卸荷条件下岩石变形特征及本构模型研究

基于岩石试件的卸荷试验，研究了卸荷条件下岩石的应力—应变全过程曲线和破裂特征，研究表明：卸荷过程中岩石向卸荷方向回弹变形强烈、扩容显著、脆性破坏特征明显；卸荷条件下岩石破坏具有较强的张性破裂特征，各种级别的张裂隙发育，其剪性破裂面追随张拉裂隙发展。基于试验认识，将卸荷条件下岩石的本构模型分为4段：弹性段、卸荷屈服段、峰后脆性段及残余理想塑性段；通过体积应变εv将Griffith和Mohr Coulomb屈服准则结合起来，建立卸荷条件下岩石的屈服准则，并在应变空间建立相应的卸荷非线性屈服段本构方程；运用应变软化理论，建立卸荷岩石峰后脆性段本构方程。

Study on Deformation Characteristics and Constitutive Model of Rock on the Condition of Unloading

Based on unloading tests of rock samples, the fracture features and complete stress strain curves of rocks on the condition of unloading are studied, The researches show that: the characteristics of intense rebound deformation, distinct dilatancy and brittleness failure of rocks are present in process of unloading; The fracture is characterized by strong tensile one, all kinds of tensile cracks are developed, the shear fractures expand following tensile cracks on the condition of unloading. Based on acquirements of the experimentation, the constitutive model is divided into four parts on the condition of unloading: elasticity, unloading nonlinear yield, brittleness after peak value and ideally remnants plasticity; The Griffith and Mohr Coulomb yield rules are combined by volume strain, the yield rule of rock is established on the condition of unloading and the relevant nonlinear constitutive equation in strain space; The constitutive equation of brittleness part after peak value is established based on strain softening theory.