CN111175468B - Pressure-relief and impact-prevention test method for water-injection-wetted coal rock under true three-dimensional stress - Google Patents
Pressure-relief and impact-prevention test method for water-injection-wetted coal rock under true three-dimensional stress Download PDFInfo
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- CN111175468B CN111175468B CN202010158919.9A CN202010158919A CN111175468B CN 111175468 B CN111175468 B CN 111175468B CN 202010158919 A CN202010158919 A CN 202010158919A CN 111175468 B CN111175468 B CN 111175468B
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- 239000003245 coal Substances 0.000 title claims abstract description 71
- 239000011435 rock Substances 0.000 title claims abstract description 32
- 238000010998 test method Methods 0.000 title claims abstract description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 85
- 238000002347 injection Methods 0.000 claims abstract description 75
- 239000007924 injection Substances 0.000 claims abstract description 75
- 238000012360 testing method Methods 0.000 claims abstract description 42
- 238000000034 method Methods 0.000 claims abstract description 15
- 230000002265 prevention Effects 0.000 claims abstract description 15
- 238000009736 wetting Methods 0.000 claims abstract description 3
- 238000007789 sealing Methods 0.000 claims description 33
- 239000003921 oil Substances 0.000 claims description 27
- 238000011068 loading method Methods 0.000 claims description 22
- 229920002379 silicone rubber Polymers 0.000 claims description 18
- 238000006073 displacement reaction Methods 0.000 claims description 11
- 238000005553 drilling Methods 0.000 claims description 5
- 230000000149 penetrating effect Effects 0.000 claims description 5
- 239000007788 liquid Substances 0.000 claims description 4
- 239000000565 sealant Substances 0.000 claims description 4
- 238000001816 cooling Methods 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 238000000227 grinding Methods 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- 238000012545 processing Methods 0.000 claims description 3
- 230000001680 brushing effect Effects 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 claims description 2
- 239000012945 sealing adhesive Substances 0.000 claims 1
- 238000005065 mining Methods 0.000 description 4
- 238000005266 casting Methods 0.000 description 3
- 239000004945 silicone rubber Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000003204 osmotic effect Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 1
- 239000004944 Liquid Silicone Rubber Substances 0.000 description 1
- 241000233805 Phoenix Species 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001066 destructive effect Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 230000005489 elastic deformation Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000004058 oil shale Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000009528 severe injury Effects 0.000 description 1
- 125000006850 spacer group Chemical group 0.000 description 1
- 238000007619 statistical method Methods 0.000 description 1
- 239000000080 wetting agent Substances 0.000 description 1
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Abstract
The invention discloses a pressure relief and impact prevention test method for water injection wetting coal rock under true three-dimensional stress, which comprises the steps of preparing a sample; installing a water injection pipe; the method comprises the following steps that a raw coal sample is installed on a true triaxial test testing device; applying a triaxial stress; pressure relief; simulating the incoming pressure of the top plate; replacing the raw coal sample, and repeating the second step to the fourth step; performing a water injection test; repeating the step six, and simulating the pressure of the top plate again; and (6) collating the test data. The method is used for researching the mechanism of preventing rock burst by water injection under the action of primary stress, and provides scientific basis for scientifically selecting relevant technological parameters.
Description
Technical Field
The invention belongs to the technical field of coal rock indoor tests, and particularly relates to a test method for pressure relief and impact prevention of water injection wetting coal rock under true three-dimensional stress.
Background
With the increase of the mining depth and the mining intensity of coal resources, dynamic disasters such as mine rock burst and the like are increasingly aggravated, and the safety of coal mining is seriously threatened. Statistical analysis shows that rock burst occurrence reports exist in various types of mines, over-impact phenomena occur in various coal beds, geological structures range from simple to complex, the coal beds range from thin to extra-thick, dip angles range from horizontal to steep, and rock burst, sandstone, limestone and oil shale roofs all generate over-impact rock burst. Rock mass around a roadway or a working face is subjected to sudden and severe damage due to instantaneous release of elastic deformation energy, and the phenomena of coal rock mass throwing, loud sound, air waves and the like are often accompanied. It is very destructive, and is one of the major disasters of coal mine.
The method for preventing rock burst by coal seam water injection is simple and easy to implement, low in prevention and control cost and wide in adaptability. Even if the coal bed is not wet by water, the method can be suitable only by adding a small amount of wetting agent, and has various effects of dust fall, temperature reduction and coal bed softening, so that the method can be used as a first-choice measure for preventing and treating rock burst. Coal seam flooding was used in the original soviet union coal mines to control rock burst since the early 50 s of the 20 th century. In all coal mining countries in the world, the method of coal seam water injection is adopted, and the method is widely applied to preventing and treating rock burst. In China, in the early 80 s of the 20 th century, coal seam water injection is successfully applied in rock burst prevention and control of the pacifying dragon and phoenix mine. At present, coal seam flooding has been popularized in rock burst control throughout the country.
Although the coal seam water injection rock burst prevention and control has a long history, reports about the mechanism of the coal seam water injection rock burst prevention and control and the research about the selection of the process parameters of the coal seam water injection rock burst prevention and control are rarely seen so far. The selection of the technological parameters for preventing and controlling the rock burst by coal seam water injection lacks scientific basis, a basically complete method does not exist, and the technological parameters are still determined by engineering analogy and experience. The main reason for this situation is that no practical test device and innovative test method are available for testing and supporting the pressure relief and impact prevention mechanism of water injection-wetted coal rocks.
Disclosure of Invention
The invention aims to solve the technical problem of providing an indoor simulation test method for pressure relief and scour prevention of water injection wetted coal rocks under true three-dimensional stress, which is used for researching the mechanism of water injection prevention and control of rock burst of a coal seam under the action of primary stress and provides scientific basis for scientifically selecting relevant process parameters.
Therefore, the technical scheme adopted by the invention is as follows: a pressure relief and impact prevention test method for water injection-wetted coal rock under true three-dimensional stress comprises the following steps:
step one, sample preparation;
cutting a raw coal block into hexahedrons, processing the hexahedrons by a grinding machine to ensure that the flatness of the end surface of the hexahedron is within +/-0.02 mm, drying the hexahedron at the temperature of 105 +/-15 ℃ for 24 +/-4 hours, and cooling the hexahedron to normal temperature for later use;
step two, installing a water injection pipe;
drilling a horizontal blind hole at the central position of the front surface of a hexahedral raw coal sample by using a drilling machine to serve as a water injection hole, selecting a water injection pipe with the outer diameter equal to the diameter of the water injection hole and the length 8-12 mm smaller than the depth of the water injection hole, uniformly coating silicon rubber on the outer wall of the water injection pipe, inserting the water injection pipe into the water injection hole, sealing a gap between the outer wall of the water injection pipe and the water injection hole by using the silicon rubber, and then installing a universal sealing joint at the opening part of the water injection hole;
step three, mounting the raw coal sample on a true triaxial test testing device;
the test device for the true triaxial test comprises a host, a host supporting assembly, a slide rail supporting assembly and servo oil cylinders, wherein six sets of servo oil cylinders are arranged in the up-down, left-right and front-back directions outside the host, the slide rail extends back and forth below the host and is supported on the ground through the slide rail supporting assembly after penetrating through the host, the host comprises an integral annular frame formed by casting, openings are formed in the front and back sides of the integral annular frame, a cover plate is arranged on the outer side of each opening position, the integral annular frame and the cover plates form a host shell, an inner cavity of the host is used for placing a sample, sample cushion blocks are respectively arranged outside the upper, lower, left, right, front and back sides of the sample, and a sample moving support capable of moving back and forth on the slide rail is arranged below the; oil cylinder moving supports capable of moving back and forth on the sliding rails are arranged below the servo oil cylinders on the front side and the rear side respectively, the cover plate can move along with the servo oil cylinders on the corresponding side, the servo oil cylinders on the upper side, the lower side, the left side and the right side are fixedly arranged outside the corresponding sides of the integral annular frame, a load sensor is arranged in the middle of the front end of a piston rod of each servo oil cylinder, and a pressure head is arranged at the front end of each load sensor after penetrating through the main case;
placing a sample into a cavity surrounded by six sample cushion blocks, mounting the sample through quick locking combination, and then sealing the sample with the edge sealant at the joint of the sample cushion blocks to form a sample sealing gasket so as to seal the sample therein; the seamed edge sealant is formed by brushing liquid silicon rubber on seamed edges to be sealed, and sealing between sample cushion blocks can be realized after the silicon rubber is solidified;
firstly, a sample sealing gasket is arranged on a lower pressure head, then an upper pressure head is controlled to move downwards to be arranged together with a universal sealing joint, meanwhile, the upper pressure head is attached to the upper surface of the sample sealing gasket, and finally, the front pressure head, the rear pressure head, the left pressure head and the right pressure head are respectively controlled to move, so that the corresponding pressure heads are respectively attached to the corresponding surfaces of the sample sealing gasket;
step four, applying triaxial stress;
applying stress to the sample to a preset value through the front, rear, left, right, upper and lower six pressure heads;
step five, releasing pressure;
keeping the stress loading mode of the upper pressure head to be constant force loading, converting the stress loading modes of the left pressure head, the right pressure head and the front pressure head into constant rigidity loading, converting the stress loading mode of the lower pressure head into constant displacement loading, and controlling the rear pressure head to retreat towards the force unloading direction until the distance from the rear surface of the raw coal sample reaches 20 +/-5 mm;
step six, simulating the coming pressure of the top plate;
increasing the pressure of the upper pressure head at a constant loading rate until the raw coal sample is damaged, recording the stress and displacement changes of each pressure head, and calculating the energy evolution condition in the test process;
step seven, replacing the raw coal sample, and repeating the step two to the step four;
step eight, water injection test;
injecting water into the raw coal sample at a preset water injection rate through a water injection hole on the front surface of the raw coal sample, and stopping after the preset water injection time is reached;
step nine, repeating the step six, and simulating the pressure of the top plate again;
step ten, replacing the raw coal sample, changing the hardness of the raw coal sample, or changing the water injection rate, the triaxial pressure and the front pressure head pressure relief rate, and repeating the steps from the first step to the ninth step;
and step eleven, finishing test data. Preferably, the hexahedral raw coal sample is a cube having a sample size of 200mm × 200mm × 200 mm.
More preferably, the diameter of the water injection hole in the raw coal sample is 12mm, and the depth of the hole is 105 mm; the outer diameter of the water injection pipe is 12mm, and the length of the water injection pipe is 95 mm; the diameter of the semicircle at the bottom of the water injection hole is 10 mm.
The invention has the beneficial effects that:
(1) the novel true triaxial test testing device is adopted, compared with a cavity structure formed by enclosing of an inner layer frame and an outer layer frame in the prior art, only an integral annular frame formed by casting is arranged on a host machine of the testing device, and six sample cushion blocks arranged outside a sample enclose a sample gasket for containing the sample, so that an independent pressure-resistant cavity formed between the inner layer and the outer layer in the prior art is omitted, a pressure head directly abuts against the sample cushion block on the corresponding side after penetrating through a host machine shell, more integral annular frames with larger space arrangement size and thickness can be made, and therefore the cavity can bear larger pressure, and a simulation test in a more complex environment can be met;
(2) because the inner layer frame is omitted, the servo oil cylinder directly applies force to each surface of the sample without penetrating through the pressure-resistant cavity, and the servo oil cylinder penetrates through the pressure-resistant cavity and also needs considering dynamic sealing, the structure is simplified, the cost is reduced, and the reliability is higher; meanwhile, the traditional inner layer frame is thinner than the outer layer frame, so that the inner layer frame is easy to expand and deform under high pressure, and the sealing property between the inner frame and the servo oil cylinder is further influenced;
(3) in the testing device, a pressure head and a sample cushion block are separately designed, and the joint of the sample cushion block is sealed after being coated with liquid silicone rubber and cured, so that injected fluid cannot seep into an external area;
(4) holes are formed in the front side and the rear side of the integral annular frame, a cover plate is arranged on the outer side of each hole, and a host shell is formed by the holes, so that parts on the front side of the sample can be more conveniently installed; in the traditional structure, a cover plate is only arranged at a rear side hole, parts at the front side need to be overhauled or assembled and disassembled, and a sample needs to be moved out of the integral annular frame through a sample moving bracket, so that the traditional structure is very troublesome;
(5) the method is used for researching the mechanism of preventing rock burst by water injection under the action of primary stress, and provides scientific basis for scientifically selecting relevant technological parameters.
Drawings
FIG. 1 is a schematic view showing the structure of a true triaxial test apparatus used in the present invention (including two states of sample loading and unloading).
FIG. 2 is a left side view of the mainframe and the mainframe support assembly of FIG. 1.
FIG. 3 is a perspective view of a sample gasket surrounded by six sample spacers.
Fig. 4 is a front view in cross-section of fig. 3.
Fig. 5 is a plan view of the cross-sectional state of fig. 3.
FIG. 6 shows the cured state of silicone rubber for sample block edge sealing.
Detailed Description
The invention will be further illustrated by the following examples in conjunction with the accompanying drawings:
a pressure relief and impact prevention test method for water injection-wetted coal rock under true three-dimensional stress comprises the following steps:
step one, sample preparation;
cutting a raw coal block into hexahedrons, processing the hexahedrons by a grinding machine to ensure that the flatness of the end surface of the hexahedron is within +/-0.02 mm, drying the hexahedron at the temperature of 105 +/-15 ℃ for 24 +/-4 hours, and cooling the hexahedron to normal temperature for later use; the hexahedral raw coal sample is preferably a cube, and the sample size is preferably 200 mm. times.200 mm.
Step two, installing a water injection pipe;
as shown in fig. 5, a horizontal blind hole is drilled at the central position of the front surface of a hexahedral raw coal sample by a drilling machine to serve as a water injection hole 15, a water injection pipe with the outer diameter equal to the diameter of the water injection hole 15 and the length 8-12 mm smaller than the depth of the water injection hole 15 is selected, silicone rubber is uniformly coated on the outer wall of the water injection pipe, the water injection pipe is inserted into the water injection hole 15, a gap between the outer wall of the water injection pipe and the water injection hole 15 is sealed by the silicone rubber, and then a universal sealing joint 16 is installed at the opening of the water.
Preferably, the diameter of the water injection hole 15 in the raw coal sample is 12mm, and the depth of the hole is 105 mm; the outer diameter of the water injection pipe is 12mm, and the length of the water injection pipe is 95 mm.
Step three, mounting the raw coal sample on a true triaxial test testing device;
as shown in fig. 1-5, the true triaxial test testing apparatus mainly comprises a main machine a, a main machine supporting assembly B, a slide rail C, a slide rail supporting assembly D and a servo oil cylinder E. The main machine A is supported on the ground through a main machine supporting component B, and six sets of servo oil cylinders E are arranged in the up-down, left-right and front-back directions (namely the three directions of XYZ) outside the main machine A. Slide rail C extends the setting around host computer A below, and slide rail C passes behind the host computer A and supports subaerial through slide rail supporting component D.
The integral annular frame 1 is formed by casting, the front side and the rear side of the integral annular frame 1 are provided with holes, and the outer side of each hole position is provided with a cover plate 2. The whole annular frame 1 and the two cover plates 2 jointly form a main chassis. At least two heating rods 17 are symmetrically arranged on the upper wall and the lower wall of the main machine shell at intervals from left to right respectively, and the heating rods can heat the sample in the main machine shell when necessary. The inner cavity of the main machine is used for placing a sample 3, and the upper side, the lower side, the left side, the right side, the front side and the rear side of the sample 3 are respectively provided with sample cushion blocks 4, so that six sample cushion blocks 4 are needed. A sample moving bracket 5 which can move back and forth on the slide rail C is arranged below the sample cushion block 4 positioned at the lower side.
The servo oil cylinders E on the front side and the rear side are arranged outside the cover plate 2 on the corresponding side, oil cylinder moving supports 6 capable of moving on the sliding rails C back and forth are arranged below the servo oil cylinders E on the front side and the rear side, and the cover plate 2 can move along with the servo oil cylinders E on the corresponding side. The servo oil cylinders E on the upper, lower, left and right sides are arranged outside the corresponding sides of the integral annular frame.
A load sensor 8 is arranged at the center of the front end of a piston rod 7 of the servo oil cylinder E, and the load sensor 8 is preferably installed in an embedded mode. The front end of the load sensor 8 is provided with a pressure head 9, and the front end of the load sensor 8 penetrates through the main case and is provided with the pressure head 9. When the sample 3 is loaded, the pressure head 9 is directly abutted against the sample cushion block 4 on the corresponding side. Before the test, the sample cushion block 4 is installed outside the sample 3, the joint of the sample cushion block 4 is sealed, after the sealing is completed, the sample 3 is placed on the sample moving support 5, the sample moving support 5 and the oil cylinder moving support 6 on the rear side are sequentially pushed into the inner cavity of the host machine and fixed, and the test is performed after all the pressure heads 9 are directly abutted to the sample cushion block 4 on the corresponding side.
Placing a sample into a cavity surrounded by six sample cushion blocks 4, assembling and installing the sample through a quick lock 14, and then sealing the sample into a sample sealing gasket by combining with the edge sealant at the joint of the sample cushion blocks 4 so as to seal the sample 3; the liquid silicon rubber is coated on the seamed edge to be sealed, and the seamed edge can be sealed between the sample cushion blocks 4 after the silicon rubber is solidified (as shown in figure 6). The pre-sealing is realized after the silicon rubber is cured, and during the test, the silicon rubber is tightly attached to the sample through the confining pressure of the inner cavity of the host, so that the sealing between the adjacent surfaces of the sample cushion blocks 4 can be realized, and the boundary effect at the edge can be weakened. Preferably, a cylinder displacement sensor 10 is arranged in the servo cylinder E, the servo cylinders E on the upper, lower, left and right sides are fixedly installed on the integral annular frame 1 through end covers 11, the servo cylinders E on the front and rear sides are fixedly installed on the integral annular frame 1 through cover plates 2, and all the positions where the piston rods 7 penetrate through the main case are provided with bushings so as to ensure the sealing property of the inner cavity of the main case.
Preferably, sample deformation displacement sensors 12 are arranged in pairs in the XYZ direction outside a sealed cavity enclosed by six sample cushion blocks 4, the sample deformation displacement sensors 12 are installed outside the edges of the sample cushion blocks 4 through displacement sensor extension rods 13, and a pair of sample deformation displacement sensors 12 in the same direction are arranged in a diagonally staggered manner, so that the measurement of unbalanced and uneven deformation under the condition of true triaxial can be realized.
Preferably, two sets of electro-hydraulic servo superchargers are also arranged to respectively provide confining pressure for the inner cavity of the main machine and provide water injection pressure or osmotic pressure for the sample, so that the confining pressure, the water injection pressure or the osmotic pressure are respectively controlled, and complicated test conditions can be completed. The working pressure of a control high-pressure valve in the electro-hydraulic servo supercharger is greater than the highest output pressure of the supercharging, so as to ensure high reliability and long service life of the work.
Preferably, the axial plunger pump hydraulic source is also arranged, and the hydraulic source is provided with high-low pressure conversion, so that the high-low pressure can be switched smoothly during the test.
Firstly, a sample is filled into a sample sealing gasket surrounded by six sample cushion blocks 4, liquid silicon rubber is coated on edges, after the silicon rubber is solidified, the sample is pushed into an inner cavity of a main machine through a sample moving support 5, finally, cover plates 2 on the front side and the rear side are installed on an integral annular frame 1 through an oil cylinder moving support 6, the inner cavity of the main machine is guaranteed to be sealed during installation, and then, a test is started.
Firstly, the sample sealing gasket is arranged on the lower pressure head, then the upper pressure head is controlled to move downwards to be arranged together with the universal sealing joint 16, meanwhile, the upper pressure head is attached to the upper surface of the sample sealing gasket, and finally, the four pressure heads in front, back, left and right are respectively controlled to move, so that the corresponding pressure heads are respectively attached to the corresponding surfaces of the sample sealing gasket.
Step four, applying triaxial stress;
the sample is stressed to a predetermined value by six front, rear, left, right, upper and lower pressure heads.
Step five, releasing pressure;
and keeping the stress loading mode of the upper pressure head to be constant force loading, converting the stress loading modes of the left pressure head, the right pressure head and the front pressure head into constant rigidity loading, converting the stress loading mode of the lower pressure head into constant displacement loading, and controlling the rear pressure head to retreat towards the force unloading direction until the distance from the rear surface of the raw coal sample reaches 20 +/-5 mm.
Step six, simulating the coming pressure of the top plate;
and increasing the pressure of the upper pressure head at a constant loading rate until the raw coal sample is damaged, recording the stress and displacement changes of each pressure head, and calculating the energy evolution condition in the test process.
And step seven, replacing the raw coal sample, and repeating the step two to the step four.
Step eight, water injection test;
and injecting water into the raw coal sample at a preset water injection rate through a water injection hole in the front surface of the raw coal sample, and stopping after the preset water injection time is reached.
And step nine, repeating the step six, and simulating the pressure of the top plate again.
Step ten, replacing the raw coal sample, changing the hardness of the raw coal sample, or changing the water injection rate, the triaxial pressure and the front pressure head pressure relief rate, and repeating the steps from the first step to the ninth step.
And step eleven, finishing test data. The following table is recorded data in the test process, wherein the failure strength refers to the acting force of an upper pressure head when the coal rock test piece is broken.
Claims (3)
1. A pressure relief and impact prevention test method for water injection wetting coal rock under true three-dimensional stress is characterized by comprising the following steps:
step one, sample preparation;
cutting a raw coal block into hexahedrons, processing the hexahedrons by a grinding machine to ensure that the flatness of the end surface of the hexahedron is within +/-0.02 mm, drying the hexahedron at the temperature of 105 +/-15 ℃ for 24 +/-4 hours, and cooling the hexahedron to normal temperature for later use;
step two, installing a water injection pipe;
drilling a horizontal blind hole at the central position of the front surface of a hexahedral raw coal sample by using a drilling machine to serve as a water injection hole (15), selecting a water injection pipe with the outer diameter equal to the diameter of the water injection hole (15) and the length 8-12 mm smaller than the depth of the water injection hole (15), uniformly coating silicon rubber on the outer wall of the water injection pipe, inserting the water injection pipe into the water injection hole (15), sealing a gap between the outer wall of the water injection pipe and the water injection hole (15) through the silicon rubber, and then installing a universal sealing joint (16) at the opening of the water injection hole (15);
step three, mounting the raw coal sample on a true triaxial test testing device;
the true triaxial test testing device comprises a host (A), a host supporting component (B), a slide rail (C), a slide rail supporting component (D) and servo oil cylinders (E), wherein six sets of servo oil cylinders (E) are arranged in the upper-lower, left-right and front-back directions outside the host (A), the slide rail (C) extends and is arranged in the front-back direction below the host (A) and passes through the host (A) and then is supported on the ground through the slide rail supporting component (D), the host (A) comprises a cast integral annular frame (1), holes are formed in the front side and the back side of the integral annular frame (1), a cover plate (2) is arranged outside each hole position, the integral annular frame (1) and the cover plate (2) enclose to form a host shell, an inner cavity of the host is used for placing a sample (3), and sample cushion blocks (4) are respectively arranged outside the upper side, the lower side, the left side, the right side, the front, a sample moving bracket (5) which can move back and forth on the slide rail (C) is arranged below the sample cushion block (4) positioned at the lower side; oil cylinder moving supports (6) capable of moving back and forth on a sliding rail (C) are arranged below the servo oil cylinders (E) on the front side and the rear side respectively, the cover plate (2) can move along with the servo oil cylinders (E) on the corresponding side, the servo oil cylinders (E) on the upper side, the lower side, the left side and the right side are fixedly arranged outside the corresponding side of the integral annular frame (1), a load sensor (8) is arranged in the middle position of the front end of a piston rod (7) of each servo oil cylinder (E), and a pressure head (9) is installed at the front end of each load sensor (8) after penetrating through the main machine shell;
placing a sample into a cavity surrounded by six sample cushion blocks (4), assembling and installing the sample through a quick lock (14), and then sealing the sample with a sealing adhesive at the edge of the joint of the sample cushion blocks (4) to form a sample sealing gasket, so that the sample (3) is sealed therein; the edge sealant is liquid silicon rubber and is coated on the edges to be sealed in a brushing mode, and the sealing between the sample cushion blocks (4) can be achieved after the silicon rubber is solidified;
firstly, a sample sealing gasket is arranged on a lower pressure head, then an upper pressure head is controlled to move downwards to be arranged with a universal sealing joint (16), meanwhile, the upper pressure head is attached to the upper surface of the sample sealing gasket, and finally, the front pressure head, the rear pressure head, the left pressure head and the right pressure head are respectively controlled to move, so that the corresponding pressure heads are respectively attached to the corresponding surfaces of the sample sealing gasket;
step four, applying triaxial stress;
applying stress to the sample to a preset value through the front, rear, left, right, upper and lower six pressure heads;
step five, releasing pressure;
keeping the stress loading mode of the upper pressure head to be constant force loading, converting the stress loading modes of the left pressure head, the right pressure head and the front pressure head into constant rigidity loading, converting the stress loading mode of the lower pressure head into constant displacement loading, and controlling the rear pressure head to retreat towards the force unloading direction until the distance from the rear surface of the raw coal sample reaches 20 +/-5 mm;
step six, simulating the coming pressure of the top plate;
increasing the pressure of the upper pressure head at a constant loading rate until the raw coal sample is damaged, recording the stress and displacement changes of each pressure head, and calculating the energy evolution condition in the test process;
step seven, replacing the raw coal sample, and repeating the step two to the step four;
step eight, water injection test;
injecting water into the raw coal sample at a preset water injection rate through a water injection hole on the front surface of the raw coal sample, and stopping after the preset water injection time is reached;
step nine, repeating the step six, and simulating the pressure of the top plate again;
step ten, replacing the raw coal sample, changing the hardness of the raw coal sample, or changing the water injection rate, the triaxial pressure and the front pressure head pressure relief rate, and repeating the steps from the first step to the ninth step;
and step eleven, finishing test data.
2. The pressure relief and impact prevention test method for water injection-wetted coal rocks under true three-dimensional stress according to claim 1, characterized by comprising the following steps: the hexahedral raw coal sample is a cube, and the sample size is 200mm × 200mm × 200 mm.
3. The pressure relief and impact prevention test method for water injection-wetted coal rocks under true three-dimensional stress as claimed in claim 2, characterized in that: the diameter of the water injection hole (15) in the raw coal sample is 12mm, and the depth of the hole is 105 mm; the outer diameter of the water injection pipe is 12mm, and the length of the water injection pipe is 95 mm.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010158919.9A CN111175468B (en) | 2020-03-09 | 2020-03-09 | Pressure-relief and impact-prevention test method for water-injection-wetted coal rock under true three-dimensional stress |
| PCT/CN2020/079422 WO2021179337A1 (en) | 2020-03-09 | 2020-03-15 | Coal rock water infusion wetting-based pressure relief and bump prevention test method under true three-dimensional stress |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010158919.9A CN111175468B (en) | 2020-03-09 | 2020-03-09 | Pressure-relief and impact-prevention test method for water-injection-wetted coal rock under true three-dimensional stress |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN111175468A CN111175468A (en) | 2020-05-19 |
| CN111175468B true CN111175468B (en) | 2020-11-27 |
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| CN112484895B (en) * | 2020-12-21 | 2023-03-07 | 天津城建大学 | Three-dimensional stress testing device and method with hexahedral base as outline |
| CN114235582B (en) * | 2021-12-20 | 2024-04-16 | 东北大学 | True triaxial test method for simulating stress state of rock at excavation boundary of underground engineering |
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| CN114624099B (en) * | 2022-04-08 | 2024-05-17 | 中南大学 | Multifunctional rock-soil compression test system and test method thereof |
| CN115950746B (en) * | 2022-12-23 | 2023-09-26 | 平顶山天安煤业股份有限公司 | Roadway protection method for multi-coal seam gob-side entry retaining in real ground stress environment |
| CN116124606B (en) * | 2023-03-02 | 2024-04-19 | 深圳大学 | Deep-ground deep space deep sea rock physical mechanical testing cavity and three-dimensional multi-field information sensing cabin |
| CN116256246B (en) * | 2023-03-02 | 2024-03-08 | 深圳大学 | Rock physical and mechanical testing system for deep space and deep sea environment |
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