砂土液化大变形本构模型的三维化及其数值实现

Multiaxial Formulation and Numerical Implementation of a Constitutive Model for the Evaluation of Large Liquefaction-induced Deformation

摘要:

基于砂土液化大变形机理和适用于二维条件的边界面弹塑性本构模型,发展了符合三维应力空间中边界面和剪胀面上的应力映射规则,建立了三维应力空间中砂土液化大变形本构模型。针对模型特点采用半显式的Cutting Plane算法进行应力积分,并采用Pegasus求根算法根据映射规则计算边界面上的应力映射点,在OpenSees开源有限元平台上实现了三维模型的数值化。结合完全耦合的u-p格式有限元单元,对饱和砂土不排水循环扭剪试验进行了模拟,并进行了一个真三维倾斜地基的动力反应分析。计算结果表明模型和所采用的数值算法具有很好的模拟和分析三维条件下砂土液化后大变形的能力。

Abstract:

Based on the physics of large post-liquefaction deformation of sand and the related elastic-plastic constitutive model suited for two dimensional stress space,mapping rules for plasticity and dilatancy are formulated in three dimensional stress space,and the three dimensional model for the analysis of post-liquefaction deformation of sand is established.According to the features of the model,for the model＇s numerical implementation into the open-source finite element platform OpenSees,the semi-explicit Cutting Plane algorithm is used as the stress integration scheme,and the Pegasus algorithm is used to locate the stress projection on the bounding surface.Combined with coupled u-p elements,simulations on an undrained cyclic torsional shear test is conducted,and a three dimensional site response analysis is also performed,the simulation and analysis exhibite the model＇s great capabilities in simulating small to large deformation in the pre-to post-liquefaction regime of sand.