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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

从小谷南部地震引起的液化和地面变形的现场观测中发现，码头附近发生较大的变形。观测数据表明，能够描述大变形的液化分析方法是必要的。在本研究中，我们提出了一种基于有限变形理论的弹粘塑性本构模型液化分析方法。将该模型应用于码头墙和路堤下基础的变形分析，结果表明，基于有限变形理论的液化分析方法可以很好地预测液化引起的变形。迄今为止，三维有限变形分析方法主要采用位移-孔隙水压力公式。在本研究中，我们引入了u-w-p（驱替-相对加速度-孔隙水压力）公式，建立了一种新的方法。考虑孔隙流体与原油的相对加速度，可以更准确地分析高频波和高渗透系数问题的液化问题。为了研究可液化地基中的土-结构相互作用问题，对1995年小谷县南部地震中填海造地码头附近桩基的破坏过程进行了数值分析。采用土-桩-建筑模型对某受损建筑进行了二维和三维有效应力分析。由于桩基严重受损，这座五层楼的建筑向大海倾斜。在建筑物周围观察到由于液化造成的砂沸腾和大面积横向扩散。我们采用了基于两相混合公式的有效应力代码，该代码结合了砂的循环弹塑性模型和粘土的循环弹粘塑性模型。二维和三维模拟定量再现了观测到的损伤桩变形模式。模拟结果表明，在填土层液化前，建筑物的惯性力引起桩顶的损伤，填土的大水平变形引起填土层内桩的损伤。目前，地表和近地表运动的数值计算方法是基于对材料性质和响应的各种假设。尽管有时也进行循环三轴试验等土壤实验室试验，但这种数值预测所需的必要土壤特性通常是通过现场SPT和CPT等简单方法获得的。需要更好的土壤测试方法，改进土壤特性的原位测试。在加州大学戴维斯分校，许多学生致力于开发非破坏性电方法来量化土壤结构，并建立与工程性质和行为的关系。如果没有一个准确的代表场地的原位特性的表示，就不可能评估原型的行为。原位状态和本构模型常数是数值计算过程中必要的输入参数。我们的目标是获得代表现场的初始状态参数和本构常数，并使用仪器化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，以便在地震发生前预测地震地点的反应。从港口岛和El Centre的案例研究中发现，采用这种非破坏性表征方法可以进行模拟。采用非线性有限元模型来考虑土柱对强运动的影响。建立了一个适用于非液化土的三维边界面塑性模型，该模型具有消失的弹性区域，以适应加载开始时塑性变形的影响。该弹塑性本构模型是在有限元土柱模型的框架内建立的，并用于重新分析1986年5月20日台湾洛东大尺度地震试验（LSST）现场阵列记录的井下运动和1989年10月17日洛马普里塔地震期间Gilory 2参考点记录的地面运动。分析结果表明，在Lotung地震和Loma Prieta地震中，土柱所经历的最大永久剪切应变分别为0.15%和0.8%，对应于模量折减因子分别约为30%和10%，这表明两个地点的土壤沉积物具有强烈的非线性响应。少