Abstract: The softening and dilatancy behaviour exhibited by the stresses on the surrounding rock of the roadway has a significant impact on the deformation and breaking of the roadway ring. In order to study the influence of softening and dilatancy characteristics on the stability of the rock surrounding the roadway. According to the softening characteristics of the rock mass,an ideal elastic softening model is established and the surrounding rock is divided into the elastic zone,the plastic softening zone and the fracture zone. Based on the Z-P criterion and the non-associative flow law,the elastic-plastic analytical solution for circular roadways with intermediate principal stresses is derived by considering the softening and dilatancy characteristics of the surrounding rock. The Z-P criterion is compared with the M-C and D-P criteria,the influence of softening modulus, dilatancy and other factors on the roadway surrounding rock is analysed. The results show that the Z-P criterion is well suited to the softening and dilatancy of the roadway. At an intermediate principal stress factor of 0. 4,the plastic zone of the surrounding rock is the smallest,the displacement of the surrounding rock is the smallest,and the stress in the plastic zone is the largest. The larger the softening modulus,the larger the radius of the fracture zone of the surrounding rock. The larger the shear expansion angle,the larger the displacement of the plastic zone and the larger the radius of the fracture zone. The stronger the support resistance,the smaller the plastic zone of the roadway,and increasing the support resistance can effectively control the deformation of the roadway surrounding rock.

Key words: Z-P criterion,softening,dilatancy,intermediate principal stress,elastic-plastic analysis