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Evaluating Liquefaction Potential of Challenging Soil Sites: Linking Geomorphological Controls and Novel Approaches for Site Characterization

评估具有挑战性的土壤场地的液化潜力：将地貌控制与场地表征新方法联系起来

基本信息

批准号：
1825189
负责人：
Russell Green
金额：
$ 120万
依托单位：
Virginia Polytechnic Institute and State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-01-01 至 2024-09-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1825189&HistoricalAwards=false
关键词：
Evaluating Liquefaction Potential Challenging Soil

项目摘要

This project focuses on improving engineering models for predicting the severity of earthquake-induced liquefaction at "challenging soil sites." Liquefaction is a phenomenon wherein loose, saturated, sandy soils lose their strength during earthquake shaking, leading to significant damage to nearby infrastructure. Field investigations performed following recent earthquakes in Christchurch, New Zealand highlighted the limitations of the current engineering liquefaction severity models for profiles having clay layers interbedded within the liquefiable sandy layers (i.e., "challenging soil sites"); similar geologic profiles are common in the US and worldwide. However, the root cause of the model shortcomings is unknown. The ramifications of not being able to accurately predict the liquefaction response of these deposits are high. For example, a recent liquefaction hazard study for the Hawke's Bay region of New Zealand (Napier and Hastings) predicts severe liquefaction for the design event. Similarly, a study performed for a stretch of levees in the northern portion of the Netherlands also predicts a high liquefaction hazard. In both cases, the deposits that are predicted to severely liquefy have similar characteristics to those in Christchurch, New Zealand that highlight the limitations in currently used evaluation procedures. As a result, government regulators are faced with the question of whether limited resources should be expended, potentially/likely unnecessarily, to mitigate the perceived risk of liquefaction based on these studies (e.g., the remediation cost for only one stretch of levees in the Netherlands is estimated to be ~$100mil, with costs potentially exceeding $1bil to remediate all the levees in the region). On the contrary, the consequences could be even higher if the results of the liquefaction hazard studies are offhandedly dismissed, and the deposits are truly susceptible to severe liquefaction when subjected shaking from future earthquakes. Challenging soil sites similar to those in Hawke's Bay, Christchurch, and the Netherlands are prevalent in regions across the US and worldwide. Towards understanding the root cause of the shortcoming in current engineering models, large vertical slices of soils will be extracted from challenging soil sites in Christchurch, New Zealand where the engineering models accurately and inaccurately predicted the severity of liquefaction. The existence of evidence of the occurrence of liquefaction at depth in these profiles will be determined by examining these "geo-slices," allowing us to determine whether the issue with current models is related to predicting the occurrence of liquefaction or whether the issue is related to predicting the severity of the manifestations of liquefaction at the ground surface. Additionally, the characteristics of these soil profiles will be documented in detail. New, advanced tools for identifying the types of profiles will be developed and used in conjunction with revised engineering models to accurately predicted the occurrence and severity of liquefaction in future earthquakes. Two doctoral students from Virginia Tech and the University of Michigan will work on this project, in collaboration with New Zealand-funded students from the University of Auckland and the University of Canterbury, New Zealand. The Principle Investigator for this project has established an outreach program for military veterans and will use the project to further his efforts of working with veterans. Comparison of predicted versus observed severity of surficial liquefaction manifestations at "challenging" soil sites (e.g., sandy soil deposits with interbedded silt and clay layers) during the 2010-2011 Canterbury, New Zealand earthquake sequence (CES) highlights significant limitations in currently used procedures for evaluating the liquefaction response of these deposits. The potential issues with current procedures include limitations in commonly used site characterization techniques and distinguishing between evaluating liquefaction triggering at depth versus severity of surficial liquefaction manifestations, where the latter has been shown to correlate with damage potential. The ramifications of not being able to accurately predict the liquefaction response of these deposits are high. Accordingly, this research will development a procedure to evaluate the liquefaction response of challenging soil sites based on the linkage of geomorphological controls of challenging soil sites and novel approaches for site characterization. This study will exploit to the extent possible the wealth of field performance data from recent earthquakes in New Zealand, as well as data from other well-documented historic liquefaction case histories, and will employ ?geo-slicing? and Vision Cone Penetration Tests, VisCPT, as well as more conventional field and laboratory testing. The project will be performed collaboratively by researchers from Virginia Tech, University of Michigan, and QuakeCoRE: New Zealand Centre for Earthquake Resilience (i.e., Univ. of Canterbury, Univ. of Auckland, and Tonkin + Taylor Ltd).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该项目的重点是改进工程模型，以预测在“具有挑战性的土壤场地”地震引起的液化的严重程度。“液化是一种现象，其中松散，饱和，桑迪土壤失去其强度在地震震动，导致重大损害附近的基础设施。新西兰基督城最近发生地震后进行的现场调查强调了当前工程液化严重度模型对于粘土层与可液化桑迪层（即，“具有挑战性的土壤地点”）;类似的地质概况在美国和世界各地都很常见。然而，模型缺陷的根本原因尚不清楚。不能准确预测这些矿床的液化反应的后果是很高的。例如，最近对新西兰豪克湾地区（纳皮耶和黑斯廷斯）的液化危害研究预测，设计事件将发生严重液化。同样，对荷兰北方一段堤坝进行的研究也预测了高度液化危险。在这两种情况下，预计将严重风化的矿床具有与新西兰基督城相似的特征，这些特征突出了目前使用的评估程序的局限性。因此，政府监管机构面临的问题是，是否应该花费有限的资源，潜在地/可能不必要地，以减轻基于这些研究的液化的感知风险（例如，荷兰仅一段堤坝的修复成本估计约为1亿美元，修复该地区所有堤坝的成本可能超过10亿美元）。相反，如果液化危害研究的结果被轻率地驳回，并且当受到未来地震的震动时，沉积物确实容易受到严重液化的影响，那么后果可能会更严重。类似于豪克湾、基督城和荷兰的土壤侵蚀在美国和世界各地都很普遍。为了了解当前工程模型缺陷的根本原因，将从新西兰基督城具有挑战性的土壤场地中提取土壤的大垂直切片，其中工程模型准确和不准确地预测了液化的严重程度。通过检查这些“地质切片”，将确定这些剖面中是否存在深层液化发生的证据，从而使我们能够确定当前模型的问题是否与预测液化发生有关，或者该问题是否与预测地面液化表现的严重程度有关。此外，将详细记录这些土壤剖面的特征。将开发用于识别剖面类型的新的先进工具，并与修订的工程模型结合使用，以准确预测未来地震中液化的发生和严重程度。来自弗吉尼亚理工大学和密歇根大学的两名博士生将与新西兰资助的来自新西兰奥克兰大学和坎特伯雷大学的学生合作开展这一项目。该项目的主要研究者已经为退伍军人建立了一个外展计划，并将利用该项目进一步努力与退伍军人合作。在“挑战性”土壤场地（例如，2010-2011年新西兰坎特伯雷地震序列（CES）期间，含有粉土和粘土夹层的桑迪沉积物突出了目前用于评估这些沉积物液化反应的程序的重大局限性。当前程序的潜在问题包括常用场地表征技术的局限性，以及在深度处评估液化触发与地表液化表现的严重程度之间的区别，后者已被证明与损害潜力相关。不能准确预测这些矿床的液化反应的后果是很高的。因此，本研究将开发一个程序来评估的挑战性土壤场地的液化反应的基础上连接的地貌控制的挑战性土壤网站和新的方法为网站特性。这项研究将利用尽可能丰富的现场性能数据，从最近的地震在新西兰，以及其他有据可查的历史液化案例的历史数据，并将采用？地理切片和视觉锥贯入试验，VisCPT，以及更传统的现场和实验室测试。该项目将由弗吉尼亚理工大学、密歇根大学和新西兰地震恢复中心（即，该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。