A field test device for strength of cohesive soil and its use method

Abstract

The present invention provides a field test device for the strength of cohesive soil and a method for using the same. The field test device for the strength of cohesive soil includes a screw-in loader, a screw rod, a torsion actuator, a test probe, a conical head, a control terminal, and a communication module. The test probe includes a pore pressure sensor. The screw-in loader provides torsion and pressing force. The screw-in loader is connected to the screw rod, and the screw-in loader is used to drive the screw rod to rotate. The control terminal establishes communication connections with the screw-in loader, the torsion actuator, and the test probe respectively through the communication module. The beneficial effects of the present invention are: the present invention avoids soil sampling while reducing the soil squeezing effect during penetration, and reduces the influence of various friction forces between the device and the soil on the measurement data, thereby better serving the design and analysis of marine engineering and underground engineering.

Description

Technical Field

[0001] The invention relates to the technical field of test equipment, and in particular to a field test device for strength of cohesive soil and a use method thereof. Background Art

[0002] In marine geotechnical engineering and underground space engineering (such as subway tunnels and foundation pits), the undrained shear strength of clay soil is an important parameter for problem analysis. However, for sensitive or structural soils such as soft soils and residual soils, the disturbance of the soil by sampling may cause the indoor test to fail to accurately reflect the mechanical parameters of the soil in situ. At the same time, the existing in-situ test methods and equipment may squeeze the soil during penetration, resulting in unreliable measured data.

[0003] Existing technologies include:

[0004] 1. There are a large number of indoor soil strength test methods, such as direct shear, triaxial shear, etc. The above methods require sampling through drilling and transporting to indoor testing.

[0005] 2. There are a large number of traditional field test methods for soil strength, such as standard penetration test (SPT), static penetration test (CPT), cross plate shear test (VST), flat shovel dilatation test (DMT), etc. The above methods require the probe to be penetrated or pressed into the soil first, and then the strength of the cohesive soil is inferred by measuring the interaction between the probe and the soil.

[0006] 3. "In-situ testing device for large-area soft soil" CN202011381179.1, this invention application combines a drone with cross-plate shear to achieve in-situ testing of large-area soft soil.

[0007] 4. "A cross-shaped full-flow sounding probe for in-situ testing of marine supersoft soil" CN107747306B, this authorized invention proposes a probe for marine supersoft soil and its use method, aiming to achieve the problem of full-flow sounding.

[0008] 5. "An In-situ Testing Instrument for Foundation Soil Strength" CN114293529A, this invention application proposes a soil strength probe installation and load application device, which aims to apply the loading mode of the marine foundation to the probe.

[0009] The defects of the prior art are:

[0010] For soft soil, granite residual soil and other clay soils with high sensitivity or structure, sampling may destroy the in-situ characteristics of the soil, that is, indoor tests cannot well reflect the in-situ strength of the soil.

[0011] There are traditional field test methods, such as directly inserting the probe from the ground to the test depth, which may produce a strong soil squeezing effect, causing the soil pressure or soil density around the device to increase, thereby affecting the reliability of the measurement results. At the same time, the probe rod connected to the probe will have friction with the soil, further affecting the measurement results; if a hole is dug to the test depth and then the probe is inserted, the problem of hole collapse may occur in deeper strata, and it is not feasible to implement it in the ocean; in addition, some methods (such as CPT and SPT) do not directly measure the strength of the soil, but infer the soil strength through the interaction between the test equipment and the soil (such as the cone tip resistance of the CPT probe).

[0012] The existing authorized inventions or invention applications have failed to solve the above problems and cannot reduce the soil squeezing effect and the friction between the probe rod and the soil. Summary of the invention

[0013] The present invention provides a field test device for the strength of cohesive soil, comprising a screw-in loader, a screw rod, a torsion actuator, a test probe, a conical head, a control terminal, and a communication module, wherein the test probe comprises a pore pressure sensor, the screw-in loader provides torsion and pressing force, the screw-in loader is connected to the screw rod, and the screw-in loader is used to drive the screw rod to rotate;

[0014] The control terminal establishes communication connections with the screw-in loader, the torsion actuator, and the test probe respectively through the communication module;

[0015] The torsion actuator is connected to the spiral rod, the torsion actuator is connected to the conical head, and the torsion actuator is used to drive the test probe to rotate;

[0016] The test probe is used to measure the shear strength of cohesive soil;

[0017] The control terminal is used to formulate action commands, which are transmitted to the screw-in loader and the torsion actuator through the communication module. The control terminal receives and stores sensor data through the communication module; the control terminal estimates the consolidation coefficient cv of the soil based on the dissipation process curve of the excess pore water pressure measured by the pore pressure sensor; the control terminal can set the torsion angular velocity ω.

[0018] As a further improvement of the present invention, the field test device for the strength of clay soil also includes a reaction frame, which is fixedly screwed into the loader to provide torsional reaction force and pushing reaction force. The reaction frame is provided with a through hole, which is aligned with the spiral rod and is used for the entry and exit of the spiral rod.

[0019] The present invention also provides a method for using a field test device for the strength of cohesive soil, comprising the following steps:

[0020] Step 1: The control terminal sets and issues an action command to the screw-in loader through the communication module, and the screw-in loader screws the test probe clockwise to a certain depth to be measured, and then stops screwing in; during the screwing in process, the conical head cuts the soil and transfers it upward along the fourth spiral blade, the third spiral blade, the second spiral blade and the first spiral blade;

[0021] Step 2: The control terminal sets and issues an action command through the communication module, and the telescopic shear piece is pushed out of the cylinder by rotating the telescopic gear clockwise;

[0022] Step 3: Measure and transmit the pore water pressure at the location through the pore pressure sensor, and estimate the consolidation coefficient cv of the soil through the dissipation process of excess pore pressure until the estimated value is stable;

[0023] Step 4: The control terminal sets the torsion angular velocity ω, which is required to satisfy cv / (ωR 2 )<0.008, ensuring that the soil is in an undrained state during the test; where R is the radius formed by the outermost edge of the telescopic shear piece when it rotates; the communication module issues an action command, and the test probe is rotated clockwise as a whole by twisting the actuator, causing mutual shearing between the cohesive soils until the torque reaches a stable value M f And record it in the control terminal;

[0024] Step 5: The telescopic gear rotates counterclockwise to retract the telescopic shear piece into the cylinder, and the test probe is rotated counterclockwise as a whole by twisting the actuator until the second spiral blade, the third spiral blade and the fourth spiral blade are continuously connected with each other;

[0025] Step 6: Control the terminal to set the next depth to be measured and add the screw rod; return to the first step until all the measuring points are completed.

[0026] The beneficial effects of the present invention are: the present invention avoids soil sampling while reducing the soil squeezing effect during penetration, and reduces the influence of various frictions between the device and the soil on the measurement data, thereby better serving the design and analysis of marine engineering and underground engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a field test device for the strength of cohesive soil according to the present invention;

[0028] Figure 2 It is a schematic diagram of the structure of the spiral rod;

[0029] Figure 3 It is a schematic diagram of the structure of the test probe;

[0030] Figure 4 It is a schematic diagram of the structure in which the telescopic shear piece is pushed out of the cylinder;

[0031] Figure 5 It is a schematic diagram of the structure of the test probe rotating clockwise. DETAILED DESCRIPTION

[0032] like Figure 1 As shown, the present invention discloses a field test device for the strength of cohesive soil, comprising a reaction frame 1, a screw-in loader 2, a screw rod 3, a torsion actuator 4, a test probe 5, a conical head 6, a control terminal 10, and a communication module. The reaction frame 1 is fixedly screwed into the loader 2 to provide a torsional reaction force and a push-in reaction force. The reaction frame 1 is provided with a through hole, which is aligned with the screw rod 3, and the through hole is used for the screw rod 3 to enter and exit.

[0033] The screw-in loader 2 provides a torsion and pressing force, and the screw-in loader 2 is connected to the screw rod 3, and the screw-in loader 2 is used to drive the screw rod 3 to rotate, so that the screw rod 3 is slowly screwed into the venue clockwise, and is slowly screwed out of the venue when rotating counterclockwise.

[0034] The control terminal 10 establishes communication connections with the screw-in loader 2, the torsion actuator 4, and the test probe 5 respectively through the communication module. The communication connection can be established by wired connection or wireless connection. In the present invention, wired connection is preferably adopted, that is, the communication module is a wired communication module, and the wired communication module includes a fixed cable 8, a cable turntable 9, and an active cable 7 installed on the cable turntable 9. One end of the fixed cable 8 is connected to the control terminal 10, and the other end of the fixed cable 8 is connected to the screw-in loader 2. The control terminal 10 communicates with the screw-in loader 2 through the fixed cable 8, and the action command is transmitted to the screw-in loader 2 through the fixed cable 8.

[0035] The spiral rod 3 is provided with a hollow part, and the movable cable 7 passes through the hollow part of the spiral rod 3. One end of the movable cable 7 is connected to the control terminal 10, and the other end of the movable cable 7 is respectively connected to the torsion actuator 4 and the test probe 5. The movable cable 7 transmits action commands and collects sensor data to the torsion actuator 4 and the test probe 5. The spiral rod 3 is provided with a detachable mechanism, through which a new spiral rod 3 can be added or removed, and the specified test depth can be reached by continuously adding the spiral rod 3. The cable turntable 9 is used to adapt to different test depths. When a new spiral rod 3 is added, more movable cables 7 are released by rotation; conversely, after the spiral rod 3 is removed, the excess movable cables 7 are rotated to recover.

[0036] like Figure 2As shown, the spiral rod 3 includes a first rod body 31 and a second rod body 32. The gap between the first rod body 31 and the second rod body 32 constitutes a hollow portion. The first rod body 31 and the second rod body 32 are both provided with a plurality of first spiral blades 33. The first spiral blades 33 are used to bring the soil to the ground, which is similar to the construction process of long spiral bored piles.

[0037] The torsional actuator 4 is rigidly connected to the spiral rod 3 and the conical head 6, and there is no mutual rotation between them; the torsional actuator 4 is provided with a first gear for applying torque, which is used to drive the test probe 5 to rotate, and the torsional actuator 4 includes a driving motor, which is connected to the first gear. When the control terminal 10 sends an action command to the driving motor via the communication module, the driving motor drives the first gear to rotate; the test probe 5 is provided with a second gear, and the first gear is meshed with the second gear, and the test probe 5 is driven to rotate as a whole through the torsional actuator 4; the torsional actuator 4 is provided with a second spiral blade, and the second spiral blade is continuously connected with the first spiral blade 33.

[0038] The test probe 5 is used to measure the shear strength of cohesive soil, such as Figure 3 As shown, the test probe 5 includes a telescopic gear 51, a connecting rod 52, a telescopic shear piece 53, a cylinder 54, a third spiral blade 55, a pore pressure sensor 56, and a motor. The telescopic gear 51 is provided with an opening, and the connecting rod 52 passes through the opening. The opening and the connecting rod 2 are clearance-matched. One end of the connecting rod 52 is connected to the torsion actuator 4, and the other end of the connecting rod 52 is connected to the conical head 6. Because the opening and the connecting rod 52 are clearance-matched, the rotation of the telescopic gear 51 will not drive the connecting rod 52 to rotate. When the spiral rod 3 drives the torsion actuator 4 to rotate, the torsion actuator 4 drives the conical head 6 to rotate through the connecting rod 52, but does not drive the telescopic gear 51 to rotate; the motor is connected to the telescopic gear 51, and when the control terminal 10 sends an action command to the motor via the communication module, the motor drives the telescopic gear 51 to rotate, and the rotation of the telescopic gear 51 drives the telescopic shear piece 53 to move, so that the telescopic shear piece 53 is pushed out of the cylinder 54, or the telescopic shear piece 53 is retracted into the cylinder 54, for example, Figure 4 As shown in FIG. 1 , the telescopic gear 51 rotates clockwise to push the telescopic shearing piece 53 out of the cylinder 54, and rotates counterclockwise to retract the telescopic shearing piece 53 into the cylinder 54. Under the torsion of the torsion actuator 4, as shown in FIG. Figure 5 As shown, the test probe 5 rotates clockwise as a whole to cause mutual shearing of the soil; the third spiral blade 55 and the second spiral blade of the torsion actuator 4 are continuously connected to each other.

[0039] The specific embodiment of the telescopic gear 51 driving the telescopic shear piece 53 to move is as follows: the telescopic shear piece 53 is provided with a rack, and the rack is meshed with the telescopic gear 51. The telescopic shear piece 53 is pushed out of the cylinder 54 or retracted into the cylinder 54 through the rotation of the telescopic gear 51.

[0040] The conical head 6 is used to cut the soil and transfer the cut soil upward along the fourth spiral blade in sequence from the third spiral blade 55, the second spiral blade to the first spiral blade 33.

[0041] The control terminal 10 is used to formulate action commands, which are transmitted to the specified object through the movable cable 7 and the fixed cable 8; at the same time, the sensor data is received and stored through the movable cable 7; the consolidation coefficient cv of the soil can be estimated based on the dissipation process curve of the excess pore water pressure measured by the pore pressure sensor 56; the torsional angular velocity ω can be set.

[0042] The installation process of the field test device for the strength of cohesive soil of the present invention is as follows:

[0043] Step 1: Install and fix the reaction frame 1 on site, fix the screw-in loader 2 on the reaction frame 1, and connect the screw-in loader 2 to the control terminal 10 via the fixed cable 8.

[0044] Step 2: Connect the torsion actuator 4, the test probe 5 and the conical head 6 from top to bottom, and the second spiral blade, the third spiral blade 55 and the fourth spiral blade are continuously connected to each other. Before the test, the telescopic shear piece 53 of the test probe 5 is kept inside the cylinder 54.

[0045] Step 3: Release a certain length of the movable cable 7 through the cable turntable 9, one end of the movable cable 7 is connected to the control terminal 10, and the other end is connected to the torsion actuator 4 and the test probe 5.

[0046] Step 4: Use the control terminal 10 to rotate the test probe 5 clockwise and then return it to the center position, so as to calibrate the friction torque M between the test probe 5 and the torsion actuator 4 and the cone head 6 before the test. 0 . M 0 The data is transmitted back and recorded in the control terminal 10 .

[0047] Step 5: Combine the first rod body 31 and the second rod body 32 to form a spiral rod 3, pass the movable cable 7 through the hollow part, and then fix the spiral rod 3 to the torsion actuator 4, requiring the second spiral blade and the first spiral blade 33 to be continuously connected with each other.

[0048] Step 6: Pass the screw rod 3 through the through hole of the reaction frame 1 and screw it into the loader 2, ensure verticality, and wait until the test starts.

[0049] The present invention also discloses a method for using a field test device for the strength of cohesive soil, comprising the following steps:

[0050] Step 1: The control terminal 10 is set and sends an action command via the fixed cable 8, and the test probe 5 is screwed clockwise to a certain depth to be measured by the screw-in loader 2, and then the screwing in is stopped; during the screwing in process, the conical head 6 cuts the soil and transfers it upward along the spiral blade, but does not cause a soil squeezing effect, and the excess soil on the ground is cleaned to enable the screw-in loader 2 to work better.

[0051] Step 2: The control terminal 10 sets and issues an action command via the movable cable 7, and the telescopic shearing piece 53 is pushed out of the cylinder 54 by rotating the telescopic gear 51 clockwise (such as Figure 4 shown).

[0052] Step 3: The pore water pressure at the location is measured and transmitted back through the pore pressure sensor 56, and the consolidation coefficient cv of the soil is estimated through the dissipation process of the excess pore pressure until the estimated value is stable.

[0053] Step 4: Control terminal 10 to set the torsion angular velocity ω, which is required to satisfy cv / (ωR 2 )<0.008, ensuring that the soil is in an undrained state during the test; wherein R is the radius formed by the outermost edge of the telescopic shear piece 53 when it rotates, which is a factory-known value. The action command is issued via the movable cable 7, and the test probe 5 is rotated clockwise as a whole by twisting the actuator 4 (such as Figure 5 As shown in the figure, the clay soils shear against each other until the torque reaches a stable value M. f and recorded in the control terminal 10. In this step, the measured M f There is no friction between the spiral rod 3 and the soil, and it is only composed of friction between the soil and friction between the equipment; there is no risk of hole collapse; the penetration of the device is achieved by cutting and transferring the soil, and there is no soil squeezing effect during penetration, only a slight soil squeezing effect when the blades are extended.

[0054] Step 5: The telescopic gear 51 rotates counterclockwise to retract the telescopic shearing piece 53 into the retracting cylinder 54, and the test probe 5 is rotated counterclockwise as a whole by twisting the actuator 4 until the second spiral blade, the third spiral blade 55 and the fourth spiral blade are continuously connected with each other.

[0055] Step 6: The control terminal 10 sets the next depth to be measured, increases the spiral rod 3 and releases the movable cable 7 through the cable turntable 9 to ensure that the measuring point can be reached; return to the first step until all measuring points are completed.

[0056] Step 7: After all the measuring points are completed, slowly unscrew the screw rod 3 by screwing in the loader 2 and rotating it counterclockwise, and recover the movable cable 7 and the screw rod 3. At the same time, add soil to the screw blades on the ground to ensure that there is enough soil backfill.

[0057] Shear strength calculation method:

[0058] The radius r and height H of the cylinder 54 are known at the factory, and the radius formed by the outermost edge of the telescopic shear piece 53 when it rotates is R. The friction torque M before the test can be obtained at a certain measurement depth. 0 and stable torque M f , so the corresponding undrained shear strength s u As shown in formula (1):

[0059]

[0060] Technical advantages of the present invention:

[0061] 1. There is no soil squeezing effect when the test probe 5 is penetrated, which improves the accuracy of measurement;

[0062] 2. Measured torque M f The friction between the probe connecting rod and the soil is not included, ensuring the accuracy of measurement even when the depth increases;

[0063] 3. There are problems of hole digging and hole collapse. By adding a spiral rod 3 and releasing a movable cable 7 to measure at different depths, multi-point measurement can be performed;

[0064] 4. During the rotation of the screw, the expelled soil can be backfilled, which can achieve no soil abandonment to a certain extent.

[0065] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A field test device for the strength of cohesive soil, characterized in that: The invention comprises a screw-in loader (2), a screw rod (3), a torsion actuator (4), a test probe (5), a conical head (6), a control terminal (10), and a communication module. The test probe (5) comprises a pore pressure sensor (56). The screw-in loader (2) provides torsion and pressing force. The screw-in loader (2) is connected to the screw rod (3), and the screw-in loader (2) is used to drive the screw rod (3) to rotate. The control terminal (10) establishes communication connections with the screw-in loader (2), the torsion actuator (4), and the test probe (5) respectively through the communication module; The torsion actuator (4) is connected to the spiral rod (3), the torsion actuator (4) is connected to the conical head (6), and the torsion actuator (4) is used to drive the test probe (5) to rotate; The test probe (5) is used to measure the shear strength of clay soil; The control terminal (10) is used to formulate an action command, and the action command is transmitted to the screw-in loader (2) and the torsion actuator (4) through the communication module. The control terminal (10) receives and stores sensor data through the communication module; the control terminal (10) estimates the consolidation coefficient cv of the soil according to the dissipation process curve of the excess pore water pressure measured by the pore pressure sensor (56); the control terminal (10) can set the torsion angular velocity ω; The test probe (5) comprises a telescopic gear (51), a motor, a telescopic shear piece (53), and a cylinder (54); the motor is connected to the telescopic gear (51); when the control terminal (10) sends an action command to the motor via the communication module, the motor drives the telescopic gear (51) to rotate; the rotation of the telescopic gear (51) drives the telescopic shear piece (53) to move, so that the telescopic shear piece (53) is pushed out of the cylinder (54), or the telescopic shear piece (53) is retracted into the cylinder (54); The test probe (5) comprises a connecting rod (52), the telescopic gear (51) is provided with an opening, the connecting rod (52) passes through the opening, the opening and the connecting rod (52) are clearance-matched, one end of the connecting rod (52) is connected to the torsion actuator (4), and the other end of the connecting rod (52) is connected to the conical head (6); The telescopic shear piece (53) is provided with a rack, and the rack is meshed with the telescopic gear (51); the torsion actuator (4) comprises a drive motor and a first gear, and the drive motor is connected to the first gear. When the control terminal (10) sends an action command to the drive motor via the communication module, the drive motor drives the first gear to rotate; the test probe (5) is provided with a second gear, and the first gear is meshed with the second gear. The test probe (5) is driven to rotate as a whole through the torsion actuator (4); The outer surface of the spiral rod (3) is provided with a plurality of first spiral blades (33); the torsion actuator (4) is provided with a second spiral blade, the second spiral blade and the first spiral blade (33) are continuously connected to each other; the test probe (5) is provided with a third spiral blade (55), the third spiral blade (55) and the second spiral blade are continuously connected to each other; the conical head (6) is provided with a fourth spiral blade, the fourth spiral blade and the third spiral blade (55) are continuously connected to each other.

2. The field test device for the strength of cohesive soil according to claim 1 is characterized in that: The field test device for the strength of cohesive soil also comprises a reaction frame (1), wherein the reaction frame (1) is fixedly screwed into the loader (2) to provide a torsional reaction force and a pushing reaction force, and the reaction frame (1) is provided with a through hole, wherein the through hole is aligned with the screw rod (3), and the through hole is used for the screw rod (3) to enter and exit.

3. The field test device for the strength of cohesive soil according to claim 1 is characterized in that: The communication module is a wired communication module, comprising a fixed cable (8), one end of the fixed cable (8) being connected to the control terminal (10), and the other end of the fixed cable (8) being connected to the screw-in loader (2), so that the control terminal (10) and the screw-in loader (2) can communicate via the fixed cable (8); The wired communication module further comprises a cable turntable (9) and an active cable (7) mounted on the cable turntable (9); the spiral rod (3) is provided with a hollow portion, the active cable (7) passes through the hollow portion of the spiral rod (3), one end of the active cable (7) is connected to the control terminal (10), and the other end of the active cable (7) is respectively connected to the torsion actuator (4) and the test probe (5); the active cable (7) transmits action commands and collects sensor data to the torsion actuator (4) and the test probe (5); The spiral rod (3) is provided with a detachable mechanism, through which a new spiral rod (3) can be added or the spiral rod (3) can be removed.

4. The field test device for the strength of cohesive soil according to claim 1 is characterized in that: The control terminal (10) calculates the undrained shear strength s u , R is the radius formed by the outermost edge of the telescopic shearing piece (53) when it rotates, M f is the torque, r is the radius of the cylinder (54), H is the height of the cylinder (54), and M0 is the friction torque between the test probe (5) and the torsion actuator (4) and the conical head (6) calibrated before the test.

5. A method for using the device for testing the strength of clay soil in situ according to claim 1, characterized in that: The steps include: The first step: the control terminal (10) sets and issues an action command to the screw-in loader (2) via the communication module, and the screw-in loader (2) screws the test probe (5) clockwise to a certain depth to be measured, and then stops screwing in; during the screwing in process, the conical head (6) cuts the soil and transfers it upward along the fourth spiral blade, the third spiral blade (55), the second spiral blade and the first spiral blade (33); Step 2: The control terminal (10) sets and issues an action command through the communication module, and the telescopic gear (51) rotates clockwise to push the telescopic shear piece (53) out of the cylinder (54); Step 3: Measure and transmit the pore water pressure at the location through the pore pressure sensor (56), and estimate the consolidation coefficient cv of the soil through the dissipation process of excess pore pressure until the estimated value is stable; Step 4: The control terminal (10) sets the torsion angular velocity ω, which is required to satisfy cv / (ωR 2 )<0.008, ensuring that the soil is in an undrained state during the test; wherein R is the radius formed by the outermost edge of the telescopic shear piece (53) when it rotates; an action command is issued by the communication module, and the test probe (5) is rotated clockwise as a whole by the torsion actuator (4), so that mutual shearing occurs between the cohesive soils until the torque reaches a stable value M f and recorded in the control terminal (10); Step 5: The telescopic gear (51) rotates counterclockwise to retract the telescopic shearing piece (53) into the cylinder (54), and the test probe (5) is rotated counterclockwise as a whole by twisting the actuator (4) until the second spiral blade, the third spiral blade (55) and the fourth spiral blade are continuously connected to each other; Step 6: The control terminal (10) sets the next depth to be measured and increases the screw rod (3); and the process returns to the first step until all the measuring points are completed.

6. The method of use according to claim 5, characterized in that: In the first step: the control terminal (10) is set and an action command is issued via the fixed cable (8), and the test probe (5) is screwed in clockwise to a certain depth to be measured by the screw-in loader (2), and then the screwing in is stopped; during the screwing in process, the conical head (6) cuts the soil and transfers it upward along the fourth spiral blade, the third spiral blade (55), the second spiral blade and the first spiral blade (33); In the second step: the control terminal (10) sets and issues an action command via the movable cable (7), and the telescopic shearing piece (53) is pushed out of the cylinder (54) by rotating the telescopic gear (51) clockwise; in the fourth step: the control terminal (10) sets the torsional angular velocity ω, which is required to satisfy cv / (ωR 2 )<0.008, ensuring that the soil is in an undrained state during the test; wherein R is the radius formed by the outermost edge of the telescopic shear piece (53) when it rotates; an action command is issued via the movable cable (7), and the test probe (5) is rotated clockwise as a whole by twisting the actuator (4), so that mutual shearing occurs between the cohesive soils until the torque reaches a stable value M f and recorded in the control terminal (10); In the sixth step: the control terminal (10) sets the next depth to be measured, increases the spiral rod (3) and releases the movable cable (7) through the cable turntable (9) to ensure that the measuring point can be reached; returns to the first step until all measuring points are completed; The control terminal (10) calculates the undrained shear strength s u , R is the radius formed by the outermost edge of the telescopic shearing piece (53) when it rotates, M f is the torque, r is the radius of the cylinder (54), H is the height of the cylinder (54), and M0 is the friction torque between the test probe (5) and the torsion actuator (4) and the conical head (6) calibrated before the test.

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