COUPLED THERMO-HYDRO-MECHANICAL FRACTOGRAPHIC ANALYSIS OF BRITTLE ROCK
LI Peng1,RAO Qiuhua1,MA Wenbo1,SU Shulan1,2,MA Chunde3
(1. School of Civil Engineering,Central South University,Changsha,Hunan 410075,China;2. School of Civil Engineering and Mechanics,Central South University of Forestry and Technology,Changsha,Hunan 410004,China;3. Center for Advanced Study, Central South University,Changsha,Hunan 410083,China)
Abstract:Coupled thermo-hydro-mechanical(THM) fracturing tests and scanning electron microscope(SEM) tests were performed to study the macroscopic and microscopic characteristics of coupled THM fracturing of brittle rocks. Finite element method and a new fracture criterion on the ratios of stress intensity factor were applied to predict the fracturing mode under THM coupled condition. The red sandstone specimens are found to have three types of modes of fracturing macroscopically with the corresponding fracturing features microscopically under different THM coupling conditions. Transverse fracturing occurs macroscopically and transgranular shear fractures occur microscopically for the specimens under low temperature,low hydraulic pressure and high confining pressure. Longitudinal fracturing occurs macroscopically and intergranular tensile fractures occur microscopically for the specimens under high temperature,high hydraulic pressure and low confining pressure. Cross directional(transverse and longitudinal) fracturing occurs macroscopically and mixed fractures(transgranular and intergranular) occur in the specimens under medium temperature,medium hydraulic pressure and medium confining pressure. The predicted modes of fracturing under THM coupling with the finite element method and the new fracture criterion of ratios of stress intensity factor are found to be in good agreements with that obtained with the fractographic analysis.
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