Mechanical Damage Evolution and a Statistical Damage Model for Frozen Sandstone

Negative temperature has an important influence on rock deformation and failure process. In a negative temperature environment, the pore water in rock partially turns into ice lenses. These changes in rock microstructure and components cause the frozen rock to exhibit temperature-related mechanical behavior. To disclose the mechanical damage process and failure mechanism of rock at different negative temperatures, we carried out acoustic emission (AE) tests on frozen sandstone. Results reveal that the cumulative AE count increases exponentially with increasing load, and the AE count mainly occurs in the yield and failure stages. According to the number and density of the AE count rate, the deformation process of frozen sandstone can be divided into four stages: compaction stage, elastic stage, yield stage, and failure stage. A sharp increase in the AE count rate implies that the rock deformation enters an unstable crack propagation section and macroscopic failure will occur. In addition, assuming that the microelement strength of rock obeys the Weibull distribution and the microelement failure conforms to the Drucker-Prager criterion, a constitutive model considering the negative temperature is proposed. A comparison between the experimental curve and the model curve shows that the model can accurately reflect the deformation process of frozen sandstone. This study is expected to improve the understanding of the damage mechanism and failure progress of frozen rock, and the constitutive model can provide a basis for calculating the deformation of frozen rock.