基于小应变非线性弹性模型的基坑开挖三维数值模拟

Three-Dimensional Modeling of Deep Excavation Using Small-Strain Hypoelastic Model

小应变弹塑性模型-HSS模型广泛应用于软土基坑工程分析中,为便于简化计算,建立一种与HSS模型主要参数相对应的小应变非线性弹性本构模型是必要的。本文首先从Benz提出的小应变Overlay模型出发,建立一个综合考虑土体小应变范围内的模量衰减特性、模量的应力路径相关特性,大应变范围内的剪切与体变耦合特性,以及全应变范围内应力-应变关系的非线性、模量应力相关性的非线性弹性本构模型。然后,基于ABAQUS的子程序UMAT进行二次开发实现三维有限元数值模拟,平行使用基于本文模型的ABAQUS和基于HSS模型的Plaxis程序对均质土层基坑开挖算例以及台北TNEC基坑工程案例进行分析对比,验证了本文模型的有效性。

Hardening Soil Small(HSS)model has been widely employed in analyzing numerically deep excavation performance in soft clays,due to its capacity to account for the non-linear stiffness variations of soils at small strains.HSS,however,is formulated with the framework of elastoplasticity,thus may suffer from convergence and computational efficiency issues.The goal of this work is to propose a simple hypoelastic model that is equivalent to HSS and share similar material properties.Based on Benz’s Overlay model,the hypoelastic model incorporates key engineering behavior of soils,including the dependence of small-strain stiffness on strain magnitudes and recent stress histories,the volume-distortion coupling at large strains,and stress-dependent moduli and nonlinearity in the fullrange stress-strain relationship.The proposed model is implemented through the UMAT subroutine of ABAQUS.Comparisons between three-dimensional simulations using the hypoelastic model and HSS model,with reference to a synthetic excavation in homogenous soil stratum and Taipei TNEC deep excavation project,validate the proposed model.