Experimental study on triaxial creep behavior of red sandstone under different pore pressures based on ultrasonic measurement

Creep behavior of red sandstone under different pore pressures with a high temperature and confining pressure condition is studied in this paper. Ultrasonic detection method is used to monitor the variation of S wave in the creep test. The attenuation coefficient and S-wave velocity in the creep process are analyzed. Fast Fourier transform is used to analyze the variation of amplitude in peak frequency and four main frequencies. The experimental results show that the creep deformation increases with increasing pore pressure for a given deviatoric stress, and the S-wave velocity and attenuation coefficient decrease with increasing pore pressure. The relationship between creep strain and damage of the sample is established. It is found that the increase of pore pressure accelerates the increased rate of sample damage. Frequency spectrum analysis shows that the generation and development rate of microcracks increases with increasing pore pressure. The research can provide a theoretical basis for mining of deep mineral resources and the structural stability analysis of deep underground engineering.