Energy dissipation and damage evolution analyses for the dynamic compression failure process of red-sandstone after freeze-thaw cycles

Based on the Split Hopkinson Pressure Bar (SHPB) system, dynamic compressive tests were done on red-sandstone specimens, which were free from freeze-thaw (F-T) or suffered from 5, 10, 15, 25 F-T cycles. Stress-strain curves and energy evolution curves of specimens were analyzed as well as the dynamic mechanical properties and energy indexes. The results indicated that red-sandstone suffered a lot from the F-T weathering, with both the dynamic uniaxial compression strength and elastic modulus reduced with the adding-up of F-T cycles. Stress-strain curves of F-T weathered red-sandstone can be broadly divided into four stages, and the energy evolution characteristics of them differed from each other. Energy dissipation ratio was put forward to appraise the energy dissipation and damage accumulation degree during the four deformation stages, and the total input energy and dissipated energy were adopt to describe the F-T-mechanical coupling damage evolution properties during deformation and failure process of red-sandstone after freeze-thaw cycles and under impact loading. F-T influenced not only the initial damage values of red-sandstone, but also the damage evolution rules during the loading process. With the adding-up of F-T cycles, growth quantity of damage factor before the peak point reduced. Strain rate also affected the damage evolution rules clearly, and with the increase of strain rate, the damage factor grew more slowly.