CN109142026B - Coal body deformation test method under coal seam water injection fracturing influence mining action - Google Patents
Coal body deformation test method under coal seam water injection fracturing influence mining action Download PDFInfo
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Abstract
The invention discloses a coal body deformation test method under the effect of coal seam water injection fracturing influencing mining, which comprises the following steps: the manufacturing test device comprises a concave-shaped seal cavity and a transparent box, wherein a notch part of the seal cavity forms a test piece placing cavity, a front pressing plate is provided with a front pressing rod, the left side, the right side and the rear side of the test piece placing cavity are provided with side pressing plates, the head ends of the side pressing plates are provided with air holes, the side pressing plates are provided with side pressing rods, an upper pressing plate is arranged above an upper backing plate in a front-back adjacent mode, the upper pressing plates are provided with upper pressing rods, and the ends of the upper pressing rods adopt a structure that spherical balls are arranged between two clamping plates; preparing coal powder; preparing a briquette test piece; mounting a molded coal test piece and a fracturing pipe; applying a triaxial stress; applying gas pressure; water injection and fracturing; carrying out a test; in other tests in the same group, the molded coal test piece is replaced, and the water injection rate of the fracturing pipe is changed; and (6) collating the test data. So as to carry out a triaxial real simulation test of coal body deformation under the coal seam water injection fracturing and mining actions.
Description
Technical Field
The invention belongs to the technical field of coal mine safety and energy exploitation, and particularly relates to a coal body deformation test method under the effect of coal seam water injection fracturing on mining.
Background
The energy is the modern foundation and power, and the energy supply and the safety concern are the whole situation of the modern modernization construction of our country. In the national strategic action plan for energy development (2014-2020), it is pointed out that the increase in production and the clean and efficient utilization of conventional fossil fuels should be accelerated, meanwhile, the bottleneck of the development of unconventional natural gas should be broken through as soon as possible, the rapid increase of the storage yield of the natural gas is promoted, the total consumption of coal is controlled to be about 42 hundred million tons by 2020, the shale gas yield strives to exceed 300 billion cubic meters, and the coal bed gas yield strives to reach 300 billion cubic meters.
In the development of conventional fossil fuels and unconventional oil and gas resources, in order to take high-efficiency exploitation and utilization of energy and safe production into consideration, the hydraulic measures become one of the main research directions, however, because the geological structure of China is complex, the understanding of the action mechanism of the hydraulic measures on the crack initiation and expansion in the coal rock mass is not deep. Coal seam water injection softens coal rock mass, reduces rock mass strength, changes stress field, and even wetting of the coal seam after water injection is not achieved but is more beneficial to outburst. The hydraulic fracturing forms a seam network, a gas seepage channel is enlarged, a new stress concentration area is formed while pressure is relieved, and meanwhile, the great interference is generated on the ground stress, so that fault activation can be caused, shearing slippage can be generated, and an earthquake can be induced in severe cases. Therefore, dynamic tests of coal body deformation and permeability under the effect of coal seam water injection fracturing influence mining are developed, the coal and gas outburst can be visualized in real time through the transparent material, and theoretical support and engineering guidance can be provided for efficient mining of coal bed gas and risk identification of mine disasters.
At present, researchers at home and abroad mostly concentrate on the field in the aspect of coal body deformation under the action of coal seam water injection fracturing influence mining, less indoor tests and theoretical researches are carried out, and an effective test device and an effective test method are still lacked to simulate the coal body deformation under the action of coal seam water injection fracturing influence mining under a true triaxial stress state, so that the influence of coal seam water injection fracturing on the coal body deformation under the true triaxial stress state is researched.
Disclosure of Invention
The invention aims to provide a coal body deformation test method under the action of coal seam water injection fracturing influence mining, which is used for researching the influence of coal seam water injection fracturing on coal body deformation under a true triaxial stress state.
Therefore, the technical scheme adopted by the invention is as follows: a coal body deformation test method under the effect of coal seam water injection fracturing influence mining comprises the following steps:
step one, manufacturing a test device;
the test device comprises a concave-shaped seal cavity, a notch of the seal cavity faces the front, a transparent box which is equal in height and width to the notch is arranged in front of the seal cavity, the rear part and the top of the transparent box are both open and just connected with the notch, the transparent box and the seal cavity share the same bottom plate, and a plurality of front pressure plates made of transparent materials are arranged between the notch of the seal cavity and the transparent box in a left-right close manner, so that the notch of the seal cavity forms a test piece placing cavity;
each front pressure plate is provided with a front pressure rod, the front pressure rods penetrate through the transparent box from front to back to be connected with the corresponding front pressure plate, the front pressure rods corresponding to the front pressure plates are independently controlled, and the tunneling speed of the working face is simulated through sequential unloading; the left side, the right side and the rear side of the test piece placing cavity are respectively provided with a side pressing plate, the head end of each side pressing plate is inserted into the corresponding side wall of the sealed cavity, the head end of each side pressing plate is provided with an air hole for communicating the test piece placing cavity with the sealed cavity, each side pressing plate is respectively provided with a side pressing rod, and the side pressing rods penetrate through the sealed cavity from outside to inside and are connected with the tail ends of the side pressing plates; the upper edge of the inner wall of the test piece placing cavity and the transparent box share the same upper base plate, a plurality of upper pressure plates are arranged above the upper base plate in a front-back adjacent mode, each upper pressure plate is provided with an upper pressure rod, the end of each upper pressure rod adopts a structure that a spherical ball is arranged between two clamping plates, the upper pressure rods corresponding to the upper pressure plates are independently controlled, and different loads are applied to reflect the uneven deformation of the coal seam roof under the non-uniform load;
the side wall of the sealed cavity is provided with a fluid inlet hole, and the side wall of the transparent box is provided with a fluid outlet hole;
step two, preparing coal powder, crushing and grinding raw coal to a required particle size range, screening the ground coal powder through a vibrating screen, and drying for later use;
step three, preparing a briquette test piece, namely mixing coal powder according to the requirement of the particle size ratio, adding a coal powder binder in proportion, uniformly stirring, filling the coal powder into a mold, pressing into a square briquette test piece, and pre-embedding a rod piece in the briquette test piece during pressing so as to reserve a fracturing hole in the briquette test piece;
step four, mounting a molded coal test piece and a fracturing pipe, namely putting the pressed molded coal test piece into a test piece placing cavity of a test device, wherein the front side of the fracturing pipe extends into a fracturing hole of the molded coal test piece and bonds and seals the outer wall of the fracturing pipe and the inner wall of the fracturing hole, the fracturing pipe penetrates through a front pressure plate and extends out of a transparent box, and sealing rings are arranged among the fracturing pipe, the front pressure plate and the transparent box;
applying triaxial stress, and applying stress to the side pressure rods, the front pressure rod and the upper pressure rod at the left, right and rear parts of the test device to make the briquette test piece be subjected to triaxial constraint;
step six, applying gas pressure, injecting gas into the test device through the fluid inlet hole, and enabling the gas to enter the molded coal test piece through the air holes in the left side pressure plate, the right side pressure plate and the rear side pressure plate, so that a certain gas pressure is formed in the molded coal test piece, and the next step is performed after the gas injection pressure is kept unchanged;
step seven, water injection and fracturing, namely injecting high-pressure water into the molded coal test piece through a fracturing pipe until part of the coal body is fractured;
step eight, performing a test, namely sequentially withdrawing the front pressing plate from left to right or from right to left in the direction away from the briquette test piece according to the set stress or displacement change rate, obtaining coal bed deformation data by recording the displacement amounts of the left side pressing plate, the right side pressing plate, the rear side pressing plate and the upper pressing plate at different positions, observing whether the front surface of the briquette test piece is obviously deformed and has gas outburst through the front pressing plate and the transparent box, and simultaneously recording the gas flow change of the fluid outlet hole;
and step nine, replacing the briquette test piece in other tests in the same group, repeating the step four to the step eight, and changing the water injection rate of the briquette test piece through the fracturing pipe until part of the coal body is fractured every time the steps are repeated.
Step ten, collating the test data.
Preferably, in the first step, there are two fluid inlet holes, and the two fluid inlet holes are symmetrically arranged on the rear side wall of the sealed cavity; the fluid outlet holes are arranged on the left side wall or the right side wall of the transparent box; accordingly, in step six, gas is simultaneously injected into the test device through the two fluid inlets. The mode that the fluid is symmetrically fed into the rear side wall of the sealed cavity body from left to right is adopted, so that the pressure of the fluid injected into the sealed cavity body is fast and stable, the fluid uniformly enters the test piece placing cavity through the air holes in the side pressure plates in three directions, the test preparation time is saved, and the test efficiency is improved.
Preferably, in the third step, the briquette test piece is a square block with the diameter of 600mm × 600mm × 100mm, the diameter of the embedded rod piece is 10mm, correspondingly, in the first step, the test piece placing cavity is also a square cavity with the diameter of 600mm × 600mm × 100mm, and the outer diameter of the fracturing pipe is 10 mm.
More preferably, in the second step, the raw coal is crushed and ground and then dried at 105-110 ℃ for 22-26 hours.
The invention has the beneficial effects that: the stress applied to each pressing plate can truly simulate the triaxial original rock stress state of a coal bed, the gas pressure can be simulated by applying a gas source, the progressive unloading of the front pressing plate simulates the tunneling process of a working face, the unloading speed can simulate the tunneling speed of the working face, the deformation of a briquette test piece is obtained by acquiring the displacement variation of each pressing rod, the real-time visualization of coal and gas outburst can be realized through a transparent material, the water injection rate of the briquette test piece through a fracturing pipe is changed until a part of coal body is fractured while the briquette test piece is replaced, and therefore the coal body deformation test method under the coal bed water injection fracturing influence mining action is provided, and theoretical support and engineering guidance are provided for the safety production of a coal mine.
Drawings
FIG. 1 is a top view of the test apparatus.
Fig. 2 is a cross-sectional view a-a of fig. 1.
Fig. 3 is a sectional view taken along line B-B of fig. 1.
Fig. 4 is an enlarged view of the end of the upper platen.
The figures are labeled as follows: the device comprises a seal cavity 1, a transparent box 2, a front pressure plate 3, a front pressure rod 4, a bottom plate 5, a test piece placing cavity 6, a side pressure plate 7, a side pressure rod 8, an upper backing plate 9, an upper pressure plate 10, an upper pressure rod 11, a fluid inlet hole 12, a fluid outlet hole 13, a first seal ring 14a, a second seal ring 14b, a third seal ring 14c, a fourth seal gasket 14d, a cover plate 15, a bolt 16, a molded coal test piece 17 and a fracturing pipe 18.
Detailed Description
The invention will be further illustrated by the following examples in conjunction with the accompanying drawings:
a coal body deformation test method under the effect of coal seam water injection fracturing influence mining comprises the following steps:
step one, manufacturing a testing device.
Referring to fig. 1-3, the testing device mainly comprises a sealed cavity 1, a transparent box 2, a front pressure plate 3, a front pressure rod 4, a side pressure plate 7, a side pressure rod 8, an upper backing plate 9, an upper pressure plate 10 and an upper pressure rod 11.
The whole sealing cavity 1 is concave, and the notch of the sealing cavity 1 faces the front.
A transparent box 2 with the same height and width as the notch part is arranged in front of the sealed cavity 1. The transparent box 2 is open at the back and the top and is just connected with the notch part. The transparent box 2 and the sealed cavity 1 share the same bottom plate 5, namely the transparent box 2 is only provided with a left side wall, a right side wall and a front side wall. A plurality of front pressing plates 3 made of transparent materials are arranged between the notch part of the seal cavity 1 and the transparent box 2 in a left-right close manner, so that the notch part of the seal cavity 1 forms a test piece placing cavity 6, and the test piece placing cavity 6 is used for placing a briquette test piece 17.
Each front pressing plate 3 is provided with a front pressing rod 4, the front pressing rods 4 penetrate through the transparent box 2 from front to back to be connected with the corresponding front pressing plate 3, the front pressing rods 4 corresponding to the front pressing plates 3 are independently controlled, and the tunneling speed of the working face is simulated through sequential unloading. The front pressing plate 3 and the transparent box 2 are both made of transparent materials, and a tester can observe the crack propagation condition of the surface of the test piece in the test process. The transparent material is especially high strength and toughness transparent polycarbonate plate, and has excellent performance.
The left side, the right side and the rear side of the test piece placing cavity 6 are respectively provided with a side pressing plate 7, the head end of the side pressing plate 7 is inserted into the corresponding side wall of the sealed cavity 1, and the head end of the side pressing plate 7 is provided with an air hole 7a for communicating the test piece placing cavity 6 and the sealed cavity 1. Each side pressure plate 7 is provided with a side pressure rod 8, and the side pressure rods 8 penetrate through the sealed cavity 1 from outside to inside to be connected with the tail ends of the side pressure plates 7. Preferably, the side pressure plate 7 adopts a structure that a vertical parting strip is arranged in a rectangular outer frame, and the vertical parting strip is just staggered with the vent hole 7a, so that fluid in the sealed cavity 1 can enter the test piece placing cavity 6 through the vent hole 7 a.
The upper edges of the inner walls of the test piece placing cavity 6 and the transparent box 2 share the same upper backing plate 9, and a plurality of upper pressure plates 10 are arranged above the upper backing plate 9 in a front-back close mode. Each upper pressure plate 10 is equipped with an upper pressure rod 11, the end of the upper pressure rod 11 adopts a structure (shown in fig. 4) that a spherical ball 11b is installed between two clamping plates 11a, and the upper pressure rod 11 corresponding to each upper pressure plate 10 is independently controlled and reflects the uneven deformation of the coal seam roof under the uneven load by applying different loads. Because the upper pressure plate 10 is arranged by a plurality of blocks, the upper base plate 9 is additionally arranged, the sealing performance of the test piece placing cavity 6 is ensured, and a coal seam roof and a goaf are simulated.
A fluid inlet hole 12 is formed in the side wall of the sealed cavity 1, and fluid is introduced into the sealed cavity 1 through the fluid inlet hole 12; the side wall of the transparent box 2 is provided with a fluid outlet 13, and fluid is discharged through the fluid outlet 13 in the test process. Preferably, the two fluid inlet holes 12 are symmetrically arranged on the rear side wall of the sealed cavity 1; the fluid outlet holes 13 are all arranged on the left side wall or the right side wall of the transparent box 2.
Further, the specimen-placing chamber 6 is preferably a square chamber having the same length and width.
The bottom plate 5 and the cover plate 15 are fixed to the side wall of the sealed cavity 1 by bolts 16. In order to ensure the sealing performance of the test device, a first sealing ring 14a is arranged between the bottom plate 5 and the sealing cavity 1 and between the bottom plate and the test piece placing cavity 6; second sealing rings 14b are arranged between the sealing cavity 1 and the side pressure rod 8 and between the sealing cavity 1 and the side pressure plate 7; a third sealing ring 14c is arranged between the sealing cavity 1 and the cover plate 15; a fourth gasket 14d is disposed between the seal cavity 1 and the upper mat 9.
Preferably, the front pressure lever 4 is in threaded connection with the front pressure plate 3, and the side pressure lever 8 is in threaded connection with the side pressure plate 7, or other fixed connection modes can be adopted.
Preferably, the number of the upper pressing plates 10 is seven, and the upper pressing rod 11 corresponding to each upper pressing plate 10 is controlled by a respective independent control part to reflect the uneven deformation of the coal seam roof; the number of the front pressing plates 3 is six, the front pressing rods 4 corresponding to the front pressing plates 3 are respectively controlled by respective independent control parts, and the tunneling speed of the working face is simulated through sequential unloading.
The test device has the characteristics that:
1. true triaxial stress can be applied from the front and back, the left and right sides and the upper side, the end of the upper pressure plate adopts a structure that a spherical ball is arranged between two clamping plates, and non-uniform load can be applied, so that non-uniform deformation of the top plate is truly simulated.
2. The front pressure plate adopts a structure of combining a plurality of blocks, and the tunneling process of the working face is simulated by gradual unloading; the upper pressure plate adopts a plurality of combined and optimized end head structures of the upper pressure rod, and the upper pressure plates are respectively and independently controlled to simulate the loading of non-uniform loads of a coal seam roof and a goaf; compared with a manual tunneling mode, the method simulates the actual working condition more truly, and therefore the test precision is improved.
3. The pressure plates on the rear side, the left side and the right side of the test piece are provided with air holes, the test piece can be inflated through the fluid inlet holes to reach certain gas pressure, and the bottom, the front and the upper part of the test piece are provided with no gas source supply holes, so that the actual working condition can be reflected more truly, and the test precision is improved.
4. The test device adopts a sealing structure, and can apply related gas pressure, so that the real working condition is reflected.
And step two, preparing coal powder, crushing and grinding raw coal to a required particle size range, screening the ground coal powder through a vibrating screen, and drying for later use. Preferably, the raw coal is crushed, ground and dried at 105-110 ℃ for 22-26 hours.
And step three, preparing a briquette test piece, namely mixing the coal powder according to the particle size ratio, adding the coal powder binder in proportion, uniformly stirring, and filling the coal powder into a mold to press the coal powder into a square briquette test piece. And during pressing, a rod piece is pre-embedded in the molded coal test piece, so that a fracturing hole is reserved in the molded coal test piece.
Preferably, the briquette test piece is a square piece with the diameter of 600mm × 600mm × 100mm, the diameter of the embedded rod piece is 10mm, correspondingly, in the step one, the test piece placing cavity 6 is also a square cavity with the diameter of 600mm × 600mm × 100mm, and the outer diameter of the fracturing pipe 18 is 10 mm.
Step four, mounting the molded coal test piece and the fracturing pipe, placing the pressed molded coal test piece into the test piece placing cavity 6 of the test device, enabling the front side of the fracturing pipe 18 to extend into a fracturing hole of the molded coal test piece and bonding and sealing the outer wall of the fracturing pipe 18 and the inner wall of the fracturing hole, enabling the fracturing pipe 18 to penetrate through the front pressing plate 3 and extend out of the transparent box 2, and arranging sealing rings between the fracturing pipe 18 and the front pressing plate 3 as well as between the fracturing pipe 18 and the transparent box 2.
And fifthly, applying triaxial stress to apply stress to the left, right and rear side compression bars 8, the front compression bar 4 and the upper compression bar 11 of the test device, so that the molded coal test piece is subjected to triaxial constraint.
And sixthly, applying gas pressure, injecting gas into the test device through the fluid inlet holes 12, and enabling the gas to enter the molded coal test piece through the air holes 7a in the left side pressure plate, the right side pressure plate and the rear side pressure plate 7, so that a certain gas pressure is formed in the molded coal test piece, and the molded coal test piece enters the next step after the gas injection pressure is kept unchanged. When there are two fluid inlet holes 12, gas is simultaneously injected into the test device through the two fluid inlet holes 12.
Step seven, water injection and fracturing, namely injecting high-pressure water into the molded coal test piece through the fracturing pipe 18 until part of the coal body is fractured;
and step eight, performing a test, namely sequentially withdrawing the front pressing plate 3 from left to right or from right to left in the direction away from the briquette test piece according to the set stress or displacement change rate, obtaining coal seam deformation data by recording the displacement of the left side pressing plate 7, the right side pressing plate 7 and the upper pressing plate 10 at different positions, observing whether the front surface of the briquette test piece is obviously deformed and has gas outburst through the front pressing plate 3 and the transparent box 2, and simultaneously recording the gas flow change of the fluid outlet 13.
And step nine, replacing the briquette test piece in other tests in the same group, repeating the step four to the step eight, and changing the water injection rate of the briquette test piece through the fracturing pipe 18 until part of the coal body is fractured every time the steps are repeated.
Step ten, collating the test data.
For example, coal powder with different particle sizes is prepared by mixing coal powder with a particle size of less than 40 meshes: 40-60 mesh: 60-80 meshes: 80-100 meshes: mixing the materials in a mass ratio of more than 100 meshes to 1:1:1:1, adding 5% of milk white glue as a bonding agent, pressing the mixture into a briquette test piece, and performing repeated tests according to the following table:
the relationship between the coal seam water injection fracturing and the coal body deformation under the mining action can be researched by repeating the test shown in the table.
Claims (4)
1. A coal body deformation test method under the effect of coal seam water injection fracturing influence mining is characterized by comprising the following steps:
step one, manufacturing a test device;
the test device comprises a concave-shaped seal cavity (1), a notch of the seal cavity (1) faces the front, a transparent box (2) which is equal in height and width to the notch is arranged in front of the seal cavity (1), the rear part and the top part of the transparent box (2) are both open and just connected with the notch, the transparent box (2) and the seal cavity (1) share the same bottom plate (5), and a plurality of front pressure plates (3) made of transparent materials are arranged between the notch of the seal cavity (1) and the transparent box (2) in a left-right close manner, so that the notch of the seal cavity (1) forms a test piece placing cavity (6);
each front pressure plate (3) is provided with a front pressure rod (4), the front pressure rods (4) penetrate through the transparent box (2) from front to back to be connected with the corresponding front pressure plate (3), the front pressure rods (4) corresponding to each front pressure plate (3) are independently controlled, and the tunneling speed of a working face is simulated through sequential unloading; the left side, the right side and the rear side of the test piece placing cavity (6) are respectively provided with a side pressing plate (7), the head end of each side pressing plate (7) is inserted into the corresponding side wall of the sealed cavity (1), the head end is provided with an air hole (7a) for communicating the test piece placing cavity (6) with the sealed cavity (1), each side pressing plate (7) is respectively provided with a side pressing rod (8), and each side pressing rod (8) penetrates through the sealed cavity (1) from outside to inside to be connected with the tail end of each side pressing plate (7); the test piece placing cavity (6) and the upper edge of the inner wall of the transparent box (2) share the same upper base plate (9), a plurality of upper pressure plates (10) are arranged above the upper base plate (9) in a front-back adjacent mode, each upper pressure plate (10) is provided with an upper pressure rod (11), the end of each upper pressure rod (11) adopts a structure that a spherical ball (11b) is arranged between two clamping plates (11a), the upper pressure rods (11) corresponding to the upper pressure plates (10) are independently controlled, and different loads are applied to reflect the uneven deformation of the coal seam roof under the non-uniform load;
a fluid inlet hole (12) is formed in the side wall of the sealed cavity (1), and a fluid outlet hole (13) is formed in the side wall of the transparent box (2);
step two, preparing coal powder, crushing and grinding raw coal to a required particle size range, screening the ground coal powder through a vibrating screen, and drying for later use;
step three, preparing a briquette test piece, namely mixing coal powder according to the requirement of the particle size ratio, adding a coal powder binder in proportion, uniformly stirring, filling the coal powder into a mold, pressing into a square briquette test piece, and pre-embedding a rod piece in the briquette test piece during pressing so as to reserve a fracturing hole in the briquette test piece;
step four, mounting a molded coal test piece and a fracturing pipe, namely putting the pressed molded coal test piece into a test piece placing cavity (6) of the test device, wherein the front side of the fracturing pipe (18) extends into a fracturing hole of the molded coal test piece, the outer wall of the fracturing pipe (18) is bonded and sealed with the inner wall of the fracturing hole, the fracturing pipe penetrates through the front pressure plate (3) and extends out of the transparent box (2), and sealing rings are arranged among the fracturing pipe (18), the front pressure plate (3) and the transparent box (2);
applying triaxial stress, and applying stress to the left, right and rear side pressure rods (8), the front pressure rod (4) and the upper pressure rod (11) of the test device to make the briquette test piece be subjected to triaxial constraint;
step six, applying gas pressure, injecting gas into the test device through the fluid inlet holes (12), and enabling the gas to enter the molded coal test piece through the air holes (7a) on the left side pressure plate, the right side pressure plate and the rear side pressure plate (7), so that a certain gas pressure is formed in the molded coal test piece, and the molded coal test piece enters the next step after the gas injection pressure is kept unchanged;
step seven, water injection and fracturing, namely injecting high-pressure water into the molded coal test piece through a fracturing pipe (18) until part of the coal body is fractured;
step eight, performing a test, namely sequentially withdrawing the front pressing plate (3) from left to right or from right to left in the direction away from the briquette test piece according to the set stress or displacement change rate, obtaining coal seam deformation data by recording the displacement amount of the left side pressing plate, the right side pressing plate, the rear side pressing plate (7) and the upper pressing plate (10) at different positions, observing whether the front surface of the briquette test piece is obviously deformed and has gas outburst through the front pressing plate (3) and the transparent box (2), and simultaneously recording the gas flow change of the fluid outlet hole (13);
step nine, replacing the briquette test piece in other tests in the same group, repeating the step four to the step eight, and changing the water injection rate of the briquette test piece through the fracturing pipe (18) until part of the coal body is fractured after repeating the step once;
step ten, collating the test data.
2. The coal body deformation test method under the coal seam water injection fracturing influence mining action of claim 1 is characterized in that in the third step, the briquette test piece is a square block with the diameter of 600mm × 600mm × 100mm, the diameter of the embedded rod piece is 10mm, correspondingly, in the first step, the test piece placing cavity (6) is also a square cavity with the diameter of 600mm × 600mm × 100mm, and the outer diameter of the fracturing pipe (18) is 10 mm.
3. The coal body deformation test method under the coal seam water injection fracturing influence mining action of claim 1, characterized by comprising the following steps: in the second step, the raw coal is dried for 22-26 hours at 105-110 ℃ after being crushed and ground.
4. The coal body deformation test method under the coal seam water injection fracturing influence mining action of claim 1, characterized by comprising the following steps: in the first step, the two fluid inlet holes (12) are arranged on the rear side wall of the sealed cavity (1) in a bilateral symmetry manner; the fluid outlet holes (13) are arranged on the left side wall or the right side wall of the transparent box (2) in a sharing mode; correspondingly, in step six, gas is injected into the test device simultaneously through two fluid inlet holes (12).
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