Study On Energy Evolution Mechanism And Catastrophe Characteristics During Rock Deformation And Failure

As the mining depth increases,the frequence and scale of dynamic disaster are increased dramatically,and the failure behavior of deep rock masses becomes more complex.Due to the fuzziness of failure mechanism,the dynamic disaster in deep mining engineering could not be accurarely forecasted and controlled.It is not capable to describe the magnitude and scale of dynamic disater by analyzing the stress and the deformation of rock.Those features are exactly critical indicators for evaluating deep underground disaster.Researches showd that the energy theory is an optimal theory for analyzing and forcasting the dynamic disaster.In this study,the energy theory was used to thoroughly study the energy evolution mechanism and the catastrophe characteristics during rock deformation and failure from four aspects,including energy evolution,the mesostructure effect on energy characteristics of rock failure,failure intensity of the rock,and the energy catastrophe criterion.(1)The full cycle loading and unloading experiments on five rock types under uniaxial and 7 typical confining pressures were conducted.A method to calaulate the post-peak strain energy was proposed based on the energy balance theory.Then,the energy evolution curves of rocks during rock deformation and failure were obtained.The energy evolution characteristics for brittle-ductile rocks were contrasted and analyzed.A new parameter was proposed to characterize the stored energy and dissipated energy features of rock.It was further suggested that the rock energy evolution patterens could be devided into four categories by the parameter.The confining pressure effect on the energy evolution was further analyzed,and the different modes of variation of the energy accumulation characteriatcs and dissipation characteriatcs could be observed in the rocks with the increase of confining pressure.(2)The differences on rock energy evolution characteristics under different confining pressures were illustrated by analyzing the shear rupture mechanism operating within fracture process zone.The micro-mechanism of the effect of confining pressure on the energy evolution characteristics was revealed.The influence of mineral composition,microstructure and fracture mode on the energy characteristics were analyzed by X-ray diffraction and scanning electron microscope.The studies indicated that the percentage of brittle mineral compositions dictated the energy accumulation characteriatcs.Besides,the resistant capacity of shear deformation and the energy dissipation characteriatcs are dertermined by the microstructure and the crystallization degree.The 3D laser scanner experiments were conducted to build the relationship between the energy characteristics and the roughness or the fractal dimension of rock fracture surface.It was obtained that the relationship between the two had osculating correlation with the micro-fracture mode and the microscopic appearance of fracture surface.(3)On the basis of the damage mechanics,the energy release rate and energy dissipation rate were proposed to describe the change of energy accumulation and dissipation per unit strain.Based on the uniaxial and triaxial experiments,the evolution of dynamic process of energy accumulation and dissipation was studied.To quantify the magnitude of the intensity of rock failure,the failure intensity index was further put forth.Then,the criterion was established for dividing the magnitude of the intensity of rock failure.Based on the characterizations of rock fracturing behavior,the relationships between failure intensity and fragmentation degree,released acoustic emission energy per unit time and fracture angle were presented and discussed.These results provided the experimental and theoretical basis for analyzing the catastrophe characteristics.(4)The uniaxial compression of rocks were conducted.Then,the acoustic emission data was clustered and analyzed to build the constitutive model.Based on the constitutive model,the critical damage energy dissipation rate and the failure intensity index of rock were deduced theoretically.The physical significance of the failure intensity index was further identified.Next,a new energy catastrophe criterion,combining the rock failure and the risk assessment,was put forward.And the energy criterion was spread into triaxial stress condition by the three-dimensional damage constitutive model.The paper has 106 figures,27 tables and 228 references.