Method and device for high-speed shear test of rock joints under initial shear stress conditions

Abstract

The present invention discloses a method and device for a high-speed shear test of rock joints under initial shear stress conditions. The experimental device includes a loading device and a data acquisition system. The loading device includes a base, a normal static pressure loading device, a tangential static force loading device, and an impact shear loading device. Therefore, the present invention can use a normal static pressure loading device to load normal static pressure on the rock joint sample, and use a tangential static force loading device to load tangential static force on the rock joint sample. It can be seen that when the present invention performs a shear test on the rock joint sample, the impact shear loading device can be used to apply impact shear force when the normal and tangential directions of the rock joint sample are loaded, thereby taking into account the initial shear stress state of the rock joint, which can better fit the actual stress environment of the jointed rock mass, so that the test results are objective and accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of dynamic shear test of rock joints, and in particular relates to a method and a device for high-speed shear test of rock joints under initial shear stress conditions. Background Art

[0002] Under engineering disturbance, rock joints may experience high-speed shear slip with a displacement rate of up to or even exceeding 1 m / s, thus inducing instability of the jointed rock mass. In addition, the stress state of the jointed rock mass is complex. Before being subjected to dynamic loads, the rock joints are not only subjected to static normal pressure, but also to static shear force. The basis for solving the problem of jointed rock mass instability is to obtain the strength and deformation parameters of rock joints in the laboratory. Therefore, it is urgent to develop a method and device that can carry out high-speed shear mechanics experiments on rock joints under initial normal pressure and shear force.

[0003] At present, direct shear loading equipment and methods are mainly used at home and abroad to conduct shear mechanics experiments on rock joints. This type of equipment and method uses servo hydraulics to first load normal pressure on rock joints, and then continuously load shear force on rock joints at a constant force rate or displacement rate until the joints slip or fail. On the one hand, due to the limitations of hydraulic servo technology, the rock joint shear rate that can be achieved by this type of equipment is relatively low, generally less than 0.1m / s. On the other hand, this type of equipment and method only simulates the normal stress state of rock joints, and does not consider the initial shear stress state of rock joints, which is different from the actual stress environment of the jointed rock mass.

[0004] At present, there are no methods and equipment at home and abroad that can conduct high-speed shear experiments on rock joints under initial shear stress conditions. Summary of the invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the background technology and provide a method and device for performing high-speed shear experiments on rock joints after the sample reaches certain initial normal pressure and shear stress conditions. The present invention can provide experimental conditions for conducting research on the high-speed shear mechanical properties of rock joints.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] A device for high-speed shear test of rock joints under initial shear stress conditions, comprising a loading device and a data acquisition system; wherein:

[0008] The loading device comprises a base and a normal static pressure loading device, a tangential static loading device and an impact shear loading device respectively arranged on the base; wherein:

[0009] The normal static pressure loading device comprises a normal power mechanism, a normal actuating end and a normal supporting end; the normal actuating end and the normal supporting end are respectively arranged on both sides of the rock joint surface in the normal direction, and the normal actuating end is connected to the power output end of the normal power mechanism, while the normal supporting end is in contact with the rock joint sample; the normal actuating end can move linearly along the normal direction of the rock joint surface toward / away from the rock joint sample under the power drive of the normal power mechanism;

[0010] The tangential static loading device comprises a tangential power mechanism, a tangential actuating end and a tangential supporting end; the tangential actuating end and the tangential supporting end are arranged on both sides of the rock joint surface in the tangential direction, and the tangential actuating end is connected to the power output end of the tangential power mechanism, while the tangential supporting end is in contact with the rock joint sample; the tangential actuating end can move linearly along the tangential direction of the rock joint surface toward / away from the rock joint sample under the power drive of the tangential power mechanism; when the tangential actuating end and the tangential supporting end are both in contact with the rock joint sample, the action line of the normal actuating end transmitting the load to the rock joint sample is staggered with the action line of the normal supporting end transmitting the load to the rock joint sample;

[0011] The impact shear loading device comprises a punch launcher and a cylindrical punch arranged at the launching end of the punch launcher; the cylindrical punch can be driven out along the tangent direction of the rock joint surface and hit the opposite end of the tangential support end under the action of the launching end of the punch launcher;

[0012] The data acquisition system includes a stress wave acquisition unit and a dynamic displacement acquisition unit; wherein:

[0013] The stress wave collection unit is used to collect stress waves in the tangential actuation end, the tangential support end, the normal actuation end and the normal support end, and includes a plurality of strain gauges respectively arranged on the tangential actuation end, the tangential support end, the normal actuation end and the normal support end;

[0014] The dynamic displacement acquisition unit is used to take images of rock joint samples.

[0015] Preferably, the stress wave information collected by the stress wave collection unit and the image information collected by the dynamic displacement collection unit can be fed back to the data processing device;

[0016] The data processing device can calculate the dynamic shear stress, dynamic normal pressure, dynamic shear displacement, and dynamic normal displacement of the rock joint sample over time based on the received stress wave information and image information; and can draw the dynamic shear stress-dynamic shear displacement curve, dynamic normal displacement-dynamic shear displacement curve, and dynamic normal pressure-dynamic shear displacement curve of the rock joint sample based on the calculated dynamic shear stress, dynamic normal pressure, dynamic shear displacement, and dynamic normal displacement.

[0017] Preferably, the loading device further comprises a reaction force frame, which comprises a central rigid frame, two X-axis reaction force frames and two Y-axis reaction force frames; the two X-axis reaction force frames correspond to the first and second X-axis reaction force frames, which are arranged along the X-axis direction of the central rigid frame and are disposed on both sides of the central rigid frame, and the inner end faces of the two X-axis reaction force frames are connected to the central rigid frame as a whole; the two Y-axis reaction force frames correspond to the first and second Y-axis reaction force frames, which are arranged along the Y-axis direction of the central rigid frame and are disposed on both sides of the central rigid frame, and the inner end faces of the two Y-axis reaction force frames are connected to the central rigid frame as a whole;

[0018] The rock joint specimens are arranged in a central rigid frame, and the tangent direction of the rock joint surface is the X-axis direction of the reaction frame, while the normal direction of the rock joint surface is the Y-axis direction of the reaction frame;

[0019] The normal static pressure loading device further comprises a Y-axis front pressure rod and a Y-axis rear pressure rod; the Y-axis front pressure rod is placed in a first Y-axis reaction force frame, and one end of the Y-axis front pressure rod is fixed to the first Y-axis reaction force frame, and the other end is a normal support end; the Y-axis rear pressure rod is placed in a second Y-axis reaction force frame, and one end of the Y-axis rear pressure rod is connected to the power output end of the normal power mechanism, and the other end is a normal actuating end;

[0020] The tangential static loading device further comprises an incident rod and a transmission rod; the incident rod is placed in the first X-axis reaction force frame, and one end of the incident rod is fixed to the first X-axis reaction force frame, and the other end is a tangential support end; the transmission rod is placed in the second X-axis reaction force frame, and one end of the X-axis rear pressure rod is connected to the power output end of the tangential power mechanism, and the other end is a tangential actuating end;

[0021] The impact shear loading device is arranged on the outside of the second X-axis reaction force frame.

[0022] Preferably, the base is a cross-shaped horizontal base; the reaction frame is installed in the cross-shaped horizontal base, and the central rigid frame is installed at the middle cross position of the cross-shaped horizontal base;

[0023] The cross-shaped horizontal base is provided with an X-axis guide rail along the X-axis direction and a Y-axis guide rail along the Y-axis direction; a plurality of pressure rod supports are movably mounted on the X-axis guide rail and the Y-axis guide rail;

[0024] The incident rod, the transmission rod, the Y-axis front pressure rod, and the Y-axis rear pressure rod are all supported by pressure rod supports arranged at corresponding positions.

[0025] Preferably, the rock joint sample is formed by splicing a front rock and a rear rock; in the data processing device, the dynamic shear stress calculation formula of the rock joint sample is:

[0026] τ d (t) = A bar E bar ε tr (t) / A shear

[0027] The calculation formula of the dynamic normal pressure of rock joint specimen is:

[0028]

[0029] The dynamic shear displacement calculation formula of rock joint specimen is:

[0030]

[0031] The calculation formula of the dynamic normal displacement of rock joint specimen is:

[0032]

[0033] Where: τ d is the nominal dynamic shear stress of the rock joint specimen; A bar is the cross-sectional area of ​​the transmission rod; E bar is the Young's modulus of the transmission rod; ε tr is the strain value of the transmitted wave in the transmission rod; A shear is the nominal shear area of ​​the rock joint specimen; σ nd is the nominal dynamic normal pressure of the rock joint specimen; ε y1 and ε y2 are the strain values ​​of stress waves in the Y-axis front pressure bar and the Y-axis rear pressure bar respectively; u sd is the dynamic shear displacement of rock joints; u i and u i ' are the X-axis displacements of the pixels symmetrical about the joint plane in the front rock and the back rock respectively; n is the number of pixels; the subscript i is the sequence number of the pixel, which takes a value of 1...n, where n is an integer; v d is the dynamic normal displacement of rock joints; v i and v i ' are the Y-direction displacements of the pixels symmetrical about the joint plane in the front rock and the back rock, respectively.

[0034] Preferably, the normal actuating end and the normal supporting end are in contact with the rock joint sample through a rigid gasket; and the tangential actuating end and the tangential supporting end are in contact with the rock joint sample through a sample adapter.

[0035] The second technical purpose of the present invention is to provide a device for high-speed shear test of rock joints under initial shear stress conditions, including a loading device and a data acquisition system; wherein:

[0036] The loading device comprises a cross-shaped horizontal base, a reaction force frame, an X-axis guide rail, a pressure rod support, a punch launcher, a cylindrical punch, an incident rod, a transmission rod, an X-axis hydraulic cylinder, an absorption rod, a Y-axis guide rail, a Y-axis front reaction force frame, a Y-axis rear pressure rod, a Y-axis hydraulic cylinder, a hydraulic servo control system, a sample adapter, and a rigid gasket;

[0037] The reaction frame is composed of an X-axis left reaction frame, a central rigid frame, an X-axis right reaction frame, a Y-axis front pressure rod and a Y-axis rear reaction frame connected by bolts; the X-axis left reaction frame, the central rigid frame and the X-axis right reaction frame are connected by bolts from left to right and are arranged on a cross-shaped horizontal base, and the central rigid frame is arranged at the intersection of two axes of the cross-shaped horizontal base; the Y-axis front reaction frame, the central rigid frame and the Y-axis rear reaction frame are connected by bolts from front to back and are arranged on the cross-shaped horizontal base;

[0038] The X-axis guide rail in the loading device is arranged on a cross-shaped horizontal base from left to right, and the Y-axis guide rail is perpendicular to the X-axis guide rail and is arranged on a cross-shaped horizontal base from front to back; on the X-axis guide rail, a punch launcher and a certain number of pressure rod supports are arranged in sequence from left to right, and the punch launcher is located on the left side of the X-axis left reaction force frame; the cylindrical punch is located in the punch launcher; the incident rod and the transmission rod are supported by the pressure rod support, and the axes of the three coincide with the axis of the cylindrical punch, the incident rod is located on the inner side of the X-axis left reaction force frame, and the transmission rod is located on the inner side of the X-axis right reaction force frame; the Y-axis front pressure rod and the Y-axis rear pressure rod are supported by the pressure rod support arranged on the Y-axis guide rail, the Y-axis front pressure rod is located on the inner side of the Y-axis front reaction force frame, the Y-axis rear pressure rod is located on the inner side of the Y-axis rear reaction force frame, and the axis of the Y-axis front pressure rod coincides with the axis of the Y-axis rear pressure rod; the axis of the incident rod and the axis of the Y-axis pressure rod are at the same horizontal height and perpendicular to each other;

[0039] The X-axis hydraulic cylinder is arranged at the right end of the X-axis right reaction force frame and connected by bolts; the absorption rod passes through the hollow piston of the X-axis hydraulic cylinder and is in close contact with the transmission rod; the Y-axis hydraulic cylinder is arranged at the rear end of the Y-axis rear reaction force frame and connected by bolts; the X-axis hydraulic cylinder and the Y-axis hydraulic cylinder are connected to the hydraulic servo control system through oil pipes;

[0040] The data acquisition system includes a stress wave acquisition unit and a dynamic displacement acquisition unit;

[0041] The stress wave collection unit is used to collect stress waves in the tangential actuation end, the tangential support end, the normal actuation end and the normal support end, and includes a plurality of strain gauges respectively arranged on the tangential actuation end, the tangential support end, the normal actuation end and the normal support end;

[0042] The dynamic displacement acquisition unit is used to capture the speckle image of the rock joint sample.

[0043] Preferably, there are four pairs of strain gauges in total; one pair is pasted on the surface of each of the incident rod, the transmission rod, the Y-axis front pressure rod and the Y-axis rear pressure rod, and the pasting position is located in the middle of the length of each rod.

[0044] Preferably, the dynamic displacement acquisition unit includes a high-speed camera; the high-speed camera is arranged directly above the central rigid frame, and the lens is perpendicular to the upper surface of the rock joint sample; the high-speed camera is connected to an oscilloscope via a cable, and the oscilloscope triggers the high-speed camera to start image acquisition.

[0045] The third technical purpose of the present invention is to provide a rock joint high-speed shear test method under initial shear stress conditions, which uses a rock joint high-speed shear test device under initial shear stress conditions provided by the present invention, comprising the following steps:

[0046] Step 1, rock joint sample preparation

[0047] The rock joint specimen is made of a cube made of a front rock and a rear rock. The size of the cube is consistent with the cross-sectional size of the incident rod, the transmission rod, and the Y-axis compression rod. The upper surface of the specimen is sprayed with randomly distributed speckles.

[0048] Step 2: Sample installation and positioning

[0049] Place the prepared sample between the incident rod and the transmission rod, with the joint surface tangent along the X-axis; set a sample adapter at the end of the incident rod and the transmission rod close to the sample, and ensure that the right end face of the sample adapter at the incident rod end coincides with the left end face of the front rock, and the left end face of the sample adapter at the transmission rod end coincides with the right end face of the rear rock; set a rigid gasket at the end of the Y-axis front pressure rod and the Y-axis rear pressure rod close to the sample; use the X-axis hydraulic cylinder and the Y-axis hydraulic cylinder to push the transmission rod and the Y-axis rear pressure rod close to the sample, when the sample is in close contact with the sample adapter and the rigid gasket, and the center of the sample coincides with the intersection of the incident rod-transmission rod axis and the Y-axis front pressure rod-Y-axis rear pressure rod axis, the sample positioning is completed;

[0050] Step 3: Static pressure and tangential static loading of joints

[0051] To ensure that the center of the specimen does not shift, the normal static pressure and tangential static force of the joint are alternately loaded in stages, and the load stage is not less than two stages; specifically, the normal pressure is first loaded by the Y-axis hydraulic cylinder, and when the pressure reaches the first-stage target value, the pressure is kept stable, and then the tangential shear stress is loaded by the X-axis hydraulic cylinder, and when the shear stress reaches the first-stage target value, it is kept stable; all load stage loading is completed in this way;

[0052] Step 4: Data acquisition system preparation

[0053] First, check the connection between the stress wave acquisition unit and the dynamic displacement acquisition unit to ensure normal communication; then set the acquisition parameters; finally, set the data acquisition system to the trigger state;

[0054] Step 5: Impact shear loading and data collection

[0055] The cylindrical punch is pushed into the punch launcher, and the high-pressure gas is used to drive the cylindrical punch to perform linear acceleration motion, so that the cylindrical punch hits the incident rod, thereby generating an incident wave in the incident rod; when the incident wave propagates to the strain gauge on the incident rod, the oscilloscope is triggered to start stress wave acquisition, and the oscilloscope simultaneously sends a signal to the high-speed camera, so that the high-speed camera starts to capture the speckle image of the sample;

[0056] Step 6: Data storage and processing

[0057] After the impact shear loading is completed, the stress wave signal cached in the oscilloscope and the image cached in the high-speed camera are saved to the computer respectively; the dynamic shear stress of the rock joint is calculated according to the transmission wave in the transmission rod according to formula (1), that is:

[0058] τ d (t) = A bar E bar ε tr (t) / A shear (1)

[0059] In formula (1): d is the nominal dynamic shear stress of the rock joint specimen; A bar is the cross-sectional area of ​​the transmission rod; E bar is the Young's modulus of the transmission rod; ε tr is the strain value of the transmitted wave in the transmission rod; A shear is the nominal shear area of ​​the rock joint specimen.

[0060] The dynamic normal pressure of the rock joint specimen is calculated according to the stress waves in the Y-axis front pressure bar and the Y-axis rear pressure bar according to formula (2), that is:

[0061]

[0062] In formula (2): nd is the nominal dynamic normal pressure of the rock joint specimen; ε y1 and ε y2 are the strain values ​​of stress waves in the Y-axis front pressure rod and the Y-axis rear pressure rod, respectively.

[0063] According to the captured speckle image, the displacement field of the measured surface of the sample at each moment is calculated; then, the X-axis displacement of the symmetrical pixel points of the front rock and the rear rock about the joint plane at each moment is subtracted, and finally the average value of all X-axis displacement differences is calculated to obtain the dynamic shear displacement of the rock joint at each moment, as shown in formula (3):

[0064]

[0065] In formula (3): u sd is the dynamic shear displacement of rock joints; u i and u i ' are the X-axis displacements of the pixels symmetrical about the joint plane in the front rock and the rear rock respectively; n is the number of pixels; the subscript i is the sequence number of the pixel, which takes a value of 1...n, where n is an integer;

[0066] Similarly, the Y-direction displacements of the symmetrical pixels of the front and rear rocks about the joint plane are subtracted at each moment, and finally the average value of all Y-direction displacement differences is calculated to obtain the dynamic normal displacement of the rock joint at each moment, as shown in formula (4):

[0067]

[0068] In formula (4): v d is the dynamic normal displacement of rock joints; v i and v i ' are the Y-direction displacements of the pixels symmetrical about the joint plane in the front rock and the rear rock respectively;

[0069] The above calculation results are used to draw the dynamic shear stress-dynamic shear displacement curve, dynamic normal displacement-dynamic shear displacement curve, and dynamic normal pressure-dynamic shear displacement curve of the rock joints.

[0070] Based on the above technical solution, the present invention will have the following beneficial effects:

[0071] The present invention adopts a normal static pressure loading device to load normal static pressure on the rock joint sample, and adopts a tangential static force loading device to load tangential static force on the rock joint sample. Therefore, the present invention can adopt an impact shear loading device to apply impact shear force when both the normal and tangential directions of the rock joint sample are loaded. It can be seen from this that when the present invention performs a shear test on a rock joint sample, the initial shear stress state of the rock joint can be taken into account, which can better fit the real stress environment of the jointed rock mass, making the test results more objective and accurate; in addition, the shear rate of the rock joint can reach the order of 10m / s, which is far higher than the existing technical equipment; at the same time, the technical solution provided by the present invention can meet the test requirements of various rock joint samples such as straight rock joints, undulating rock joints, and rough rock joints. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 This is a schematic diagram of the high-speed impact shear test principle of rock joints;

[0073] Figure 2 Three-dimensional diagram of the loading device for high-speed impact shear experiment on rock joints.

[0074] In the figure, 1 is a cross-shaped horizontal base; 2 is an X-axis guide rail; 3 is a pressure rod support; 4 is a punch launcher; 5 is a cylindrical punch; 6 is an X-axis left reaction frame; 7 is an incident rod; 8 is a central rigid frame; 9 is an X-axis right reaction frame; 10 is a transmission rod; 11 is an X-axis hydraulic cylinder; 12 is an absorption rod; 13 is a Y-axis guide rail; 14 is a Y-axis front reaction frame; 15 is a Y-axis front pressure rod; 16 is a Y-axis rear reaction frame; 17 is a Y-axis rear pressure rod; 18 is a Y-axis hydraulic cylinder; 20 is a sample adapter; and 30 is a rigid gasket. DETAILED DESCRIPTION

[0075] The technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

[0076] like Figure 1 , Figure 2 As shown, the device for high-speed shear test of rock joints under initial shear stress conditions of the present invention comprises a loading device and a data acquisition system; wherein:

[0077] The loading device comprises a base, a reaction force frame, and a normal static pressure loading device, a tangential static loading device, and an impact shear loading device respectively arranged on the base; wherein:

[0078] The base is a cross-shaped horizontal base.

[0079] The reaction frame is installed in a cross-shaped horizontal base and is arranged in a cross shape, including a central rigid frame, two X-axis reaction frames and two Y-axis reaction frames; the central rigid frame is installed at the middle intersection of the cross-shaped horizontal base, the two X-axis reaction frames correspond to the first and second X-axis reaction frames, both are arranged along the X-axis direction of the central rigid frame and are arranged on both sides of the central rigid frame, and the inner end faces of the two X-axis reaction frames are connected to the central rigid frame as a whole; the two Y-axis reaction frames correspond to the first and second Y-axis reaction frames, both are arranged along the Y-axis direction of the central rigid frame and are arranged on both sides of the central rigid frame, and the inner end faces of the two Y-axis reaction frames are connected to the central rigid frame as a whole; the rock joint sample is arranged in the central rigid frame, and the tangent direction of the joint surface of the rock joint sample is the X-axis direction of the reaction frame, and the normal direction of the joint surface of the rock joint sample is the Y-axis direction of the reaction frame.

[0080] The normal static pressure loading device includes a normal power mechanism, a Y-axis front pressure rod, a Y-axis rear pressure rod, a normal actuating end and a normal supporting end; the Y-axis front pressure rod is placed in a first Y-axis reaction force frame, and one end of the Y-axis front pressure rod is fixed to the first Y-axis reaction force frame, and the other end is the normal supporting end; the Y-axis rear pressure rod is placed in a second Y-axis reaction force frame, and one end of the Y-axis rear pressure rod is connected to the power output end of the normal power mechanism, and the other end is the normal actuating end; the normal actuating end and the normal supporting end are respectively arranged on both sides of the joint surface of the rock joint sample in the normal direction, and the normal actuating end can move linearly toward / away from the rock joint sample along the normal direction of the joint surface of the rock joint sample under the power drive of the normal power mechanism.

[0081] The tangential static loading device comprises a tangential power mechanism, an incident rod, a transmission rod, a tangential actuating end and a tangential supporting end; the incident rod is placed in a first X-axis reaction force frame, and one end of the incident rod is fixed to the first X-axis reaction force frame, and the other end is a tangential supporting end; the transmission rod is placed in a second X-axis reaction force frame, and one end of the X-axis rear pressure rod is connected to the power output end of the tangential power mechanism, and the other end is a tangential actuating end; the tangential actuating end and the tangential supporting end are arranged on both sides of the joint surface of the rock joint sample in the tangential direction, and the tangential supporting end is in contact with the rock joint sample; the tangential actuating end can move linearly along the tangential direction of the rock joint surface toward / away from the rock joint sample under the power drive of the tangential power mechanism; when the tangential actuating end and the tangential supporting end are both in contact with the rock joint sample, the action line of the normal actuating end transmitting the load to the rock joint sample is staggered with the action line of the normal support end transmitting the load to the rock joint sample.

[0082] In the present invention, the normal power mechanism and the tangential power mechanism are both hydraulic cylinders.

[0083] The impact shear loading device is arranged on the outside of the second X-axis reaction frame, and includes a punch launcher and a cylindrical punch arranged at the launching end of the punch launcher; the cylindrical punch can be driven out along the tangent of the rock joint surface and hit the opposite end of the tangential support end under the actuation of the launching end of the punch launcher.

[0084] The data acquisition system includes a stress wave acquisition unit and a dynamic displacement acquisition unit; wherein:

[0085] The stress wave collection unit is used to collect stress waves in the tangential actuation end, the tangential support end, the normal actuation end and the normal support end, and includes a plurality of strain gauges respectively arranged on the tangential actuation end, the tangential support end, the normal actuation end and the normal support end.

[0086] The dynamic displacement acquisition unit is used to capture the speckle image of the rock joint sample.

[0087] The cross-shaped horizontal base is provided with an X-axis guide rail along the X-axis direction and a Y-axis guide rail along the Y-axis direction; a plurality of pressure rod supports are movably mounted on the X-axis guide rail and the Y-axis guide rail; the incident rod, the transmission rod, the Y-axis front pressure rod and the Y-axis rear pressure rod are all supported by the pressure rod supports arranged at corresponding positions.

[0088] Some preferred embodiments are provided below in combination with the technical solution of the present invention.

[0089] Example 1

[0090] Figure 1 The figure shows the experimental principle of high-speed shear of rock joints under initial shear stress conditions. Figure 1 Medium x0 , σ y0 are the initial shear force and initial normal pressure on the rock joint sample before impact shear; during the impact process, the loading wave σ is first generated in the incident rod 7 xI The loading wave passes through the sample adapter 20 and further acts on the front rock 40, driving the front rock 40 to slide to the right; thereby generating friction resistance on the rock joints, driving the rear rock 41 to slide to the right, and squeezing the sample adapter 20 at the left end of the transmission rod 10, and finally acting on the transmission rod 10, generating a transmission wave σ in the transmission rod 10. xT Due to the normal expansion and deformation of the rock joints, the rigid gasket 30 is squeezed, and finally a stress wave σ is formed in the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17 y1 and σ y2 .

[0091] A high-speed shear test device for rock joints under initial shear stress conditions, comprising a loading device and a data acquisition system;

[0092] Figure 2 The three-dimensional diagram of the loading device is shown, which includes a cross-shaped horizontal base 1, an X-axis guide rail 2, a pressure rod support 3, a punch launcher 4, a cylindrical punch 5, an X-axis left reaction force frame 6, an incident rod 7, a central rigid frame 8, an X-axis right reaction force frame 9, a transmission rod 10, an X-axis hydraulic cylinder 11, an absorption rod 12, a Y-axis guide rail 13, a Y-axis front reaction force frame 14, a Y-axis front pressure rod 15, a Y-axis rear reaction force frame 16, a Y-axis rear pressure rod 17, a Y-axis hydraulic cylinder 18, a hydraulic servo control system 19, a sample adapter 20, and a rigid gasket 30;

[0093] The X-axis left reaction frame 6, the central rigid frame 8, the X-axis right reaction frame 9, the Y-axis front reaction frame 14 and the Y-axis rear reaction frame 16 are connected by bolts to form a reaction frame; the X-axis left reaction frame 6, the central rigid frame 8 and the X-axis right reaction frame 9 are connected by bolts from left to right and are arranged on the cross-shaped horizontal base 1, and the central rigid frame 8 is arranged at the intersection of the two axes of the cross-shaped horizontal base 1; the Y-axis front reaction frame 14, the central rigid frame 8 and the Y-axis rear reaction frame 16 are connected by bolts from front to back and are arranged on the cross-shaped horizontal base 1;

[0094] The X-axis guide rail 2 is arranged on the cross-shaped horizontal base 1 from left to right, and the Y-axis guide rail 13 is perpendicular to the X-axis guide rail 2 and is arranged on the cross-shaped horizontal base 1 from front to back; on the X-axis guide rail 2, a punch launcher 4 and a certain number of pressure rod supports 3 are arranged in sequence from left to right, and the punch launcher 4 is located on the left side of the X-axis left reaction force frame 6; the cylindrical punch 5 is located in the punch launcher 4; the incident rod 7 and the transmission rod 10 are supported by the pressure rod support 3, and the axes of the three coincide with the axis of the cylindrical punch 5. The incident rod 7 is located on the inner side of the X-axis left reaction force frame 6, and the transmission rod 10 is located on the inner side of the X-axis right reaction force frame 9; the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17 are supported by the pressure rod support provided on the Y-axis guide rail, the Y-axis front pressure rod is located on the inner side of the Y-axis front reaction force frame, the Y-axis rear pressure rod is located on the inner side of the Y-axis rear reaction force frame, and the axis of the Y-axis front pressure rod 15 coincides with the axis of the Y-axis rear pressure rod 17; the axis of the incident rod 7 and the axis of the Y-axis pressure rod 15 are located at the same horizontal height and are perpendicular to each other;

[0095] The X-axis hydraulic cylinder is arranged on the outside of the X-axis right reaction force frame and connected by bolts; the absorption rod 12 passes through the hollow piston of the X-axis hydraulic cylinder 11 and is in close contact with the transmission rod 10; the Y-axis hydraulic cylinder 18 is arranged on the outside of the Y-axis rear reaction force frame 16 and connected by bolts; the X-axis hydraulic cylinder 11 and the Y-axis hydraulic cylinder 18 are connected to the hydraulic servo control system 19 through oil pipes;

[0096] The incident rod 7, the transmission rod 10, the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17 have the same cross section, the cross section size is 50mm×50mm, the incident rod 7 is 2.5m long, the transmission rod 10, the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17 are the same length, all of which are 2.0m;

[0097] The cross-sectional diameter of the cylindrical punch 5 is 40 mm and the length is 200 mm to 700 mm;

[0098] The sample adapter 20 has a thickness of 5 mm, a length of 50 mm, and a width of 25 mm. The material is the same as that of the incident rod 7. Its function is to transfer the loads of the incident rod 7 and the transmission rod 10 to the sample and ensure that the load action lines at the left and right ends of the sample are not collinear.

[0099] The rigid gasket 30 has a thickness of 5 mm, a length of 50 mm, and a width of 50 mm. The material is consistent with that of the Y-axis front pressure rod 15. Its function is to reduce the friction between the sample and the Y-axis pressure rods 15 and 17, and ensure that the sample can slide freely along the X-axis.

[0100] The data acquisition system includes a stress wave acquisition unit and a dynamic displacement acquisition unit;

[0101] The stress wave acquisition unit consists of a strain gauge, a Wheatstone bridge, an ultra-dynamic strain gauge, and an oscilloscope;

[0102] The dynamic displacement acquisition unit is composed of a high-speed camera and a high-energy fill light;

[0103] Four pairs of strain gauges are respectively pasted on the surfaces of the incident rod 7, the transmission rod 10, the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17, and the pasting position is located in the middle of the length of each rod; the strain gauge, the Wheatstone bridge, the ultra-dynamic strain gauge and the oscilloscope are connected in sequence through special cables to measure the stress waves in the incident rod 7, the transmission rod 10, the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17;

[0104] The high-speed camera is arranged directly above the central rigid frame 8, with the lens perpendicular to the upper surface of the sample; the high-speed camera is connected to the oscilloscope via a dedicated cable, and the oscilloscope triggers the high-speed camera to start image acquisition.

[0105] Example 2

[0106] This embodiment provides a rock joint high-speed shear test method under initial shear stress conditions, which is implemented using the rock joint high-speed shear test device under initial shear stress conditions, and specifically includes the following steps:

[0107] Step 1: Preparation of rock joint samples

[0108] The rock joint sample is formed into a cube by splicing a front rock 40 and a rear rock 41, and the geometric dimensions of each rock are: length×width×thickness=50mm×25mm×50mm; the upper surface of the sample is sprayed with randomly distributed speckles.

[0109] Step 2: Sample installation and positioning

[0110] Place the prepared sample between the incident rod 7 and the transmission rod 10, with the joint surface tangent along the X-axis; a sample adapter 20 is respectively provided at one end of the incident rod 7 and the transmission rod 10 close to the sample, and ensure that the right end face of the sample adapter 20 at the incident rod 7 end coincides with the left end face of the front rock 40, and the left end face of the sample adapter 20 at the left end of the transmission rod 10 coincides with the right end face of the rear rock 41; a rigid gasket 30 is respectively provided at one end of the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17 close to the sample; the X-axis hydraulic cylinder 11 and the Y-axis hydraulic cylinder 18 are respectively used to push the transmission rod 10 and the Y-axis rear pressure rod 17 close to the sample, when the sample is in close contact with the sample adapter 20 and the rigid gasket 30, and the center of the sample coincides with the intersection of the incident rod 7-transmission rod 10 axis and the Y-axis front pressure rod 15-Y-axis rear pressure rod 17 axis, the sample positioning is completed;

[0111] Step 3: Static pressure and tangential static loading of joints

[0112] To ensure that the center of the specimen does not shift, the normal static pressure and tangential static force of the joint are loaded alternately and graded; for example, the normal static pressure to be loaded is 10MPa, and the tangential static force is 4MPa, the normal static pressure is divided into three levels of 3MPa, 6MPa, and 10MPa, and the tangential static force is divided into three levels of 1MPa, 2MPa, and 4MPa; first, the normal pressure is loaded to 3MPa using the Y-axis hydraulic oil, and the pressure is kept stable, and then the tangential static force is loaded to 1MPa using the X-axis hydraulic cylinder, and the tangential static force is kept stable; then, the normal pressure is continued to be loaded to 6MPa, and after the pressure is kept stable, the tangential static force is loaded to 2MPa and kept stable; finally, the normal pressure is loaded to 10MPa, and after the pressure is kept stable, the tangential static force is loaded to 4MPa.

[0113] Step 4: Data Acquisition System Preparation

[0114] Check the connections between the various parts of the stress wave acquisition unit and the dynamic displacement acquisition unit to ensure normal communication; then set the acquisition parameters; finally set the data acquisition system to the trigger-waiting state.

[0115] Step 5: Impact shear loading and data collection

[0116] The cylindrical punch 5 is pushed into the punch emitter 4, and the cylindrical punch 5 is driven by high-pressure gas to perform linear acceleration motion, so that the cylindrical punch 5 hits the incident rod 7, thereby generating an incident wave in the incident rod 7; when the incident wave propagates to the strain gauge on the incident rod 7, the oscilloscope is triggered to start stress wave acquisition, and the oscilloscope will simultaneously send a signal to the high-speed camera, so that the high-speed camera starts to capture the speckle image of the sample;

[0117] Step 6: Data storage and processing

[0118] After the impact shear loading is completed, the stress wave signal cached in the oscilloscope and the image cached in the high-speed camera are saved in the computer respectively; the dynamic shear stress of the rock joint sample is calculated according to the transmission wave in the transmission rod 10 according to formula (1), that is:

[0119] τ d (t) = A bar E bar ε tr (t) / A shear (1)

[0120] In formula (1): d is the nominal dynamic shear stress of the rock joint specimen; A bar E is the cross-sectional area of ​​the transmission rod 10; bar is the Young's modulus of the transmission rod 10; ε tr A is the strain value of the transmission wave in the transmission rod 10; shear is the nominal shear area of ​​the rock joint specimen.

[0121] The dynamic normal pressure of the rock joint specimen is calculated according to the stress waves in the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17 according to formula (2), that is:

[0122]

[0123] In formula (2): nd is the nominal dynamic normal pressure of the rock joint specimen; ε y1 and ε y2 are the strain values ​​of stress waves in the Y-axis front pressure rod 15 and the Y-axis rear pressure rod 17 respectively.

[0124] According to the captured speckle image, the displacement field of the measured surface of the sample is calculated at each moment; then, the X-direction displacements of the symmetrical pixels about the joint plane in the front rock 40 and the rear rock 41 at each moment are subtracted, and finally the average value of all X-direction displacement differences is calculated to obtain the dynamic shear displacement of the rock joint at each moment, as shown in formula (3):

[0125]

[0126] In formula (3): u sd is the dynamic shear displacement of rock joints; u i and u i ' are the X-direction displacements of the symmetrical pixels about the joint plane in the front rock 40 and the rear rock 41 respectively; n is the number of pixels; the subscript i is the sequence number of the pixel, and the value is 1...n, where n is an integer;

[0127] Similarly, the Y-direction displacements of the symmetrical pixels about the joint plane in the front rock 40 and the rear rock 41 at each moment are subtracted, and finally the average value of all Y-direction displacement differences is calculated to obtain the dynamic normal displacement of the rock joint at each moment, as shown in formula (4):

[0128]

[0129] In formula (4): v sd is the dynamic normal displacement of rock joints; v i and v i ' are the Y-direction displacements of the pixels symmetrical about the joint plane in the front rock 40 and the rear rock 41;

[0130] The above calculation results are used to draw the dynamic shear stress-dynamic shear displacement curve, dynamic normal displacement-dynamic shear displacement curve, and dynamic normal pressure-dynamic shear displacement curve of the rock joints.

[0131] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless defined as herein.

[0132] The above embodiments are only for explaining the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the present invention. The above embodiments of the present invention are described in detail, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the field without departing from the purpose of the present invention.

Claims

1. A device for high-speed shear test of rock joints under initial shear stress conditions, characterized in that: It includes a loading device and a data acquisition system; wherein: The loading device comprises a base and a normal static pressure loading device, a tangential static loading device and an impact shear loading device respectively arranged on the base; wherein: The normal static pressure loading device comprises a normal power mechanism, a normal actuating end and a normal supporting end; the normal actuating end and the normal supporting end are respectively arranged on both sides of the rock joint surface in the normal direction, and the normal actuating end is connected to the power output end of the normal power mechanism, while the normal supporting end is in contact with the rock joint sample; the normal actuating end can move linearly along the normal direction of the rock joint surface toward / away from the rock joint sample under the power drive of the normal power mechanism; The tangential static loading device comprises a tangential power mechanism, a tangential actuating end and a tangential supporting end; the tangential actuating end and the tangential supporting end are arranged on both sides of the rock joint surface in the tangential direction, and the tangential actuating end is connected to the power output end of the tangential power mechanism, while the tangential supporting end is in contact with the rock joint sample; the tangential actuating end can move linearly along the tangential direction of the rock joint surface toward / away from the rock joint sample under the power drive of the tangential power mechanism; when the tangential actuating end and the tangential supporting end are both in contact with the rock joint sample, the action line of the normal actuating end transmitting the load to the rock joint sample is staggered with the action line of the normal supporting end transmitting the load to the rock joint sample; The impact shear loading device comprises a punch launcher and a cylindrical punch arranged at the launching end of the punch launcher; the cylindrical punch can be driven out along the tangent direction of the rock joint surface and hit the opposite end of the tangential support end under the action of the launching end of the punch launcher; The data acquisition system comprises a stress wave acquisition unit and a dynamic displacement acquisition unit; wherein: The stress wave collection unit is used to collect stress waves in the tangential actuation end, the tangential support end, the normal actuation end and the normal support end, and includes a plurality of strain gauges respectively arranged on the tangential actuation end, the tangential support end, the normal actuation end and the normal support end; The dynamic displacement acquisition unit is used to take images of rock joint samples; The rock joint sample is formed by splicing a front rock and a rear rock; The stress wave information collected by the stress wave collection unit and the image information collected by the dynamic displacement collection unit can be fed back to the data processing device; The data processing device can calculate the dynamic shear stress, dynamic normal pressure, dynamic shear displacement and dynamic normal displacement of the rock joint sample over time based on the received stress wave information and image information; In the data processing device, the dynamic shear stress calculation formula of the rock joint sample is: t d (t)=A bar E bar e tr (t) / A shear ; The calculation formula of the dynamic normal pressure of rock joint specimen is: The dynamic shear displacement calculation formula of rock joint specimen is: The calculation formula of the dynamic normal displacement of rock joint specimen is: Where: τ d is the nominal dynamic shear stress of rock joints; A bar is the cross-sectional area of ​​the transmission rod; E bar is the Young's modulus of the transmission rod; ε tr is the strain value of the transmitted wave in the transmission rod; A shear is the nominal shear area of ​​rock joints; σ nd is the nominal dynamic normal pressure of rock joints; ε y1 and ε y2 are the strain values ​​of stress waves in the Y-axis front pressure bar and the Y-axis rear pressure bar respectively; u sd is the dynamic shear displacement of rock joints; u i and u i ' are the X-axis displacements of the pixels symmetrical about the joint plane in the front rock and the back rock respectively; the subscript i is the number of the pixel; n is the number of pixels; v d is the dynamic normal displacement of rock joints; v i and v i ' is the Y-direction displacement of the pixel points symmetrical about the joint plane in the front rock and the rear rock; t is the dynamic loading time.

2. The device for high-speed shear test of rock joints under initial shear stress conditions according to claim 1, characterized in that: The data processing device can draw the dynamic shear stress-dynamic shear displacement curve, the dynamic normal displacement-dynamic shear displacement curve, and the dynamic normal pressure-dynamic shear displacement curve of the rock joint sample according to the calculated dynamic shear stress, dynamic normal pressure, dynamic shear displacement, and dynamic normal displacement.

3. The device for high-speed shear test of rock joints under initial shear stress conditions according to claim 2, characterized in that: The loading device also includes a reaction force frame, which includes a central rigid frame, two X-axis reaction force frames and two Y-axis reaction force frames; the two X-axis reaction force frames correspond to the first and second X-axis reaction force frames, which are arranged along the X-axis direction of the central rigid frame and are disposed on both sides of the central rigid frame, and the inner end faces of the two X-axis reaction force frames are connected to the central rigid frame as a whole; the two Y-axis reaction force frames correspond to the first and second Y-axis reaction force frames, which are arranged along the Y-axis direction of the central rigid frame and are disposed on both sides of the central rigid frame, and the inner end faces of the two Y-axis reaction force frames are connected to the central rigid frame as a whole; The rock joint specimens are arranged in a central rigid frame, and the tangent direction of the rock joint surface is the X-axis direction of the reaction frame, while the normal direction of the rock joint surface is the Y-axis direction of the reaction frame; The normal static pressure loading device further comprises a Y-axis front pressure rod and a Y-axis rear pressure rod; the Y-axis front pressure rod is placed in a first Y-axis reaction force frame, and one end of the Y-axis front pressure rod is fixed to the first Y-axis reaction force frame, and the other end is a normal support end; the Y-axis rear pressure rod is placed in a second Y-axis reaction force frame, and one end of the Y-axis rear pressure rod is connected to the power output end of the normal power mechanism, and the other end is a normal actuating end; The tangential static loading device further comprises an incident rod and a transmission rod; the incident rod is placed in the first X-axis reaction force frame, and one end of the incident rod is fixed to the first X-axis reaction force frame, and the other end is a tangential support end; the transmission rod is placed in the second X-axis reaction force frame, and one end of the X-axis rear pressure rod is connected to the power output end of the tangential power mechanism, and the other end is a tangential actuating end; The impact shear loading device is arranged on the outside of the second X-axis reaction force frame.

4. The device for high-speed shear test of rock joints under initial shear stress conditions according to claim 3, characterized in that: The base is a cross-shaped horizontal base; the reaction frame is installed in the cross-shaped horizontal base, and the central rigid frame is installed at the middle cross position of the cross-shaped horizontal base; The cross-shaped horizontal base is provided with an X-axis guide rail along the X-axis direction and a Y-axis guide rail along the Y-axis direction; a plurality of pressure rod supports are movably mounted on the X-axis guide rail and the Y-axis guide rail; The incident rod, the transmission rod, the Y-axis front pressure rod, and the Y-axis rear pressure rod are all supported by pressure rod supports arranged at corresponding positions.

5. The device for high-speed shear test of rock joints under initial shear stress conditions according to claim 4, characterized in that: The normal actuating end and the normal supporting end are both in contact with the rock joint specimen via a rigid gasket; The tangential actuating end and the tangential supporting end are both in contact with the rock joint sample through a sample adapter.

6. The device for high-speed shear test of rock joints under initial shear stress conditions according to claim 1, characterized in that: There are four pairs of strain gauges in total; one pair is pasted on the surface of the incident rod, the transmission rod, the Y-axis front pressure rod and the Y-axis rear pressure rod, and the pasting position is located in the middle of the length of each rod.

7. The device for high-speed shear test of rock joints under initial shear stress conditions according to claim 1, characterized in that: The dynamic displacement acquisition unit comprises a high-speed camera; the high-speed camera is arranged directly above the central rigid frame, and the lens is perpendicular to the upper surface of the rock joint sample; the high-speed camera is connected to the oscilloscope through a cable, and the oscilloscope triggers the high-speed camera to start image acquisition.

8. A method for high-speed shear test of rock joints under initial shear stress conditions, based on a device for high-speed shear test of rock joints under initial shear stress conditions, characterized in that: The device for high-speed shear test of rock joints under initial shear stress conditions includes a loading device and a data acquisition system; wherein: the loading device includes a cross-shaped horizontal base, a reaction force frame, an X-axis guide rail, a pressure rod support, a punch emitter, a cylindrical punch, an incident rod, a transmission rod, an X-axis hydraulic cylinder, an absorption rod, a Y-axis guide rail, a Y-axis front reaction force frame, a Y-axis rear pressure rod, a Y-axis hydraulic cylinder, a hydraulic servo control system, a sample adapter, and a rigid gasket; the reaction force frame is composed of an X-axis left reaction force frame, a central rigid frame, an X-axis right reaction force frame, a Y-axis front reaction force frame, and a Y-axis rear pressure rod. The pressure rod and the Y-axis rear reaction force frame are connected by bolts; the X-axis left reaction force frame, the central rigid frame, and the X-axis right reaction force frame are connected by bolts from left to right and are arranged on a cross-shaped horizontal base, and the central rigid frame is arranged at the intersection of two axes of the cross-shaped horizontal base; the Y-axis front reaction force frame, the central rigid frame, and the Y-axis rear reaction force frame are connected by bolts from front to back and are arranged on a cross-shaped horizontal base; the X-axis guide rail in the loading device is arranged on the cross-shaped horizontal base from left to right, and the Y-axis guide rail is perpendicular to the X-axis guide rail, and from front to back It is arranged on a cross-shaped horizontal base; on the X-axis guide rail, a punch launcher and a certain number of pressure rod supports are arranged from left to right, and the punch launcher is located on the left side of the X-axis left reaction force frame; the cylindrical punch is located in the punch launcher; the incident rod and the transmission rod are supported by the pressure rod support, and the axes of the three coincide with the axis of the cylindrical punch, the incident rod is located on the inner side of the X-axis left reaction force frame, and the transmission rod is located on the inner side of the X-axis right reaction force frame; the Y-axis front pressure rod and the Y-axis rear pressure rod are supported by the pressure rod support arranged on the Y-axis guide rail, and the Y-axis front pressure rod is located inside the Y-axis front reaction force frame. The Y-axis rear pressure rod is located on the inner side of the Y-axis rear reaction force frame, and the axis of the Y-axis front pressure rod coincides with the axis of the Y-axis rear pressure rod; the axis of the incident rod and the axis of the Y-axis pressure rod are at the same horizontal height and are perpendicular to each other; the X-axis hydraulic cylinder is arranged at the right end of the X-axis right reaction force frame and is connected by bolts; the absorption rod passes through the hollow piston of the X-axis hydraulic cylinder and is in close contact with the transmission rod; the Y-axis hydraulic cylinder is arranged at the rear end of the Y-axis rear reaction force frame and is connected by bolts; the X-axis hydraulic cylinder and the Y-axis hydraulic cylinder are connected to the hydraulic servo control system through oil pipes; The data acquisition system includes a stress wave acquisition unit and a dynamic displacement acquisition unit, and the dynamic displacement acquisition unit includes a high-speed camera; The high-speed shear test method of rock joints under initial shear stress conditions includes the following steps: Step 1: Preparation of rock joint samples: The rock joint specimen is made of a cube made of a front rock and a rear rock. The size of the cube is consistent with the cross-sectional size of the incident rod, the transmission rod, and the Y-axis compression rod. The upper surface of the specimen is sprayed with randomly distributed speckles. Step 2: Sample installation and positioning: The prepared rock joint sample is placed between the incident rod and the transmission rod, with the rock joint surface tangentially along the X-axis; a sample adapter is respectively arranged at one end of the incident rod and the transmission rod close to the sample, and it is ensured that the right end face of the sample adapter at the incident rod end coincides with the left end face of the front rock, and the left end face of the sample adapter at the transmission rod end coincides with the right end face of the rear rock; a rigid gasket is respectively arranged at one end of the Y-axis front pressure rod and the Y-axis rear pressure rod close to the sample; the X-axis hydraulic cylinder and the Y-axis hydraulic cylinder are used to push the transmission rod and the Y-axis rear pressure rod close to the sample, and when the sample is in close contact with the sample adapter and the rigid gasket, and the center of the sample coincides with the intersection of the incident rod-transmission rod axis and the Y-axis front pressure rod-Y-axis rear pressure rod axis, the sample positioning is completed; Step 3: Static pressure and tangential static loading of joints: To ensure that the center of the specimen does not shift, the normal static pressure and tangential static force of the joint are alternately loaded in stages, and the load level is not less than two levels: First, the Y-axis hydraulic cylinder is used to load the normal pressure. When the normal pressure reaches the first-level target value, the normal pressure is kept stable. Then, the X-axis hydraulic cylinder is used to load the tangential shear stress. When the tangential shear stress reaches the first-level target value, the tangential shear stress is kept stable. In this way, all load levels are loaded. Step 4: Data acquisition system preparation: First, check the connection between the stress wave acquisition unit and the dynamic displacement acquisition unit to ensure normal communication; then set the acquisition parameters; finally, set the data acquisition system to the trigger state; Step 5: Impact shear loading and data collection The cylindrical punch is pushed into the punch launcher, and the high-pressure gas is used to drive the cylindrical punch to perform linear acceleration motion, so that the cylindrical punch hits the incident rod, thereby generating an incident wave in the incident rod; when the incident wave propagates to the strain gauge on the incident rod, the oscilloscope is triggered to start stress wave acquisition, and the oscilloscope simultaneously sends a signal to the high-speed camera, so that the high-speed camera starts to capture the speckle image of the sample; Step 6: Data storage and processing After the impact shear loading is completed, the stress wave signal cached in the oscilloscope and the image cached in the high-speed camera are saved in the computer respectively; the dynamic shear stress of the rock joint sample is calculated according to the transmission wave in the transmission rod according to formula (1), that is: t d (t)=A bar E bar e tr (t) / A shear (1) In formula (1): d is the nominal dynamic shear stress of the rock joint specimen; A bar is the cross-sectional area of ​​the transmission rod; E bar is the Young's modulus of the transmission rod; ε tr is the strain value of the transmitted wave in the transmission rod; A shear is the nominal shear area of ​​the rock joint specimen; t is the dynamic loading time; The dynamic normal pressure of the rock joint specimen is calculated according to the stress waves in the Y-axis front pressure bar and the Y-axis rear pressure bar according to formula (2), that is: In formula (2): nd is the nominal dynamic normal pressure of the rock joint specimen; ε y1 and ε y2 are the strain values ​​of stress waves in the Y-axis front pressure bar and the Y-axis rear pressure bar respectively; According to the captured speckle image, the displacement field of the measured surface of the sample at each moment is calculated; then, the X-axis displacement of the symmetrical pixel points of the front rock and the rear rock about the joint plane at each moment is subtracted, and finally the average value of all X-axis displacement differences is calculated to obtain the dynamic shear displacement of the rock joint at each moment, as shown in formula (3): In formula (3): u sd is the dynamic shear displacement of rock joints; u i and u i ' are the X-axis displacements of the symmetrical pixels about the rock joint plane in the front rock and the back rock respectively; n is the number of pixels; the subscript i is the sequence number of the pixel, which takes a value of 1...n, where n is an integer; Similarly, the Y-direction displacements of the symmetrical pixels of the front and rear rocks about the joint plane are subtracted at each moment, and finally the average value of all Y-direction displacement differences is calculated to obtain the dynamic normal displacement of the rock joint at each moment, as shown in formula (4): In formula (4): v d is the dynamic normal displacement of rock joints; v i and v i ' are the Y-direction displacements of the pixels symmetrical about the joint plane in the front rock and the rear rock respectively; The above calculation results can be used to draw the dynamic shear stress-dynamic shear displacement curve, dynamic normal displacement-dynamic shear displacement curve, and dynamic normal pressure-dynamic shear displacement curve of rock joints.

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