Shear creep characteristics of red sandstone after freeze-thaw with different water contents

According to the deterioration characteristics and long-term stability of rock mass in high altitude under the action of freeze-thaw and in water-saturated state, the nuclear magnetic resonance (NMR) technique is used to test the red sandstone samples subjected to freeze-thaw cycles under different water contents, and the shear creep experiments are conducted. Based on the experimental phenomena, the effects of freeze-thaw cycles and water content on the microstructure and creep characteristics of red sandstone are analyzed, and a reasonable creep model is proposed. The results show that the microstructure of wet red sandstone evolves from the main increase of small-size pore to the mutual increase of small-size pore and mesopore with the increasing freeze-thaw cycles, while the mesopore and macropore propagate mainly inside the saturated red sandstone. With the increase of water content, the creep strain of red sandstone generally increases, while the long-term strength and long-term reduction coefficient decrease significantly, the accelerated creep characteristics of red sandstone appear more easily before rock failure, and the macroscopic modes become more fragmented after rock failure. Considering the effects of freeze-thaw damage and time-dependent damage, a new shear creep model for red sandstone subjected to freeze-thaw cycles is established. The parameters of the model are identified by applying the 1stOpt mathematical analysis software, and the correctness and rationality of the model are verified. The research results have reference value for the prevention and evaluation of rock disasters in cold regions.