Along with the initial elastic and strength properties, the deformation and fracture process in rocks is significantly affected by their degradation during loading. In the present work, we supplement the DruckerPrager model of the medium by the equation for cohesion degradation. Growing irreversible plastic deformation weakens the rock. Upon complete failure, the rock behaves like dry sand, which resists only compressive and shear loads. The model gives results that are in good agreement with field observations and physical modeling predictions. A possibility is shown of forming positive structures without setting additional boundary conditions of transverse compression for rocks like clays, sands, and soft sandstone.