Meso-structure based numerical simulations of deformation and failure of granite: Thermal-mechanical coupling

Scanning electron microscopy(SEM) was used to obtain non-homogeneous digital images of rocks.The corresponding element mass centroid method has been presented to establish three-dimensional finite element model of rock based on SEM images in this paper.This method considers existing defects and approximates a truly non-homogeneous micro-structure characteristic of geo materials.Simulation of thermal-mechanical coupling on thermal cracking and failure in Beishan granite has been done.Thermal cracking in the granite is theoretically estimated to occur at 82 ℃,in good agreement with our recent experimental estimate of 68 to 88 ℃.Inter-granular thermal cracking is the main cracking mechanism at low temperatures.In this case cracks propagate along mineral grain boundaries.At high temperatures the cracking mechanism is a trans-granular coupled with an inter-granular mechanism.Deformation changes from brittle,at low temperatures,to ductile at high temperatures.Crack distributions at final failure change from that typical of low temperature,a load failure,to those typical of high temperature,namely thermal failure.Numerical predictions are higher than the experimental load at failure when working at low temperatures.However,the numerical predictions and experimental results are in good agreement at higher temperatures.