Research on Microscopic Fracture Morphology and Damage Constitutive Model of Red Sandstone Under Seepage Pressure

Abstract

To explore the influence of seepage pressure on rock failure, the high-pressure triaxial automatic system was used to carry out a triaxial compression test under the condition of seepage pressure on rock samples, and then, the fracture surface of the rock was tested by scanning electron microscope (SEM). The fractal dimension features of rock fractures under different seepage pressures were analyzed by the image segmentation principle and optimal threshold method, and a segmental statistical damage constitutive model considering seepage pressure was established based on the Weibull distribution theory. The results show that (1) the SEM image after binarization has better fractal characteristics, which can represent the roughness of the fracture surface; (2) the fractal dimension ranges from 1.818 to 1.950, which shows a variation law of decreasing with the increase in the seepage pressure; and (3) a piecewise damage constitutive model considering the seepage pressure is proposed, and it provides a more precise prediction for the stress–strain curve characteristics before the peak stress. The research results are beneficial and useful for the analysis of the damage evolution characteristics of engineering rock masses, as well as for the monitoring and prediction of engineering geological hazards.