Crack Propagation Test And Energy Evolution Analysis Of Fractured Rock

In the process of bearing deformation and instability failure of jointed rock mass,the complex evolution of energy is accompanied by the complex evolution of energy.The engineering rock mass in some special position will bear the repeated action of external load,which weakens the strength and stability of rock mass.It is of great engineering significance to correctly analyze the mechanical properties and deformation-failure process of fractured rock mass.From the angle of energy,the mechanical characteristics and essential characteristics of rock mass deformation and failure are studied.By synthetically analyzing the propagation characteristics of rock cracks and the evolution law of internal energy,the failure law of jointed rock mass can be reflected more realistically.This paper combines the digital speckle correlation method and acoustic emission monitoring.The load-bearing deformation and strength characteristics of fractured rock are obtained by step loading and unloading test.The evolution of surface deformation field and crack propagation are analyzed,and the correlation between acoustic emission parameters,crack propagation and energy evolution of fractured rock is studied.The characteristics of instability and failure of fractured rock are preliminarily discussed,and made the following conclusions:(1)Deformation and load-bearing characteristics of prefabricated fractured rock,combined with fracture morphology of fractured rock,initiation stress,peak stress and residual strain,analyzed under different loading and unloading stress levels,different number and location of cracks,etc.The loading time,loading and unloading stress level,crack initiation stress and peak stress decrease in turn,and the decreasing rate decreases gradually with the number of cracks increasing,while the initial strain,peak strain and residual strain increase in turn.The increasing rate decreases with the increase of the number of fractures.(2)Loading and unloading test combined with DSCM based on the characteristics of crack rock fractures with different fracture number and position under the condition of expansion,failure mode and crack propagation angle of crack propagation.With the increase in the number of prefabricated crack,the crack number increased respectively by 33.3%and 24.8%,the double fractured rock overall crack length,single fracture rock of fractured rock,three minimum;crack propagation angle distribution between 450°?90°,mainly distributed within the range of 60°?90°,the three fractured rock overall crack angle,single fracture rock of fractured rock,double minimum.(3)The energy principle is used to study the evolution of energy release,dissipation energy and crack initiation energy of fractured rock under different loading stress levels.The correlation characteristics and response relationships between energy evolution and acoustic emission parameters,crack propagation mode and crack initiation energy of fractured rock are analyzed.The characteristics of failure precursor and instability of fractured rock are discussed preliminarily.The release energy and dissipation energy of fractured rock increase linearly with the increase of loading stress level.With the increase of the number of prefabricated fractures,the release energy decreases by 8.8%and 10.2%,the dissipation energy decreases by 12.4%and 15.6%.The acoustic emission ringing number and the total strain energy and the release energy have good correlation,and the energy rate of acoustic emission is basically consistent with the evolution law of dissipative energy.