Based on stress dropping model, an elastoplastic-brittle model was established by using a softening threshold value to model the features of the geotechnical materials. According to the Mohr-Coulomb criterion, the radius of the rupture and plastic zone, the displacement and stress expressions of surrounding rock were obtained with the consideration of the strain-softening and dilatancy of geotechnical materials. Furthermore, the model was verified by case study and the influence of strain-softening, dilatancy and elastic modulus deterioration on calculation result were presented.