CN118376523A - Experimental system and method for in-situ cracking of coal and rock mass by multi-channel micro-difference high-intensity electric explosion and real-time non-destructive observation of cracks - Google Patents

Abstract

The invention relates to a test system of a multichannel differential high-intensity electric detonation in-situ fractured coal rock mass and real-time nondestructive observation of cracks, which comprises a test box, a confining pressure applying device, a shaft pressure applying device, an in-situ CT scanning system, a power supply, a system main switch, a power-on switch, a high-voltage energy storage capacitor, an intelligent millisecond delay switch and a discharge electrode, and the test method of the test system based on the multichannel differential high-intensity electric detonation in-situ fractured coal rock mass and real-time nondestructive observation of cracks comprises the following steps: the invention has the beneficial effects of real-time nondestructive observation of cracks, ensuring to develop in-situ visual environment coal rock electric knock cracking mechanism research, researching the relation between electric knock shock wave millisecond superposition effect and coal rock crack expansion mechanism and researching the relation between deep coal rock destruction rules and electric knock energy control and differential action.

Description

Experimental system and method for in-situ cracking of coal and rock mass by multi-channel micro-difference high-intensity electric explosion and real-time non-destructive observation of cracks

Technical Field

The invention relates to the technical field of high-intensity electric explosion cracking, and in particular to an experimental system and method for in-situ cracking of coal and rock mass by multi-channel micro-difference high-intensity electric explosion and real-time non-destructive observation of cracks.

Background technique

The working principle of high-intensity electric detonation technology is to use electric energy as a conversion medium in a water medium environment. The electric energy stored in the high-voltage electric energy storage container group is released and converted into mechanical energy in the discharge channel to produce a shock wave effect, which ultimately destroys the surrounding coal and rock mass. It is a green and environmentally friendly technology without chemical pollution. The fracturing method based on electric detonation technology can solve the problems of environmental pollution, low efficiency, and large economic losses faced in the mining process of coal and metal mines. It can also achieve coal reservoir fracturing, permeability enhancement, and enhanced coalbed methane extraction, and has a wide range of applications. However, the current electric detonation technology cannot simulate the loaded coal and rock samples in situ during the test and visualize them in real time. The fracture characteristics formed are not sufficient to characterize the damage of the in-situ environment, which limits the research on the fracture propagation mechanism during the electric detonation fracturing of coal and rock masses.

Summary of the invention

In order to solve the technical problem of insufficient characterization of in-situ simulation fracture characteristics in traditional electric explosion test processes, the present invention provides a test system and method for in-situ fracture of coal rock mass by multi-channel micro-difference high-intensity electric explosion and real-time non-destructive observation of fractures. The crack expansion characteristics of the samples during the test are observed in real time by an in-situ CT scanning system, which is beneficial to studying the relationship between the millisecond superposition effect of electric explosion shock waves and the mechanism of coal rock fracture expansion, and studying the relationship between the destruction law of deep coal rock mass and the energy control and micro-difference effect of electric explosion.

In order to achieve the above object, the present invention adopts the following technical solutions:

The test system for in-situ cracking of coal and rock mass by multi-channel micro-difference high-intensity electric explosion and real-time non-destructive observation of cracks includes a test box, a confining pressure applying device, an axial pressure applying device, an in-situ CT scanning system, a power supply, a system main switch, a power switch, a high-voltage electric energy storage container, an intelligent millisecond delay switch, and a discharge electrode. The test method of the test system for in-situ cracking of coal and rock mass by multi-channel micro-difference high-intensity electric explosion and real-time non-destructive observation of cracks is as follows:

S1. Build a test system

The test sample is set in the test box, and two detonation holes are set on the top of the test sample. The distance between the detonation holes is 10 cm. The detonation holes are filled with water, and a discharge electrode is set in each detonation hole; each discharge electrode is connected to its own high-voltage electric energy storage container, and each high-voltage electric energy storage container is connected to the power supply in parallel. An intelligent millisecond delay switch is set between the input end of the discharge electrode and the output end of the high-voltage electric energy storage container, a system master switch is set at the output end of the power supply, and a power-on switch is set at the input end of each high-voltage electric energy storage container. An axial pressure applying device is set on the top of the test sample, and a confining pressure applying device is set around the test sample;

S2. Set up the test environment

The test chamber provides an in-situ sealing test environment, the axial pressure applying device provides different axial pressures for the test sample, and the confining pressure applying device provides different confining pressures for the test sample;

S3. Set the delay time

The two discharge electrodes are set with a delay time through an intelligent millisecond delay switch. The delay time is set to 0-30ms, increasing by 1ms. The same delay time is set between the two discharge electrodes for simultaneous fracture effect test, and different delay times are set between the two discharge electrodes for inter-hole delayed fracture effect test.

S4. Set output energy

The output energy of the two discharge electrodes is set to 0-600 kJ, and the experimental research on multi-channel micro-difference high-intensity electric explosion cracking of coal and rock mass under different axial pressure and confining pressure conditions is completed at different energies;

S5. In situ CT scanning observation

Through the in-situ CT scanning system, the in-situ test samples were observed under different axial pressures and different confining pressures, and the coal rock crack extension characteristics in the simultaneous fracturing effect and the delayed fracturing effect between holes under the action of electric explosion were studied. The millisecond superposition effect of electric explosion shock waves and the coal rock crack extension mechanism were studied. The relationship between the destruction law of deep coal rock and the energy control and micro-difference effect of electric explosion was studied, revealing the fracturing mechanism of coal rock in the in-situ environment caused by high-intensity electric explosion.

Furthermore, the test box is made of a high-strength transparent material that is resistant to pressure and impact. The upper end of the test box can be opened. A processing hole corresponding to the detonation hole is provided on the upper end surface of the test box. A sealed outer cover is provided in the processing hole, and a sealing hole for cable access is provided on the outer cover.

Furthermore, a scanning box of the in-situ CT scanning system is arranged outside the test box, and a movable rod is arranged at the left end of the scanning box, and the movable rod controls the in-situ CT scanning system to move leftward or rightward.

Furthermore, the axial pressure applying device is composed of a pressure rod and a pressure plate. The pressure rod is coupled to the center hole of the upper end face of the test box, the pressure plate is fitted to the upper surface of the test sample, and the pressure plate is provided with holes corresponding to the detonation holes of the test sample. The axial pressure applying device controls the pressure plate to apply different axial pressures to the test sample by applying downward pressure through the pressure rod.

Furthermore, the confining pressure applying device is provided with partitions around the test sample, a sealed space is formed between the partitions and the test box, and pipeline I and pipeline II are respectively provided in the left wall panel and the left bottom sealed space of the test box. Pipeline I, pipeline II and the sealed space constitute the confining pressure applying device, pipeline I and pipeline II are connected in series, and confining pressure liquid is introduced into the inside, and different confining pressures are applied to the test sample by adjusting and controlling the flow rate and pressure between pipeline I and pipeline II.

Furthermore, the discharge electrode is a columnar high-voltage electrode.

Compared with the prior art, the present invention has the following beneficial effects:

The test system for real-time and non-destructive observation of cracks through the in-situ CT scanning system ensures the research on the mechanism of coal rock fracturing induced by electric explosion in an in-situ visible environment, which is conducive to real-time observation of the crack expansion characteristics of in-situ test samples under the action of electric explosion, research on the relationship between the millisecond superposition effect of electric explosion shock wave and the mechanism of coal rock crack expansion, research on the relationship between the destruction law of deep coal rock and the energy control and micro-difference effect of electric explosion, and revealing the mechanism of coal rock fracturing induced by high-intensity electric explosion in the in-situ environment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the structure of the test system for in-situ fracturing of coal and rock mass and real-time nondestructive observation of cracks by multi-channel micro-difference high-intensity electric explosion according to the present invention.

FIG2 is a schematic structural diagram of the in-situ CT scanning system, the test chamber, and the axial pressure applying device provided by the present invention.

FIG. 3 is a schematic diagram of a test sample provided by the present invention with electrodes placed therein.

FIG4 is a schematic diagram of crack expansion of an in-situ coal rock sample observed by the in-situ CT scanning system provided by the present invention.

In the figure: 1 power supply; 2 high-voltage energy storage container; 3 intelligent millisecond delay switch; 4 discharge electrode; 5 axial pressure application device; 6 test box; 7 in-situ CT scanning system; 8 pipeline I; 9 pipeline II; 10 test sample; 11 system main switch; 12 power switch; 13 water; 14 partition; 5a hole; 5b pressure plate; 5c pressure rod; 6a sealing outer cover; 6b sealing hole; 6c center hole; 7a scanning box; 7b movable rod; 10a detonation hole; 15a surface crack; 15b internal crack; 15c bottom crack; 15d side crack.

Detailed ways

The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

As shown in Figures 1 to 4, a test system for in-situ cracking of coal and rock mass by multi-channel micro-difference high-intensity electric explosion and real-time non-destructive observation of cracks comprises a test box 6, a confining pressure applying device, an axial pressure applying device 5, an in-situ CT scanning system 7, a power supply 1, a system main switch 11, a power switch 12, a high-voltage electric energy storage container 2, an intelligent millisecond delay switch 3, and a discharge electrode 4. The test method of the test system for in-situ cracking of coal and rock mass by multi-channel micro-difference high-intensity electric explosion and real-time non-destructive observation of cracks is as follows:

S1. Build a test system

As shown in Figures 1 to 3, two detonation holes 10a are set on the top of the test sample 10, the detonation holes 10a are 10 cm apart, the detonation holes 10a are filled with water, and a discharge electrode 4 is set in each detonation hole 10a; each discharge electrode 4 is connected to its own high-voltage electrical energy storage container 2, each high-voltage electrical energy storage container 2 is connected in parallel to the power supply 1, an intelligent millisecond delay switch 3 is set between the input end of the discharge electrode 4 and the output end of the high-voltage electrical energy storage container 2, a system master switch 11 is set at the output end of the power supply 1, and a power-on switch 12 is set at the input end of each high-voltage electrical energy storage container 2. The two discharge electrodes 4 are separately distributed in the detonation holes 10a, and the two discharge electrodes 4 are connected to the power supply 1. The high-voltage electric energy storage containers 2 are arranged in parallel and electrically connected to the output end of the power supply 1. The upstream of the input end of each high-voltage electric energy storage container 2 is provided with a power switch 12 for controlling on and off. The power switch 12 controls the power supply to supply power to the high-voltage electric energy storage container 2. The discharge electrodes 4 are arranged in parallel and electrically connected to the output ends of two high-voltage electric energy storage containers 2 respectively. Each discharge electrode 4 can form a separate power supply circuit with the power supply 1 through the high-voltage electric energy storage container 2. An axial pressure applying device 5 is arranged on the top of the test sample 10, and its main function is to provide controllable axial pressure for the test sample. A surrounding pressure applying device is arranged around the test sample 10;

S2. Set up the test environment

As shown in FIG. 1-2 , the test box 6 provides an in-situ sealed test environment. Due to the needs of the electric detonation test, the test box 6 requires a sealed environment to simulate the in-situ environment of underground rock detonation. The axial pressure applying device 5 provides different axial pressures for the test sample, and the confining pressure applying device provides different confining pressures for the test sample. During the test, the test sample 10 under different axial pressures and confining pressures is adjusted and controlled to perform simultaneous fracturing and delayed fracturing;

S3. Set the delay time

As shown in FIG1 , the two discharge electrodes 4 are set with a delay time through an intelligent millisecond delay switch 3. The delay time is set to 0 to 30 ms, increasing by 1 ms. The same delay time is set between the two discharge electrodes 4 to conduct a simultaneous fracturing effect test. Different delay times are set for the two discharge electrodes 4 to conduct an inter-hole delayed fracturing effect test. Each high-voltage energy storage container 2 is connected to a discharge electrode 4. An intelligent millisecond delay switch 3 for setting the delay time is provided upstream of the input end of each discharge electrode 4. The intelligent millisecond delay switch 3 is provided at the input end of the discharge electrode 4. The intelligent millisecond delay switch 3 controls the delayed discharge time of the discharge electrode 4. The two discharge electrodes 4 are respectively provided with intelligent millisecond delay switches 3. The two functional millisecond delay switches 3 can be set to the same The delay time of the discharge electrode 4 is controlled to discharge simultaneously, and different delay times can be set to control the two discharge electrodes 4 to discharge at different times. The two discharge electrodes 4 discharge with a slight difference. When the discharge electrodes 4 in the two detonation holes 10a are set with the same delay time, a simultaneous fracturing effect will be generated. When the discharge electrodes 4 in the two detonation holes 10a are set with different delay times, an inter-hole delayed fracturing effect will be generated. The detonation-induced fracturing rock mass damage of the test sample under the simultaneous fracturing effect of the discharge electrodes 4 and the detonation-induced fracturing rock mass damage under the millisecond superposition of shock waves under the inter-hole delayed fracturing effect are observed. The millisecond delay characteristics of the test system and the high-voltage electric energy storage container can be used to safely regulate the electric detonation energy to fracture the rock mass, thereby ensuring the high accuracy of energy output.

S4. Set output energy

The output energy of the two discharge electrodes 4 is set to 0-600 kJ, and the experimental research on multi-channel micro-difference high-intensity electric explosion cracking of coal and rock mass under different axial pressure and confining pressure conditions is completed at different energies;

S5. In situ CT scanning observation

As shown in FIG4 , the in-situ test sample 10 is observed under different axial pressures and different confining pressures by the in-situ CT scanning system 7, and the crack extension characteristics of the test sample 10 in the electric explosion simultaneous fracturing effect and the inter-hole delayed fracturing effect under different axial pressures and confining pressures can be visually observed. The surface cracks 15a, internal cracks 15b, bottom cracks 15c and side cracks 15d generated in the test sample 10 after the simultaneous fracturing effect test under different axial pressures and different confining pressures, and the surface cracks 15a, internal cracks 15b, bottom cracks 15c and side cracks 15d generated in the test sample 10 after the inter-hole delayed fracturing effect test are scanned by the in-situ CT scanning system, so as to study the millisecond superposition effect of electric explosion shock waves and the crack extension mechanism of coal rock mass, study the relationship between the destruction law of deep coal rock mass and the electric explosion energy control and micro-difference effect, and reveal the high-intensity electric explosion fracturing mechanism of coal rock mass in the in-situ environment.

As shown in Figures 1 and 2, further, the test box 6 is made of a high-strength transparent material that is resistant to pressure and impact. The upper end of the test box 6 can be opened. A processing hole corresponding to the detonation hole 10a is provided on the upper end face of the test box 6. A sealed outer cover 6a is provided in the processing hole. A sealing hole 6b for cable access is provided on the sealed outer cover 6a. A sealed outer cover 6a matching the detonation hole 10a is provided on the upper end face of the test box 6. A sealing hole 6b is provided in the middle of the sealed outer cover 6a to connect the cable. The cable not only transmits electricity to the discharge electrode 4, but also fixes the discharge electrode 4 at the center of the detonation hole 10a. The sealed outer cover 6a can also ensure that the test environment is closed and no pressure relief occurs.

As shown in FIG3 , further, the scanning box 7a of the in-situ CT scanning system 7 is arranged outside the test box, and a movable rod 7b is arranged at the left end of the scanning box 7a, and the movable rod 7b controls the in-situ CT scanning system 7 to move leftward or rightward.

As shown in Figures 1 and 2, further, the axial pressure applying device 5 is composed of a pressure rod 5c and a pressure plate 5b. The pressure rod 5c is coupled to the center hole 6c on the upper end surface of the test box, and the pressure plate 5b is fitted with the upper surface of the test sample 10. The pressure plate 5b is provided with a hole 5a corresponding to the detonation hole 10a of the test sample 10. The axial pressure applying device controls the pressure plate 5b to apply different axial pressures to the test sample 10 by applying downward pressure through the pressure rod 5c.

As shown in FIG1 , further, the confining pressure applying device is to set a partition 14 around the test sample 10, and a sealed space is formed between the partition 14 and the test box 6. A pipeline I8 and a pipeline II9 are respectively arranged in the left wall plate and the left bottom sealed space of the test box 6. The pipeline I8, the pipeline II9 and the sealed space constitute the confining pressure applying device. The pipeline I8 and the pipeline II9 are connected in series, and the confining pressure liquid is passed into the inside. Different confining pressures are applied to the test sample 10 by adjusting the flow rate and pressure between the pipeline I8 and the pipeline II9. The left side of the test box 6 is provided with Pipeline I8, confining pressure liquid is passed into pipeline I8, pipeline II9 is arranged at the bottom left position, pipeline II9 recovers confining pressure liquid, and is used to be connected in series to form a confining pressure applying device, pipeline I8, pipeline II9 and sealed space are a closed space, confining pressure liquid is passed into pipeline I8, pipeline II9 recovers confining pressure liquid, pipeline I8 and pipeline II9 are a liquid flow passage, and the flow rate and pressure of the confining pressure liquid in pipeline I8 and pipeline II9 can adjust the pressure of the liquid in the sealed space around the test sample 10, thereby adjusting the confining pressure around the test sample 10.

Furthermore, the discharge electrode 4 is a columnar high-voltage electrode.

The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims (6)

1. The test system is characterized by comprising a test box, a confining pressure applying device, a shaft pressure applying device, an in-situ CT scanning system, a power supply source, a system main switch, a power-on switch, a high-voltage energy storage capacitor, an intelligent millisecond delay switch and a discharge electrode, and the test method of the test system based on the multichannel differential high-intensity electric detonation in-situ fracturing coal rock mass and capable of realizing real-time nondestructive observation of cracks is as follows:

S1, constructing a test system

A test sample is arranged in the test box, two detonation holes are arranged at the top of the test sample, the distance between the detonation holes is 10cm, water is filled in the detonation holes, and a discharge electrode is arranged in each detonation hole; each discharge electrode is connected with a respective high-voltage energy storage capacitor, each high-voltage energy storage capacitor is connected with a power supply in parallel, an intelligent millisecond delay switch is arranged between the input end of each discharge electrode and the output end of each high-voltage energy storage capacitor, the output end of the power supply is provided with a system master switch, the input end of each high-voltage energy storage capacitor is provided with an electrifying switch, the top of a test sample is provided with a shaft pressure applying device, and the periphery of the test sample is provided with a confining pressure applying device;

S2, setting a test environment

The test box provides an in-situ sealing test environment, the axial pressure applying device provides different axial pressures for the test sample, and the confining pressure applying device provides different confining pressures for the test sample;

S3, setting delay time

The two discharge electrodes are set with delay time through an intelligent millisecond delay switch, the delay time is set to 0-30 ms, the delay time is increased every 1ms, the same delay time is set between the two discharge electrodes for carrying out a simultaneous fracturing effect test, and the two discharge electrodes are set with different delay times for carrying out an inter-hole delay fracturing effect test;

s4, setting output energy

Setting the output energy of the two discharge electrodes, wherein the output energy is 0-600 kJ, and completing the experimental study of the multichannel differential high-intensity electric detonation fracturing coal rock mass under different axial pressures and confining pressures under different energies;

s5, in-situ CT scanning observation

And observing the coal rock crack expansion characteristics in the in-situ test sample under the conditions of different axial pressures and different confining pressures and simultaneously causing cracking effect and inter-hole delay cracking effect under the action of electric knocking through an in-situ CT scanning system, researching the millisecond superposition effect of electric knocking shock waves and the coal rock crack expansion mechanism, researching the relation between the deep coal rock damage rule and the electric knocking energy control and differential action, and revealing the in-situ environment coal rock high-strength electric knocking cracking mechanism.

2. The test system for in-situ fracturing coal rock mass by multichannel differential high-intensity electric knocking and real-time nondestructive observation of cracks is characterized in that the test box is made of a compressive and impact-resistant high-strength transparent material, the upper end of the test box can be opened, a processing hole corresponding to the knocking hole is formed in the upper end face of the test box, a sealing outer cover is arranged in the processing hole, and a sealing hole for cable access is formed in the outer cover.

3. The test system for in-situ fracturing coal and rock mass by multichannel differential high-intensity electric knocking and real-time nondestructive observation of cracks, according to claim 1, wherein a scanning box body of the in-situ CT scanning system is arranged outside the test box, a movable rod is arranged at the left end of the scanning box body, and the movable rod controls the in-situ CT scanning system to move leftwards or rightwards.

4. The test system for in-situ fracturing coal and rock mass by multichannel differential high-intensity electric knocking and real-time nondestructive observation of cracks is characterized in that the axial pressure applying device consists of a pressure rod and a pressure plate, the pressure rod is connected with a central hole of the upper end face of the test box in a coupling way, the pressure plate is attached to the upper surface of a test sample, holes corresponding to knocking holes of the test sample are formed in the pressure plate, and the axial pressure applying device downwards applies pressure to the pressure plate through the pressure rod to control the pressure plate to apply different axial pressures to the test sample.

5. The multi-channel differential high-intensity electric detonation in-situ fractured coal rock mass real-time nondestructive fracture observation test system according to claim 1, wherein the confining pressure applying device is characterized in that a baffle is arranged around a test sample, a sealing space is formed between the baffle and the test box, a pipeline I and a pipeline II are respectively arranged in a left side wall plate and a left side bottom sealing space of the test box, the pipeline I, the pipeline II and the sealing space form the confining pressure applying device, the pipeline I and the pipeline II are communicated in series, confining pressure liquid is introduced into the pipeline I and the pipeline II, and different confining pressures are applied to the test sample by adjusting and controlling flow and pressure between the pipeline I and the pipeline II.

6. The test system for in-situ fracturing of coal and rock mass by multichannel differential high-intensity electric detonation and real-time nondestructive observation of cracks according to claim 1, wherein the discharge electrode is a columnar high-voltage electrode.