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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.

Uncontrollable leakage has significant effects on the safety of fractured rock mass, and microbially induced carbonate precipitation (MICP) is an effective way to control the seepage. In this study, four sets of seepage experiments are conducted on transparent rock-like specimens containing MICP filled single cracks to investigate the effects of bacterial concentration, crack inclination angle, crack roughness, and crack opening on fracture permeability. The experimental results show that calcium carbonate precipitation is produced when Sporosarcina pasteurii and cementing fluid are injected into the cracks, which can seal the cracks and reduce the permeability of the cracks. Moreover, the calcium carbonate produced by Sporosarcina pasteurii increases with increasing bacterial concentration. Furthermore, the fracture permeability of the MICP filled crack increases first and then decreases with increasing inclination, roughness, and opening of cracks. The experimental results provide a better understanding of the influence of different construction conditions on fracture permeability when the MICP technology is applied in rock engineering.

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