soil composite under confining pressure in a negative temperature environment is obtained based on the relationship curve between shear stress and shear strain.

Images