Abstract

The dilatancy equation plays a significant role in establishing an elastoplastic constitutive model for soils. The rockfills will show strain-softening or strain-hardening behaviour according to the testing confining pressure and/or initial void ratio. Therefore, a new dilatancy equation for rockfill materials incorporating strain hardening and strain softening was studied. A series of triaxial compression tests on rockfills were carried out to investigate the material constants and applicability of the proposed dilatancy equation (PDE). The material constants M_c, β, a and c of the PDE were found to be independent of the initial void ratio and confining pressure. At the dilatancy point and critical state, the observed dilatancy of soils is zero, while the PDE was proved to fully meet these conditions. In addition, the PDE can well depict the trends of the observed dilatancy behaviour during the whole shearing, even though the dilatancy behaviour from the peak point to the critical state is difficult to be simulated for many existing equations. By comparing with three widely used dilatancy equations, the simulated strain-volume curves by a constitutive model using the PDE are significantly acceptable, no matter whether the rockfill is strain hardening or strain softening.

摘要

剪胀方程在建立土的弹塑性本构模型中起着重要作用。堆石将根据测试围压和/或初始空隙率表现出应变软化或应变硬化行为。因此，研究了一种新的结合应变硬化和应变软化的堆石材料剪胀方程。对堆石进行了一系列三轴压缩试验，以研究所提出的剪胀方程（PDE）的材料常数和适用性。材料常数M _c , β , a和c发现 PDE 与初始空隙率和围压无关。在剪胀点和临界状态，观察到的土体剪胀为零，而 PDE 被证明完全满足这些条件。此外，PDE 可以很好地描绘在整个剪切过程中观察到的剪胀行为的趋势，尽管对于许多现有方程来说，从峰值点到临界状态的剪胀行为很难模拟。通过与三个广泛使用的剪胀方程进行比较，无论堆石是应变硬化还是应变软化，使用偏微分方程的本构模型模拟的应变-体积曲线都具有明显的可接受性。