Rock joints always have a smaller strength,and it plays an important influence on the overall strength of rock mass.The mechanical behavior of rock joints is mainly governed by the surface topography,normal stress,and failure degree.In this study,a series of direct shear tests for four different rough rock joints under five normal stresses was carried out.The shear and normal stiffnesses were first determined,and the shear shrinkage effect was represented by a shear-normal coupling coefficient.Assuming that the strength of the joint is composed of frictional and cohesive parts,the evolutions of cohesion,friction angle with joint roughness coefficient(JRC),and plastic shear displacement are obtained.The dilatancy behavior is described by the dilation angle,which is considered a function of JRC,plastic shear displacement,and normal stress.A cohesive-frictional elastoplastic constitutive model is hence proposed.The theoretical curves under constant normal stress conditions of the proposed model are in good agreement with the experimental results.The shear behaviors under constant normal stiffness and constant normal displacement conditions can be predicted using the new constitutive model.
Elastoplastic constitutive equation of glass is proposed in this article,which is formulated based on the subloading surface model which possesses the various distinguished advantages for the description of the plastic deformation,i.e.,the smooth elastic-plastic transition,the continuous variation of the tangent stiff-ness modulus tensor,the automatic controlling function to attract the stress to the yield surface during the plastic deformation process,etc.It would be the firstly proposed three-dimensional elastoplastic con-stitutive equation of glass,which is furnished with the basic properties,e.g.the ellipsoidal yield surface with the dependence of the third deviatoric stress invariant,undergoing the flattering to the deviatoric direction with the plastic compression and the plastic volumetric hardening with the associated flow rule.The validity of the description of the deformation behavior of glass will be verified by comparisons with some test data for silica glass specimens.
