Strength Characteristics and Failure Mechanisms of Silty Mudstone with Preexisting Cracks

Abstract

Understanding the cracking behaviors and failure mechanisms of soft rocks with existing cracks is crucial in designing rock engineering structures. Hence, we studied the influence of crack parameters, including crack inclination angle, crack number, and crack form, on the strength characteristics and cracking behaviors of silty mudstone using uniaxial compression tests and numerical simulation. The mechanisms of crack initiation, propagation, and coalescence in silty mudstone with preexisting cracks are discussed in this paper. The results showed that the stress-strain curves of silty mudstone with preexisting cracks can be divided into three stages: the load compaction, crack extension, and postpeak damage stages. Preexisting cracks had a weakening effect on the mechanical properties of silty mudstone, and the main order of influence of the various factors was crack inclination angle, crack number, and crack form. The failure mode of silty mudstone with preexisting vertical cracks was mainly composite tensile-shear failure; the failure modes of rocks with single and double cracks were tensile failure, shear failure, and composite tensile-shear failure. The damage process of silty mudstone with preexisting cracks under stress was as follows. The propagation and coalescence of cracks caused cracking of weak surfaces within the rock mass. The cracks propagated along the axial stress direction or preexisting crack direction under different stress states to form macroscopic crack surfaces, which ultimately led to rock mass failure. In addition, the strength characteristics and cracking behaviors of silty mudstone simulated using FLAC3D version 6.0 were consistent with the experimental results.