Modeling Lateral Flow and Liquefaction-Induced Ground Movement

模拟横向流和液化引起的地面运动

• 批准号: 9613906
• 负责人: Ronaldo Borja
• 金额: $ 23.86万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1997
• 资助国家: 美国
• 起止时间: 1997-10-01 至 2002-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9613906&HistoricalAwards=false
• 关键词: Modeling; Lateral; Flow; Liquefaction; Induced

ABSTRACT: CMS-9613906, Ronaldo Borja, Stanford U. The objective of this research program is to develop a mathematical model for analyzing the problem of lateral flow and liquefaction-induced large ground movement during and following an earthquake. The model is based on a two-phase mixture theory, and involves the development of a finite element code capable of representing the behavior of saturated soils prior to and during liquefaction. Prior to liquefaction, the soil is represented by an already- validated effective-stress phenomenological constitutive model based on an elastoplastic formulation with nonlinear kinematic hardening. During liquefaction, the liquefied soil is represented by a total-stress viscoplastic model whose viscosity is determined from extensive numerical simulations with random suspensions of spheres. The two constitutive models are developed within the framework of a finite deformation theory based on multiplicative plasticity. The resulting finite element model is used to study the mechanism of liquefaction-related large ground displacement, including the lateral flow and prediction of the free ground surface resulting from such flow. Two case studies are considered in order to validate the model. The first involves a loose saturated sample of Toyoura sand submerged in water and sloped inside a test subjected to dynamic excitation, causing the soil to liquefy and flow like a viscous fluid. The second study involves a re-analysis of the nonlinear ground response recorded by a downhole array in Port Island (reclaimed ground near downtown Kobe City, Japan) during the earthquake of January 17, 1995, focusing on the impact of this changed soil behavior during liquefaction. The ground response is simulated assuming a condition of vertically propagating seismic waves, with a full kinematical coupling of the three components of motion.

摘要：CMS-9613906，Ronaldo Borja，斯坦福大学。该研究项目的目标是开发一个数学模型，用于分析地震期间和地震后的侧流和液化引起的大地面运动问题。该模型基于两相混合理论，并涉及有限元代码的开发，该代码能够表示饱和土壤在液化之前和液化过程中的行为。在液化之前，土壤由已验证的有效应力唯象本构模型表示，该模型基于具有非线性运动硬化的弹塑性公式。在液化过程中，液化土壤由总应力粘塑性模型表示，其粘度是通过球体随机悬浮的广泛数值模拟确定的。这两个本构模型是在基于乘法塑性的有限变形理论框架内开发的。由此产生的有限元模型用于研究与液化相关的大地面位移的机制，包括侧向流动和由这种流动产生的自由地面的预测。 为了验证模型，考虑了两个案例研究。第一个是将丰浦沙的松散饱和样品浸入水中并在动态激励下倾斜进行测试，导致土壤液化并像粘性流体一样流动。第二项研究涉及对 1995 年 1 月 17 日地震期间波特岛（日本神户市市中心附近的填海土地）井下阵列记录的非线性地面响应的重新分析，重点关注液化过程中土壤行为变化的影响。假设地震波垂直传播的条件下模拟地面响应，并具有三个运动分量的完全运动学耦合。