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Liquefaction Evaluations of Finely Interlayered Sands, Silts and Clays

细夹层砂、粉砂和粘土的液化评估

基本信息

批准号：
1635398
负责人：
Ross Boulanger
金额：
$ 57.19万
依托单位：
University of California-Davis
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-10-01 至 2020-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1635398&HistoricalAwards=false
关键词：
Liquefaction Evaluations Finely Interlayered Sands

项目摘要

Recent earthquakes, including the 2010-2011 Canterbury Earthquake Sequence (CES) in New Zealand (NZ), have shown that current engineering procedures have a strong tendency to over-predict liquefaction effects in thinly interlayered sand, silt, and clay deposits. This was observed in the Riccarton area in Christchurch, NZ where minimal damage occurred, but various engineering analyses predicted that at least one of the 2010-11 CES events should have caused significant ground surface damage due to liquefaction of the soils between depths of 1 and 10 m. The over-prediction of liquefaction effects in these types of deposits is a major concern in engineering practice worldwide because it leads to potentially unnecessary and expensive ground improvement or structural strengthening efforts. This research will contribute to eliminating this bias in current liquefaction evaluation procedures by addressing fundamental limitations associated with: (1) insufficient stratigraphic resolution with cone penetrometer measurements, (2) biases in the liquefaction triggering models for intermediate soil types, and (3) insufficient accounting of spatial variability in the analysis models used to estimate ground deformations. The development of improved methods for interpreting cone penetration measurements and accounting for geologic variability has broad applicability and benefit to the geotechnical profession. The correction of over-prediction biases in liquefaction procedures will contribute to more realistic risk assessments and improved land use planning for communities. The collaboration with NZ researchers will enable direct implementation of results in the Christchurch area and thereby contribute to more efficient rebuilding efforts. The student training and module development will increase the exposure of civil engineering to girls and the enhanced mentoring of our graduate student group will foster more diverse and engaged leaders in industry and academia.This research will address a major limitation in current liquefaction evaluation procedures by seeking to eliminate the strong bias toward over-predicting liquefaction effects in finely interlayered sand, silt and clay deposits. The first task will use physical modeling on a geotechnical centrifuge and axisymmetric numerical simulations of the cone penetration process to refine procedures for using cone penetration test (CPT) data to delineate stratigraphic layering and material types. The second task will update a CPT-based liquefaction triggering model using recent field data from New Zealand with improved mechanics-based functional forms for intermediate soil types. The third task will use nonlinear dynamic analyses with spatially correlated geostatistical realizations of subsurface stratigraphy to examine how one-dimensional liquefaction vulnerability indices, with their inherent assumption of horizontal layering, are biased toward over-predicting earthquake-induced ground deformations in these types of deposits. The fourth task will reevaluate the performance of Riccarton sites in the 2010-11 CES using findings from tasks one through three, and evaluate the extent to which those findings resolve the differences between the predicted and observed performances of the Riccarton area in these different earthquake events. This research will thereby integrate experimental, theoretical, and case history findings toward resolving fundamental issues affecting liquefaction evaluations, with the broader findings regarding the interpretation of cone penetration test data in finely interlayered soils and the representation of spatial variability in ground deformation models also having potentially major impacts on general practice.

最近的地震，包括2010-2011年新西兰（NZ）的坎特伯雷地震序列（CES），表明当前的工程程序具有过度预测薄夹层砂、粉土和粘土沉积物液化效应的强烈倾向。这是在新西兰基督城的Riccarton地区观察到的，那里发生的破坏最小，但各种工程分析预测，2010-11年CES事件中至少有一次应该会造成严重的地表破坏，原因是1到10 m深度之间的土壤液化。这些类型的沉积物中液化效应的过度预测是世界范围内工程实践中的主要问题，因为它导致潜在的不必要和昂贵的地基改善或结构加固工作。这项研究将有助于消除这种偏见，在目前的液化评价程序，解决基本的限制与：（1）不足的地层分辨率与锥形旋量仪测量，（2）偏见的液化触发模型的中间土壤类型，（3）不充分的会计空间变异性的分析模型用于估计地面变形。开发用于解释锥贯入测量和解释地质变异性的改进方法对岩土工程专业具有广泛的适用性和益处。纠正液化程序中的过度预测偏差将有助于更现实的风险评估和改善社区的土地使用规划。与新西兰研究人员的合作将使成果能够在基督城地区直接实施，从而有助于更有效的重建工作。学生培训和模块开发将增加土木工程的女孩和我们的研究生组的加强指导将培养更多样化和参与的领导人在工业界和学术界。这项研究将解决当前液化评价程序的主要局限性，通过寻求消除过度预测液化效果的强烈偏见，在细夹层砂，粉土和粘土矿床。第一项任务将使用土工离心机上的物理建模和锥贯入过程的轴对称数值模拟，以完善使用锥贯入试验（CPT）数据来描绘地层分层和材料类型的程序。第二个任务将更新CPT为基础的液化触发模型，使用最近的现场数据从新西兰与改进的力学为基础的功能形式的中间土壤类型。第三项任务将使用非线性动态分析与空间相关的地下地层地质统计学实现，以研究如何一维液化脆弱性指数，其固有的假设水平分层，偏向于过度预测地震引起的地面变形，在这些类型的存款。第四个任务将重新评估的表现Riccarton网站在2010-11 CES使用任务1至3的结果，并评估这些发现解决的程度之间的差异预测和观察到的表现Riccarton地区在这些不同的地震事件。因此，这项研究将整合实验，理论和案例历史的结果，解决影响液化评价的基本问题，更广泛的调查结果，在细夹层土壤中的静力触探试验数据的解释和地面变形模型的空间变异性的表示也有潜在的重大影响一般做法。

项目成果

期刊论文数量（15）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Centrifuge modeling of cone penetration testing in layered soil

层状土锥入试验的离心机模型

DOI：
10.1061/9780784481455.013
发表时间：
2018
期刊：
ASCE
影响因子：
0
作者：
Khosravi, Mohammad;Boulanger, Ross W.;DeJong, Jason T.;Khosravi, Ali;Hajialilue-Bonab, Masoud;Wilson, Daniel W.
通讯作者：
Wilson, Daniel W.

Nonlinear Dynamic Analyses of Austrian Dam in the 1989 Loma Prieta Earthquake