Damage Constitutive Model Based on Energy Dissipation for Frozen Sandstone Under Triaxial Compression Revealed by X-Ray Tomography

Abstract

A series of triaxial compression tests, with real-time computed tomography (CT) scanning performed in the loading process, were conducted on frozen sandstones at confining pressures of 0, 1, 2, and 3 MPa at different temperatures of −2, −6, −10, and 20 °C, respectively. The experimental results indicate that the strength of frozen sandstone increases with a decrease in temperature. The strength of frozen sandstone increases with an increase in the confining pressure at freezing temperatures. In the loading process, the evolution law of the CT value of the whole sandstone is explored, and three-dimensional reconstruction of CT images, which denote postfailure models of frozen sandstone, is also performed. According to energy dissipation theory, an isotropic damage variable is introduced. Based on the CT value of the whole sandstone, the concept of the compaction coefficient K, which describes the compaction degree, is proposed to modify the damage model obtained by Lemaitre’s strain equivalence hypothesis. The validity of the model is verified by comparing its computed results with the experimental results obtained from triaxial compression tests. The results indicated that the modified damage model can adequately predict the stress-strain relationship of the frozen sandstone.