Small dynamic in-hole shear test device and test method

Abstract

The invention relates to a small dynamic in-hole shear test device and method.The small dynamic in-hole shear test device comprises a computer data acquisition system, a control panel system, a test host, a steel cable and a force bearing mechanism, and the test host comprises a host frame, a pushing system, a force transmission mechanism, a normal loading system and a shear loading system; the main machine frame abuts against the hole wall of the detection hole through the pushing system, the normal loading system is used for driving the force transmission mechanism to load normal force to the sample soil body, and the shear loading system is used for driving the force transmission mechanism to load shear force to the sample soil body. The in-situ in-hole shear test device has the beneficial effects that in-situ in-hole shear tests of a soil body, a soft rock and a soil-rock mixture can be realized, so that the dynamic characteristics of a rock-soil body can be researched under a DNL condition, and a slope instability mechanism can be disclosed.

Description

Technical Field

[0001] The invention relates to the technical field of geotechnical engineering in-situ testing, and in particular to a small dynamic in-hole shear test device and a test method. Background Art

[0002] The strength parameter values ​​used in the stability analysis of rock and soil are generally obtained through indoor direct shear tests or conventional triaxial tests. Indoor geotechnical tests are not only affected by the size effect, but also by the stress release and transportation disturbances during the on-site excavation of the specimens, which inevitably affect their natural properties and mechanical characteristics, resulting in deviations in the indoor test results. In-situ tests make up for many of the shortcomings of indoor tests and can basically maintain the original saturation, stress state and structure of the rock and soil to determine the mechanical property indicators.

[0003] The main in-situ tests include large direct shear test, cross-plate shear test and in-hole shear test. Large direct shear test has the disadvantages of expensive test, long cycle and complicated operation; cross-plate shear test can only obtain cohesion C, but cannot obtain internal friction angle φ. Practical engineering experience shows that cross-plate shear test cannot be used for soft clay containing sand layer, gravel, shell and other components. When there is silt sand interlayer, the test result is often too large; in-hole shear test is to measure the shear strength of in-situ soil under different normal stresses. It has the characteristics of convenient operation, high repeatability and short test time. The degree of disturbance to rock and soil is almost negligible compared with indoor test. It is not only suitable for strata such as clay, sand, soft rock, soil-rock mixture, but also suitable for slope stability analysis where it is not easy to obtain original samples and the soil properties change greatly.

[0004] Existing in-hole shear test equipment has certain limitations. It is generally driven and data collected manually, which makes it difficult to control a constant shear rate, affecting the accuracy of the test results, and it is impossible to set parameters for working conditions under seismic conditions. Earthquakes and rock bursts are very complex dynamic events. In these events, shearing directly under dynamic normal load (DNL) conditions is a common phenomenon. Therefore, the strength attenuation law and dynamic characteristics of rock and soil under seismic loads need to be studied in depth. However, due to functional limitations, existing in-hole shear test equipment and methods cannot fully meet the relevant research requirements. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a small dynamic in-hole shear test device and test method, which can realize in-situ in-hole shear test of soil, soft rock, and soil-rock mixture, and then study the dynamic characteristics of rock and soil under DNL conditions, which is conducive to revealing the instability mechanism of slope.

[0006] The purpose of the present invention is achieved through the following technical solutions: A small dynamic in-hole shear test device, comprising: A computer data acquisition system and a control panel system, wherein the control panel system is electrically connected to the computer data acquisition system; The test host, steel cable and load-bearing mechanism are provided. The test host is lowered into the detection hole of the sample soil through the steel cable. The steel cable is fixed to the load-bearing mechanism. The load-bearing mechanism is supported at the opening of the detection hole on the sample soil. The test host includes a host frame, a pushing system, a force transmission mechanism, a normal loading system, and a shear loading system. The steel cable is connected to the host frame. The pushing system, the force transmission mechanism, the normal loading system, and the shear loading system are all arranged on the host frame. The pushing system, the normal loading system, and the shear loading system are all electrically connected to the control panel system through the steel cable. The host frame is abutted against the wall of the detection hole through the pushing system. The normal loading system is used to drive the force transmission mechanism to load normal force to the sample soil. The shear loading system is used to drive the force transmission mechanism to load shear force to the sample soil.

[0007] Furthermore, the load-bearing mechanism includes a fixing bolt, a fixing column, a load-bearing steel plate, and a casing. A casing inserted into the drilled hole is provided at the bottom of the fixing column. The load-bearing steel plate is provided at the connection between the fixing column and the casing. The fixing column is supported at the mouth of the drilled hole by the load-bearing steel plate. The steel cable passes through the fixing column and the casing in sequence and is connected to the top of the fixing column through the fixing bolt.

[0008] Furthermore, a third inner cavity is provided in the main frame, and the pushing system includes a third reduction stepper motor, a second lead screw, a screw, a fixed block, a connecting rod, a pushing force transmission shaft, a pushing plate, and a streamlined protrusion. The third reduction stepper motor is arranged in the third inner cavity and is electrically connected to the control board system through a steel cable. A first opening is provided on the side wall of the main frame, and the pushing force transmission shaft is slidably passed through the main frame through the first opening. The output end of the third reduction stepper motor is connected to the second lead screw, and the second lead screw is connected to the fixed block through a screw. Both ends of the connecting rod are rotatably connected to the fixed block and the pushing force transmission shaft respectively. A pushing plate is provided on the end of the pushing force transmission shaft away from the connecting rod, and a streamlined protrusion is provided on the pushing plate for abutting against the sample soil.

[0009] Furthermore, a second opening is provided on the side wall of the main frame, and the force transmission mechanism includes a vertical slide rail, an L-shaped force transmission pad, and loading serrations. The vertical slide rail is provided at the second opening, and the vertical section of the L-shaped force transmission pad is slidably connected to the vertical slide rail. The front side of the vertical section of the L-shaped force transmission pad is provided with loading serrations that abut against the sample soil. The normal loading system acts on the vertical end of the L-shaped force transmission pad, and the shear loading system acts on the horizontal end of the L-shaped force transmission pad.

[0010] Furthermore, a first inner cavity and a second inner cavity are also provided in the main frame, and the normal loading system includes a first reduction stepper motor, a second reduction stepper motor, a first lead screw, a first lead screw connector, a first follower lead screw, a normal force sensor, and a normal loading piston. The first reduction stepper motor is arranged in the first inner cavity, and the second reduction stepper motor is arranged in the second inner cavity. The first reduction stepper motor and the second reduction stepper motor are connected in series and are electrically connected to the control board system through a steel cable. The output end of the second reduction stepper motor is connected to the first lead screw, the first lead screw is connected to the first follower lead screw through the first lead screw connector, the first follower lead screw is connected to the normal loading piston, the normal loading piston is abutted against the back side of the vertical end of the L-shaped force transmission pad, and the normal force sensor is arranged in the normal loading piston and is electrically connected to the control board system.

[0011] Furthermore, a fourth inner cavity is provided in the main frame, and the shear loading system includes a fourth reduction stepper motor, a third lead screw, a second lead screw connector, a second follower lead screw, a tangential force sensor, and a shear loading piston. The fourth reduction stepper motor is arranged in the fourth inner cavity and is electrically connected to the control board system through a steel cable. The output end of the fourth reduction stepper motor is connected to the third lead screw, the third lead screw is connected to the second follower lead screw through the second lead screw connector, the second follower lead screw is connected to a shear loading piston abutting against the bottom of the horizontal end of the L-shaped force transmission pad, and the tangential force sensor is arranged in the shear loading piston and is electrically connected to the control board system.

[0012] Furthermore, the normal loading piston and the shear loading piston both include a piston column and a piston base. One end of the piston column in the normal loading piston is connected to the first follower screw through a nut, and the other end of the piston column in the normal loading piston is connected to the piston base abutting against the back side of the vertical end of the L-shaped force transmission pad. The normal force sensor is arranged in the piston column in the normal loading piston, one end of the piston column in the shear loading piston is connected to the second follower screw through a nut, and the other end of the piston column in the shear loading piston is connected to the piston base abutting against the bottom of the horizontal end of the L-shaped force transmission pad, and the tangential force sensor is arranged in the piston column in the shear loading piston.

[0013] Furthermore, based on the above-mentioned small-scale dynamic in-hole shear test device, the present invention also provides a small-scale dynamic in-hole shear test method, comprising the following steps: S1. Drill a detection hole on the sample soil with a drilling rig and clean the loose soil at the bottom of the detection hole. Lower the test host into the detection hole through a steel cable. Insert the casing into the detection hole and support the fixed column at the mouth of the detection hole through a bearing steel plate. S2. When the test host is lowered to the set depth, a push command is sent to the control panel system through the computer data acquisition system, so that the control panel system controls the third reduction stepping motor to drive the push force transmission axis to slide outside the host frame, so that the streamlined protrusion on the push plate is tightly in contact with the wall of the detection hole, and then the steel cable is fixed to the fixed column by the fixing bolt; S3, sending a normal loading instruction to the control panel system through the computer data acquisition system, so that the control panel system controls the first deceleration stepper motor and the second deceleration stepper motor to drive the normal loading piston to press against the L-shaped force transmission pad, so that the L-shaped force transmission pad loads the normal force to the sample soil through the loading sawtooth, and the data detected by the normal force sensor in the normal loading piston is transmitted to the control panel system and then transmitted to the computer data acquisition system by the control panel system; S4, keeping the normal force applied to the sample soil unchanged, sending a shear loading instruction to the control panel system through the computer data acquisition system, so that the control panel system controls the fourth deceleration stepper motor to drive the shear loading piston to press against the L-shaped force transmission pad, so that the L-shaped force transmission pad applies a shear force to the sample soil, and the data detected by the tangential force sensor in the shear loading piston is transmitted to the control panel system and then transmitted to the computer data acquisition system by the control panel system; S5. According to steps S2-S4, lower the test host to positions of different depths in the detection hole and conduct no less than three tests; S6. End the test and process the test data.

[0014] Furthermore, when loading the normal force, the actual seismic records collected are corrected, and then the corrected acceleration-time curve records are integrated twice to obtain the displacement-time curve. Finally, discrete points are extracted from the displacement-time curve and input into the computer data acquisition system. The computer data acquisition system processes the discrete points through the operating software to obtain the seismic wave load required for the test, and then sends a normal loading instruction to the control panel system according to the seismic wave load.

[0015] Furthermore, when the shear force is loaded, the peak shear strength of the sample soil follows the Coulomb strength criterion form. During the process of loading the shear force, when the peak shear strength reaches its maximum value, the maximum shear stress is taken as the shear stress when the sample soil is damaged and input into the computer data acquisition system. If the peak shear strength does not reach a maximum value, the shear stress at a shear displacement of 40 mm is selected and input into the computer data acquisition system. Then the computer data acquisition system sends a shear loading instruction to the control panel system according to the input shear force.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention can realize in-situ in-hole shear tests on soil, soft rock, and soil-rock mixtures, and further study the dynamic characteristics of rock and soil under DNL conditions, which is beneficial to revealing the mechanism of slope instability and solving dynamic engineering problems under the influence of complex dynamic conditions such as earthquakes and rock bursts.

[0017] 2. The present invention can solve the problem that when a drill rig drills a hole under a loose soil layer, the drilled hole is larger than the actual design, resulting in the front end of the normal loading system being unable to embed into the soil layer through the setting of the pushing system. This makes it possible to smoothly load the normal force even when the borehole size deviates from the design size, thereby ensuring the accuracy of the test results.

[0018] 3. The present invention replaces the traditional hydraulic drive with a push stepper motor, a normal stepper motor and a shear stepper motor, which has a simple structure and high reliability. It is not affected by the external environment during operation. The motor has a long life and is not affected by the load. It has good motion repeatability, thereby achieving an ideal control effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a structural schematic diagram of the outer side of the main frame in the present invention; Figure 3 It is a schematic diagram of the structure of the other side of the main frame of the present invention; Figure 4 It is a schematic diagram of the internal structure of the host frame in the present invention; Figure 5 It is a structural schematic diagram of the piston in the present invention; Figure 6 It is a schematic diagram of the load waveform in the present invention.

[0020] In the figure: 1. Computer data acquisition system; 2. Control panel system; 3. Steel cable; 4. Fixing bolt; 5. Fixing column; 6. Load-bearing steel plate; 7. Casing; 8. Test host; 9. Connecting port; 10. Host frame; 11. Slide rail; 12. L-shaped force transmission pad; 13. Loading sawtooth; 14. Pushing system; 15. Pushing force transmission shaft; 16. Streamlined bump; 17. Pushing plate; 18. First reduction stepping motor; 19. Second reduction stepping motor; 20. First lead screw; 21. First lead screw connector ; 22. First follow-up screw; 23. First inner cavity; 24. Second inner cavity; 25. Third inner cavity; 26. Third reduction stepping motor; 27. Second lead screw; 28. Normal force sensor; 29. ​​Screw; 30. Fixing block; 31. Connecting rod; 32. Fourth reduction stepping motor; 33. Fourth inner cavity; 34. Third lead screw; 35. Second lead screw connector; 36. Second follow-up screw; 37. Tangential force sensor; 38. Piston column hole; 39. Piston column; 40. Guide groove; 41. Piston base. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings, but the protection scope of the present invention is not limited to the following description.

[0022] like Figure 1 As shown, a small dynamic in-hole shear test device includes a computer data acquisition system 1, a control panel system 2, a test host 8, a steel cable 3, and a load-bearing mechanism. The control panel system 2 is electrically connected to the computer data acquisition system 1, the test host 8 is lowered into the detection hole of the sample soil body through the steel cable 3, the steel cable 3 is fixed to the load-bearing mechanism, and the load-bearing mechanism is supported at the detection hole opening on the sample soil body.

[0023] The test host 8 includes a host frame 10, a pushing system 14, a force transmission mechanism, a normal loading system, and a shear loading system. A connection port 9 is provided on the top of the host frame 10. The steel cable 3 is connected to the host frame 10 via the connection port 9. The pushing system 14, the force transmission mechanism, the normal loading system, and the shear loading system are all arranged on the host frame 10. The pushing system 14, the normal loading system, and the shear loading system are all electrically connected to the control panel system 2 through the steel cable 3. The host frame 10 is abutted against the wall of the detection hole through the pushing system 14. The normal loading system is used to drive the force transmission mechanism to load normal force to the sample soil. The shear loading system is used to drive the force transmission mechanism to load shear force to the sample soil. The computer data acquisition system 1 sends instructions to the control panel system 2, so that the control panel system 2 controls the test host 8 to apply load to the sample soil for testing. During the test, the load applied by the test host 8 is fed back to the control panel system 2, and the control panel system 2 then feeds back the load data to the computer data acquisition system 1. The computer data acquisition system 1 then sends instructions to the control panel system 2 based on the fed-back load data, so that the control panel system 2 controls the load applied by the test host 8 until the applied load meets the test requirements. The test data obtained after the test is completed is then collected and processed by the computer data acquisition system 1.

[0024] In this embodiment, the main frame 10 is a cylinder made of high-strength rigid material, with a height of 300 mm and a diameter of 110 mm, and has the characteristics of good mechanical properties, high precision, and strong overall stability.

[0025] like Figure 1 As shown, the load-bearing mechanism includes a fixing bolt 4, a fixing column 5, a load-bearing steel plate 6, and a sleeve 7. A sleeve 7 inserted into a drilled hole is provided at the bottom of the fixing column 5. The load-bearing steel plate 6 is provided at the connection between the fixing column 5 and the sleeve 7. The fixing column 5 is supported at the mouth of the detection hole by the load-bearing steel plate 6. The steel cable 3 passes through the fixing column 5 and the sleeve 7 in sequence and is connected to the top of the fixing column 5 through the fixing bolt 4.

[0026] like Figure 3 , Figure 4As shown, a third inner cavity 25 is provided in the main frame 10, and the pushing system 14 includes a third reduction stepper motor 26, a second lead screw 27, a screw 29, a fixed block 30, a connecting rod 31, a pushing force transmission shaft 15, a pushing plate 17, and a streamlined protrusion 16. The third reduction stepper motor 26 is arranged in the third inner cavity 25 and is electrically connected to the control board system 2 through the steel cable 3. A first opening is provided on the side wall of the main frame 10, and the pushing force transmission shaft 15 is slidably penetrated through the first opening on the main frame 10. The output end of the third reduction stepper motor 26 is connected to the second lead screw 27, and the second lead screw 27 is connected to the fixed block 30 through the screw 29. Both ends of the connecting rod 31 are rotatably connected with the fixed block 30 and the pushing force transmission shaft 15 respectively. A pushing plate 17 is provided on the end of the pushing force transmission shaft 15 away from the connecting rod 31, and a streamlined protrusion 16 abutting against the sample soil is provided on the pushing plate 17. The third reduction stepper motor 26 drives the second lead screw 27 to rotate, so that the fixed block 30 moves up and down along the second lead screw 27. During the up and down movement of the fixed block 30, the connecting rod 31 can pull or push the push-pull force transmission shaft 15 to slide along the first opening. When the fixed block 30 is driven to move downward, the connecting rod 31 can push the push-pull force transmission shaft 15 to slide outside the main frame 10, so that the push plate 17 can abut against the sample soil on the wall of the detection hole through the streamlined protrusion 16, thereby stabilizing the main frame 10 in the detection hole.

[0027] like Figure 2 , Figure 4 As shown, a second opening is provided on the side wall of the main frame 10, and the force transmission mechanism includes a vertical slide rail 11, an L-shaped force transmission pad 12, and a loading serration 13. The vertical slide rail 11 is fixed at the second opening, and the vertical section of the L-shaped force transmission pad 12 is slidably connected to the vertical slide rail 11. The front side of the vertical section of the L-shaped force transmission pad 12 is provided with a loading serration 13 that abuts against the sample soil. The normal loading system acts on the vertical end of the L-shaped force transmission pad 12, and the shear loading system acts on the horizontal end of the L-shaped force transmission pad 12.

[0028] like Figure 2 , Figure 4As shown, the main frame 10 is further provided with a first inner cavity 23 and a second inner cavity 24, and the normal loading system includes a first reduction stepper motor 18, a second reduction stepper motor 19, a first lead screw 20, a first lead screw connector 21, a first follower lead screw 22, a normal force sensor 28, and a normal loading piston. The first reduction stepper motor 18 is arranged in the first inner cavity 23, and the second reduction stepper motor 19 is arranged in the second inner cavity 24 and can move left and right in the second inner cavity 24. The first reduction stepper motor 18 and the second reduction stepper motor 19 are connected in series and are electrically connected to the control board system 2 through the steel cable 3. The output end of the second reduction stepper motor 19 is connected to the first lead screw 20, and the first lead screw 20 is connected to the first follower lead screw 22 through the first lead screw connector 21. The first follower lead screw 22 is connected to the normal loading piston, and the normal loading piston is abutted against the back side of the vertical end of the L-shaped force transmission pad 12. The normal force sensor 28 is arranged in the normal loading piston and is electrically connected to the control board system 2. The first reduction stepper motor 18 and the second reduction stepper motor 19 are connected in series and jointly drive the first lead screw 20 to rotate. The first lead screw 20 drives the first follower lead screw 22 to rotate through the first lead screw connector 21. The first follower lead screw 22 then drives the normal loading piston to press against the L-shaped force transmission pad 12, so that the loading serrations 13 on the L-shaped force transmission pad 12 are embedded in the sample soil and apply a normal force to the sample soil. The normal force sensor 28 can measure the normal force in real time.

[0029] like Figure 2 , Figure 4 As shown, a fourth inner cavity 33 is also provided in the main frame 10, and the shear loading system includes a fourth reduction stepper motor 32, a third lead screw 34, a second lead screw connector 35, a second follower lead screw 36, a tangential force sensor 37, and a shear loading piston. The fourth reduction stepper motor 32 is arranged in the fourth inner cavity 33 and is electrically connected to the control board system 2 through the steel cable 3. The output end of the fourth reduction stepper motor 32 is connected to the third lead screw 34, and the third lead screw 34 is connected to the second follower lead screw 36 through the second lead screw connector 35. The second follower lead screw 36 is connected to a shear loading piston abutting against the bottom of the horizontal end of the L-shaped force transmission pad 12, and the tangential force sensor 37 is arranged in the shear loading piston and is electrically connected to the control board system 2. The fourth reduction stepper motor 32 drives the third lead screw 34 to rotate, and the third lead screw 34 drives the second follower lead screw 36 to rotate through the second lead screw connector 35. The second follower lead screw 36 rotates and applies a tangential force to the shear loading piston. The applied tangential force acts on the L-shaped force transmission pad 12, so that the L-shaped force transmission pad 12 shears the sample soil along the vertical slide rail 11. The tangential force can be measured in real time by the tangential force sensor 37, and the tangential displacement during the shearing process can be measured by the rotation of the third lead screw 34 and the second follower lead screw 36 or the displacement of the shear loading piston.

[0030] like Figure 4 , Figure 5As shown, both the normal loading piston and the shear loading piston include a piston column 39 and a piston base 41. One end of the piston column 39 in the normal loading piston is connected to the first follower screw 22 through a nut, and the other end of the piston column 39 in the normal loading piston is connected to the piston base 41 that abuts against the back of the vertical end of the L-shaped force transmission pad 12. The normal force sensor 28 is arranged in the piston column 39 in the normal loading piston. One end of the piston column 39 in the shear loading piston is connected to the second follower screw 36 through a nut, and the other end of the piston column 39 in the shear loading piston is connected to the piston base 41 that abuts against the bottom of the horizontal end of the L-shaped force transmission pad 12. The tangential force sensor 37 is arranged in the piston column 39 in the shear loading piston. In addition, a piston column hole 38 is provided on the piston column 39, and a guide groove 40 is provided on the piston base 41. The piston column hole 38 and the guide groove 40 facilitate the routing of the normal force sensor 28 and the tangential force sensor 37 when they are electrically connected to the control board system 2.

[0031] The computer acquisition system realizes data acquisition, data processing and command sending based on the computer; the control panel system 2 includes a single-chip microcomputer, a drive circuit and a constant current source control circuit, and adopts a system to realize closed-loop control in order to improve the control accuracy of the deceleration stepper motor. The computer sends a control instruction to the single-chip microcomputer, so that the single-chip microcomputer controls the first deceleration stepper motor 18, the second deceleration stepper motor 19, the third deceleration stepper motor 26 and the fourth deceleration stepper motor 32 to work. The deceleration stepper motor replaces the traditional hydraulic drive, which has a simple structure and high reliability. It is not affected by the external environment during operation, the motor has a long life, is not affected by the load, and has good motion repeatability, thereby achieving an ideal control effect. The analog signal of the load detected by the normal force sensor 28 and the tangential force sensor 37 can be converted into a digital signal by an analog-to-digital converter and then transmitted to the single-chip microcomputer, and then transmitted to the computer by the single-chip microcomputer.

[0032] When the shear test is performed by the small dynamic in-hole shear test device, the following steps are included: S1. Drill a detection hole on the sample soil with a drilling rig and clean the loose soil at the bottom of the detection hole. Lower the test host 8 into the detection hole through the steel cable 3. Insert the casing 7 into the detection hole and support the fixed column 5 at the mouth of the detection hole through the bearing steel plate 6. S2. When the test host 8 is lowered to the set depth, a pushing instruction is sent to the control board system 2 through the computer data acquisition system 1, so that the control board system 2 controls the third reduction stepping motor 26 to drive the pushing force transmission shaft 15 to slide outside the host frame 10, so that the streamlined protrusion 16 on the pushing plate 17 is tightly in contact with the wall of the detection hole, and then the steel cable 3 is fixed to the fixing column 5 by the fixing bolt 4.

[0033] S3. Send a normal loading instruction to the control panel system 2 through the computer data acquisition system 1, so that the control panel system 2 controls the first deceleration stepper motor 18 and the second deceleration stepper motor 19 to drive the normal loading piston to press against the L-shaped force transmission pad 12, so that the L-shaped force transmission pad 12 loads the normal force to the sample soil through the loading serrations 13. The data detected by the normal force sensor 28 in the normal loading piston is transmitted to the control panel system 2 and then transmitted to the computer data acquisition system 1 by the control panel system 2.

[0034] Specifically, when loading normal power, the actual seismic records collected are corrected, and then the corrected acceleration-time curve records are integrated twice to obtain a displacement-time curve. Finally, discrete points are extracted from the displacement-time curve and input into a computer data acquisition system 1. The computer data acquisition system 1 processes the discrete points through operating software to obtain the seismic wave load required for the test, and then sends a normal loading instruction to the control panel system 2 according to the seismic wave load.

[0035] like Figure 6 As shown, in this embodiment, according to the actual earthquake records collected, sine waves of different frequencies and amplitudes (see a-1), displacement-time curves of sine waves (see a-2) and NS component earthquake motions recorded by the El-Centro station in the Imperial Valley, USA, magnitude 7.1 earthquake on May 18, 1940 (see b-1) are obtained, with a main frequency of 1.46 Hz, which is recorded as the El-Centro earthquake motion in this embodiment. After the displacement-time curve is obtained according to the El-Centro earthquake motion, since the actual normal loading amplitude is small, the displacement-time curve is compressed according to the actual situation and the compressed displacement-time curve is obtained (see b-2).

[0036] S4. Keep the normal force applied to the sample soil unchanged, and send a shear loading instruction to the control panel system 2 through the computer data acquisition system 1, so that the control panel system 2 controls the fourth reduction stepper motor 32 to drive the shear loading piston to press against the L-shaped force transmission pad 12, so that the L-shaped force transmission pad 12 applies shear force to the sample soil. The data detected by the tangential force sensor 37 in the shear loading piston is transmitted to the control panel system 2 and then transmitted to the computer data acquisition system 1 by the control panel system 2.

[0037] Specifically, when the shear force is loaded, the peak shear strength of the sample soil follows the Coulomb strength criterion, that is, it satisfies the formula τ=c+σn•tanφr, where τ is the peak shear strength; c is the cohesion of the rock and soil; σn is the effective normal stress; φr is the residual friction angle. In the process of loading the shear force, when the peak shear strength presents a maximum value, the maximum shear stress is taken as the shear stress when the sample soil is damaged and input into the computer data acquisition system 1. If the peak shear strength does not have a maximum value, the shear stress when the shear displacement is 40mm is selected and input into the computer data acquisition system 1, and then the computer data acquisition system 1 sends a shear loading instruction to the control board system 2 according to the input shear force.

[0038] S5. Based on the consolidation quick shear method test in the current specification "Standard for Geotechnical Test Methods" (GBT50123-1999), the test host 8 is lowered to positions at different depths of the detection hole according to steps S2-S4 and no less than three tests are performed; S6. End the test and process the test data.

[0039] In the process of loading the normal force, the magnitude of the loaded normal force can be controlled by controlling the rotation speed of the first follower screw 22 by the first reduction stepper motor 18 and the second reduction stepper motor 19; the deformation displacement of the sample soil is determined by the displacement of the normal loading piston, and the displacement of the normal loading piston can be calculated by the rotation of the first follower screw 22 controlled by the first reduction stepper motor 18 and the second reduction stepper motor 19; the normal force exerted on the sample soil is measured by the normal force sensor 28 in the normal loading piston; therefore, the pressure exerted on the sample soil and the deformation data generated can be obtained.

[0040] During the process of loading the shear force, the shear displacement of the sample soil is determined by the displacement of the shear loading piston; the shear force on the sample soil is measured by the tangential force sensor 37 in the shear loading piston; therefore, the magnitude of the shear force on the sample and the resulting deformation displacement can be obtained. In this embodiment, referring to the method test of consolidation quick shear in the current specification "Standard for Geotechnical Test Methods" (GBT50123-1999), the maximum shear stroke is 6 mm and the shear rate is 0.8 mm / min.

[0041] During the test, by setting the pushing system 14, the test host 8 can be stabilized in the detection hole, thereby solving the problem that the drill rig drills a hole under the loose soil layer, resulting in the drilled hole being larger than the actual design, causing the front end of the normal loading system to be unable to embed into the soil layer. Even if the borehole size deviates from the design size, the normal force can be smoothly loaded, thereby ensuring the accuracy of the test results.

[0042] Based on the above-mentioned small-scale dynamic in-hole shear test device and its corresponding test method, the present invention can realize in-situ in-hole shear tests on soil, soft rock, and soil-rock mixtures, and further study the dynamic characteristics of rock and soil under DNL conditions, which is beneficial to revealing the mechanism of slope instability and solving dynamic engineering problems under the influence of complex dynamic conditions such as earthquakes and rock bursts.

[0043] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A small dynamic in-hole shear test device, characterized in that: include: A computer data acquisition system (1) and a control panel system (2), wherein the control panel system (2) is electrically connected to the computer data acquisition system (1); A test host (8), a steel cable (3), and a load-bearing mechanism, wherein the test host (8) is lowered into the detection hole of the sample soil body through the steel cable (3), the steel cable (3) is fixedly connected to the load-bearing mechanism, and the load-bearing mechanism is supported at the mouth of the detection hole on the sample soil body; The test host (8) comprises a host frame (10), a pushing system (14), a force transmission mechanism, a normal loading system, and a shear loading system. The steel cable (3) is connected to the host frame (10). The pushing system (14), the force transmission mechanism, the normal loading system, and the shear loading system are all arranged on the host frame (10). The pushing system (14), the normal loading system, and the shear loading system are all electrically connected to the control panel system (2) through the steel cable (3). The host frame (10) is in contact with the wall of the detection hole through the pushing system (14). The normal loading system is used to drive the force transmission mechanism to load a normal force onto the sample soil body. The shear loading system is used to drive the force transmission mechanism to load a shear force onto the sample soil body.

2. The small dynamic in-hole shear test device according to claim 1, characterized in that: The load-bearing mechanism comprises a fixing bolt (4), a fixing column (5), a load-bearing steel plate (6), and a sleeve (7). The bottom of the fixing column (5) is provided with a sleeve (7) inserted into a drilled hole. The load-bearing steel plate (6) is provided at the connection between the fixing column (5) and the sleeve (7). The fixing column (5) is supported at the opening of the drilled hole by the load-bearing steel plate (6). The steel cable (3) passes through the fixing column (5) and the sleeve (7) in sequence and is connected to the top of the fixing column (5) by the fixing bolt (4).

3. The small dynamic in-hole shear test device according to claim 2, characterized in that: A third inner cavity (25) is provided in the main frame (10), and the pushing system (14) comprises a third reduction stepping motor (26), a second lead screw (27), a screw (29), a fixing block (30), a connecting rod (31), a pushing force transmission shaft (15), a pushing plate (17), and a streamlined protrusion (16). The third reduction stepping motor (26) is provided in the third inner cavity (25) and is electrically connected to the control panel system (2) through a steel cable (3). A first opening is provided on a side wall of the main frame (10), and the pushing force transmission shaft ( 15) is slidably inserted into the main frame (10) through the first opening, the output end of the third reduction stepping motor (26) is connected to the second lead screw (27), the second lead screw (27) is connected to the fixed block (30) through the screw (29), the two ends of the connecting rod (31) are respectively rotatably connected to the fixed block (30) and the push-to-force transmission shaft (15), the end of the push-to-force transmission shaft (15) away from the connecting rod (31) is provided with a push plate (17), and the push plate (17) is provided with a streamlined protrusion (16) that abuts against the sample soil.

4. The small dynamic in-hole shear test device according to claim 2, characterized in that: A second opening is provided on the side wall of the main frame (10); the force transmission mechanism comprises a vertical slide rail (11), an L-shaped force transmission pad (12), and a loading sawtooth (13); the vertical slide rail (11) is provided at the second opening; the vertical section of the L-shaped force transmission pad (12) is slidably connected to the vertical slide rail (11); the front face of the vertical section of the L-shaped force transmission pad (12) is provided with a loading sawtooth (13) that abuts against the sample soil; the normal loading system acts on the vertical end of the L-shaped force transmission pad (12); and the shear loading system acts on the horizontal end of the L-shaped force transmission pad (12).

5. The small dynamic in-hole shear test device according to claim 4, characterized in that: A first inner cavity (23) and a second inner cavity (24) are further provided in the main frame (10); the normal loading system comprises a first reduction stepping motor (18), a second reduction stepping motor (19), a first lead screw (20), a first lead screw connector (21), a first follower lead screw (22), a normal force sensor (28), and a normal loading piston; the first reduction stepping motor (18) is provided in the first inner cavity (23), the second reduction stepping motor (19) is provided in the second inner cavity (24), and the first reduction stepping motor (18) After being connected in series with a second reduction stepping motor (19), the motor is electrically connected to a control panel system (2) through a steel cable (3); an output end of the second reduction stepping motor (19) is connected to a first lead screw (20); the first lead screw (20) is connected to a first follower lead screw (22) through a first lead screw connector (21); the first follower lead screw (22) is connected to a normal loading piston; the normal loading piston abuts against the back side of the vertical end of the L-shaped force transmission pad (12); a normal force sensor (28) is disposed in the normal loading piston and is electrically connected to the control panel system (2).

6. The small dynamic in-hole shear test device according to claim 5, characterized in that: A fourth inner cavity (33) is also provided in the main frame (10), and the shear loading system comprises a fourth reduction stepping motor (32), a third lead screw (34), a second lead screw connector (35), a second follower lead screw (36), a tangential force sensor (37), and a shear loading piston. The fourth reduction stepping motor (32) is provided in the fourth inner cavity (33) and is electrically connected to the control board system (2) via a steel cable (3). The output end of the fourth reduction stepping motor (32) is connected to the third lead screw (34), the third lead screw (34) is connected to the second follower lead screw (36) via the second lead screw connector (35), the second follower lead screw (36) is connected to a shear loading piston abutting against the bottom of the horizontal end of the L-shaped force transmission pad (12), and the tangential force sensor (37) is provided in the shear loading piston and is electrically connected to the control board system (2).

7. The small dynamic in-hole shear test device according to claim 6, characterized in that: The normal loading piston and the shear loading piston both comprise a piston column (39) and a piston base (41). One end of the piston column (39) in the normal loading piston is connected to the first follower screw (22) via a nut, and the other end of the piston column (39) in the normal loading piston is connected to the piston base (41) which abuts against the back of the vertical end of the L-shaped force transmission pad (12). A normal force sensor (28) is arranged in the piston column (39) in the normal loading piston. One end of the piston column (39) in the shear loading piston is connected to the second follower screw (36) via a nut, and the other end of the piston column (39) in the shear loading piston is connected to the piston base (41) which abuts against the bottom of the horizontal end of the L-shaped force transmission pad (12). A tangential force sensor (37) is arranged in the piston column (39) in the shear loading piston.

8. A small-scale dynamic in-hole shear test method, characterized in that: The following steps are involved: S1. Drill a detection hole in the soil sample using a drilling rig and clean the loose soil at the bottom of the detection hole. Lower the test host (8) into the detection hole via a steel cable (3). Insert the casing (7) into the detection hole and support the fixed column (5) at the mouth of the detection hole via a bearing steel plate (6). S2. When the test host (8) is lowered to a set depth, a pushing instruction is sent to the control panel system (2) through the computer data acquisition system (1), so that the control panel system (2) controls the third reduction stepping motor (26) to drive the pushing force transmission shaft (15) to slide outward from the host frame (10), so that the streamlined protrusion (16) on the pushing plate (17) is tightly in contact with the wall of the detection hole, and then the steel cable (3) is fixed to the fixing column (5) through the fixing bolt (4); S3, sending a normal loading instruction to the control panel system (2) through the computer data acquisition system (1), so that the control panel system (2) controls the first deceleration stepper motor (18) and the second deceleration stepper motor (19) to drive the normal loading piston to press against the L-shaped force transmission pad (12), so that the L-shaped force transmission pad (12) loads a normal force on the sample soil through the loading sawtooth (13), and the data detected by the normal force sensor (28) in the normal loading piston is transmitted to the control panel system (2) and then transmitted from the control panel system (2) to the computer data acquisition system (1); S4, keeping the normal force applied to the sample soil unchanged, sending a shear loading instruction to the control board system (2) through the computer data acquisition system (1), so that the control board system (2) controls the fourth reduction stepping motor (32) to drive the shear loading piston to press against the L-shaped force transmission pad (12), so that the L-shaped force transmission pad (12) applies a shear force to the sample soil, and the data detected by the tangential force sensor (37) in the shear loading piston is transmitted to the control board system (2) and then transmitted from the control board system (2) to the computer data acquisition system (1); S5. According to steps S2-S4, lower the test host (8) to positions of different depths in the detection hole and perform no less than three tests; S6. End the test and process the test data.

9. The small-scale dynamic in-hole shear test method according to claim 8, characterized in that: When the normal force is loaded, the collected actual seismic record is corrected, and then the corrected acceleration-time curve record is integrated twice to obtain a displacement-time curve. Finally, discrete points are extracted from the displacement-time curve and input into a computer data acquisition system (1). The computer data acquisition system (1) processes the discrete points through an operating software to obtain a seismic wave load required for the test, and then sends a normal loading instruction to the control panel system (2) according to the seismic wave load.

10. The small-scale dynamic in-hole shear test method according to claim 8, characterized in that: When the shear force is loaded, the peak shear strength of the sample soil follows the Coulomb strength criterion. During the shear force loading process, when the peak shear strength presents a maximum value, the maximum shear stress is taken as the shear stress when the sample soil is damaged and input into the computer data acquisition system (1). If the peak shear strength does not present a maximum value, the shear stress when the shear displacement is 40 mm is selected and input into the computer data acquisition system (1). Then, the computer data acquisition system (1) sends a shear loading instruction to the control panel system (2) according to the input shear force.

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