3-D LIQUEFACTION ANALYSIS CONSIDERING A LARGE DEFORMATION

考虑大变形的 3-D 液化分析

基本信息

批准号：
11694147
负责人：
OKA Fusao
金额：
$ 4.03万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

From the field observation of liquefaction and ground deformation due to Hyogoken Nambu Earthquake, it was found that that larger deformation occurred near the quay wall. The observed data show that liquefaction analysismethod that can describe large deformation is necessary. In the present study, we have proposed a liquefaction analysis method using an elasto-viscoplastic constitutive model based on finite deformation theory. From the application of the proposed model to the behaviors of quay wall and the foundation beneath embankment it was found that the liquefaction analysis method based on the finite deformation theory is well applicable to predict the liquefaction induced deformation.So far u-p(displacement-pore water pressure) formulation has been used in the 3D- finite deformation analysis method. In the present study we introduced u-w-p(displacement-relative acceleration-pore water pressure) formulation to develop a new method. By considering a relative acceleration between so … More il and pore fluid, we can analyze more accurately liquefaction problems for the problem with higher frequency wave and higher permeability coefficient.In order to study soil-structure interaction problems in the liquefiable ground, the process of the damage to the pile foundation adjacent to quay wall on the reclaimed land during the 1995 Hyogoken Nanbu earthquake wasnumerically analyzed. Two dimensional and three dimensional effective stress analyses using a soil-pile-building model was conducted on a damaged building. The five stories building tilted toward to sea due to serious damage to the pile foundations. Sand boils and large lateral spreading due to liquefaction were observed around the building. We used an effective stress code based on two phase mixture formulation, which was incorporated with a cyclic elasto-plastic model for sand and a cyclic elasto-viscoplastic model for clay. 2-D and 3-D simulation quantitatively reproduced the observed deformation mode of damaged piles. The simulated results show that the inertia force of the building caused the damage at the top of piles and the large horizontal deformation of thereclaimed soil caused the damage at the piles in the reclaimed ground layer before liquefaction of the reclaimed layer.At present the ground surface and near-surface motions are obtained using several numerical methods whichare based on various assumptions as to the material properties and response. The necessary soil properties required for such numerical predictions are usually obtained from simple methods such as SPT and CPT at the site although soil laboratory test such as cyclic triaxial tests are done sometimes. Better soil testing methods, improvements in in-place in-situ testing of soil properties are required. At University California Davis, many students have worked on the development of the non-destructive electrical method to quantify the soil structure and to establish relationship to engineering properties and behavior. Without an accurate representation of in-situ properties which are representative of the site, it is impossible to evaluate prototype behavior. The in-situ state and constitutive model constants are necessary input parameters for numerical procedures. Our vision is to obtain initial state parameters and constitutive constants representative of site and to verify the numericalprocedures using the results of instrumented site. This approach will enable us to perform Model Base Simulation reliably to predict before the event the response ofsites to earthquakes. From the case studies of Port Island and El Centre, it is found the simulation is possible by this non-destructive characterization methods.A non-linear finite element model is used to account for soil column effects on strong motion. A three-dimensional bounding surface plasticity model with a vanishing elastic region, appropriate for non-liquefiable soils, is formulated to accommodate the effects of plastic deformation right at the onset of loading. The elasto-plastic constitutive model is cast within the framework of a finite element soil column model, and is used to re-analyze the downhole motion recorded by an array at a large scale sismic test(LSST) site in Lotung in Taiwan during the Lotung earthquake of 20 May 1986 as well as the ground motion recorded at Gilory 2 reference site during the Loma Prieta earthquake of 17 October 1989. Results of the analysis show maximum permanent shearing strains experienced by the soil column in the order of 0.15 per cent for the Lotung event and 0.8 per cent for the Loma Prieta earthquake, which correspond to modulus reduction factors of about 30 and 10 per cent respectively, implying strong non-linear response of the soil deposit at the two sites. Less

通过对兵库县南部地震造成的液化和地面变形的现场观测，发现码头壁附近发生了较大的变形。观测数据表明，在本研究中需要能够描述大变形的液化分析方法。提出了一种基于有限变形理论的弹粘塑性本构模型的液化分析方法。通过对路堤下墙体和地基的研究发现，基于有限变形理论的液化分析方法非常适用于预测液化引起的变形。目前，u-p（位移-孔隙水压力）公式已用于三维有限变形在本研究中，我们引入了 u-w-p（位移-相对加速度-孔隙水压力）公式来开发一种新方法，通过考虑 so … More il 和之间的相对加速度。为了研究可液化地基中的土-结构相互作用问题，对邻岸桩基的破坏过程进行了研究。使用土桩建筑模型对 1995 年兵库县南部地震期间开垦的土地进行了数值分析，对一座向倾斜的五层建筑进行了分析。由于桩基严重损坏，建筑物周围出现了沙沸腾和液化引起的大面积横向扩散，我们使用了基于两相混合物公式的有效应力代码，该代码与循环弹塑性模型相结合。沙子的循环弹粘塑性模型定量再现了受损桩的观察变形模式，模拟结果表明建筑物的惯性力导致了损坏。填海土层液化前，由于桩顶的振动和填海土的较大水平变形，造成了填海地层中桩的破坏。尽管有时会进行更好的土壤测试，但对材料特性和响应的各种假设通常是通过现场的 SPT 和 CPT 等简单方法获得的。在加州大学戴维斯分校，许多学生致力于开发无损电学方法来量化土壤结构并建立与工程特性和行为的关系。如果没有代表现场的原位属性的准确表示，就不可能评估原位状态和本构模型常数是数值程序的必要输入参数。和代表的本构常数现场并使用仪器现场的结果验证数值程序，这种方法将使我们能够可靠地进行模型基础模拟，以在事件发生前预测现场对地震的反应。发现通过这种非破坏性表征方法可以进行模拟。非线性有限元模型用于解释土柱对强运动的影响，具有消失弹性区域的三维边界表面塑性模型，适用于。弹塑性本构模型是在有限元土柱模型的框架内铸造的，用于重新分析井下运动。 1986 年 5 月 20 日罗东地震期间，台湾罗东大型地震试验场 (LSST) 阵列记录的地面运动，以及 Gilory 2 参考地点记录的地面运动1989 年 10 月 17 日洛马普列塔地震。分析结果显示，Lotung 事件中土柱所经历的最大永久剪切应变约为 0.15%，洛马普列塔地震中为 0.8%，对应的模量折减系数为分别约为 30% 和 10%，这意味着两个地点的土壤沉积物具有强烈的非线性响应。