The failure of geomaterials has been well recognized as a process of crack evolution due to heterogeneity. However, the influence of confining stresses on the progressive failure process has still not been fully understood. In this study, a series of numerical simulations were conducted to study the confinement effects after being calibrated by the existing experimental observations. A Gaussian distribution function and a plastic strain-dependent strength model were adopted to depict the heterogeneity and the variable mechanical parameters of the materials, respectively. The results reveal that the tensile cracks are dominant for experiments under low confining stresses, while shear cracks become more dominant as the confinement increases. The total acoustic emission (AE) events demonstrates a “U" shape, i.e. decrease firstly, and then keep nearly invariant, subquentently increase as confining stress increases. These investigations indicate that the dominant effects of confining stress on cracking mechanisms are constraint on tensile cracks under low confining stresses and promotion for shear damages under high confining stresses. The results of AE events intensity disclose that macro failure always occurs in the post-peak domain. The confining stress can advance the macro failure occurrence from the post-failure domain towards the pre-peak stress domain, and increase the uniformity of damages occurred in materials. The fitting analysis shows that the relation of crack initiation stresses to confining stresses can be well represented by a nonlinear equation. This study can improve our understanding of the failure features of geomaterials resulting from stress state changes in engineering.