An Improved Statistical Damage Constitutive Model for Rock Considering the Temperature Effect

Abstract

Thermal–mechanical damage is an important feature of natural rock containing internal defects (microcracks and microvoids). However, this damage has not been studied thoroughly. This study improved a statistical damage constitutive model for heat-treated rock subject to external load by assuming the strengths of micro-elements following a Weibull distribution. First, the statistical damage constitutive model at room temperature was developed based on continuum damage mechanics. Then, a modified coefficient for thermal damage was introduced. The damage evolution equation of rock samples was derived at different temperatures. Third, the model parameters were determined with the feature points on the stress–strain curve. Finally, the model was verified against measured data available in literature and parameter analysis was conducted. It is found that the prediction results of the improved model are in good agreement with the measured data, whose parameters are few and have definite physical meanings. The thermal damage of rock increases with the increase of temperature. The curve of total damage evolution is in the “S” shape under the thermal–mechanical combining action. At a constant confining pressure, the slope of the ascending segment in the middle of the damage evolution curve increases with the decrease of temperature. At the same temperature, confining pressure considerably affects the slope of middle segment of the damage evolution curve and weakens the thermal damage effect.