Study On Charge Laws Of Coal And Rock Fracture Under Different Loading Rates And Its Application

In the actual mine production,excessive speed in backstopping will lead to the increase of the peak of the advance support pressure,and the storage of the elasticity of the unmasked coal body and the upper roof which will induce the rock burst disaster.From the theory of rock mechanics,it can be seen that roof coal and rock mass has a significant effect on the the increase of loading rate and mechanical properties,impact tendency and failure law of coal and rock mass.The effect is not only reflected in the stress field and displacement field of the coal and rock system,but also on the storage and dissipation energy changes of the loaded coal.In particular,the charge physical signal released by the process that coal was loaded will changes with loading rate.In order to establish load-charge criterion of different coal instability under different loading rates,charge monitoring test of coal and rock failure process under different loading rates were carried out by physical research and signal analysis methods with Fuxin Wulong mining area and Xin Qiu mining area.Mechanical properties of coal and rock mass under different loading rates,the law of fracture and the relation between energy dissipation and charge signal of coal and rock fracture process were deeply studied.The results show that:with the increasing of the loading rate,uniaxial compressive strength and cumulative deformation energy dissipation of coal and rock mass increases.Instability forms of coal rock mass change from static load instability to dynamic load instability.Under the low loading rate,the first signal mutation of charge appears in the later stage of the strengthening phase,and the mutation stress is close to the peak stress.After increasing the loading rate,the first mutation of the charge signal is moved forward,mainly concentrated in the early stage of the damage strengthening.The quantitative analysis shows that the change rate of charge after the stress peak of coal and rock mass increases with loading rate increases.Also,the charge judgment method of coal and rock mass instability is initially raised In different mining areas on the working surface,based on the field data obtained by monitoring the charge of mining stress field,we can predict and warn the occurrence probability of coal compression type rock burst caused by mining excessive speed.