基于损伤扰动的土体本构关系研究

A soil constitutive model based on disturbed state concept

邓肯E-B模型无法描述软化土体的应力应变关系以及土体的剪胀效应;采用抛物线型体应变曲线的南水模型破坏时的剪胀率趋于定值,与实际土体不符。但南水模型适合描述应力应变峰值点前或最大剪胀率前土体的本构关系,邓肯模型适合描述的应变范围更小。因此,若要进行土工结构渐进破坏的分析计算,则需要建立一个适合于描述直至破坏的更大应变范围的土体本构关系。采用损伤扰动概念,将变形过程中的土体视为“相对完整”的未损伤土体和“完全调整”扰动土体的混合体,其应力应变关系可根据损伤扰动程度,由各自的应力应变关系组合确定。并根据试验提出了确定损伤扰动函数的计算公式。对体应变曲线,则采用抛物线加双曲线的形式加以描述。

Duncan-Zhang model is not suitable to describe strain softening and volume strain from compression to dilatancy. A parabola is proposed to describe volume strain curve in Nan-Shui model, but the stress-dilatancy is a constant during failure, which has remarkable inaccuracy compared with observed response. Nan-Shui model can describe stress-axial strain-volume strain relationships only before failure or maximum dilatancy, but then Duncan model can describe the range of strain that is much smaller. So it＇s necessary to establish a constitutive model to describe suitably the stress-axial strain-volume strain relationships in a large range of strain for the progressive failure analysis in geotechnical engineering. In this paper, a constitutive model based on the disturbed state concept is proposed to characterize the behavior of rockfill materials. The disturbed state concept （DSC） is based on the idea that a deforming material element can be treated as a mix of two constituent parts in the relative intact （RI） and fully adjusted （FA） state, referred as reference states. The disturbed function, D, is defined to express the observed response in terms of the responses under two reference states, and expression is suggested to determine D based on the analysis of experimental data. The volume change characteristics are described by parabola and hyperbolic model.