Effects of Void Redistribution on Liquefaction Flow of Layered Soils

0070111 Kutter，布鲁斯L.液化后土壤抗剪性能的评估被广泛认为是国内和世界上许多大型修复工程的控制因素。 决定是否进行昂贵的地基加固工程，以减轻液化危害往往取决于高度不确定的估计后液化的土壤抗剪强度。 这些研究项目的目的是为了更好地了解不确定性的来源。一个可能的不确定性来源是缺乏程序来评估孔隙重新分布对液化后剪切强度的影响。 孔隙重新分布可能与地震引起的孔隙压力在渗透性和非渗透性土壤之间的界面附近的积累和颗粒混合有关。 提出了一个动态离心模型试验和实验室三轴试验的方案，与日本中央大学Kokusho教授提出的l-g振动台试验方案合作，研究这个问题。 将在加州大学戴维斯分校的9米离心机上进行的离心机试验将包括具有多层收缩渗透性的模型。日本中央大学的Kokusho教授观察到即使在陡峭的倾斜地面中，也会出现流动故障，并在不渗透层下形成水夹层。 水夹层，一种极端形式的空隙重新分布提出了严重的问题，典型的稳定性计算的有效性。 通过与Kokusho教授的合作，可以在一系列测试条件下对振动台和离心机测试进行比较，从而大大提高这项研究的效益。拟议的工作包括为研究生和本科生提供支持、培训和宝贵经验的资金。 加州大学戴维斯分校的梅萨，MORE和WIE计划已同意帮助招募多样化的本科职位申请者。 学生有机会设计，进行和分析大规模的实验，并会见来自美国和日本的知名专家将是一个非常宝贵的。这个项目是在NSF 98-36下的第三年比赛的支持下。“美日城市地震减灾合作研究。"

0070111Kutter, Bruce L.The assessment the post-liquefaction shear resistance behavior of soil is widely recognized as a controlling factor in many large remediation projects throughout the country and world. Decisions on whether to proceed with costly ground improvement projects to mitigate liquefaction hazards often hinge on highly uncertain estimations of post-liquefaction shear resistance of the soil. The objective of these research projects is to better understand the sources of uncertainty.One likely source of uncertainty is the lack of procedures to evaluate the effects of void redistribution on the post-liquefaction shear strength. Void redistribution may be associated with accumulation of earthquake induced pore pressures near interfaces between permeable and impermeable soil and by particle intermixing. A program of dynamic centrifuge modeling tests and laboratory triaxial tests are proposed, in collaboration with a proposed program of l-g shaking table tests conducted by Professor Kokusho at Chuo University, Japan, to study this problem. The centrifuge tests, to be conducted on the 9 m centrifuge at UC Davis will include models with multiple layers of contracting permeability.Professor Kokusho of Chuo University, Japan has observed flow failures and the formation of water interlayers beneath impermeable layers even in steeply sloping ground. Water interlayers, an extreme form of void redistribution raise serious questions regarding validity of typical stability calculations. Collaboration with Professor Kokusho will greatly enhance the benefits of this research by allowing comparisons between shaking table and centrifuge tests over a range of testing conditions.The proposed work includes funding to support, train, and provide valuable experience to graduate and undergraduate students. The MESA, MORE and WIE programs at UC Davis have agreed to help recruit a diverse pool of applicants for the undergraduate positions. The opportunities for students to design, conduct and analyze the large-scale experiments and to meet renowned experts from the US and Japan will be an extremely valuable.This project is supported under the 3rd-year competition under NSF 98-36. "US Japan Cooperative Research in Urban Earthquake Disaster Mitigation."