Rock crack evolution test device under dry-wet cycle

Abstract

The utility model discloses a rock crack evolution test device under dry-wet circulation. The rock crack evolution test device comprises a sample box filled with rock, a dry-wet circulation module used for creating dry-wet circulation conditions in the sample box, a damage detection module used for detecting rock damage and an image acquisition module used for acquiring cracks on the surface of the rock, a water level detector A is arranged in the sample box; the damage detection module comprises an acoustic emission instrument, a strain gauge and an amplification module; the strain gauge is adhered to the surface of the rock, and a probe of the acoustic emission instrument is attached to the surface of the rock; and the amplification module comprises an acoustic emission acquisition instrument electrically connected with the acoustic emission instrument and a strain acquisition instrument electrically connected with the strain gauge. According to the scheme, cracking of the internal structure of the rock and development of cracks on the surface of the rock can be detected at the same time, then the mechanical property degradation rule and the crack evolution coupling rule of the rock under the dry-wet cycle condition are analyzed, and reference is provided for evaluation of the service performance of rock slopes and cutting.

Description

Technical Field

[0001] The utility model relates to the technical field of rock mechanics test equipment, and particularly relates to a test device for rock crack evolution under dry-wet cycles. Background Art

[0002] Rainfall can cause an increase in the moisture content of exposed rock and soil masses, and sunlight exposure can cause a decrease in the moisture content of exposed rock and soil masses. Such repeated dry-wet cycles will have a very significant impact on the strength and deformation characteristics of rock and soil masses.

[0003] Under the action of dry-wet cycles, a large number of microcracks are first generated inside the rock, and the internal structure of the rock deteriorates to a certain extent. Then, the microcracks continue to expand and connect with each other, and obvious cracks are generated on the rock surface. The structural deterioration and crack development of the rock under such dry-wet cycles have a significant impact on engineering construction. For example, during the excavation of a high cutting slope, the mudstone at the newly excavated surface can maintain the stability of the excavated slope because it has not been affected by dry-wet cycles. However, after several rains, due to the action of dry-wet cycles, the rock structure deteriorates and a large number of cracks are generated, and the slope cannot maintain stability and collapses.

[0004] Therefore, exploring the evolution of rock cracks under dry-wet cycles has important guiding significance for actual engineering construction. However, the existing technologies and test platforms do not simultaneously detect the deterioration of the internal structure of the rock and the development of cracks on the rock surface, and cannot analyze the coupling law between structural deterioration and crack evolution of the rock during dry-wet cycles. Content of the Utility Model

[0005] In view of the above deficiencies of the prior art, the utility model provides a test device for rock crack evolution under dry-wet cycles, which solves the problem that the prior art does not simultaneously detect the internal deterioration of the rock and the development of surface cracks.

[0006] To achieve the above object, the technical solution adopted by the utility model is as follows:

[0007] Provide a test device for rock crack evolution under dry-wet cycles, which includes a specimen box for placing the rock, a dry-wet cycle module for providing dry-wet cycle conditions for the specimen box, a damage detection module for detecting the damage degree of the rock, and an image acquisition module for collecting images of cracks on the rock surface; a water level detector A is arranged in the specimen box; the damage detection module includes an acoustic emission instrument, a strain gauge, and an amplification module; the strain gauge is pasted on the surface of the rock, and the probe of the acoustic emission instrument is attached to the surface of the rock;

[0008] The amplification module includes an acoustic emission acquisition instrument electrically connected to the acoustic emission instrument and a strain acquisition instrument electrically connected to the strain gauge; the dry-wet cycle module, the water level detector, the acoustic emission acquisition instrument, the strain acquisition instrument, and the image acquisition module are all electrically connected to the control module.

[0009] The beneficial effects of the present utility model are as follows: Under wet-dry cycling conditions, the rock will gradually deform and generate cracks. The acoustic emission collector can collect the wave velocity of the rock during wet-dry cycling. By comparing the wave velocity values at different time periods, the development of internal cracks in the rock can be preliminarily judged. The strain collector can collect the strain data of the rock during wet-dry cycling. Both the wave velocity and strain data can be transmitted to the control module for storage. The image acquisition module can collect pictures of the crack evolution on the rock surface during wet-dry cycling.

[0010] Subsequently, a computer can be used to record the wave velocity, strain data, and pictures of the evolution of rock cracks. The deterioration and damage of the internal structure of the rock can be judged based on the wave velocity, the change in the stiffness of the rock can be analyzed based on the strain data, and the evolution law of external cracks on the rock can be analyzed based on the pictures. Therefore, this solution can simultaneously collect data on the cracking of the internal structure of the rock and the development of surface cracks, providing data support for subsequent analysis.

[0011] Further, the wet-dry cycling module includes a water storage tank. The water storage tank is connected to the water inlet of the specimen box through a water inlet pipe. A water pump is provided on the water inlet pipe. The water outlet of the specimen box is connected to the water storage tank through a water outlet pipe. A solenoid valve is provided at the water outlet. Both the water pump and the solenoid valve are electrically connected to the control module.

[0012] The beneficial effects of the above technical solution are as follows: The control module makes water enter the specimen box by turning on the water pump and soaks the rock to humidify the rock, and makes the water in the specimen box drain out by turning on the solenoid valve to dry the rock again. The drying method of the rock is natural air drying, so as to automatically execute the humidification and drying processes.

[0013] Further, the number of acoustic emission instruments is two, and the included angle between the probes of the two acoustic emission instruments is 180°. The fixed height of the probe of the acoustic emission instrument is higher than 1 / 2 of the rock height. By symmetrically arranging on the left and right, different parts of the rock 6 can be effectively covered to obtain more comprehensive acoustic wave signal data, making the analysis result more accurate and reliable.

[0014] Further, a support plate that divides the inside of the specimen box into two spaces is provided inside the specimen box. A number of through holes are provided on the surface of the support plate. The rock is fixed above the support plate, and the water outlet of the specimen box is provided below the support plate. The support plate can lift the rock, and water can drain out of the specimen box from below the support plate, avoiding incomplete drainage at the bottom of the rock and difficult drying due to long-term soaking in water during the drying stage, resulting in local wetting and affecting the test results.

[0015] Further, a water level detector B electrically connected to the control module is provided inside the water storage tank; the water inlet of the water storage tank is connected to a water source through a water pipe, and a solenoid valve electrically connected to the control module is provided on the water pipe. The water level detector B is used to detect the water level height inside the water storage tank so as to send a signal to the control module, and the control module timely drives the solenoid valve to open to supplement the water storage volume.

[0016] Further, the image acquisition module includes a camera, and the camera lens extends into the specimen box and is fixed directly above the rock. The camera lens is a high-definition camera, which is used to take crack photos of the upper surface of the rock and can be uploaded to a computer.

[0017] Further, a base is fixedly connected to the upper surface of the support plate, the upper surface of the base is fixedly connected to the rock, and a number of drain holes are provided on the base.

[0018] Further, the acoustic emission instrument is fixed on a fixing frame, and the fixing frame is fixed on the upper surface of the base. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of a test device for rock crack evolution under wet-dry cycles;

[0020] Figure 2 It is a table of the evolution law of rock cracks under wet-dry cycles;

[0021] Figure 3 It is a curve graph of the change of rock stiffness damage with the crack ratio.

[0022] Among them, 1. Water storage tank; 2. Water level detector B; 3. Water pump; 4. Specimen box; 5. Solenoid valve; 6. Rock; 7. Strain gauge; 8. Acoustic emission instrument; 9. Water level detector A; 11. Amplification module; 12. Image acquisition module; 13. Control module; 14. Base; 15. Support plate; 16. Fixing frame. Detailed Embodiments

[0023] The following describes the detailed embodiments of the present invention to facilitate those skilled in the art of this technology to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the detailed embodiments. For those of ordinary skill in the art of this technology, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all utility models created using the concept of the present invention are within the scope of protection.

[0024] As Figure 1As shown in the figure, the test device for rock crack evolution under wet-dry cycles of this solution includes a specimen box 4 containing a rock 6, a wet-dry cycle module for creating wet-dry cycle conditions inside the specimen box 4, a damage detection module for detecting damage to the rock 6, and an image acquisition module 12 for collecting images of cracks on the surface of the rock 6; a water level detector A9 is provided in the specimen box 4.

[0025] The damage detection module includes an acoustic emission instrument 8, a strain gauge 7, and an amplification module 11. The strain gauge 7 is pasted on the surface of the rock 6, and the probe of the acoustic emission instrument 8 is in contact with the surface of the rock 6. The amplification module 11 includes an acoustic emission acquisition instrument electrically connected to the acoustic emission instrument 8 and a strain acquisition instrument electrically connected to the strain gauge 7. The wet-dry cycle module, the water level detector, the acoustic emission acquisition instrument, the strain acquisition instrument, and the image acquisition module 12 are all electrically connected to the control module 13.

[0026] The acoustic emission instrument 8 is a device used to capture weak acoustic wave signals inside materials. The acoustic emission acquisition instrument is a device used to capture, amplify, digitize, and analyze the signals of the acoustic emission instrument 8. By analyzing the signals of the acoustic emission instrument 8 collected, the damage, crack propagation, etc. of materials or structures can be judged. During the wet-dry cycle experiment of the rock, the acoustic emission instrument is used to regularly measure the wave velocity inside the rock. Analyze the change trend of the wave velocity over time. If the wave velocity gradually decreases, it indicates that the cracks inside the rock 6 are gradually developing; on the contrary, if the wave velocity remains stable or slightly increases, it may indicate that the degree of crack development is small or tends to be stable. By comparing the wave velocity values at different time periods, the development of cracks inside the rock can be preliminarily judged. In order to more accurately judge the degree of crack development, other physical parameters (such as the density, elastic modulus, etc. of the rock) and geological data can also be combined for comprehensive analysis.

[0027] The strain gauge 7 is a sensor that can change its resistance with strain. The strain acquisition instrument is used to record the signals measured by the strain gauge 7 and convert them into digital signals for analysis and recording.

[0028] The utility model can, under wet-dry cycle conditions, take pictures and record the evolution of surface fissures of the rock 6 while recording the deterioration and damage of its internal structure, and study the mechanical properties of the rock 6 under wet-dry cycles by combining internal and external methods.

[0029] The control module 13 includes a single-chip microcomputer and a computer that are electrically connected. The computer can perform subsequent analysis and processing on the collected data. The single-chip microcomputer can realize humidification and drying control. When the water level detector A9 detects that the water level in the specimen box 4 reaches the set value, it transmits a signal to the single-chip microcomputer. The single-chip microcomputer controls the wet-dry cycle module to stop humidification. After a set time, the single-chip microcomputer controls the wet-dry cycle module to execute the drying process again, and the wet-dry cycle process repeats the above humidification and drying processes.

[0030] In this solution, the reagents, materials, and instruments used, unless otherwise specified, are all products in the prior art and can be commercially purchased.

[0031] The acoustic emission instrument 8 can be a KTL acoustic wave (acoustic emission) detector with an input bandwidth of 10 kHz - 100 kHz and a digital filtering range of 1 kHz - 100 kHz.

[0032] In one embodiment, the number of acoustic emission instruments 8 is two, and the included angle between the probes of the two acoustic emission instruments 8 is 180°; the fixed height of the probes of the acoustic emission instrument 8 is higher than 1 / 2 of the height of the rock 6. The probes of the acoustic emission instrument 8 need to be smeared with vaseline and then closely attached to the surface of the rock 6 for installation. By setting them symmetrically left and right, different parts of the rock 6 can be effectively covered to obtain more comprehensive acoustic wave signal data, making the analysis results more accurate and reliable.

[0033] Reference Figure 1 , the number of strain gauges 7 can be set to four. Three of the strain gauges 7 are evenly pasted vertically along the surface of the rock 6, and the other strain gauge 7 is pasted at the center point on the front of the rock 6 with the pasting direction perpendicular to that of the other strain gauges 7. The strain gauges 7 can be pasted on the surface of the rock 6 with 502 glue to continuously monitor the volume change of the rock 6 during the soaking and drying processes.

[0034] In one embodiment of the present utility model, the wet-dry cycling module includes a water storage tank 1. The water storage tank 1 is connected to the water inlet of the specimen box 4 through a water inlet pipe. A water pump 3 is provided on the water inlet pipe. The water outlet of the specimen box 4 is connected to the water storage tank 1 through a water outlet pipe, and a solenoid valve 5 is provided at the water outlet; both the water pump 3 and the solenoid valve 5 are electrically connected to the control module 13.

[0035] The control module 13 makes water enter the specimen box 4 by turning on the water pump 3 and soaks the rock 6 to humidify the rock 6, and makes the water in the specimen box 4 drain by turning on the solenoid valve 5 to re-dry the rock 6. The drying method of the rock 6 is natural air drying to automatically execute the humidification and drying processes.

[0036] The complete operation process in this embodiment is as follows: Step 1, turn on the water pump 3 until the water level reaches the set value to humidify the rock 6; Step 2, after soaking for the set time, turn on the solenoid valve 5 to drain water; Step 3, let the rock 6 dry naturally; Step 4, repeat Steps 1 - 3 after the set time. After the rock 6 disintegrates and breaks, the test is completed.

[0037] Inside the sample box 4, there is a support plate 15 that divides its interior into two spaces. A number of through holes are provided on the surface of the support plate 15. The rock 6 is fixed above the support plate 15, and the water outlet of the sample box 4 is arranged below the support plate 15. The support plate 15 can lift the rock 6, and water can be discharged from the sample box 4 from below the support plate 15, avoiding incomplete drainage at the bottom of the rock 6 and being not easily dried due to long-term soaking in water during the drying stage, resulting in local wetness and affecting the test results.

[0038] The upper surface of the support plate 15 is fixedly connected with a base 14. The upper surface of the base 14 is fixedly connected with the rock 6. A number of drainage holes are provided on the base 14, which is beneficial to the drainage of the base 14 and avoids waterlogging at the bottom of the rock 6. The acoustic emission instrument 8 is fixed on the fixing frame 16, and the fixing frame 16 is fixed on the upper surface of the base 14.

[0039] A water level detector B2 electrically connected to the control module 13 is arranged in the water storage tank 1. The water inlet of the water storage tank 1 is connected to the water source through a water pipe, and a solenoid valve 5 electrically connected to the control module 13 is arranged on the water pipe. The water level detector B2 is used to detect the water level height inside the water storage tank 1 to send a signal to the control module 13, and the control module 13 timely drives the solenoid valve 5 to open to supplement the water storage. The logic of automatic control can be: the water storage in the water storage tank 1 is V1, the water demand of the sample box 4 is V2, and the difference V = V1 - V2. When V is less than the set value, it is necessary to supplement the water storage tank 1 to V.

[0040] The image acquisition module 12 includes a camera. The camera lens extends into the sample box 4 and is fixed directly above the rock 6. The fixing method of the camera is: a hoop is sleeved on the camera body, and then the hoop and the acrylic plate on the top of the sample box 4 are connected by screws. The camera lens is a 4K high-definition camera, which is used to take crack photos of the upper surface of the rock 6, and can take pictures at regular intervals according to the test needs and upload them to the computer in real time.

[0041] Subsequently, crack processing software with the programming language Matlab can be used to automatically extract the crack images and calculate the crack rate on the upper surface of the rock 6. (Both are processing software and processing methods in the prior art)

[0042] As Figure 2 shown, the table shows the crack evolution of the rock 6. The first row in the table represents the soaking or drying duration of the rock 6, the second row represents the pictures of the upper surface of the rock 6 collected by the image acquisition module 12 at the corresponding time points, the third row represents the binary images of the cracks collected by the crack acquisition software, and the third row represents the crack rate of the rock 6 in the wet-dry cycle calculated from the binary images. The crack rate can be calculated by measuring the number of black and white pixel points and using a formula, and this formula is an existing formula.

[0043]

[0044] Where: δ f is the fracture rate, A i is the area of the i-th fracture, S B is the total area of the specimen, n b is the number of black pixels, n w is the number of white pixels, and n is the total number of pixels.

[0045] As Figure 3 shown, the figure shows the evolution law of the stiffness decay of rock 6 with the fracture rate during the wet-dry cycle. It can be seen that as the fracture rate increases, the stiffness of rock 6 gradually decays, and there is a correlation between the two.

[0046] In summary, this solution can simultaneously detect the cracking of the internal structure of rock 6 and the development of surface fractures of rock 6, and then analyze the coupling law between the degradation law of the mechanical properties of rock 6 and the fracture evolution under wet-dry cycle conditions, providing a reference for the service performance evaluation of rock slopes and road cuts.

Claims

1. A rock crack evolution test device under dry-wet cycles, characterized by: The invention comprises a sample box (4) for placing a rock (6), a dry-wet cycle module for providing dry-wet cycle conditions for the sample box (4), a damage detection module for detecting the degree of damage to the rock (6), and an image acquisition module (12) for acquiring cracks on the surface of the rock (6); a water level detector A (9) is arranged in the sample box (4); the damage detection module comprises an acoustic emission instrument (8), a strain gauge (7), and an amplification module (11); the strain gauge (7) is adhered to the surface of the rock (6), and the probe of the acoustic emission instrument (8) is in contact with the surface of the rock (6); The amplification module (11) comprises an acoustic emission acquisition instrument electrically connected to the acoustic emission instrument (8) and a strain acquisition instrument electrically connected to the strain gauge (7); the dry-wet cycle module, the water level detector, the acoustic emission acquisition instrument, the strain acquisition instrument and the image acquisition module (12) are all electrically connected to the control module (13).

2. The rock crack evolution test device under dry-wet cycles according to claim 1 is characterized by: The dry-wet cycle module comprises a water storage tank (1), the water storage tank (1) is connected to the water inlet of a sample box (4) through a water inlet pipe, a water pump (3) is arranged on the water inlet pipe, the water outlet of the sample box (4) is connected to the water storage tank (1) through a water outlet pipe, and a solenoid valve (5) is arranged at the water outlet; the water pump (3) and the solenoid valve (5) are both electrically connected to a control module (13).

3. The rock crack evolution test device under dry-wet cycles according to claim 1 is characterized by: The number of the acoustic transmitters (8) is two, and the angle between the probes of the two acoustic transmitters (8) is 180°; the fixed height of the probes of the acoustic transmitter (8) is higher than 1 / 2 of the height of the rock (6).

4. The rock crack evolution test device under dry-wet cycles according to claim 3 is characterized by: The sample box (4) is provided with a support plate (15) inside thereof for dividing the inside thereof into two spaces, and a plurality of through holes are provided on the surface of the support plate (15); the rock (6) is fixed above the support plate (15), and the water outlet of the sample box (4) is provided below the support plate (15).

5. The rock crack evolution test device under dry-wet cycles according to claim 2 is characterized by: A water level detector B (2) electrically connected to the control module (13) is arranged in the water storage tank (1); a water inlet of the water storage tank (1) is connected to a water source via a water pipe, and a solenoid valve (5) electrically connected to the control module (13) is arranged on the water pipe.

6. The rock crack evolution test device under dry-wet cycles according to claim 1 is characterized by: The image acquisition module (12) comprises a camera, the camera head of which extends into the sample box (4) and is fixed directly above the rock (6).

7. The rock crack evolution test device under dry-wet cycles according to claim 4 is characterized by: The upper surface of the support plate (15) is fixedly connected to a base (14), the upper surface of the base (14) is fixedly connected to the rock (6), and a plurality of drainage holes are arranged on the base (14).

8. The rock crack evolution test device under dry-wet cycles according to claim 7 is characterized by: The acoustic emission instrument (8) is fixed on a fixing frame (16), and the fixing frame (16) is fixed on the upper surface of the base (14).

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