Study On The Influence Mechanism Of Mining Speed On Rock Burst

Rock burst is one of the most typical coal and rock dynamic disasters in coal mining.For high strength and large mining height working face,the influence mechanism of mining speed on rock burst is very important,and there are few researches in related aspects.Therefore,the influence mechanism of the mining speed on the rock burst is studied by theoretical analysis,laboratory test,numerical simulation and field practice,which provide a theoretical basis for the optimization of the field mining strength.The roof model of cantilever beam with triangular booster load is set up in theory,and the factors under the influence of the mining speed are obtained by the control variable method,including the length of cantilever,the load of the cantilever section,the size of the peak load peak load,the position and the influence range of the supercharging load on the deflection,bending moment and bending bullet of the roof beam.The effect of the mining speed on the breaking of the masonry beam structure is that the high-speed propulsion makes the fracture length of the key block A increasing and the possibility of the impact caused by the impact.The high speed propelling the rock block A from the lower free space of the rock mass becomes larger,which is not conducive to the hinges of the rock block A and the rock block B,which may cause the original low level unbroken gangue to break.The structure of the masonry beam is changed into a high position cantilever beam,and it can also make the breaking of the high level gangue masonry beam break into a non-touch break,and the energy of the former is much less than the energy of the latter.The experimental research on loading rate of coal sample has been carried out,and the mechanism of strength evolution under different loading rates has been revealed,and a model of coal impact damage has been established.The laboratory study shows that the increase of loading rate can inhibit the fracture and expansion of small cracks in the elastic phase of coal sample and the stable rupture stage,reduce the number of small energy events,reduce the cracks in the coal rock and then increase the peak strength of coal samples,and eventually lead to a large number of micro units inside the coal samples at the same time.When the strength limit is destroyed,the size of the instantaneous rupture is much larger than that at low velocity,and the energy of the micro rupture event is proportional to the fracture size,so the increase of the loading rate increases the large energy ratio in the number of micro rupture events,and the large size fracture and ejection results in the ultimate impact damage of the coal sample.The numerical simulation of energy and stress changes under the conditions of different mining speed of three dimensional stope is carried out.The results are as follows: under the same condition of the same excavation,the less the single equilibrium time step,the more the cumulative excavation times,the higher the peak value of the total elastic energy released by the model,and the single excavation in the case of the same step in the balance.The greater the total energy released in the unit time,the greater the total energy,especially the peak value,the greater the maximum elastic energy released in the unit step.The number of units in the unit time step release elastic properties also increases with the increase of the amount of excavation;the stress transfer and adjustment process of the surrounding rock has cumulative effect;in the process of continuous excavation,the balance is balanced.The smaller the time step is,the higher the proportion of large energy events.Under the same step in the single calculation,the greater the excavation,the greater the change rate of the main stress difference,the sudden change in the stress state will drive the strain of the coal and rock unit to be abrupt,and the possibility of the impact will increase.Through the statistical analysis of the footage and microseismic energy of the 402103 working face of the Hu Jia-He Mine,the relationship between the propelling speed and the release energy is verified,and the reasonable speed of the different dangerous areas is determined,and the effect of the shock reduction and shock reduction is achieved in the subsequent recovery process.