A device and method for rapidly measuring mechanical properties of rock mass by combining impact-induced fracture and fractal dimension

Abstract

The application discloses a kind of rock mass mechanical property fast measuring device and measuring method combined with impact fracturing and fractal dimension, belong to rock mass exploration technical field, including driving unit, in-situ rock sample preparation unit, impact control unit and information acquisition and processing unit, the in-situ rock sample preparation unit with the impact control unit are detachably connected with driving unit, the information acquisition and processing unit with the driving unit, the impact control unit signal connection.The application is used in cooperation with other elements by hand-held motor, simple structure, optimizes the portability and versatility of measuring device, reduces artificial operation measurement step, directly acts on rock mass surface, improves the accuracy of rock strength and elastic modulus measurement.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of rock mass exploration, and in particular to a rock mass mechanical property rapid measurement device and method combining impact fracturing and fractal dimension. BACKGROUND

[0002] In the process of underground rock engineering construction, the uncertainty of geological conditions is a major challenge in engineering implementation. Rock mechanical properties, including rock strength, integrity, elastic modulus, and fracture characteristics, are key factors in determining the safety and economy of underground engineering. Rapid and accurate determination of rock mechanical properties is of great significance for structure design optimization, dynamic adjustment of construction organization, and construction safety assurance.

[0003] Currently, some in-situ rock mass mechanical property measurement methods applied in engineering include plate load test, side pressure test, borehole in-situ test, and in-situ CT technology. These methods can obtain some rock mass mechanical information to some extent through field operation, but have some defects. For example, the patent with the patent name of "Rock drillability testing device and experimental method under impact mode" and the publication number CN113310829B can simulate the process of breaking rock by drill bit impact, providing equipment for rock drillability testing under impact conditions. The experimental method takes into account the brittle characteristics of rock during impact breaking, uses the action time of a fixed micro drill bit, and distinguishes the drillability levels of different rock samples through the displacement of the micro drill bit. Both static and dynamic impact modes of the drill bit are considered, and the test results are more consistent with actual drilling conditions. Although this device measures rock drillability using the impact failure principle and focuses on the load conditions of failure, it is limited to laboratory use and requires specific size rock samples, which cannot meet the needs of in-situ testing.

[0004] In addition, current in-situ measurement devices mainly rely on drilling and hydraulic loading and unloading to test the mechanical properties of in-situ rock mass. The test equipment is large in size and often requires some large supporting equipment to assist the test, which has poor portability and universality, making it difficult to quickly and accurately obtain in-situ rock mass mechanical parameters.

[0005] Based on the above problems, a rock mass mechanical property rapid measurement device and method combining impact fracturing and fractal dimension are proposed. SUMMARY

[0006] The purpose of the present application is to provide a rock mass mechanical property rapid measurement device and method combining impact fracturing and fractal dimension, which uses a handheld motor in combination with other elements, has a simple structure, optimizes the portability and universality of the measurement device, reduces human operation measurement steps, directly acts on the rock mass surface, and improves the accuracy of rock strength and elastic modulus measurement.

[0007] In order to achieve the above object, the application provides a rock mass mechanical property rapid measurement device and method combining impact induced fracture and fractal dimension, which comprises a driving unit, an in-situ rock sample preparation unit, an impact control unit and an information acquisition and processing unit, the in-situ rock sample preparation unit and the impact control unit are detachably connected with the driving unit, and the information acquisition and processing unit is signal connected with the driving unit and the impact control unit.

[0008] Preferably, the driving unit comprises a motor and a drill chuck connected with a driving shaft of the motor, and the motor is arranged on a handle.

[0009] Preferably, the in-situ rock sample preparation unit comprises a rock polishing disc and a hollow drill bit.

[0010] Preferably, the impact control unit comprises a shell and an impact assembly arranged in the shell, the shell is arranged in a barrel structure, symmetrical energy storage limiting guide grooves are arranged on the side wall of the shell, a limiting sliding block is slidably connected on the energy storage limiting guide grooves, and a clamping groove for limiting the movement of the limiting sliding block is arranged on the energy storage limiting guide grooves; an impact port is arranged on the bottom of the shell, a fixed support is connected outside the impact port of the shell, and a screw hole is arranged on the fixed support.

[0011] Preferably, the impact assembly comprises a power gear and two driven gears engaged with the power gear, the two driven gears are symmetrically arranged, a screw rod is engaged in the inner hole of the driven gear, the upper end of the screw rod is rotatably connected to the top wall of the shell, the lower end of the screw rod penetrates through the limiting sliding block and is rotatably connected to the bottom wall of the shell, and a nut lock is engaged and connected on the screw rod.

[0012] Preferably, the inner hole of the power gear is engaged with a rotating shaft, the rotating shaft protrudes out of the top wall of the shell, a high-energy spring is connected to the power gear through a connecting block, the other end of the high-energy spring is connected with an impact seat, an impact rod is connected to the bottom of the impact seat, an impact cone head is connected to the bottom of the impact rod, symmetrical grooves are arranged on the side wall of the impact seat, and a reset spring sliding block is arranged in the groove through a spring.

[0013] Preferably, the end of the limiting sliding block away from the energy storage limiting guide groove and the free end of the reset spring sliding block are both arranged as inclined surfaces, and the inclined surface of the reset spring sliding block is matched with the inclined surface of the limiting sliding block.

[0014] Preferably, the information acquisition and processing unit comprises an operation panel, a single-chip microcomputer and a camera, the camera is arranged outside the impact port of the shell, the operation panel is arranged outside the shell, and the camera and the operation panel are signal connected with the single-chip microcomputer.

[0015] The application is based on a rock mass mechanical property rapid measurement device combining impact cracking and fractal dimension, and proposes a measurement method, which comprises the following steps:

[0016] S1, selecting a to-be-impacted area of a to-be-measured rock mass, connecting a rock polishing disc on a drill chuck of a motor, and pre-polishing the to-be-impacted area;

[0017] S2, after the to-be-impacted area is polished flat, replacing the rock polishing disc with a hollow drill bit, drilling an in-situ rock sample with a diameter D and a depth H, H≥3mm, 300mm≥D≥150mm;

[0018] S3, after the drilling is completed, checking whether the in-situ rock sample is loose or broken and separated from the rock mass, if the to-be-measured rock sample is not loose or broken, the next step of impact measurement is carried out, and if the to-be-measured rock sample is loose or broken and separated from the rock mass, a position 3D away from the in-situ rock sample is selected, and the steps S1-S3 are re-performed until the impact measurement requirement is met;

[0019] S4, drilling four expansion screw holes around the in-situ rock sample, and using the expansion screws to cooperate with the screw holes of the fixed support to fix the impact assembly on the rock mass, which ensures that the center of the impact cone head is aligned with the center of the upper surface of the in-situ rock sample, and the stability of the whole device is checked after the fixing;

[0020] S5, estimating the rock mass strength, setting the position of the limiting slide on the operation panel according to the rock mass strength, and setting the impact times according to the calibration library;

[0021] S6, controlling the direction of the motor, and performing impact test on the in-situ rock sample, collecting image information of each impact by using a camera until the set impact times are completed;

[0022] S7, completing fractal dimension calculation of the crack image and calibration library search through the built-in program of the single-chip microcomputer, and giving the measurement data of the uniaxial compressive strength, shear strength and elastic modulus on the display screen of the operation panel.

[0023] Preferably, in S7, the image information collected by the two cameras is subjected to image correction to obtain clear cracks on the surface of the in-situ rock sample, and the crack fractal dimension is calculated after image gray scale processing;

[0024] Then, the crack fractal dimension after each impact is calculated, the fractal dimension curve of five repeated crackings under the same impact energy is obtained, and the rock mass mechanical property is obtained in combination with the calibration library.

[0025] Therefore, the rock mass mechanical property rapid measurement device and measurement method combining impact cracking and fractal dimension have the following beneficial effects:

[0026] (1) The measuring device can directly carry out drilling and impact operation on the local area with a diameter of not more than 300 mm on the rock mass surface, and the disturbance to the in-situ rock mass is small; the impact process only includes polishing, drilling and impact operation procedures, the operation is simple, the manual operation is less, the automatic control and measurement of the impact fracturing process ensure that the test time is short, and the test results can be obtained in real time based on the constructed rock mechanics characteristic calibration library.

[0027] (2) The measuring device is composed of a handheld motor, a rock polishing disc, a hollow drill bit and an impact assembly, the components are less, the volumes are small, the device can be conveniently moved and carried, the impact test can be directly carried out on the rock mass surface, the in-situ test can be carried out by selecting a relatively complete rock sample, the influence of the environment and the construction method is small, and the universality is good.

[0028] (3) The device is used for carrying out the test, and the crack propagation characteristics of the rock mass under multiple impact damages are mainly quantified in the test process, the damage law of the rock mass under the action of external force is included, and the obtained rock mechanics characteristic results are accurate.

[0029] The technical solutions of the present application will be further described in detail below with the help of the drawings and the embodiments. DRAWINGS

[0030] Figure 1 It is a connection diagram of the driving unit and the rock polishing disc of the embodiment of the present application.

[0031] Figure 2 It is a working process diagram of the driving unit and the hollow drill bit of the embodiment of the present application.

[0032] Figure 3 It is a structure diagram of the impact control unit of the embodiment of the present application.

[0033] Figure 4 It is a sectional view of the impact control unit of the embodiment of the present application.

[0034] Figure 5 It is a spring energy storage reset structure diagram of the embodiment of the present application.

[0035] Figure 6 It is a partial structure explosion diagram of the spring energy storage reset of the embodiment of the present application.

[0036] Figure 7 It is a flowchart of the measuring test of the embodiment of the present application.

[0037] REFERENCE NUMERALS:

[0038] 1. Motor; 2. Drill chuck; 3. Handle; 4. Rock polishing disc; 5. Hollow drill bit; 6. Housing; 7. Energy storage and limiting guide groove; 8. Limiting slider; 9. Slot; 10. Fixed support; 11. Rock working face; 12. Power gear; 13. Driven gear; 14. Lead screw; 15. Nut lock; 16. High-energy spring; 17. Impact seat; 18. Impact rod; 19. Impact cone; 20. Return spring slider; 21. Control panel; 22. Camera. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0041] Example

[0042] like Figures 1-6 As shown, the present invention provides a rapid measurement device and method for rock mass mechanical properties that combines impact-induced fracturing and fractal dimension, including a drive unit, an in-situ rock sample preparation unit, an impact control unit, and an information acquisition and processing unit. The in-situ rock sample preparation unit and the impact control unit are detachably connected to the drive unit, and the information acquisition and processing unit is signal-connected to the drive unit and the impact control unit.

[0043] The drive unit includes a motor 1 and a drill chuck 2 connected to the drive shaft of the motor 1. The motor 1 is mounted on a handle 3, allowing it to be held by hand. The motor 1 is configured as a forward and reverse motor, and its forward and reverse rotation is controlled by a switch on the motor 1. The drill chuck 2 is connected to other components to complete the entire measurement process.

[0044] The in-situ rock sample preparation unit includes a rock polishing disc 4 and a hollow drill bit 5. Its main function is to generate cylindrical rock samples of a certain size on the surface of the rock working face through polishing and drilling, so as to ensure that the impact surface is smooth and flat and the cracking range of the rock mass is controllable.

[0045] The impact control unit comprises a shell 6 and an impact assembly arranged inside the shell 6, the shell 6 is arranged in a columnar structure, symmetrical energy storage limiting guide grooves 7 are arranged on the side wall of the shell 6, limiting sliding blocks 8 are slidably connected to the energy storage limiting guide grooves 7, clamping grooves 9 are arranged on the energy storage limiting guide grooves 7 for limiting the movement of the limiting sliding blocks 8, in order to ensure that the impact kinetic energy can be adjusted, the limiting sliding blocks 8 can move back and forth along the energy storage limiting guide grooves 7 and are fixed at different positions through the clamping grooves 9, which represents that different impact energies can be stored. An impact port is arranged at the bottom of the shell 6, a fixed support 10 is connected outside the impact port, screw holes are arranged on the fixed support 10, the impact assembly can be fixed on the upper end of the rock working surface 11 of the original rock mass through expansion screws, and stable contact between the impact cone head 19 and the rock surface under the action of multiple impacts in the subsequent test process is ensured.

[0046] The impact assembly comprises a power gear 12 and two driven gears 13 engaged with the power gear 12, the two driven gears 13 are symmetrically arranged, a screw rod 14 is engaged in the inner hole of the driven gear 13, the upper end of the screw rod 14 is rotatably connected to the top wall of the shell 6, the lower end of the screw rod 14 penetrates through the limiting sliding block 8 and is rotatably connected to the bottom wall of the shell 6, the limiting sliding block 8 does not move with the rotation of the screw rod 14, a nut lock 15 is engaged and connected to the screw rod 14, and the nut lock 15 moves linearly with the rotation of the screw rod 14.

[0047] A rotating shaft is engaged in the inner hole of the power gear 12, the rotating shaft extends out of the top wall of the shell 6, a high-energy spring 16 is connected to the lower part of the power gear 12 through a connecting block, the other end of the high-energy spring 16 is connected to an impact seat 17, the bottom of the impact seat 17 is fixedly connected to an impact rod 18, the bottom of the impact rod 18 is fixedly connected to an impact cone head 19, symmetrical grooves are arranged on the side wall of the impact seat 17, reset spring sliding blocks 20 are slidably arranged in the grooves through springs, one end of the spring is fixedly connected to the groove bottom, and the other end is fixedly connected to the reset spring sliding block 20.

[0048] The end of the limiting sliding block 8 away from the energy storage limiting guide groove 7 and the free end of the reset spring sliding block 20 are both arranged as inclined surfaces, the inclined surface of the reset spring sliding block 20 is matched with the inclined surface of the limiting sliding block 8, so that the limiting sliding block 8 is retracted when it contacts the reset spring sliding block 20.

[0049] The impact fracturing process of the in-situ rock sample includes three stages: energy storage, impact and reset. In the energy storage stage, the motor 1 drives the driving gear 12 to transmit power to the driven gear 13, so that the nut lock 15 moves linearly along the screw rod 14. Under the driving action of the motor 1, the impact rod 18 can pull the high-energy spring 16 to complete the preparation of the elastic potential energy required for impact, because the nut lock 15 is in close contact with the reset spring slider 20. In the impact release stage, due to the elastic structure and inclined surface design of the reset spring slider 20, when it contacts the inclined surface of the limiting slider 8, the reset spring slider 20 moves along the inclined surface and compresses the spring inward until it is separated from the nut lock 15. Under the action of the high-energy spring 16, the impact rod 18 drives the impact cone head 19 to contact the rock mass, so that cracks are generated on the surface of the in-situ rock sample. The control range of the impact energy needs to ensure that the surface of the in-situ rock sample produces certain clear and visible cracks, and the rock sample is not completely broken and separated. In the reset stage, the control motor 1 is reversely rotated to drive the nut lock 15 to move reversely linearly along the screw rod 14 until it exceeds the reset spring slider 20, and then the impact rod 18 is pulled back to the original position under the action of the motor 1, preparing for the next impact fracturing action.

[0050] The impact control system uses elastic potential energy to make the impact cone head 19 impact the surface of the rock sample to generate local cracks, ensures that the crack propagation law under different impact energies can be observed and recorded, and uses the operation panel 21 to realize parameter monitoring and instruction operation during the working process, to complete the whole process of automatic control of impact fracturing.

[0051] The connections between the above-mentioned components are all conventional connection modes, such as threaded or bolted connections.

[0052] The information acquisition and processing unit includes the operation panel 21, a single-chip microcomputer (not shown in the figure) and the cameras 22. The cameras 22 are symmetrically arranged outside the impact port of the shell 6, and the operation panel 21 is arranged outside the shell 6. The single-chip microcomputer is built-in the operation panel 21. The cameras 22 and the operation panel 21 are signal-connected with the single-chip microcomputer. The built-in cameras 22 are used to collect image information of the cracks on the surface of the rock sample under different impact energies, which are uploaded to the single-chip microcomputer. The calculation of the fractal dimension is completed synchronously by using the built-in program of the single-chip microcomputer, and the mechanical properties of the rock sample are directly and quickly obtained in combination with the rock mechanics characteristic calibration library, and are displayed on the operation panel.

[0053] After each impact, the single-chip microcomputer controls the cameras 22 to collect the crack pictures of the in-situ test surface, adopts semantic segmentation to obtain the circular area of the rock sample, and uses the two cameras 22 to correct the images, so that the obtained cracks are clear, flat and distortion-free. After the calculation and extraction of the circular area perpendicular to the impact direction are completed, the image is processed by gray scale, and then the crack damage law under the impact is quantified by using the fractal dimension method. The fractal dimension expression of the i-th impact is as follows:

[0054]

[0055] where D i is the box dimension, N i is the number of boxes covering the fractal body when the grid size is ε i is the grid size. i is the grid size.

[0056] Based on the established calibration library, five times of fractal dimension of in-situ rock sample are continuously acquired under the same energy impact for five times to observe the crack evolution law. According to the calibration library of different crack evolution laws, the uniaxial compressive strength, shear strength, elastic modulus, Poisson's ratio and other rock mass mechanical properties of the current rock sample can be found, and displayed on the display screen of the operation panel 21.

[0057] As Figure 7 shown, the impact test is carried out on a certain rock area, and the process is as follows:

[0058] S1, select a relatively flat and no obvious crack area in the rock mass to be tested as the impact area, connect the rock polishing disc 4 to the drill chuck of the motor 1, polish the impact area to ensure the consistency of the contact between the impact cone head 19 and the rock surface, and reduce the test error;

[0059] S2, after the impact area is polished flat, replace the rock polishing disc 4 with a hollow drill bit 5, drill a certain diameter and depth of in-situ rock sample in the polished area, H≥3mm, 300mm≥D≥150mm, and the drill bit cannot be swung greatly during drilling;

[0060] S3, after the drilling is completed, in order to ensure that the rock sample is fixed on the rock surface and produces clear cracks, check whether the in-situ rock sample is loose or broken and separated from the rock mass, if the rock sample to be tested is not loose or broken, the next step of impact determination is carried out; if the rock sample to be tested is loose or broken and separated from the rock mass, select a position away from the in-situ rock sample 3D, and re-operate steps S1-S3 until the impact determination requirements are met;

[0061] S4, drill four expansion screw holes around the in-situ rock sample, use the expansion screws to cooperate with the screw holes of the fixed support 10 to fix the impact assembly on the rock mass, ensure the stability of the connection, and ensure that the center of the impact cone head 19 is aligned with the center of the upper surface of the in-situ rock sample, and check whether the whole device is stable after fixing;

[0062] S5, according to the rough estimation of rock mass strength according to the lithology, set the position of the limiting slide block 8 on the operation panel 21 according to the rock mass strength, so that the energy storage is larger, for the rock mass with lower strength, adjust the limiting slide block 8 to the position with smaller energy storage, and set the impact times according to the calibration library;

[0063] S6, control the steering of the motor 1, carry out the impact test to the in-situ rock sample, use the camera 22 to collect the image information of each impact until the set impact number is completed;

[0064] S7, the fractal dimension of the crack image is calculated and the calibration library is searched through the built-in program of the single-chip microcomputer, the image information collected by the two cameras is corrected, the clear crack on the surface of the in-situ rock sample is obtained, the crack fractal dimension is calculated after the image is processed by the gray scale method;

[0065] Then the crack fractal dimension after each impact is calculated, the fractal dimension curve of five repeated crackings under the same impact energy is obtained, and the mechanical properties of the rock mass are obtained by combining the calibration library.

[0066] Therefore, the rock mass mechanical property rapid measurement device and method combining impact cracking and fractal dimension, through the cooperation of the handheld motor and other elements, has the advantages of simple structure, optimized portability and universality of the measurement device, reduced manual operation measurement steps, direct action on the rock mass surface and improved accuracy of rock strength and elastic modulus measurement.

[0067] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: the technical solutions of the present application can still be modified or replaced by the equivalent, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A rock mass mechanical property rapid measurement device combining impact induced fracture and fractal dimension, characterized in that: it comprises a driving unit, an in-situ rock sample preparation unit, an impact control unit and an information acquisition and processing unit, the in-situ rock sample preparation unit and the impact control unit are detachably connected with the driving unit, and the information acquisition and processing unit is signal connected with the driving unit and the impact control unit; the driving unit comprises a motor and a drill chuck connected with a driving shaft of the motor, and the motor is arranged on a handle; the in-situ rock sample preparation unit comprises a rock polishing disc and a hollow drill bit; the impact control unit comprises a shell and an impact assembly arranged in the shell, the shell is arranged in a barrel structure, symmetrical energy storage limiting guide grooves are formed on the side wall of the shell, a limiting sliding block is slidably connected on the energy storage limiting guide grooves, and a clamping groove for limiting the movement of the limiting sliding block is arranged on the energy storage limiting guide grooves; an impact port is formed on the bottom of the shell, a fixed support is connected outside the impact port of the shell, and a screw hole is formed on the fixed support; the impact assembly comprises a power gear and two driven gears engaged with the power gear, the two driven gears are symmetrically arranged, a screw rod is engaged in the inner hole of the driven gear, the upper end of the screw rod is rotatably connected to the top wall of the shell, the lower end of the screw rod penetrates through the limiting sliding block and is rotatably connected to the bottom wall of the shell, and a nut lock is engaged and connected on the screw rod; a rotating shaft is engaged in the inner hole of the power gear, the rotating shaft extends out of the top wall of the shell, a high-energy spring is connected to the lower part of the rotating shaft, the other end of the high-energy spring is connected to an impact seat, an impact rod is connected to the bottom of the impact seat, an impact cone head is connected to the bottom of the impact rod, symmetrical grooves are formed on the side wall of the impact seat, and a reset spring sliding block is arranged in the groove through a spring; the information acquisition and processing unit comprises an operation panel, a single-chip microcomputer and a camera, the camera is arranged outside the impact port of the shell, the operation panel is arranged outside the shell, and the camera and the operation panel are signal connected with the single-chip microcomputer. The end of the limiting sliding block away from the energy storage limiting guide grooves and the free end of the reset spring sliding block are both arranged as inclined surfaces, and the inclined surface of the reset spring sliding block is matched with the inclined surface of the limiting sliding block. The device comprises the following steps: S1, selecting an impact area of a rock mass to be measured, connecting a rock polishing disc to a drill chuck of a motor, and pre-polishing the impact area; S2, after the impact area is polished flat, replacing the rock polishing disc with a hollow drill bit, drilling an in-situ rock sample with a diameter D and a depth H, H≥3 mm, 300 mm≥D≥150 mm; S3, after the drilling is completed, checking whether the in-situ rock sample is loose or broken and separated from the rock mass, if the in-situ rock sample is not loose or broken, the next step of impact measurement is carried out, and if the in-situ rock sample is loose or broken and separated from the rock mass, a position 3 times the diameter of the in-situ rock sample away from the in-situ rock sample is selected, and steps S1-S3 are re-performed until the impact measurement requirements are met. ​ 2. The device for rapidly measuring the mechanical properties of rock mass by combining the stress wave and fractal dimension according to claim 1, characterized in that: ​ 3. A measuring method based on the rock mass mechanical property rapid measuring device combining the stress wave and the fractal dimension according to any one of claims 1-2, characterized in that, ​ ​ ​ ​ S4, drill four expansion screw holes around the in-situ rock sample, use the expansion screw to cooperate with the screw hole of the fixed support to fix the impact assembly on the rock mass, ensure the center of the impact cone head aligns with the center of the in-situ rock sample surface during the process, check the stability of the whole device after fixing; S5, estimate the strength of the rock mass, set the position of the limiting slide block on the operation panel according to the strength of the rock mass, and set the impact times according to the calibration library; S6, control the direction of the motor, and perform impact test on the in-situ rock sample, use the camera to collect image information of each impact until the set impact times are completed; S7, complete the calculation of crack image fractal dimension and calibration library search through the built-in program of the single-chip microcomputer, and give the measurement data on the display screen of the operation panel.

4. The method of claim 3, wherein: In S7, the image information collected by the two cameras is corrected to obtain clear cracks on the surface of the in-situ rock sample, and the crack fractal dimension is calculated after image grayscale processing; Then calculate the crack fractal dimension after each impact, obtain the fractal dimension curve of five repeated cracking under the same impact energy, and obtain the mechanical properties of the rock mass by combining the calibration library.

Images