K_(0)超固结结构性黏土的本构模型

CONSTITUTIVE MODEL FOR K_(0) VERCONSOLIDATED STRUCTURE CLAY

K_(0)固结黏土在自然界广泛分布,其通常同时具有超固结性与天然结构性,而K_(0)超固结性又与K_(0)正常固结性质存在很大差异.为了有效的描述K_(0)超固结性质,在结构性模型基础上,做了如下3点改进,使得原模型拓展为同时考虑K_(0)超固结特性与天然结构性影响的本构模型.(1)引入相对应力比来描述屈服面,并引入初始各向异性转轴参量ξ来表达初始各向异性对屈服面在p-q空间的位置影响.(2)基于给定的屈服面方程,推导得到变相应力比参量,并将变相应力比引入到统一硬化参数中,利用统一硬化参数可以有效描述初始各向异性固结黏土在剪切加载下的剪缩与剪胀,应变硬化及软化现象.(3)引入反映结构性胶结强度性质的胶结参量pe,并给出pe随塑性偏应变的衰减演化方程,利用胶结参量可描述结构性黏土的剪胀特性.预测与试验结果对比表明,所提的K_(0)超固结结构性模型可有效描述K_(0)超固结黏土的刚度提高效应,黏土的包辛格效应,结构性黏土胶结强度的损失现象以及结构性黏土的应变软化现象.证明了所提模型的适用性以及合理性.

K_(0)consolidated clay is widely distributed in nature.It usually has both overconsolidation property and natural structural property,and it is a significant difference for the property of overconsolidation of K_(0)to the normal consolidation of K_(0)clay.In order to effectively describe the overconsolidation properties of K_(0)consolidated clay,three improvements were made on the basis of the natural structure consolidated model for clay,so that the original model can be extended to a constitutive model that consider both the properties of K_(0)overconsolidation clay and the effects of natural structures for natural clay.(1)The relative stress ratio is introduced into the yield surface equation to describe the yield property,and the initial anisotropic consolidation stress ratio parameterξis introduced into the yield surface equation to express the influence of the initial anisotropy on the position of the yield surface in p-q space.(2)Based on the given yield surface equation,the phase transformation stress ratio parameter was derived,and the phase transformation stress ratio was introduced into the unified hardening parameter.The unified hardening parameter can effectively describe both the initial anisotropic shearing behavior and the dilatancy behavior,strain hardening and softening phenomenon for initial anisotropic consolidated clay.(3)The cementation parameter p;,which reflects the structural cementation,is introduced into the yield surface equation and the decay evolution equation of p;with deviatoric plastic strain is given.The dilatancy properties of structural clay can be described by using the cementation parameter.The comparison between the prediction and the test results shows that the proposed K_(0)consolidation model can effectively describe the stiffness enhancement effect of K_(0)overconsolidated clay,the Bauschinger effect of clay,the cementation strength loss phenomenon and the strain softening phenomenon of structural clay.The applicability and rationality of the proposed model are proved.