Simulation device, experimental system and method based on crack distribution law

Abstract

The present invention discloses a simulation device based on the law of crack distribution, comprising a base plate, a grouting pipe connected upward from the center of the base plate, the bottom end of the grouting pipe opening at the lower surface of the base plate; an inner tube made of a screen is provided on the periphery of the grouting pipe, a middle tube made of a screen is provided on the periphery of the inner tube, and an outer tube is provided on the periphery of the middle tube; the space inside the inner tube is a simulated fracture zone, the annular space between the inner tube and the middle tube is a simulated plastic zone, and the annular space between the middle tube and the outer tube is a simulated elastic zone; the present invention also discloses a corresponding experimental system and method. The present invention can more accurately determine the radius range of each zone and the porosity of the coal in each zone, more realistically simulate the actual conditions of the fracture zone, plastic zone and elastic zone around the coal seam drilling hole, obtain the diffusion law of the slurry in the simulated actual coal seam through the grouting experiment, thereby determining the optimal grouting parameters and better guiding the grouting and sealing operation in the actual coal seam.

Description

Technical Field

[0001] The present invention relates to the technical field of coal mines, in particular to a grouting and hole sealing technology. Background Art

[0002] Coal seam gas extraction is a fundamental measure to control coal and gas outbursts. It can quickly reduce gas content and gas pressure, and the extracted gas can also be used as clean energy.

[0003] Drilling grouting and sealing is a key technology for coal seam gas extraction, and the sealing effect of the sealing material on the cracks in the borehole surrounding rock directly affects the quality of drilling sealing.

[0004] The diffusion of borehole grouting slurry within cracks is highly uncertain and hidden, making it difficult to directly observe with the naked eye. For a long time, underground grouting has relied on traditional worker experience, without prior scientific grouting parameters. This often leads to significant waste of manpower and materials, resulting in poor grouting results.

[0005] Carrying out corresponding physical model simulation experiments for dynamic monitoring of the grouting process will help to study and reveal the laws and mechanisms of slurry diffusion in cracks around the borehole. This has important practical significance and economic value for setting more targeted grouting parameters in advance and guiding actual grouting and sealing in the well, so as to better achieve the sealing effect of cement mortar grouting and sealing in gas extraction boreholes and avoid the trouble of secondary grouting.

[0006] Conducting experiments requires proper simulation of coal seams and simulated drilling, and the production of coal samples specific to the target coal seam. Typically, coal seam sampling involves first collecting a sample from the target coal seam, then preparing it into a sample of the desired shape and size. Alternatively, the target coal seam's composition and content are determined by preparing loose coal with the same composition and content using raw coal or other materials, and then preparing the sample from the loose coal.

[0007] In the actual coal seam drilling area, a fracture zone of the coal body will be formed within a certain radius space adjacent to the drill hole. Outside the fracture zone, a plastic zone of the coal body will be formed within a certain radius space. Outside the plastic zone, an elastic zone of the coal body will be formed within a certain radius range.

[0008] The fracture zone refers to the area where the coal body is affected by drilling and the stress change exceeds its strength limit, resulting in cracking and fracture.

[0009] The plastic zone refers to the area where the coal body is affected by drilling and the stress change reaches the limit of elastic deformation, causing deformation. Even if the stress effect is removed, the coal body in this area will not completely return to its original state.

[0010] The elastic zone is the area where the coal body undergoes reversible deformation due to the impact of drilling. The coal body in this area can also return to its original state after the stress is removed.

[0011] Outside the elastic zone is the area not affected by drilling.

[0012] In short, in previous coal seam experiments, the process of making coal samples failed to simulate the coal body crack conditions at the sealing point. The coal samples made could not well reflect the diffusion of slurry in the real coal body cracks when used in grouting experiments. The experimental results were quite different from the actual coal seam grouting and sealing operations.

[0013] The research and development idea of ​​this patent is to study the crack distribution law, determine the size of the fracture zone, plastic zone and elastic zone, determine the porosity of the coal sample in the fracture zone, plastic zone and elastic zone, and solve the problem of making simulated coal samples based on the crack distribution law, so that the simulated coal samples can reflect the crack conditions of the coal body at the sealing point, and then use the produced coal samples to carry out grouting experiments. The experiments reveal the diffusion law and mechanism of the slurry in different fracture zones around the borehole, and suggest the grouting sealing effect of different grouting parameters for specific coal bodies, thereby effectively guiding the determination of grouting parameters in real coal mines. Summary of the Invention

[0014] The purpose of the present invention is to provide a simulation device based on the crack distribution law, which determines the size of the fracture zone, plastic zone and elastic zone according to the crack distribution law, and is used to carry out grouting and sealing experiments on the simulated coal seam.

[0015] To achieve the above-mentioned purpose, the simulation device based on the crack distribution law of the present invention comprises a circular base plate, a grouting pipe is connected upwardly to the center of the base plate, the grouting pipe is a flower pipe, and the bottom end of the grouting pipe opens at the lower surface of the base plate; an inner cylinder made of a screen is provided on the periphery of the grouting pipe, a middle cylinder made of a screen is provided on the periphery of the inner cylinder, an outer cylinder is provided on the periphery of the middle cylinder, and the inner cylinder, the middle cylinder and the outer cylinder are all connected downwardly to the base plate;

[0016] The space inside the inner tube is the simulated fracture zone, the annular space between the inner tube and the middle tube is the simulated plastic zone, and the annular space between the middle tube and the outer tube is the simulated elastic zone. The simulated fracture zone, simulated plastic zone, and simulated elastic zone are all filled with coal mined from the simulated coal seam.

[0017] The outer radius of the simulated fracture zone is greater than or equal to R0 and less than or equal to R1; wherein R0 is a predetermined borehole radius in the actual coal seam being simulated, in meters;

[0018] R1=R0×{(P0+C×cotφ)×(1-sinφ)÷(1+sinφ)÷(Pr+C×cotφ)} (1－sinφ)÷2sinφ ;

[0019] P0 is the original stress, measured from the actual coal seam being simulated before drilling, in MPa;

[0020] C is the coal cohesion, in MPa, measured from the actual coal seam being simulated;

[0021] φ is the internal friction angle of the coal body, in degrees, which is measured from the actual coal seam being simulated;

[0022] Pr is the borehole support force, in MPa, which is the borehole support force of the actual coal seam being simulated and is determined and implemented by the staff of the actual coal seam being simulated;

[0023] The outer radius of the simulated plastic zone is less than or equal to R2;

[0024] R2=R0×{(P0+C×cotφ)×(1-sinφ)÷(Pr+C×cotφ)} (1－sinφ)÷2sinφ ;

[0025] The outer radius of the simulated elastic area is R2=5R0.

[0026] The porosity of the coal filled in the simulated fracture zone is Equal to the maximum porosity around the drill hole Measured from the coal body around the drill hole in the simulated coal seam;

[0027] The porosity of the coal filled in the simulated plastic zone is

[0028]

[0029] It is the porosity per unit volume when the coal body is in elastic compression state.

[0030] a is the gas adsorption constant of coal, which physically means the combustible limit gas adsorption capacity of coal when the gas pressure tends to infinity. It is obtained by taking samples of the filled coal and measuring them through adsorption experiments.

[0031] σ is the normal total pressure per unit area of ​​coal mass acting on the borehole wall after drilling, in MPa;

[0032] σ c is the shear elastic modulus in MPa, measured on coal;

[0033] σ s is the yield strength of coal, measured in MPa, obtained by compression testing of coal samples obtained from actual coal seams;

[0034] is the initial porosity of the coal body, which is measured on the coal sample obtained from the actual coal seam;

[0035] εv It is the volume strain of coal body, dimensionless, i.e. the volume change of coal body when subjected to stress, and is measured on coal samples obtained from actual coal seams;

[0036] β is the thermal expansion coefficient of coal, in cubic meters per kelvin, and is measured on coal samples obtained from actual coal seams;

[0037] ΔT is the temperature difference between the temperature of coal when it is buried in the actual coal seam and the room temperature (i.e., the room temperature when the grouting experiment in the present invention is carried out).

[0038] The temperature difference, measured in Kelvin;

[0039] α is the pore pressure coefficient, in MPa / m³, which is obtained by measuring the coal sample obtained from the actual coal seam;

[0040] u is the deformation displacement of the coal body, measured in meters; it is obtained by measuring coal samples obtained from actual coal seams (through compression and tensile tests);

[0041] p0 is the initial pore pressure of the coal seam, in MPa, which is measured in the actual coal seam;

[0042] p1 is the pore pressure of the coal seam before drilling, and p2 is the pore pressure of the coal seam after drilling. The units of p1 and p2 are both MPa, which are measured on the coal seam before and after the test drilling.

[0043] E is the elastic modulus of the coal body, in MPa, measured on coal samples obtained from actual coal seams;

[0044] ρ is the apparent density of coal, in tons / cubic meter, which is obtained by measuring the coal sample obtained from the actual coal seam;

[0045] R is the gas molar constant;

[0046] T is the actual coal body temperature in the coal seam, in Kelvin;

[0047] k v is the bulk modulus of coal, in MPa, measured on coal samples obtained from actual coal seams;

[0048] V m is the gas molar volume, in cubic meters per mole, measured from the actual coal seam gas;

[0049] b is the gas adsorption constant of coal, b = 1 / pl; pl is the Langmuir pressure, which physically means the pressure at which the methane adsorption capacity of coal reaches half of the Langmuir volume. It is determined by taking samples of the filled coal through adsorption experiments.

[0050] The porosity of the coal filled in the simulated elastic zone is

[0051] A plurality of pressure sensors are evenly arranged on the inner wall of the outer tube and the inner wall of the middle tube along the circumferential direction; the grouting pipe extends downward from the bottom plate and is connected with the grouting inner pipe.

[0052] The present invention also discloses an experimental system, which uses the above-mentioned simulation device based on the crack distribution law, including a slurry container, the outlet of the slurry container is connected to a grouting outer pipe, the downstream end of the grouting outer pipe is connected to a grouting inner pipe; a slurry pump, a high-pressure container and a pulse valve are connected in series in the upstream and downstream directions along the grouting outer pipe, and the pulse valve is connected to a pulse controller;

[0053] An infrared thermal imager is provided above the simulation device based on the crack distribution law, and the shooting direction of the infrared thermal imager is toward the simulation device based on the crack distribution law;

[0054] A flow sensor is provided on the inner grouting tube;

[0055] The infrared thermal imager, each pressure sensor, flow sensor and slurry pump are all connected to an electric control device, and the electric control device is connected to a display screen.

[0056] The present invention also discloses an experimental method using the above experimental system, which is carried out in the following steps:

[0057] The first step is the preparation step;

[0058] The coal samples are collected from the actual coal seam to be simulated, and the porosity of the coal samples is and There are 3 kinds of coal samples in total; the filling gap ratio in the simulated fracture zone of the simulation device based on the crack distribution law is The coal sample has a filling rate of The coal sample has a filling rate of Use a constant temperature box to uniformly adjust the temperature of each coal sample to the actual temperature of the coal in the simulated coal seam;

[0059] Connect the outer grouting pipe and the inner grouting pipe, and control the slurry temperature in advance to the ambient temperature of the simulated actual coal seam operation through a constant temperature box, so that there is a temperature difference between the slurry temperature and the coal sample temperature; after stirring the slurry, fill the slurry container and the high-pressure container with slurry;

[0060] Turn on the infrared thermal imager and the electronic control device; set the pulse cycle of the pulse controller;

[0061] The second step is grouting;

[0062] Turn on the slurry pump to form high-pressure slurry in the high-pressure container; control the pulse valve to open and close periodically through the pulse controller to provide pulse slurry to the grouting pipe through the grouting outer pipe and the grouting inner pipe;

[0063] The electronic control device collects flow information during the grouting experiment and pressure information at various locations in the simulation device based on the crack distribution law through flow sensors and pressure sensors. At the same time, it uses an infrared thermal imager to collect slurry flow images. The frequency of the infrared thermal imager's image acquisition is the same as the pulse period of the pulse controller.

[0064] The electronic control device generates a slurry diffusion trajectory diagram based on the slurry flow image collected by the infrared thermal imager;

[0065] The third step is analysis;

[0066] Based on the data collected by the flow sensors and pressure sensors during the grouting process, the experimenters analyzed the slurry diffusion pressure, flow change characteristics and trajectory motion state in the simulation device based on the crack distribution law at different times, described and analyzed the diffusion characteristics of the slurry in the simulated rupture zone, simulated plastic zone and simulated elastic zone under pulse pressure conditions, analyzed the diffusion law and diffusion mechanism of the slurry in the simulated rupture zone, simulated plastic zone and simulated elastic zone, and predicted the sealing effect under different grouting parameters based on the diffusion results and analysis results of the slurry in the simulation device based on the crack distribution law, and then determined the optimal grouting parameters.

[0067] The present invention has the following advantages:

[0068] The present invention sets up simulated fracture zones, simulated plastic zones and simulated elastic zones. The calculation formulas of R1, R2 and R3 take into account various parameters related to the simulated coal seam and the radius of each zone, and can more accurately determine the radius range of each zone (consistent with the actual conditions of the fracture zone, plastic zone and elastic zone around the drill hole in the simulated coal seam). When conducting grouting experiments, it can better reflect the diffusion of slurry in the real coal body cracks. The experimental results are closer to the real coal seam grouting and sealing operations, and are more instructive for the real coal seam grouting and sealing operations, avoiding the problem that the grouting parameters determined according to the experimental results do not achieve the desired effect when used in the actual coal seam.

[0069] In the present invention, and The calculation formula takes into account various parameters of coal in a specific coal seam, and the calculated porosity of the coal used in the simulated fracture zone, simulated plastic zone and simulated elastic zone is closer to the actual porosity of each zone formed around the borehole after actual drilling. Therefore, the simulation device based on the crack distribution law in the present invention not only more accurately determines the radius range of each zone, but also more accurately determines the porosity of the coal sample filled in each zone, thereby more accurately simulating the crack conditions in the fracture zone, plastic zone and elastic zone (the higher the porosity, the more cracks, and conversely, the more cracks, the higher the porosity), making the experimental results of the present invention more in line with reality and having stronger guiding significance for actual coal seam grouting operations.

[0070] The pressure sensor can detect the pressure changes during the slurry flow process during the grouting experiment.

[0071] The experimental method of the present invention and the drilling grouting and sealing experimental system used therein are closer to the objective conditions of actual grouting in actual coal seams (the range of the fracture zone, plastic zone and elastic zone, and the crack conditions in each zone), can obtain the slurry diffusion law, and thus determine the optimal grouting parameters, better guide the grouting and sealing operations in actual coal seams, and have good promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a three-dimensional diagram of the simulation device based on the crack distribution law after removing the pressure sensor;

[0073] Figure 2 This is a schematic diagram of the top view of the simulation device based on the crack distribution law;

[0074] Figure 3 It is a structural diagram of the drilling grouting and plugging experimental system. DETAILED DESCRIPTION

[0075] like Figures 1 to 3 As shown, the simulation device based on the crack distribution law of the present invention includes a circular base plate 1, a grouting pipe 2 is connected to the center of the base plate 1 upward, the grouting pipe 2 above the base plate 1 is a flower pipe (that is, a plurality of openings for grouting are evenly distributed on the pipe wall of the grouting pipe 2 above the base plate), and the bottom end of the grouting pipe 2 is opened at the lower surface of the base plate 1; an inner cylinder 3 made of a screen is provided on the periphery of the grouting pipe 2, a middle cylinder 4 made of a screen is provided on the periphery of the inner cylinder 3, an outer cylinder 5 is provided on the periphery of the middle cylinder 4, and the inner cylinder 3, the middle cylinder 4 and the outer cylinder 5 are all connected to the base plate 1 downward; the inner cylinder 3 and the middle cylinder 4 are both thin-walled structures (so the wall thickness of the inner cylinder 3 and the middle cylinder 4 is ignored in the calculation formula);

[0076] The space inside the inner tube 3 is the simulated fracture zone 6, the annular space between the inner tube 3 and the middle tube 4 is the simulated plastic zone 7, and the annular space between the middle tube 4 and the outer tube 5 is the simulated elastic zone 8. The simulated fracture zone 6, the simulated plastic zone 7, and the simulated elastic zone 8 are all filled with coal mined from the simulated coal seam.

[0077] The outer radius of the simulated fracture zone 6 is greater than or equal to R0 and less than or equal to R1; wherein R0 is a predetermined drill hole radius in the actual coal seam being simulated, in meters;

[0078] R1=R0×{(P0+C×cotφ)×(1-sinφ)÷(1+sinφ)÷(Pr+C×cotφ)} (1－sinφ)÷2sinφ ;

[0079] P0 is the original stress, which is measured from the actual coal seam being simulated before drilling, and the unit is megapascal (i.e., MPa);

[0080] C is the coal cohesion, in MPa, measured from the actual coal seam being simulated (also the coal cohesion of the coal sample filled in the present invention);

[0081] φ is the internal friction angle of the coal body, in degrees, which is measured from the actual coal seam being simulated (it is also the internal friction angle of the coal sample filled in the present invention);

[0082] Pr is the borehole support force, measured in MPa. It is the borehole support force of the actual coal seam being simulated and is determined and implemented by the staff of the actual coal seam being simulated (the staff increases the stability of the borehole wall by installing casing or support pipes and grouting, etc., to apply a predetermined borehole support force to the borehole wall);

[0083] The outer radius of the simulated plastic zone 7 is less than or equal to R2;

[0084] R2=R0×{(P0+C×cotφ)×(1-sinφ)÷(Pr+C×cotφ)} (1－sinφ)÷2sinφ ;

[0085] The outer radius of the simulated elastic area 8 is R2=5R0.

[0086] The present invention sets up a simulated fracture zone 6, a simulated plastic zone 7 and a simulated elastic zone 8. The calculation formulas of R1, R2 and R3 take into account various parameters related to the simulated coal seam and the radius of each zone, and can more accurately determine the radius range of each zone (consistent with the actual conditions of the fracture zone, plastic zone and elastic zone around the drill hole in the simulated coal seam). When conducting grouting experiments, it can better reflect the diffusion of slurry in the real coal body cracks. The experimental results are closer to the real coal seam grouting and sealing operations, and are more instructive for the real coal seam grouting and sealing operations, avoiding the problem that the grouting parameters determined according to the experimental results do not achieve the desired effect when used in the actual coal seam.

[0087] The porosity of the coal filled in the simulated fracture zone 6 is Equal to the maximum porosity around the drill hole Measured from the coal body around the drill hole in the simulated coal seam;

[0088] The porosity of the coal filled in the simulated plastic zone 7 is

[0089]

[0090] It is the porosity per unit volume when the coal body is in elastic compression state.

[0091] a is the gas adsorption constant of coal, which physically means the combustible limit gas adsorption capacity of coal when the gas pressure tends to infinity. It is obtained by taking samples of the filled coal and measuring them through adsorption experiments.

[0092] σ is the normal total pressure per unit area of ​​coal mass acting on the borehole wall after drilling, in MPa;

[0093] σ c is the shear modulus of elasticity, expressed in MPa, measured on the coal (e.g., using a shear tester);

[0094] σ s is the yield strength of coal, measured in MPa, obtained by compression testing of coal samples obtained from actual coal seams;

[0095] is the initial porosity of the coal body (in percentage), measured on coal samples obtained from actual coal seams;

[0096] ε v It is the volume strain of coal body, dimensionless, i.e. the volume change of coal body when subjected to stress, and is measured on coal samples obtained from actual coal seams;

[0097] β is the thermal expansion coefficient of coal, and its unit is cubic meter / Kelvin (m 3 / K), measured on coal samples obtained from actual coal seams;

[0098] ΔT is the temperature difference between the actual temperature of coal buried in the coal seam and the room temperature (i.e., the room temperature during the grouting experiment in the present invention) (i.e., the burial temperature minus the room temperature during the experiment).

[0099] The temperature difference, measured in Kelvin;

[0100] α is the pore pressure coefficient, in MPa / m³, which is obtained by measuring the coal sample obtained from the actual coal seam;

[0101] u is the deformation displacement of the coal body, measured in meters; it is obtained by measuring coal samples obtained from actual coal seams (through compression and tensile tests);

[0102] p0 is the initial pore pressure of the coal seam, in MPa, which is measured in the actual coal seam;

[0103] p1 is the pore pressure of the coal seam before drilling, and p2 is the pore pressure of the coal seam after drilling. The units of p1 and p2 are both MPa, which are measured on the coal seam before and after the test drilling.

[0104] E is the elastic modulus of the coal body, in MPa, measured on coal samples obtained from actual coal seams;

[0105] ρ is the apparent density of coal, in tons / cubic meter, which is obtained by measuring the coal sample obtained from the actual coal seam;

[0106] R is the gas molar constant, in joules / (mole × Kelvin);

[0107] T is the actual coal body temperature in the coal seam, in Kelvin;

[0108] k v is the bulk modulus of coal, in MPa, measured on coal samples obtained from actual coal seams;

[0109] V m is the gas molar volume, in cubic meters per mole, measured from the actual coal seam gas;

[0110] b is the gas adsorption constant of coal, b = 1 / pl; pl is the Langmuir pressure, which physically means the pressure at which the methane adsorption capacity of coal reaches half of the Langmuir volume. It is determined by taking samples of the filled coal through adsorption experiments.

[0111] The porosity of the coal filled in the simulated elastic zone 8 is

[0112] In the present invention, and The calculation formula takes into account various parameters of coal in a specific coal seam, and the calculated porosity of the coal used in the simulated fracture zone 6, the simulated plastic zone 7 and the simulated elastic zone 8 is closer to the actual porosity of each zone formed around the borehole after actual drilling. Therefore, the simulation device based on the crack distribution law in the present invention not only more accurately determines the radius range of each zone, but also more accurately determines the porosity of the coal sample filled in each zone, making the experimental results of the present invention more in line with reality and having stronger guiding significance for actual coal seam grouting operations.

[0113] Several pressure sensors 9 are evenly distributed along the circumference of the inner wall of the outer tube 5 and the inner wall of the middle tube 4. The grouting pipe 2 extends downward from the bottom plate 1 and is connected to the grouting inner pipe 10. The pressure sensors 9 can detect the pressure changes during the grouting experiment.

[0114] The present invention also discloses an experimental system using the above-mentioned simulation device based on the crack distribution law, comprising a slurry container 11, an outlet of the slurry container 11 is connected to a grouting outer pipe 12, and a downstream end of the grouting outer pipe 12 is connected to a grouting inner pipe 10 of the simulation device based on the crack distribution law;

[0115] The grouting outer pipe 12 is connected in series in the upstream and downstream directions with a slurry pump 13, a high-pressure container 14 and a pulse valve 15, and the pulse valve 15 is connected to a pulse controller 16;

[0116] An infrared thermal imager 17 is provided above the simulation device based on the crack distribution law, and the shooting direction of the infrared thermal imager 17 is toward the simulation device based on the crack distribution law;

[0117] A flow sensor 18 (or electronic flow meter) is provided on the grouting inner tube 10;

[0118] The infrared thermal imager 17 , the pressure sensors 9 , the flow sensor 18 and the slurry pump 13 are all connected to an electronic control device 19 . The electronic control device 19 adopts a single chip microcomputer or an industrial computer. The electronic control device 19 is connected to a display screen 20 .

[0119] The present invention also discloses a method for conducting an experiment using the above experimental system, which is carried out in the following steps:

[0120] The first step is the preparation step;

[0121] The coal samples are collected from the actual coal seam to be simulated, and the porosity of the coal samples is and There are three types of coal samples in total. When making them, the coal samples collected from the actual coal seam to be simulated are first crushed and then sieved into different particle size groups using a sieve.

[0122] Select crushed coal of a certain particle size group and put it into a container of known volume (V11) and fill it up. Then apply a specific compaction force P11 to the crushed coal in the container. After the crushed coal no longer drops (that is, this compaction force can only compact the crushed coal to this extent), gradually add water to the container and record the volume of water added V12. (V12 / V11)×100% is the porosity of the coal sample obtained under the compaction force P11 of the crushed coal of this particle size group.

[0123] According to the above method, by adjusting the size of the compaction force and selecting crushed coal of different particle size groups, multiple pressing and measurement are carried out until the porosity is determined to be and These three coal samples.

[0124] The filling ratio in the simulated fracture zone 6 of the simulation device based on the crack distribution law is The coal sample has a filling rate of 7 in the simulated plastic zone of the simulation device based on the crack distribution law. The coal sample is filled with a void ratio of Use a constant temperature box to uniformly adjust the temperature of each coal sample to the actual temperature of the coal in the simulated coal seam;

[0125] Connect the outer grouting pipe 12 and the inner grouting pipe 10, and control the slurry temperature in advance to the ambient temperature of the simulated actual coal seam operation through a constant temperature box, so that there is a temperature difference between the slurry temperature and the coal sample temperature; after the slurry is stirred, fill the slurry container 11 and the high-pressure container 14 with slurry;

[0126] Turn on the infrared thermal imager 17 and the electronic control device 19; set the pulse period of the pulse controller 16 (set to 2 seconds in this embodiment);

[0127] The second step is grouting;

[0128] The slurry pump 13 is turned on to form high-pressure slurry in the high-pressure container 14; the grouting pressure is usually 0.5 MPa (the actual coal seam grouting pressure is usually also 0.5 MPa); the pulse valve 15 is controlled by the pulse controller 16 to open and close periodically, and pulse slurry is supplied to the grouting pipe 2 through the grouting outer pipe 12 and the grouting inner pipe 10;

[0129] The electronic control device 19 collects flow information during the grouting experiment and pressure information at various locations of the simulation device based on the crack distribution law through the flow sensor 18 and the pressure sensors 9. At the same time, the infrared thermal imager 17 collects slurry flow images (because the slurry temperature is different from the coal sample temperature, the image generated by the slurry flow can be identified); the frequency of the infrared thermal imager 17 collecting images is the same as the pulse period of the pulse controller 16;

[0130] The electronic control device 19 generates a slurry diffusion trajectory diagram based on the slurry flow image collected by the infrared thermal imager 17; specifically, the slurry diffusion trajectory diagram is drawn into a CAD file through the software in the electronic control device 19.

[0131] The third step is analysis;

[0132] Based on the data collected by the flow sensor 18 and each pressure sensor 9 during the grouting process, the experimenters analyzed the slurry diffusion pressure, flow change characteristics and trajectory motion state in the simulation device based on the crack distribution law at different times, described and analyzed the diffusion characteristics of the slurry in the simulated fracture zone 6, simulated plastic zone 7 and simulated elastic zone 8 under pulse pressure conditions, analyzed the diffusion law and diffusion mechanism of the slurry in the simulated fracture zone 6, simulated plastic zone 7 and simulated elastic zone 8, and predicted the sealing effect under different grouting parameters based on the diffusion results and analysis results of the slurry in the simulation device based on the crack distribution law, and then determined the optimal grouting parameters.

[0133] The experimental method of the present invention and the drilling grouting and sealing experimental system used therein are closer to the objective conditions of actual grouting in actual coal seams, can obtain the slurry diffusion law, thereby determining the optimal grouting parameters, and better guide the grouting and sealing operations in actual coal seams, and have good promotion and application value.

[0134] The above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A simulation device based on crack distribution law, characterized by: It includes a circular bottom plate, the center of the bottom plate is connected upward with a grouting pipe, the grouting pipe is a flower pipe, and the bottom end of the grouting pipe opens at the lower surface of the bottom plate; an inner cylinder made of a screen is provided on the periphery of the grouting pipe, a middle cylinder made of a screen is provided on the periphery of the inner cylinder, an outer cylinder is provided on the periphery of the middle cylinder, and the inner cylinder, the middle cylinder and the outer cylinder are all connected downward with the bottom plate; The space inside the inner tube is the simulated fracture zone, the annular space between the inner tube and the middle tube is the simulated plastic zone, and the annular space between the middle tube and the outer tube is the simulated elastic zone. The simulated fracture zone, simulated plastic zone, and simulated elastic zone are all filled with coal mined from the simulated coal seam. The outer radius of the simulated fracture zone is greater than or equal to R0 and less than or equal to R1; wherein R0 is the radius of the drill hole in the actual coal seam being simulated, in meters; R1=R0{(P0+Ccotφ)(1-sinφ) / (1+sinφ) / (Pr+Ccotφ)} (1－sinφ) / 2 sinφ ; P0 is the original stress, measured from the actual coal seam being simulated before drilling, in MPa; C is the coal cohesion, in MPa, measured from the actual coal seam being simulated; φ is the internal friction angle of the coal body, in degrees, which is measured from the actual coal seam being simulated; Pr is the borehole support force, in MPa, which is the borehole support force of the actual coal seam being simulated and is determined and implemented by the staff of the actual coal seam being simulated; The outer radius of the simulated plastic zone is less than or equal to R2; R2= R0{(P0+Ccotφ)(1-sinφ) / (Pr+ Ccotφ)} (1－sinφ) / 2 sinφ ; The outer radius of the simulated elastic zone is R2 = 5 R0; The porosity of the coal filling the simulated fracture zone is ∅1, which is equal to the maximum porosity ∅max around the drill hole, measured by the coal body around the drill hole in the simulated coal seam; The porosity of the coal filled in the simulated plastic zone is ∅2; ∅2 = (∅max - ∅a) (σ - σ s ) / (σ c -σ s )+∅0; ∅a=1(1―∅0) / (1+ε v ){1+β∆T03α(102u)(p1―p2) / E2 a ρRTk v / 3V m ln[(1+bp1) / (1+bp2)]}. ∅a is the porosity per unit volume when the coal body is in elastic compression state, a is the gas adsorption constant of coal, which physically means the combustible limit gas adsorption capacity of coal when the gas pressure tends to infinity. It is obtained by taking samples of the filled coal and measuring them through adsorption experiments. σ is the normal total pressure per unit area of ​​coal mass acting on the borehole wall after drilling, in MPa; σ c is the shear elastic modulus in MPa, measured on coal; σ s is the yield strength of coal, measured in MPa, obtained by compression testing of coal samples obtained from actual coal seams; ∅0 is the initial porosity of the coal body, which is obtained by measuring the coal sample obtained from the actual coal seam; ε v It is the volume strain of coal body, dimensionless, i.e. the volume change of coal body when subjected to stress, and is measured on coal samples obtained from actual coal seams; β is the thermal expansion coefficient of coal, in cubic meters per kelvin, and is measured on coal samples obtained from actual coal seams; ∆T is the temperature difference between the actual temperature of coal buried in the coal seam and the room temperature, The temperature difference, measured in Kelvin; α is the pore pressure coefficient, in MPa / m³, which is obtained by measuring the coal sample obtained from the actual coal seam; u is the deformation displacement of the coal body, measured in meters; it is obtained by measuring the coal sample obtained from the actual coal seam; p0 is the initial pore pressure of the coal seam, in MPa, which is measured in the actual coal seam; p1 is the pore pressure of the coal seam before drilling, and p2 is the pore pressure of the coal seam after drilling. The units of p1 and p2 are both MPa, which are measured on the coal seam before and after the test drilling. E is the elastic modulus of the coal body, in MPa, which is measured on coal samples obtained from actual coal seams; ρ is the apparent density of coal, in tons / cubic meter, which is obtained by measuring the coal sample obtained from the actual coal seam; R is the gas molar constant; T is the actual coal body temperature in the coal seam, in Kelvin; k v is the bulk modulus of coal, in MPa, measured on coal samples obtained from actual coal seams; V m is the gas molar volume, in cubic meters per mole, measured from the actual coal seam gas; b is the gas adsorption constant of coal, b=1 / pl; pl is the Langmuir pressure, which physically means the pressure at which the methane adsorption capacity of coal reaches half of the Langmuir volume. It is determined by taking samples of the filled coal through adsorption experiments. The porosity of the coal filled in the simulated elastic zone is ∅3; ∅3 = 1-(1-∅0) / (1+ε v ){1+βΔT-α(p1―p2) / (k v E)-(2aρRTk v ) / 3V m ln[(1+bp1) / (1+bp2)]}.

2. The simulation device based on crack distribution law according to claim 1, characterized in that: A plurality of pressure sensors are evenly arranged on the inner wall of the outer tube and the inner wall of the middle tube along the circumferential direction; the grouting pipe extends downward from the bottom plate and is connected with the grouting inner pipe.

3. An experimental system, using the simulation device based on the crack distribution law described in claim 2, comprising a slurry container, the outlet of the slurry container being connected to an outer grouting pipe, the downstream end of the outer grouting pipe being connected to an inner grouting pipe; characterized in that: A slurry pump, a high-pressure container and a pulse valve are sequentially connected in series along the upstream and downstream directions of the grouting outer pipe, and the pulse valve is connected to a pulse controller; An infrared thermal imager is provided above the simulation device based on the crack distribution law, and the shooting direction of the infrared thermal imager is toward the simulation device based on the crack distribution law; A flow sensor is provided on the inner grouting tube; The infrared thermal imager, each pressure sensor, flow sensor and slurry pump are all connected to an electric control device, and the electric control device is connected to a display screen.

4. The experimental method according to claim 3 is characterized in that Follow these steps in order: The first step is the preparation step; Coal samples are collected from the actual coal seam to be simulated, and the samples are made into three types of coal samples with porosities of ∅1, ∅2, and ∅3; the coal sample with a porosity of ∅1 is filled in the simulated fracture zone of the simulation device based on the crack distribution law, the coal sample with a porosity of ∅2 is filled in the simulated plastic zone of the simulation device based on the crack distribution law, and the coal sample with a porosity of ∅3 is filled in the simulated elastic zone of the simulation device based on the crack distribution law; and the temperature of each coal sample is uniformly adjusted to the actual temperature of the coal in the simulated coal seam using a constant temperature box; Connect the outer grouting pipe and the inner grouting pipe, and control the slurry temperature in advance to the ambient temperature of the simulated actual coal seam operation through a constant temperature box, so that there is a temperature difference between the slurry temperature and the coal sample temperature; after stirring the slurry, fill the slurry container and the high-pressure container with slurry; Turn on the infrared thermal imager and electronic control device; Set the pulse period of the pulse controller; The second step is grouting; Turn on the slurry pump to form high-pressure slurry in the high-pressure container; The pulse valve is controlled to open and close periodically by a pulse controller, and pulse slurry is supplied to the grouting pipe through the grouting outer pipe and the grouting inner pipe; The electronic control device collects flow information during the grouting experiment and pressure information at various locations in the simulation device based on the crack distribution law through flow sensors and pressure sensors. At the same time, it uses an infrared thermal imager to collect slurry flow images. The frequency of the infrared thermal imager's image acquisition is the same as the pulse period of the pulse controller. The electronic control device generates a slurry diffusion trajectory diagram based on the slurry flow image collected by the infrared thermal imager; The third step is analysis; Based on the data collected by the flow sensors and pressure sensors during the grouting process, the experimenters analyzed the slurry diffusion pressure, flow change characteristics and trajectory motion state in the simulation device based on the crack distribution law at different times, described and analyzed the diffusion characteristics of the slurry in the simulated rupture zone, simulated plastic zone and simulated elastic zone under pulse pressure conditions, analyzed the diffusion law and diffusion mechanism of the slurry in the simulated rupture zone, simulated plastic zone and simulated elastic zone, and predicted the sealing effect under different grouting parameters based on the diffusion results and analysis results of the slurry in the simulation device based on the crack distribution law, and then determined the optimal grouting parameters.

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