Shearing test device and method for soil body in drill hole

Abstract

The invention discloses a shear test device and method for a soil body in a drill hole, relates to the technical field of soil body shear strength tests, and aims to solve the problems of sampling disturbance, narrow application range, low test efficiency and the like in a traditional soil body shear strength test. The test device comprises a connecting rod, three groups of round rollers, a shearing assembly, a pressurizing assembly and a data acquisition assembly. The shearing assembly drives a shearing plate to be inserted into a soil body through a hydraulic jack for shearing, the pressurizing assembly applies horizontal radial pressure through an air bag to simulate different stress conditions, and the data collecting assembly records bending moment, rotating angle and pressure changes in real time. The test method comprises the following steps: drilling to a test depth, then installing the test device, pressing the shear plate, applying pressure, carrying out a shear test, and obtaining the friction angle and cohesive force in the soil body through data analysis. The in-situ test is directly carried out in the drill hole, sampling disturbance is avoided, the device is suitable for stratums difficult to sample such as sandy soil and fully-strongly weathered bedrock, and the device can go deep into different depths to research the mechanical properties of deep soil bodies.

Description

Technical Field

[0001] The present invention relates to the technical field of soil shear strength tests, and particularly relates to a soil shear test device and test method in a borehole. Background Art

[0002] The soil shear strength parameters are one of the core indicators in geotechnical mechanics research and engineering design, and are directly related to the safety, stability, economy and sustainability of engineering. By conducting shear strength tests and analyses on different types and states of soils, the strength characteristics, deformation characteristics and stress-strain relationships of soils can be deeply understood, providing a basis for establishing more accurate soil mechanics models. In actual engineering, the shear strength parameters are important mechanical indicators for calculating the bearing capacity of foundations, analyzing the stability of slopes, and evaluating the effect of foundation treatment. Reasonably determining the soil shear strength parameters can not only optimize the engineering design scheme, but also reduce the project cost on the premise of ensuring safety.

[0003] At present, the determination of soil shear strength parameters is mainly divided into two categories: laboratory tests and in-situ tests. Among them, laboratory tests include direct shear tests and triaxial tests, etc., while in-situ tests include large direct shear tests, vane shear tests, etc. However, these traditional methods have many problems in practical applications, which are specifically as follows:

[0004] Sampling disturbance problem: Laboratory tests rely on on-site drilling sampling and transportation to the laboratory for testing. However, during the sampling and transportation process, the soil structure is extremely vulnerable to disturbance. Especially for highly sensitive soils such as saturated soft soils, their natural structure may be damaged, resulting in distorted test data. In addition, for strata such as sandy soils, completely weathered bedrocks and strongly weathered bedrocks, which contain large rock blocks or gravels, it is difficult to obtain regular specimens, and even impossible to make standard specimens suitable for laboratory tests.

[0005] Insufficient representativeness and human error: Laboratory tests usually use small-sized specimens, which have poor representativeness and are difficult to reflect the overall mechanical properties of soils. At the same time, the empirical criteria and manual operations during the test process may lead to large discreteness of the results. In addition, the laboratory test period is relatively long. For example, a set of triaxial shear tests on cohesive soil usually takes about a week, which to a certain extent limits the application of triaxial shear tests.

[0006] Limitations of in-situ tests: Although in-situ tests can directly test the shear strength of soils on-site and avoid the influence of sampling disturbance, the existing methods still have obvious deficiencies. Large direct shear test: Although it can be tested on-site, it is only applicable to shallow surface foundation soils, and the test equipment is expensive, the operation is complex, and the period is long; Vane shear test: It is mainly used for soft clay, and can only obtain the cohesion and cannot measure the internal friction angle. In addition, this method is not applicable to soft clay containing sand layers, cobbles and gravels, etc.

[0007] In summary, the existing soil shear strength test methods have obvious defects in terms of application scope, test efficiency, data accuracy, etc. Therefore, there is an urgent need for a new test method and device that can overcome the above problems. Summary of the Invention

[0008] To solve the above problems, the present invention provides a shear test device and method for soil in a borehole, aiming to solve the problems existing in the prior art and provide a more efficient and accurate solution for geotechnical engineering investigation and design.

[0009] The technical solution adopted by the present invention is as follows:

[0010] A shear test device for soil in a borehole, the shear test device for soil in a borehole includes a connecting rod installed at the end of the drill rod of a drilling rig. Three groups of cylindrical rollers are vertically coaxially installed on the connecting rod. The upper and lower two groups of cylindrical rollers are rotatably installed on the connecting rod, and the cylindrical roller in the middle position is fixedly installed on the connecting rod; a shear assembly is installed inside the cylindrical roller in the middle position, and the shear assembly includes a hydraulic jack and a shear plate that can horizontally expand and contract relative to the cylindrical roller.

[0011] The shear test device for soil in a borehole further includes a pressurizing assembly and a data acquisition assembly; the pressurizing assembly includes airbags installed on the circumferential outer side of the cylindrical rollers, and a pressure pump connected to each airbag and the hydraulic jack; the data acquisition assembly includes pressure sensors arranged in each airbag, a bending moment and rotation angle sensor installed on the connecting rod, and an industrial computer connected to the pressure sensors, the bending moment and rotation angle sensor, and the pressure pump.

[0012] Further, in the three groups of cylindrical rollers, spherical turntable bearings are installed at the upper and lower parts of the upper and lower two groups of cylindrical rollers, and the cylindrical rollers are rotatably installed on the connecting rod through the spherical turntable bearings; the rubber airbags on the circumferential outer sides of the upper and lower two groups of cylindrical rollers are cylindrical rubber airbags.

[0013] Further, in the three groups of cylindrical rollers, four groups of expansion holes for cooperating with the shear plate are arranged on the circumference of the cylindrical roller in the middle position; there are four groups of shear plates, and the four groups of shear plates are arranged in a cross shape. The four groups of shear plates are respectively controlled by four groups of hydraulic jacks or controlled by two groups of two-way hydraulic jacks or controlled by one group of four-way hydraulic jacks.

[0014] Further, the four groups of expansion holes equally divide the outer wall of the cylindrical roller in the middle position, and a sheet-shaped rubber airbag is installed on each equally divided outer wall.

[0015] A shear test method for soil in a borehole, the shear test method for soil in a borehole is based on the above shear test device for soil in a borehole, and includes the following steps:

[0016] S1 Test preparation: After drilling to the test depth, lower the test device into the test section in the hole through connection with the drill pipe.

[0017] S2 Shear plate insertion: Use a hydraulic jack to press the shear plate into the soil mass on the hole wall to a certain depth.

[0018] S3 Data recording: Start the data acquisition component and record the pressure in the rubber airbag, the bending moment and the rotation angle during the rotation of the shear plate.

[0019] S4 Pressure application: Pressurize the rubber airbag through a pressure pump and maintain a constant pressure to simulate the deviator stress.

[0020] S5 Shear test: Start the drill to rotate the drill pipe at a constant speed to shear the soil mass with the shear plate until the soil mass fails, and record the maximum bending moment and rotation angle.

[0021] S6 Repeated test: Repeat the test at different positions in the same stratum to obtain the shear strength data under different deviator stresses.

[0022] S7 Data analysis: Draw a curve of deviator stress versus shear strength according to the test data, and fit a straight line using the least squares method to obtain the internal friction angle and cohesion of the soil mass.

[0023] S8 Test termination: After the data acquisition is completed, stop the test and remove the device.

[0024] Furthermore, during the S5 shear test, when the shear plate shears the soil mass until the soil mass fails, a curve of the change in the bending moment and rotation angle of the shear plate during the shear process can be generated; based on the generated curve of the change in the bending moment and rotation angle of the shear plate during the shear process, the maximum bending moment M max is obtained, and at the same time, the rotation angle ω max at the moment of the maximum bending moment M is obtained.

[0025] Furthermore, based on the maximum bending moment M maxi perform shear strength calculation;

[0026] The shear strength τ i of the soil mass in the test section under the deviator stress P v0i between the horizontal radial pressure and the self-weight stress σ i - σ v0i generates a resisting moment on the shear plate, and its value is the same as the bending moment input by the drill to the shear plate. Calculate the shear strength τ of the soil mass according to Equation 1 i ; i ;

[0027]

[0028] After expanding Equation 1, Equation 2 is obtained:

[0029]

[0030] In the formula, M maxi is the maximum bending moment recorded by the bending moment sensor; D is the horizontal length at both ends of the shear plate after it is pressed into the soil; H is the height of the shear plate; τ i is the shear strength of the soil in the test section; d is the borehole diameter; x represents the radial distance from a certain point within the action area at the upper and lower ends of the shear plate to the central axis of the borehole, which is a variable, and its value range is from to

[0031] Furthermore, during the S7 data analysis process, based on the shear strength data τ i -σ v0i under different deviator stresses P i , with P i -σ v0i as the abscissa and τ i as the ordinate, import P i -σ v0i and τ i into the coordinate system, fit them into a σ-τ straight line by the least squares method, then the angle between the straight line and the abscissa is the internal friction angle φ of the test soil, and the intersection point of the straight line and the ordinate is the cohesion c of the test soil.

[0032] The beneficial effects of the present invention are as follows:

[0033] The in-situ soil shear test device and method proposed by the present invention overcome many limitations of traditional laboratory tests and in-situ tests by directly conducting in-situ shear tests in boreholes, and have the following remarkable beneficial effects:

[0034] 1. Avoid sampling disturbance and improve data accuracy: The test device directly conducts shear tests on the soil in the borehole without sampling and transportation, avoiding the disturbance of the soil structure during the sampling process, especially for highly sensitive soils such as saturated soft soils, so as to obtain shear strength parameters closer to the natural state.

[0035] 2. Wide application range and break through traditional limitations: This device is applicable to strata such as sandy soil, completely weathered bedrock, and strongly weathered bedrock where it is difficult to sample or make regular specimens. For strata containing components such as gravel and cobbles, traditional test methods are often inapplicable, while this method can effectively solve this problem by directly acting on the soil with a shear plate.

[0036] 3. Simple operation and high test efficiency: Compared with traditional large-scale direct shear tests and triaxial tests, this device has a compact structure and simple operation, and can complete the test in a shorter time. At the same time, by simulating different stress conditions through a pressurization system, multiple groups of test data can be quickly obtained, greatly shortening the test cycle.

[0037] 4. Provide comprehensive mechanical parameters: By fitting the σ-τ curve with multiple groups of test data, the internal friction angle φ and cohesion c of the soil can be obtained simultaneously, solving the problem that the vane shear test cannot measure the internal friction angle and providing more comprehensive mechanical parameter support for engineering design.

[0038] 5. Deep soil testing ability: Traditional in-situ tests, such as large direct shear tests, are only applicable to shallow surface soils, while this device can conduct tests at different depths through drilling to study the shear characteristics of deep soils and provide a reliable basis for engineering design under complex geological conditions.

[0039] 6. Economy and environmental protection: The test device can be reused and does not require complex on-site equipment, reducing the test cost. At the same time, since large-scale excavation or sampling is not required, the damage to the environment is reduced, meeting the concept of green exploration.

[0040] In summary, through innovative design and efficient test methods, the present invention solves the problems existing in the prior art, such as sampling disturbance, narrow application range, low test efficiency, etc., providing a more accurate, efficient and economical solution for geotechnical engineering investigation and design, and having important engineering application value. Brief Description of the Drawings

[0041] Figure 1 is a schematic diagram of the overall structure of the in-borehole soil shear test device of the present invention;

[0042] Figure 2 is a schematic cross-sectional view of the middle-position cylindrical roller of the present invention;

[0043] Figure 3 is a schematic diagram of the curve of the pressure plate torque changing with the rotation angle of the present invention;

[0044] Figure 4 is a schematic diagram of the σ-τ curve and the least squares fitting straight line of the present invention;

[0045] In the figures, 1 - borehole, 2 - connecting rod, 3 - cylindrical roller, 4 - cylindrical rubber airbag, 5 - middle-position cylindrical roller, 6 - sheet rubber airbag, 7 - shear plate, 8 - spherical turntable bearing, 9 - pressure sensor, 10 - bending moment and rotation angle sensor, 11 - pressure pump, 12 - industrial computer, 13 - hydraulic jack. Detailed Embodiments

[0046] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0047] For ease of explanation, spatial relative terms such as "upper", "lower", "left", "right", etc. may be used herein to describe the relationship of one element or feature shown in the figure with respect to another element or feature. It should be understood that, in addition to the orientation shown in the figure, the spatial terms are intended to include different orientations during the use or operation of the device. For example, if the device in the figure is inverted, the element described as being "below" other elements or features will be located "above" the other elements or features. Thus, the exemplary term "lower" can include both upper and lower orientations. The device may be positioned in other ways, and the spatial relative descriptions used herein can be interpreted accordingly.

[0048] Aiming at the problems such as sampling disturbance, narrow application range, and low test efficiency in the traditional soil shear strength test, this embodiment provides a shear test device for soil in boreholes. As Figure 1 shown, the shear test device for soil in boreholes includes a connecting rod 2 installed at the end of the drill rod of the drill rig. Three groups of round rollers 3 are vertically and coaxially installed on the connecting rod 2. In the three groups of round rollers 3, spherical turntable bearings 8 are installed at the upper and lower parts of the upper and lower groups of round rollers 3, and the round rollers 3 are rotatably installed on the connecting rod 2 through the spherical turntable bearings 8. A shear assembly is installed inside the middle-position round roller 5. The shear assembly includes a hydraulic jack 13 and a shear plate 7 that can horizontally expand and contract relative to the round roller 3. Considering the installation of the shear assembly, as Figure 1 and Figure 2 shown, four groups of expansion holes for cooperating with the shear plate 7 are arranged circumferentially on the middle-position round roller 5 in this embodiment. At the same time, the shear plate 7 is provided with four groups, and the four groups of shear plates 7 are arranged in a cross shape. The four groups of shear plates 7 are controlled by two groups of double-acting hydraulic jacks 13. Of course, four groups of hydraulic jacks can also be used to control respectively or controlled by a group of four-way hydraulic jacks.

[0049] The shear test device for soil in boreholes transmits the power of the drill rig to the shear plate 7 through the connecting rod 2 to ensure that the shear plate 7 can apply torque and perform a shearing operation. The middle-position round roller 5 is fixedly connected to the connecting rod 2 to provide stable support; the upper and lower groups of round rollers 3 are freely connected through the spherical turntable bearings 8, allowing the device to flexibly adjust its posture under complex geological conditions. The hydraulic jack 13 pushes the shear plate 7 into the soil in the test section to a certain depth to ensure full contact between the shear plate 7 and the soil; under the drive of the drill rig, the shear plate 7 rotates in the soil to apply a shearing force to the soil in the test section, simulating the actual shear failure process of the soil.

[0050] Further, as Figure 1 and Figure 2As shown in the figure, the in - borehole soil shear test device further includes a pressurizing component and a data acquisition component. Among them, the pressurizing component includes airbags installed on the outer circumference of the circular roller 3, and a pressure pump 11 connected to each airbag and the hydraulic jack 13; for the upper and lower groups of circular rollers 3, in this embodiment, cylindrical rubber airbags 4 are installed on the outer circumference of the upper and lower groups of circular rollers 3; for the circular roller 5 in the middle position, since the outer wall of the circular roller 5 in the middle position is equally divided by four telescopic holes, in this embodiment, a sheet - shaped rubber airbag 6 is installed on each equally divided outer wall. The data acquisition component includes pressure sensors 9 arranged in each cylindrical rubber airbag 4 and each sheet - shaped rubber airbag 6, a bending moment and rotation angle sensor 10 installed on the connecting rod 2, and an industrial computer 12 connected to the pressure sensors 9, the bending moment and rotation angle sensor 10, and the pressure pump 11.

[0051] The bending moment and rotation angle sensor 10 is installed at the upper end of the connecting rod 2 and is used to monitor the changes in bending moment and rotation angle during the shearing process in real - time; through the rotation of the shear plate 7, the bending moment and rotation angle sensor 10 records the bending moment and rotation angle data generated during the shearing process, providing a basis for calculating the shear strength of the soil. The pressure sensor 9 records the pressure value in the rubber airbag in real - time and is used to analyze the horizontal radial pressure exerted on the soil in the test section. By using the pressure pump 11 to inflate or fill the cylindrical rubber airbag 4 and the sheet - shaped rubber airbag 6 with gas or liquid, each rubber airbag expands and exerts a horizontal radial pressure on the soil in the test section and the adjacent soils above and below it, simulating the stress conditions of the soil in its natural state. The industrial computer 12 can adjust the pressure in the rubber airbag in cooperation with the data detected by the pressure sensor 9, thereby precisely controlling the deviator stress between the horizontal radial pressure and the self - weight stress of the soil in the test section, and meeting the requirement of studying the shear characteristics of the soil under different stress states.

[0052] Based on the above - mentioned in - borehole soil shear test device, this embodiment also proposes an in - borehole soil shear test method, which includes the following steps:

[0053] S1 Test preparation: After the construction of the borehole 1 is completed or the drill reaches the test depth, the bending moment and rotation angle sensor 10 is installed at the upper end of the connecting rod 2, and the in - borehole soil shear test device is placed into the test soil section in the borehole 1 by extending the drill pipe.

[0054] S2 Shear - plate insertion: Use the hydraulic jack 13 to press the shear plate 7 into the soil of the hole wall to a certain depth.

[0055] S3 Data recording: Start the data acquisition component and record the pressure in the rubber airbag, the bending moment and rotation angle during the rotation of the shear plate 7.

[0056] S4 Pressure application: Pressurize each rubber airbag through the pressure pump, pressurize to the test pressure and keep the pressure constant to simulate the deviator stress.

[0057] S5 Shear Test: Start the drill rig and slowly rotate the drill pipe at a constant speed so that the shear plate 7 shears the test soil mass at a constant speed. Record the changes in bending moment and rotation angle during the shearing process until the test soil sample is sheared and fails.

[0058] During the process of the shear plate 7 shearing the soil mass until the soil mass fails, a curve of the bending moment and rotation angle of the shear plate 7 during the shearing process can be generated. The curve of the bending moment and rotation angle of the shear plate 7 is as Figure 3 shown; based on the generated curve of the bending moment and rotation angle of the shear plate 7 during the shearing process, the maximum bending moment M maxi is obtained, and at the same time, the rotation angle ω maxi at the moment of the maximum bending moment M i is obtained.

[0059] Furthermore, based on the maximum bending moment M maxi perform shear strength calculation:

[0060] The shear strength τ i of the soil mass in the test section under the deviator stress P v0i and the self-weight stress σ i -σ v0i exerts a resisting moment on the shear plate 7, and its value is the same as the bending moment input by the drill rig to the shear plate 7. Calculate the shear strength τ i of the soil mass according to Equation 1; i ;

[0061]

[0062] After expanding Equation 1, Equation 2 is obtained:

[0063]

[0064] In the formula, M maxi is the maximum bending moment recorded by the bending moment sensor; D is the horizontal length of both ends of the shear plate 7 after being pressed into the soil mass; H is the height of the shear plate; τ i is the shear strength of the soil mass in the test section; d is the diameter of the borehole 1; x represents the radial horizontal distance from a certain point within the action area at the upper and lower ends of the shear plate 7 to the central axis of the borehole 1, which is a variable, and its value range is from to

[0065] In Equation 1, represents the resisting moment generated by the soil mass on the vertical shear plane of the vertical end of the shear plate 7. This part of the moment comes from the product of the shear resistance of the soil mass on the vertical shear plane of the shear plate 7 and its distance to the borehole center line; the shear resistance of the soil mass on the vertical shear plane of the shear plate 7 is the product of the shear strength τ i of the soil mass and its acting area πDH. In Equation 1, It represents the resisting moment generated by the soil mass on the horizontal shear planes at the upper and lower ends of the shear plate 7. This part of the moment is obtained from the integral calculation of the product of the shear resistance of the soil mass on the horizontal shear planes at the upper and lower ends of the shear plate 7 and the distance x from these planes to the center line of the borehole; the shear resistance of the soil mass on the horizontal shear planes at the upper and lower ends of the shear plate 7 is the shear strength τ of the soil mass i and its acting area The integration limits range from the radius of the borehole 1 to the outer radius of the shear plate 7 It reflects the contribution of the shear resistance moment of the soil mass at different positions on the shear planes at the upper and lower ends of the shear plate 7

[0066] In Equation 2 is the same as that in Equation 1, representing the resisting moment of the soil mass on the vertical shear plane at the vertical end of the shear plate 7 It represents the resisting moment of the soil mass on the horizontal shear planes at the upper and lower ends of the shear plate 7. The result obtained through integral calculation is simplified to .

[0067] According to the test data, the maximum bending moment M maxi can be directly measured by a bending moment sensor. Substituting M maxi , π, D, and d into Equation 2, the shear strength τ of the soil mass under the deviator stress P i -σ v0i can be solved i :

[0068]

[0069] The physical meaning of the formula is to decompose the resisting moment of the shear plate 7 on the soil mass into two parts: the resisting moment at the end and the resisting moment on the side; through the superposition of these two parts, the shear resistance characteristics of the soil mass during the shearing process can be accurately reflected. This formula is applicable to any shear plate 7 with a regular shape, such as a cross shape or a circular shape, and can consider the actual acting range of the shear plate 7 in the soil mass, which is determined by D and d

[0070] S6 Repeated tests: Adjust the test device to different positions of the same test soil layer by raising and lowering the drill pipe of the drill rig, and repeat steps two to five to conduct shear tests on the test soil samples of the same stratum under different pressures to obtain the shear strength τ of the samples under different deviator stresses P i -σ v0i i .

[0071] S7 Data analysis: Based on the shear strength data τ under different deviator stresses P i -σ v0i , with P i -σ i as the abscissa and τ v0i as the ordinate, plot P i i ​​-σ v0i , τ i Import the coordinate system and fit it into a σ-τ straight line by the least squares method. The fitted σ-τ straight line is as shown in Figure 4 ;

[0072] Element description in the figure: Each test point represents a set of test data. The abscissa is the deviator stress σ = P - σ v0i , and the ordinate is the corresponding shear strength τ i ; These points are the actual measured values obtained from multiple tests under different pressure conditions.

[0073] Use the least squares method to linearly fit the test data points to obtain an optimal fitting straight line. The form of the straight line equation is:

[0074] τ = c + σtanφ

[0075] In the formula, c is the cohesion, that is, the intercept of the straight line and the vertical axis; φ is the internal friction angle, that is, the arctangent value of the slope of the straight line.

[0076] The least squares method determines the optimal fitting straight line by minimizing the sum of the squares of the perpendicular distances from the test points to the fitting straight line. The specific steps are as follows:

[0077] First, assume the fitting straight line equation is τ = aσ + b, where a = tanφ and b = c.

[0078] Secondly, according to the test data points (σ i , τ i ), calculate the slope a and the intercept b:

[0079]

[0080] In the formula, n is the number of test points.

[0081] Finally, calculate the internal friction angle φ = arctan(a) and the cohesion c = b.

[0082] In summary, by plotting the σ-τ curve and using the least squares method to fit the straight line, the shear strength characteristics of the soil can be intuitively analyzed, and the cohesion c and the internal friction angle φ can be accurately obtained; this method is simple and efficient and is applicable to the determination of mechanical parameters in geotechnical engineering.

[0083] S8 Test termination: After the data acquisition is completed, stop the test and remove the device.

[0084] The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A soil shear test device in a borehole, characterized in that: The borehole soil shear test device comprises a connecting rod installed at the end of the drill rod of the drilling rig, three groups of round rollers are installed vertically and coaxially on the connecting rod, the upper and lower groups of round rollers are rotatably installed on the connecting rod, and the middle position round roller is fixedly installed on the connecting rod; a shear assembly is installed inside the middle position round roller, and the shear assembly includes a hydraulic jack and a shear plate that can be horizontally extended and retracted relative to the round roller; The borehole soil shear test device also includes a pressurizing component and a data acquisition component; the pressurizing component includes an air bag installed on the outer side of the circumference of the drum, and a pressure pump connected to each air bag and a hydraulic jack; the data acquisition component includes a pressure sensor arranged in each air bag, a bending moment and rotation angle sensor installed on a connecting rod, and an industrial computer connected to the pressure sensor, the bending moment and rotation angle sensor, and the pressure pump.

2. The drilling soil shear test device according to claim 1, characterized in that: Among the three groups of cylinders, the upper and lower parts of the upper and lower groups of cylinders are both equipped with ball turntable bearings, and the cylinders are rotatably installed on the connecting rods through the ball turntable bearings; the rubber airbags on the outer sides of the circumferences of the upper and lower groups of cylinders are cylindrical rubber airbags.

3. The soil shear test device in a borehole according to claim 1, characterized in that: Among the three groups of round drums, four groups of telescopic holes cooperating with shear plates are arranged on the circumference of the middle round drum; there are four groups of shear plates, which are arranged in a cross shape, and the four groups of shear plates are controlled separately by four groups of hydraulic jacks or by two groups of two-way hydraulic jacks or by one group of four-way hydraulic jacks.

4. The drilling soil shear test device according to claim 3, characterized in that: The four groups of telescopic holes divide the outer wall of the cylinder at the middle position into equal parts, and a sheet-shaped rubber airbag is installed on each divided outer wall.

5. A method for shearing test of soil in a borehole, the method for shearing test of soil in a borehole being based on the device for shearing test of soil in a borehole according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1 Test preparation: After drilling to the test depth, place the test device into the test section in the hole through the drill pipe connection; S2 Shear plate insertion: Use a hydraulic jack to press the shear plate into the hole wall soil to a certain depth; S3 data recording: Start the data acquisition component to record the pressure inside the rubber airbag, the bending moment and the rotation angle of the shear plate during rotation; S4 applies pressure: pressurizes the rubber airbag through a pressure pump and maintains a constant pressure to simulate deflection stress; S5 shear test: Start the drilling rig and rotate the drill rod at a constant speed, so that the shear plate shears the soil until the soil is destroyed, and record the maximum bending moment and rotation angle; S6 Repeat test: Repeat the test at different locations in the same formation to obtain shear strength data under different deviation stresses; S7 Data Analysis: The deviation stress and shear strength curves were plotted based on the test data, and the internal friction angle and cohesion of the soil were obtained by fitting the straight line using the least squares method. S8 Test termination: After data collection is completed, stop the test and dismantle the device.

6. The in-hole soil shear test method according to claim 5, characterized in that: During the S5 shear test, the shear plate shears the soil until the soil is destroyed, and the shear plate bending moment and rotation angle change curve during the shear process can be generated; based on the generated shear plate bending moment and rotation angle change curve during the shear process, the maximum bending moment M max , and the maximum bending moment M max The turning angle ω at the moment.

7. The in-hole soil shear test method according to claim 6, characterized in that: Based on the maximum bending moment M maxi Shear strength τ i calculate; The soil in the test section is under horizontal radial pressure P i and self-weight stress σ v0i Deviation stress P i -σ v0i Shear strength under action τ i The resistance moment generated on the shear plate is the same as the bending moment input to the shear plate by the drilling rig. The soil shear strength τ is calculated according to formula 1. i ; Expanding formula 1 yields formula 2: Where M maxi is the maximum bending moment recorded by the bending moment sensor; D is the horizontal length of the two ends of the shear plate after it is pressed into the soil; H is the height of the shear plate; τ i is the shear strength of the soil in the test section; d is the diameter of the borehole; x represents the radial distance from a point in the upper and lower action areas of the shear plate to the central axis of the borehole, which is a variable with a value range of arrive 8. The in-hole soil shear test method according to claim 5, characterized in that: During the S7 data analysis, based on different deviation stress P i -σ v0i Shear strength data under τ i , with P i -σ v0i is the horizontal axis, τ i Set P as the vertical coordinate i -σ v0i , τ i Import the coordinate system and fit it into a σ-τ straight line using the least squares method. The angle between the straight line and the abscissa is the internal friction angle φ of the test soil, and the intersection of the straight line and the ordinate is the cohesion c of the test soil.

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