An energy-based damage model for red-bed sandstones subjected to drying–wetting cycles

A series of experiments is performed to determine the damage behaviour and energy evolution of red-bed sandstones subjected to drying–wetting (D–W) cycles. The experimental results reveal that accompanied by the strain increases, the input energy density gradually increases, the elastic energy density increases slowly first, then increases linearly, and reaches the maximum value at the peak strength, then gradually decreases. The dissipated energy density continuously increases and then maintains a steady-state level before it finally increases rapidly. Furthermore, with the increase in the number of D–W cycles, all three energy densities of specimens present a linear downward trend. According to the damage variable defined by the energy principle, the damage evolution models of the uniaxial compression strength (UCS) and peak strain of the D–W specimen are established, which can well characterise the evolution of the UCS and peak strain of rocks after different numbers of D–W cycles.