CN113624593B - Dynamic and static load impact test device and method for simulating dip angle-containing coal rock combination - Google Patents
Dynamic and static load impact test device and method for simulating dip angle-containing coal rock combination Download PDFInfo
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Abstract
The invention provides a dynamic and static load impact test device and method for simulating a coal-rock combination with an inclination angle, wherein the device can construct a coal-rock combination structure with the inclination angle and limit the lateral deformation of an upper rock block and a lower rock block; the sample fixing system consists of a U-shaped frame, a lateral supporting part and springs, the lateral supporting part comprises an upper group and a lower group which are connected through the springs, an opening is formed in the upper right side of the U-shaped frame, a limiting column is arranged on a right baffle plate of the upper part of the U-shaped frame and extends into the opening, and the lateral supporting part slides when being loaded; the length of the cushion block is matched with that of the inner frame of the U-shaped frame, meanwhile, the elastic coefficient of the spring is the same as that of the coal block, ore pressure prevents the upper bolt from sliding down due to gravity, and the left and right loading forces of the cushion block are balanced; simple structure, convenient operation and good safety. The test method researches the influence of the characteristics, loading modes and size effects of the coal rock contact surface on the strength and destruction mechanism of the dip angle-containing combined coal rock mass, and guides the control of the impact mine pressure under the condition of the buckled stratum based on the research results.
Description
Technical Field
The invention belongs to the field of coal mine rock burst prevention and control, and particularly relates to a dynamic and static load impact test device and method for simulating a coal rock combination with an inclination angle.
Background
Coal is one of main energy sources in China, however, with the increase of the mining age of coal, mines enter a deep development stage. As the depth of mining increases, the frequency and intensity of the occurrence of underground dynamic disasters represented by rock burst gradually increase. Coal mine rock burst is a dynamic disaster phenomenon that coal and rock masses are subjected to instability destruction in the mining process and accumulated elastic energy is released instantly, and the dynamic phenomenon is often accompanied with extrusion displacement of the coal masses to the side near the air. The research shows that energy accumulation can be formed under the clamping action of the top and bottom plates on the coal seam, and the coal rock mass is subjected to local longitudinal deformation and discordance under the action of horizontal stress, so that impact damage to the coal rock mass is caused. However, the existing physical model test device for researching the physical mechanical properties and rock burst damage of the coal rock mass usually ignores the occurrence condition of the coal rock mass in the mining process in a natural state, and cannot test samples with different inclination angles and different sizes; in addition, disturbance power on the coal rock mass in actual engineering is very complex, the loading mode of most of the conventional test devices is static load, the influence of dynamic load on the damage of the coal rock mass is ignored, and the rock burst generation process of the coal rock mass under the action of the dynamic and static load cannot be researched.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a dynamic and static load impact-causing test device and a method for simulating a coal rock combination with an inclination angle.
Specifically, the dynamic and static load impact test device for simulating the dip angle-containing coal and rock combination comprises a loading system, a sample fixing system and a monitoring system; the loading system comprises a static load system/dynamic load system and a cushion block, and the cushion block plays a role in connecting the static load system/dynamic load system with the sample;
preferably, a TAW-2000 uniaxial testing machine is used for loading in the static load stress loading test, and a displacement loading mode is used in the test; the dynamic and static load fatigue testing machine is adopted in the dynamic load stress loading test, the stress loading mode and the displacement loading mode can be switched, and different dynamic load frequencies and amplitudes can be set.
The sample fixing system consists of a U-shaped frame, a lateral supporting part and a spring, wherein the left side in the U-shaped frame is used for placing a sample, the right side is the lateral supporting part and comprises an upper group and a lower group which are connected through the spring and respectively apply lateral supporting force to an upper rock block and a lower rock block, the lateral supporting part consists of a left baffle, a bolt and a right baffle from left to right, the bolt is connected with the left baffle and the right baffle in a threaded connection mode, and the left baffle is contacted with the rock block in the sample; the length of the cushion block is matched with that of the inner frame of the U-shaped frame, an opening is formed in the right upper side of the wall of the U-shaped frame, a limiting column is arranged on the right side of the right baffle on the upper portion of the wall of the U-shaped frame, and the limiting column penetrates into the opening;
preferably, the elastic coefficient of the spring is the same as that of the coal briquette, so that the upper bolt is prevented from sliding downwards due to gravity, and the left and right loading forces of the cushion block are balanced; the inner side wall of the U-shaped frame needs to be as smooth as possible, so that the lateral displacement of the rock is restrained without restraining the vertical displacement, and the purpose that the load is transmitted to the coal briquette without being influenced by the lateral friction force between the sample and the device is achieved.
The monitoring system comprises a strain measurement system, an acoustic emission monitoring system and a high-speed camera acquisition system, wherein the strain monitoring system adopts a strain gauge, the acoustic emission monitoring system is an acoustic emission sensor, the high-speed camera acquisition system is used for recording the process of coal rock body destruction, and the monitoring system is also provided with a monitoring data collection device which is connected with the strain measurement system, the acoustic emission monitoring system and the high-speed camera acquisition system;
the sample is an inclination angle-containing combination of an upper rock mass, a coal mass and a lower rock mass from top to bottom, the upper rock mass and the lower rock mass are laterally constrained but have no lateral friction, so that an upper top plate and a lower bottom plate under the condition of mine mining are simulated, and one side of a middle coal mass has no lateral constraint and is used for researching dynamic and static load induced impact damage of a coal rock mass; the sample rock mass and the coal block are connected by the adhesive to form a whole sample.
The dynamic and static load impact test method for simulating the combination of the coal and rock with the inclination angle is adopted to research the influence of the characteristics, the loading mode and the size effect of the coal and rock contact surface on the strength and the damage mechanism of the combination coal and rock with the inclination angle, and comprises the following steps:
s1, designing and processing a combined sample;
the combined sample comprises an upper rock block, a coal block and a lower rock block from top to bottom, a coal-rock body with impact tendency is selected to make the sample, the sizes of the coal block and the rock block are designed, the samples are respectively set according to different contact surface inclination angles and contact surface properties and static load and dynamic load test requirements, and coal-rock combinations with different sizes are designed to study size effects; selecting different materials as binders between the coal blocks and the rock blocks to provide different contact surface properties, namely the shearing strength of different contact surfaces;
specifically, the overall size of a sample is a cube with the side length of 100mm, 10 groups of samples are respectively set in a static load test and a dynamic load test according to different contact surface inclination angles and contact surface properties, wherein the samples are S1-S10 and D1-D10 (table 1), white latex is used as a binder to provide different contact surface shear strengths, and the coating thickness is 1 mm; in order to study the influence of size effect, 2 sets of samples with the width of 200mm SS1-SS2/SD1-SD2 are respectively arranged to carry out static load/dynamic load experiments, and the properties of the contact surface are referred to as samples S1-S2/D1-D2.
TABLE 1 static/dynamic/static test contact surface Property set
| Combination sample number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Inclination of contact surface phi/ |
10 | 15 | 20 | 30 | 15 | 15 | 15 | 15 | 15 | 15 |
| Shear strength/ |
5 | 5 | 5 | 5 | 2 | 8 | 10 | 15 | 5 | 5 |
Preferably, double-side polishing is carried out after the sample is cut, and the unevenness and the verticality are controlled; the overall unevenness and verticality of the steel plate are specifically controlled to be less than 0.02mm, and the overall precision meets the specification of CB 23561.7-2009.
S2, performing instability characteristic tests of the coal rock combined samples with different inclination angles under the action of static load stress;
selecting a coal-rock mass combined sample to carry out a static load test, researching the instability characteristic of the sample under the action of static load stress, and adopting a displacement control mode for stress loading;
specifically, a combined sample S1-S4 is selected for a static load experiment, and the loading rate is set to be 0.3 mm/min.
S3, performing instability characteristic tests of the coal rock combined samples with different inclination angles under the action of dynamic load stress;
selecting a combined sample to carry out a dynamic load test, researching the instability characteristics of the sample under the action of dynamic load stress, dividing the whole loading process into an initial static load stress loading stage and a cyclic dynamic load stress loading stage, wherein in the initial static load stress loading process, the stress loading adopts a displacement control mode, then the dynamic loading process is started, the stress loading adopts a stress control mode, and then the dynamic load cyclic loading is continuously carried out until the combined sample is unstable;
specifically, a combined sample D1-D4 is selected to perform a dynamic load experiment, in the initial static load stress loading process, stress is loaded to 80% of the peak pressure of the corresponding static load experiment, then a dynamic loading process is started, a stress control mode is adopted for stress loading instead, sine dynamic load stress loading is started after the static test for 10s, the sine amplitude is set to 10% of the pressure peak value of the static load experiment, the frequency is set to 10Hz, each dynamic load cycle lasts for 2s and then stops, the static test for 10s is stopped, at the moment, the static maintaining force is the pressure peak value of the previous dynamic load experiment, and then dynamic load cycle loading is continued until the combined sample is unstable.
S4, performing combined sample instability characteristic tests under the effects of different contact surface shear strengths, different loading speeds and different sizes: the method comprises the following steps of (1) setting different loading speeds, different loading frequencies and different sample sizes for tests by adopting samples of different binders between rock blocks and coal blocks, researching the instability characteristics of the samples with different contact surface shear strengths, different loading speeds, loading frequencies and sample sizes under the action of dynamic load/static load, and adopting a controlled variable method in the test process;
s41, combining a sample S2/D2, selecting samples S5-S8/D5-D8 for testing, and performing a sample instability characteristic test of different contact surface shear strengths under the action of static load/dynamic load;
s42, combining with a sample S2, selecting samples S9-S10, respectively setting different loading speeds for testing, and performing a test on instability characteristics of the combined sample at different loading speeds, wherein the loading speeds are 0.9mm/min and 1.5mm/min respectively;
s43, combining the sample D2, selecting samples D9-D10, respectively setting different dynamic load loading frequencies for testing, and performing instability characteristic tests on the combined sample at different loading frequencies, wherein the loading frequencies are 20Hz and 30Hz respectively;
s44, combining samples S1-S2 and D1-D2, selecting samples SS1-SS2 and SD1-SD2 for testing, and performing a instability characteristic test of samples with different sizes under the action of static load/dynamic load.
A coal mine impact mine pressure control method under the condition of buckling is characterized in that engineering guidance is carried out based on test results obtained by the test method, and a coal rock layer under the condition of buckling is a typical dip angle-containing coal rock combination, and the following control measures can be adopted:
A. changing the contact surface property; test results show that the larger the inclination angle of the coal rock contact surface is, the larger the shearing strength of the contact surface is, the more unstable slippage of a sample is easy to occur, and further obvious power display in the damage process is caused; the water can be injected along the coal rock interface to change the shearing strength of the contact surface, or the transverse top cutting is carried out along the interface to change the angle of the contact surface, so that the unstable slippage occurrence probability of the contact surface is reduced;
B. reducing the static load stress level of the coal rock mass; the test result shows that the larger the static load stress borne by the coal rock body is, the larger the lateral restraining force is, the larger the integral instability strength of the structure is, and the more obvious dynamic damage phenomenon is easily caused; therefore, the suspended roof area can be reduced by means of roof cutting pressure relief and presplitting blasting, and further the vertical and lateral stress of the coal bed is reduced;
C. reducing the dynamic load stress level of the coal rock mass; the test result shows that the larger the dynamic load stress borne by the coal rock body is, the more easily the dynamic damage phenomenon is caused under the action of the same static load horizontal force; therefore, dynamic load stress caused by roof breakage or fault slippage can be reduced by means of filling and grouting in a goaf to reinforce the fault;
D. increasing the size of the coal pillar; the test result shows that the smaller the size of the coal-rock mass sample, namely the larger the height-width ratio of the sample, the more easily the coal-rock mass dynamic damage phenomenon occurs, and the coal pillar area is more easily subjected to dynamic disaster compared with the coal face in engineering; therefore, large-size coal pillars can be reserved, and roadside hydraulic column supporting means are additionally arranged to increase the supporting area of the coal pillar region, so that the risk of power disasters is reduced.
The beneficial technical effects of the invention are as follows: the invention provides a dynamic and static load impact test device and method for a coal-rock combination with an inclination angle, wherein the device can construct a coal-rock combination structure with the inclination angle and limit the lateral deformation of an upper rock block and a lower rock block, so that the clamped coal-rock combination has the tendency of deforming and damaging towards the side near the empty space; the sample fixing system consists of a U-shaped frame, a lateral supporting part and springs, the lateral supporting part comprises an upper group and a lower group which are connected through the springs, an opening is formed in the upper right side of the U-shaped frame, a limiting column is arranged on a right baffle plate of the upper part of the U-shaped frame and extends into the opening, and the lateral supporting part slides when being loaded; the length of the cushion block is matched with that of the inner frame of the U-shaped frame, meanwhile, the elastic coefficient of the spring is the same as that of the coal block, ore pressure prevents the upper bolt from sliding down due to gravity, and the left and right loading forces of the cushion block are balanced; the device has simple structure, convenient operation and good safety. The test method researches the influence of the characteristics, loading modes and size effects of the coal rock contact surface on the strength and destruction mechanism of the dip angle-containing combined coal rock mass, and guides the control of the impact mine pressure under the condition of the buckled stratum based on the research results.
Drawings
FIG. 1 is a schematic view of the overall structure of the test apparatus of the present invention;
FIG. 2 is a side view of the U-shaped frame of the present invention with one side open;
FIG. 3 is a schematic view of the manner in which the sample is held during the test according to the present invention;
FIG. 4 shows a coal rock composite sample with dip angle;
FIG. 5 is a dynamic load test stress loading path;
in the figure, a static load system/dynamic load system 1, a cushion block 2, a U-shaped frame 3, a left baffle 4, a bolt 5, a right baffle 6, a spring 7, an opening 8, an upper rock block 9, a coal block 10, a lower rock block 11, a strain gauge 12, an acoustic emission sensor 13, a high-speed camera acquisition system 14 and a monitoring data collection device 15 are adopted.
Detailed Description
As shown in fig. 1-3, a dynamic and static load impact test device for simulating a combination of coal and rock with an inclination angle comprises a loading system, a sample fixing system and a monitoring system;
the loading system comprises a static load system/dynamic load system 1 and a cushion block 2, a static load stress loading test can be loaded by adopting a TAW-2000 single-shaft testing machine, and a displacement loading mode is adopted during the test; the dynamic and static load fatigue testing machine can be adopted in the dynamic load stress loading test, the stress loading mode and the displacement loading mode can be switched, and different dynamic load frequencies and amplitudes can be set; the cushion block 2 plays a role in connecting the static load system/dynamic load system 1 with the sample, and the height of the cushion block can change along with the change of the height of the sample when the size of the sample needs to be adjusted in a test;
the sample fixing system consists of a U-shaped frame 3, a lateral supporting part and a spring 7, wherein the left side in the U-shaped frame 3 is used for placing a sample, the right side is the lateral supporting part and comprises an upper group and a lower group which are connected through the spring 7 and respectively apply lateral supporting force to an upper rock block 9 and a lower rock block 11, the lateral supporting part consists of a left baffle 4, a bolt 5 and a right baffle 6 from left to right, the bolt 5 is connected with the left baffle 4 and the right baffle 6 in a screw connection mode, so as to be convenient for placing a sample, the right baffle 6 can prevent the bolt 5 from horizontally displacing, the left baffle 4 can be replaced, the left baffle 4 is contacted with a rock block in the sample, the inner side wall of the U-shaped frame 3 needs to be as smooth as possible, therefore, the lateral displacement of the sample rock is restrained without restraining the vertical displacement, and the purpose that the load is transmitted to the coal briquette and is not influenced by the lateral friction force between the sample and the device is achieved; the length of the cushion block 2 is matched with that of an inner frame of the U-shaped frame 3, an opening 8 is formed in the right upper side of the wall of the U-shaped frame, a limiting column is arranged on the right side of a right baffle 6 on the upper portion of the U-shaped frame, the limiting column extends into the opening 8, and when the right baffle on the upper portion is loaded by the cushion block 2, the right baffle can slide downwards;
preferably, the spring 7 has the same elastic coefficient as the coal 10, so as to prevent the upper bolt from sliding down due to gravity and balance the left and right loading forces of the cushion block.
The monitoring system comprises a strain measurement system, an acoustic emission monitoring system and a high-speed camera acquisition system, wherein the strain monitoring system adopts a strain gauge 12 and can directly record micro-strain on a monitoring surface, the acoustic emission monitoring system is an acoustic emission sensor 13, the high-speed camera acquisition system 14 is used for recording the process of coal rock destruction, and a monitoring data collection device 15 is further arranged and connected with the strain measurement system, the acoustic emission monitoring system and the high-speed camera acquisition system;
the sample is an inclination angle combination of an upper rock mass 9, a coal mass 10 and a lower rock mass 11 from top to bottom, the upper rock mass 9 and the lower rock mass 11 are laterally constrained but have no lateral friction, so that an upper top plate and a lower bottom plate under the condition of mine exploitation are simulated, and one side of a middle coal mass 10 has no lateral constraint and is used for researching dynamic and static load induced impact damage of a coal rock mass; the sample rock mass and the coal block are connected by the adhesive to form the whole sample, and the fixing mode of the sample in the test process is shown in figure 3.
The dynamic and static load impact test method for simulating the combination of the coal and rock with the inclination angle is adopted to research the influence of the characteristics, the loading mode and the size effect of the coal and rock contact surface on the strength and the damage mechanism of the combination coal and rock with the inclination angle, and comprises the following steps:
the method comprises the following steps: designing and processing a combined sample;
the combined sample comprises an upper rock block, a coal block and a lower rock block from top to bottom, a coal-rock body with impact tendency is selected to make the sample, the sizes of the coal block and the rock block are designed, the samples are respectively set according to different contact surface inclination angles and contact surface properties and static load and dynamic load test requirements, and coal-rock combinations with different sizes are designed to study size effects; selecting different materials as binders between the coal blocks and the rock blocks to provide different contact surface properties, namely the shearing strength of different contact surfaces;
as shown in fig. 4, specifically, the overall size of the sample is a cube with a side length of 100mm, 10 groups of samples are respectively set in a static load test and a dynamic load test according to different contact surface inclination angles and contact surface properties, wherein the groups are respectively S1-S10 and D1-D10 (table 1), white latex (or gypsum and yellow mud) is adopted as a binder according to GB/T25217.3-2019 to provide different contact surface shear strengths, and the coating thickness is 1 mm; to investigate the influence of the size effect, 2 groups of samples with a width of 200mm were set up for static/dynamic tests SS1-SS2/SD1-SD2, contact surface properties reference samples S1-S2/D1-D2.
TABLE 1 static/dynamic/static test contact surface Property set
| Combination sample number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| Inclination of contact surface phi/ |
10 | 15 | 20 | 30 | 15 | 15 | 15 | 15 | 15 | 15 |
| Shear strength/ |
5 | 5 | 5 | 5 | 2 | 8 | 10 | 15 | 5 | 5 |
Preferably, double-side polishing is carried out after the sample is cut, and the unevenness and the verticality are controlled; the overall unevenness and verticality of the steel plate are specifically controlled to be less than 0.02mm, and the overall precision meets the specification of CB 23561.7-2009.
Step two, performing instability characteristic tests on coal and rock combined samples with different inclination angles under the action of static load stress;
selecting a coal-rock mass combined sample to carry out a static load test, researching the instability characteristic of the sample under the action of static load stress, wherein the stress loading adopts a displacement control mode, and a certain number of acoustic emission sensors and strain gauges are arranged on the surface of the sample before the test;
specifically, a combined sample S1-S4 is selected for a static load experiment, and the loading rate is set to be 0.3 mm/min.
Performing instability characteristic tests on the coal rock combination samples with different inclination angles under the action of dynamic load stress;
selecting a combined sample to carry out a dynamic load test, researching the instability characteristics of the sample under the action of dynamic load stress, dividing the whole loading process into an initial static load stress loading stage and a cyclic dynamic load stress loading stage, wherein in the initial static load stress loading process, the stress loading adopts a displacement control mode, then the dynamic loading process is started, the stress loading adopts a stress control mode, and then the dynamic load cyclic loading is continuously carried out until the combined sample is unstable;
specifically, a combined sample D1-D4 is selected to perform a dynamic load experiment, in the initial static load stress loading process, stress is loaded to 80% of the peak pressure of the corresponding static load experiment, then a dynamic loading process is started, the stress loading mode is changed into a stress control mode, sine dynamic load stress loading is started after the static test for 10s, the sine amplitude is set to 10% of the pressure peak value of the static load experiment, the frequency is set to 10Hz, each dynamic load cycle lasts for 2s and then stops, the static test for 10s is stopped, the static maintaining force is the pressure peak value of the previous dynamic load experiment, then dynamic load cycle loading is continued until the combined sample is unstable, and the specific loading path is shown in FIG. 5.
Step four, performing combined sample instability characteristic tests under the effects of different contact surface shear strengths, different loading speeds and different sizes: the method comprises the following steps of (1) setting different loading speeds, different loading frequencies and different sample sizes for tests by adopting samples of different binders between rock blocks and coal blocks, researching the instability characteristics of the samples with different contact surface shear strengths, different loading speeds, loading frequencies and sample sizes under the action of dynamic load/static load, and adopting a controlled variable method in the test process;
s41, combining a sample S2/D2, selecting samples S5-S8/D5-D8 for testing, and performing a sample instability characteristic test of different contact surface shear strengths under the action of static load/dynamic load;
s42, combining with a sample S2, selecting samples S9-S10, setting different loading speeds respectively for testing (0.9 mm/min and 1.5mm/min respectively), and performing instability characteristic tests on the combined sample at different loading speeds;
s43, combining the sample D2, selecting samples D9-D10, respectively setting different dynamic load loading frequencies for testing (respectively 20Hz and 30 Hz), and performing instability characteristic test of the combined sample by different loading frequencies;
s44, combining samples S1-S2 and D1-D2, selecting samples SS1-SS2 and SD1-SD2 for testing, and performing a instability characteristic test of samples with different sizes under the action of static load/dynamic load.
A coal mine impact mine pressure control method under the condition of buckling is characterized in that engineering guidance is carried out based on test results obtained by the test method, and a coal rock layer under the condition of buckling is a typical dip angle-containing coal rock combination, and the following control measures can be adopted:
A. changing the contact surface property; test results show that the larger the inclination angle of the coal rock contact surface is, the larger the shearing strength of the contact surface is, the more unstable slippage of a sample is easy to occur, and further obvious power display in the damage process is caused; the water can be injected along the coal rock interface to change the shearing strength of the contact surface, or the transverse top cutting is carried out along the interface to change the angle of the contact surface, so that the unstable slippage occurrence probability of the contact surface is reduced;
B. reducing the static load stress level of the coal rock mass; the test result shows that the larger the static load stress borne by the coal rock body is, the larger the lateral restraining force is, the larger the integral instability strength of the structure is, and the more obvious dynamic damage phenomenon is easily caused; therefore, the suspended roof area can be reduced by means of roof cutting pressure relief and presplitting blasting, and further the vertical and lateral stress of the coal bed is reduced;
C. reducing the dynamic load stress level of the coal rock mass; the test result shows that the larger the dynamic load stress borne by the coal rock body is, the more easily the dynamic damage phenomenon is caused under the action of the same static load horizontal force; therefore, dynamic load stress caused by roof breakage or fault slippage can be reduced by means of filling and grouting in a goaf to reinforce the fault;
D. increasing the size of the coal pillar; the test result shows that the smaller the size of the coal-rock mass sample, namely the larger the height-width ratio of the sample, the more easily the coal-rock mass dynamic damage phenomenon occurs, and the coal pillar area is more easily subjected to dynamic disaster compared with the coal face in engineering; therefore, large-size coal pillars can be reserved, and roadside hydraulic column supporting means are additionally arranged to increase the supporting area of the coal pillar region, so that the risk of power disasters is reduced.
Claims (9)
1. A dynamic and static load impact test device for simulating a coal and rock combination with an inclination angle comprises a loading system, a sample fixing system and a monitoring system;
the device is characterized in that the loading system comprises a static load system/a dynamic load system and a cushion block, and the cushion block plays a role in connecting the static load system/the dynamic load system with a sample;
the sample fixing system consists of a U-shaped frame, a lateral supporting part and a spring, wherein the left side in the U-shaped frame is used for placing a sample, the right side is the lateral supporting part and comprises an upper group and a lower group which are connected through the spring and respectively apply lateral supporting force to an upper rock block and a lower rock block, the lateral supporting part consists of a left baffle, a bolt and a right baffle from left to right, the bolt is connected with the left baffle and the right baffle in a threaded connection mode, and the left baffle is contacted with the rock block in the sample; the length of the cushion block is matched with that of the inner frame of the U-shaped frame, an opening is formed in the right upper side of the wall of the U-shaped frame, a limiting column is arranged on the right side of the right baffle on the upper portion of the wall of the U-shaped frame, and the limiting column penetrates into the opening;
the monitoring system comprises a strain measurement system, an acoustic emission monitoring system and a high-speed camera acquisition system, wherein the strain monitoring system adopts a strain gauge, the acoustic emission monitoring system is an acoustic emission sensor, the high-speed camera acquisition system is used for recording the process of coal rock body destruction, and the monitoring system is also provided with a monitoring data collection device which is connected with the strain measurement system, the acoustic emission monitoring system and the high-speed camera acquisition system;
the sample is an inclination angle-containing combination of an upper rock mass, a coal mass and a lower rock mass from top to bottom, the upper rock mass and the lower rock mass are laterally constrained but have no lateral friction, so that an upper top plate and a lower bottom plate under the condition of mine mining are simulated, and one side of a middle coal mass has no lateral constraint and is used for researching dynamic and static load induced impact damage of a coal rock mass; the sample rock mass and the coal block are connected by the adhesive to form a whole sample.
2. The test device according to claim 1, wherein the static load stress loading test is carried out by using a TAW-2000 uniaxial tester, and a displacement loading mode is adopted during the test; the dynamic and static load fatigue testing machine is adopted in the dynamic load stress loading test, the stress loading mode and the displacement loading mode can be switched, and different dynamic load frequencies and amplitudes can be set.
3. The test device according to claim 1, wherein the spring has the same elastic coefficient as that of the coal briquette, so that the upper bolt is prevented from sliding down due to gravity, and the left and right loading forces of the cushion block are balanced; the inner side wall of the U-shaped frame needs to be as smooth as possible, so that the lateral displacement of the rock is restrained without restraining the vertical displacement, and the purpose that the load is transmitted to the coal briquette without being influenced by the lateral friction force between the sample and the device is achieved.
4. A dynamic and static load impact test method for simulating a coal-rock combination with an inclination angle adopts the test device of any one of claims 1 to 3, and is characterized by comprising the following steps:
s1, designing and processing a combined sample;
the combined sample comprises an upper rock block, a coal block and a lower rock block from top to bottom, a coal-rock body with impact tendency is selected to make the sample, the sizes of the coal block and the rock block are designed, the samples are respectively set according to different contact surface inclination angles and contact surface properties and static load and dynamic load test requirements, and coal-rock combinations with different sizes are designed to study size effects; selecting different materials as binders between the coal blocks and the rock blocks to provide different contact surface properties, namely the shearing strength of different contact surfaces;
s2, performing instability characteristic tests of the coal rock combined samples with different inclination angles under the action of static load stress;
selecting a coal-rock mass combined sample to carry out a static load test, researching the instability characteristic of the sample under the action of static load stress, and adopting a displacement control mode for stress loading;
s3, performing instability characteristic tests of the coal rock combined samples with different inclination angles under the action of dynamic load stress;
selecting a combined sample to carry out a dynamic load test, researching the instability characteristics of the sample under the action of dynamic load stress, dividing the whole loading process into an initial static load stress loading stage and a cyclic dynamic load stress loading stage, wherein in the initial static load stress loading process, the stress loading adopts a displacement control mode, then the dynamic loading process is started, the stress loading adopts a stress control mode, and then the dynamic load cyclic loading is continuously carried out until the combined sample is unstable;
s4, performing combined sample instability characteristic tests under the action of different contact surface shear strengths, different loading speeds and different sizes; the method is characterized in that samples of different binders between rock blocks and coal blocks are adopted, different loading speeds, different loading frequencies and different sample sizes are set for testing, the sample instability characteristics of different contact surface shear strengths, different loading speeds, different loading frequencies and different sample sizes under the action of dynamic load/static load are researched, and a controlled variable method is adopted in the testing process.
5. The test method as claimed in claim 4, wherein the overall size of the sample is a cube with a side length of 100mm, 10 groups of samples are respectively set in the static load test and the dynamic load test according to different contact surface inclination angles and contact surface properties, the groups are S1-S10 and D1-D10, white latex is used as a binder to provide different contact surface shear strengths, and the smearing thickness is 1 mm; 2 groups of samples SS1-SS2/SD1-SD2 with the width of 200mm are also arranged to carry out static load/dynamic load experiments, and contact surface properties are referred to as samples S1-S2/D1-D2; after the sample is cut, polishing the two sides of the sample, and controlling the unevenness and the verticality; the inclination angles phi/DEG of the contact surfaces from S1/D1 to S10/D10 are respectively 10, 15, 20, 30, 15 and 15; the shear strength/MPa is respectively 5, 2, 8, 10, 15, 5 and 5.
6. The test method as claimed in claim 5, wherein the combined sample S1-S4 is selected for static load test, and the loading rate is set to 0.3 mm/min.
7. The test method of claim 6, wherein the combined sample D1-D4 is selected for dynamic load test, during initial static load stress loading, the stress is loaded to 80% of the peak pressure of the corresponding static load test, then the dynamic load process is started, the stress loading is changed to adopt a stress control mode, after 10s of rest, sinusoidal dynamic load stress loading is started, the sinusoidal amplitude is set to 10% of the peak pressure of the static load test, the frequency is set to 10Hz, after each dynamic load cycle lasts for 2s, the dynamic load cycle is stopped, the dynamic load test is stopped for 10s, and then the static maintaining force is the last dynamic load test pressure peak, and then the dynamic load cycle loading is continued until the combined sample is unstable.
8. The test method of claim 7, wherein S41 is combined with S2/D2, and samples S5-S8/D5-D8 are selected for testing, and the instability characteristic test of the samples with different contact surface shear strengths under static/dynamic load is carried out;
s42, combining with a sample S2, selecting samples S9-S10, respectively setting different loading speeds for testing, and performing a test on instability characteristics of the combined sample at different loading speeds, wherein the loading speeds are 0.9mm/min and 1.5mm/min respectively;
s43, combining the sample D2, selecting samples D9-D10, respectively setting different dynamic load loading frequencies for testing, and performing instability characteristic tests on the combined sample at different loading frequencies, wherein the loading frequencies are 20Hz and 30Hz respectively;
s44, combining samples S1-S2 and D1-D2, selecting samples SS1-SS2 and SD1-SD2 for testing, and performing a instability characteristic test of samples with different sizes under the action of static load/dynamic load.
9. A coal mine impact mine pressure control method under a buckling condition is used for carrying out engineering guidance based on a test result obtained by the test method of claim 8, and a coal rock layer under a buckling stratum condition is a typical dip angle-containing coal rock combination, and is characterized in that the following control means are adopted:
A. changing the contact surface property; test results show that the larger the inclination angle of the coal rock contact surface is, the larger the shearing strength of the contact surface is, the more unstable slippage of a sample is easy to occur, and further obvious power display in the damage process is caused; injecting water along the coal rock interface to change the shearing strength of the contact surface, or performing transverse top cutting along the interface to change the angle of the contact surface, thereby reducing the occurrence probability of unstable slippage of the contact surface;
B. reducing the static load stress level of the coal rock mass; the test result shows that the larger the static load stress borne by the coal rock body is, the larger the lateral restraining force is, the larger the integral instability strength of the structure is, and the more obvious dynamic damage phenomenon is easily caused; in contrast, the suspended ceiling area is reduced by means of roof cutting pressure relief and presplitting blasting, so that the vertical and lateral stress of the coal seam is reduced;
C. reducing the dynamic load stress level of the coal rock mass; the test result shows that the larger the dynamic load stress borne by the coal rock body is, the more easily the dynamic damage phenomenon is caused under the action of the same static load horizontal force; for the method, the dynamic load stress caused by roof breakage or fault slippage is reduced by means of filling and grouting in the goaf to reinforce the fault;
D. increasing the size of the coal pillar; the test result shows that the smaller the size of the coal-rock mass sample, namely the larger the height-width ratio of the sample, the more easily the coal-rock mass dynamic damage phenomenon occurs, and the coal pillar area is more easily subjected to dynamic disaster compared with the coal face in engineering; and large-size coal pillars are reserved, and a roadside hydraulic column supporting means is additionally arranged to increase the supporting area of the coal pillar region and reduce the risk of power disasters.
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