考虑黏聚效应的黏土应力路径本构模型

Complex Stress Paths Constitutive Model for Clay Considering the Effect of Cohesion

为了合理描述平均主应力增大或减小时黏土的弹塑性变形,尤其对最小主应力小于零时加载路径下土的弹塑性变形问题,利用摩擦块模型揭示土的摩擦强度和黏聚强度机理,给出土的抗剪强度公式.结合土的黏聚强度特性,将子午面划分为φ硬化区和c硬化区.在φ硬化区,将超固结状态对塑性变形的影响考虑进应力路径本构模型中,从而得到塑性变形的计算方法;在c硬化区,利用双曲线关系来描述黏聚力与剪应变的关系,结合剪胀方程确定塑性体应变,建立考虑黏聚效应的黏土应力路径本构模型.该模型仅有6个材料参数,且各参数的物理意义明确.通过试验结果对模型的验证表明,建立的本构模型能合理描述复杂应力条件,尤其是拉伸荷载作用下土的应力应变关系.

The existing constitutive model considering the tensile properties of clay cannot reasonably reflect the elastoplastic deformation of clay when the average principal stress increases or decreases,especially the elastoplastic deformation of the soil under the loading path when the minimum principal stress is less than zero. A new constitutive model need to be established to solve the above problem. The mechanical mechanism of cohesive strength and friction strength on soils was revealed by the friction block model. Then an expression of shear strength for soils was given. Combining the features of cohensive strength,c hardening area and φ hardening area were denoted in the meridian plane. In φ hardening area,the influence of overconsolidated state was taken into the complex stress paths constitutive model and then the plastic strain was determined. In c hardening area,the realtion between the cohensive stress and the deviatoric strain was fitted by a hyperbolic curve,then the volumetric strain increment was determined through the dilatancy equation. Based on the above view,a complex stress paths constitutive model for clay considering the effect of cohesion was built. The established model has only 6 material parametes and all of them have clear physical meanings. Comparisons between model predictions and experimental results indicate that the established model can reasonably describe the stress strain relationship of soils under tensile condition.