Research On Transmission Law Of Stress Wave Propagation Under Bearing Damage Of Coal-rock Structural Plane

The study of the stress wave propagation attenuation law under the loading damage of coal-rock structural plane can predict the dynamic stress distribution of local coal-rock mass in the process of coal mining.Based on the actual coal-rock structural plane,the similarity model of coal-rock structural plane was designed and made.Combined with a series of experiments,the axial compressive strength of coal-rock structural plane,the attenuation of stress wave passing through the structural plane and the change of C、φof coal-rock structural plane under different static loads were studied.Then FLAC^3D software was used to simulated the stress wave attenuation,combined with the actual coal mine geological conditions,the vertical stress of the roof and floor of the roadway with different pillar widths was simulated.The main research results include:（1）Through the uniaxial compression test of the coal-rock structural plane similarity model,the uniaxial compressive strength of the coal-rock structural plane similarity model was 0.264MPa.Based on this,the SHPB test shows that with increase of axial pressure,when angle is 0°and 30°,transmission coefficient of structural plane decreases first then increases;transmission coefficient of structural plane increases first and then decreases at 15°;transmission coefficient increases first at 45°;transmission coefficient decreases first,then increases and then decreases at 60°.With the increase of angle,transmission coefficient under 0.13MPa and 1.63MPa axial pressures increases first and then decreases.Transmission coefficient under axial pressure of 0.29MPa,0.37MPa and 0.78MPa shows an overall increasing.The function relation between the transmission coefficient of stress wave and the angle、between the transmission coefficient of stress wave and the axial pressure under the specific angle were fitted by MATLAB software.（2）Based on the uniaxial compressive strength of the similar model of coal-rock structural plane,the shear test of the structural plane was carried out.It was concluded that under the same normal stress condition,with the increase of static load,the failure mode of structural plane changes from shear failure without static load to compression failure under dynamic and static load combination;with the increase of the normal stress,the shear strength of the coal and rock structural plane increases after the combination of no static and dynamic load,small static and dynamic load and large static and dynamic load;with the increase of static load,the cohesion of coal-rock structural plane increases while the angle of internal friction decreases.（3）FLAC^3D software was used to simulate the dynamic carrier transmission under the combined action of static and static loads.The results show that with the increase of static load,when structural plane is 0°and 15°,transmission coefficient increases first,then decreases and increases,transmission coefficient increases first and then decreases at 30°,transmission coefficient increases first and then decreases,then increases and then decreases at 45°,transmission coefficient decreases first and then increases at 60°.When the axial pressure is 0.09 MPa,transmission coefficient decreases first and then increases with the increase of angle,transmission coefficient decreases first,then increases and then decreases for other axial pressures.When structural plane is 0°and15°,the difference between experimental transmission coefficient and simulated transmission coefficient is 0.2～0.7,the difference was 0.17-0.45 at 30°,the difference is0.1～0.67 at 45°,the difference is 0.4～0.54 at 60°except for 0.17MPa,0.23MPa and0.37MPa axial pressure.When the model is small axial pressure,the simulated transmission coefficient differs greatly from the experimental transmission coefficient,the specimens with 45°and 60°angles have slippage phenomenon in the test,which is different from the simulation results.（4）With the geological conditions of Fuyan Coal mine,the displacement changes of surrounding rock of roadway with different pillar widths after coal mining were simulated under the combined action and static load.It is concluded that when the coal pillar width is less than 15m,the displacement of the roof,floor and two sides of the roadway is large,and when the coal pillar width is greater than 15m,the displacement is small.Based on this,the coal pillar width is determined,saving 5m coal pillar width compared with the actual situation.There are 54 figures,24 tables and 90 references.