Study on Physical Properties and Energy Evolution of Natural Gypsum Rock under Freeze-thaw Cycles

The physical and mechanical properties, microstructure deterioration characteristics and damage mechanism of natural gypsum rock under freeze-thaw cycles were studied by using a self-developed programmed freeze-thaw experimental device, results showed: Compared with that before freeze-thaw, with the increase of freeze-thaw cycles, the surface dissolution of gypsum rock samples becomes more obvious, the longitudinal wave velocity decreases linearly, the uniaxial compressive strength and elastic modulus decrease exponentially, the compaction stage of stress-strain curve is significantly prolonged, and the plasticity of post-peak failure process is enhanced. With the increase of axial strain, the total input energy curve rises at a faster rate, and the elastic energy curve also rises, but the rising rate slows down significantly after the freeze-thaw cycle, and the dissipation energy curve gradually evolves from a smooth rise to an ' S ' type. The research results have reference significance for the construction scheme design and frost damage prevention of gypsum surrounding rock tunnels in cold regions.