Analyzing Failure Process For Fractured Rocks Using Experimental Evidence And Extended Finite Element Method

Rock is an extremely heterogeneously anisotropic material that contains discontinues in both macroscale, such as joints, weak surface, holes and inclusions, and microscale like microcrack and pore structure. It is of significance to describe mechanisms of crack generation and propagation throughout progressive failure process of rock, and to identify premonition of rock breaking from observed signals. Therefore, mechanical properties of intact and crack red sandstones were studied at laboratory scale using a material testing system. Phenomena and mechanisms of energy transform during experiments were discussed. A comparision study between experimental and numerical results were performed finally. Major results and conclusions are:1) Analyzing acoustic emission signals and corresponding rock mechanisms throughout rock failure process using spectral analysis based on Hilbert–Huang transform. Effects of transmission characteristics to acoustic emission signals by pore structure was discussed using Biot theory. Influence by changing crack angle on energy and crack evolution were considered in this thesis.2) An energy-based method for analysis of rock fracturing process was presented using surface displace information. Influence by changing crack angle on energy release process were explained. Effects of volume deformation and geometric distortion on crack propagation mode were compared. Impression of inclusions to energy release and crack path were also discussed.3) A new formulation of displace correlation method for the calculation of stress intensity factor that appropriate for extended finite element method was reported. Misconvergence of classical formulation was discussed in this thesis. Accordingly, rules for parameter select of new formulation was considered. The correction of this method was verified by three Numerical examples.4) A spectral analysis system for rock acoustic emission signals in parallel version and a characteristic analysis code for transform energy at rock surface were performed using Matlab. A code for the calculation of stress intensity factor was finished using C++ under Linux. All these programs have been used in the study of fracturing process of both intact and cracked rocks in this thesis.