RAPID/Collaborative Research: Liquefaction Triggering & Consequences for Low-Plasticity Silty Soils, Christchurch, New Zealand

在2010- 2011年新西兰坎特伯雷地震中，尽管最先进的液化程序表明应该发生了严重的地面破坏，但在强烈震动但没有表现出液化证据的场地，迫切需要调查粉质土的地震反应。 当前程序对液化引起的地面破坏的高估，除了在全球范围内产生的成本外，还可能在基督城恢复期间浪费数百万美元，因为工程师需要昂贵的地面改善或建筑基础，而这些程序表明液化是可能的。 新西兰政府热衷于资助这一重要课题的研究，并希望国际参与。 已经制定了一项全面的新西兰提案，以进行额外的测试，以提高他们对液化触发和地面故障中细粒作用的理解。 他们渴望与美国研究人员合作开展这项工作。 通过既定程序对液化触发的过度预测似乎是由于它们无法捕捉粉土的响应。 用于开发这些程序的经验数据库主要由来自干净沙地的触发数据组成。 经验液化触发程序的保守性也有助于液化的过度预测。 要对低塑性粉质土的液化潜力作出决定性的评价，需要进行先进的室内试验。 随着基督城恢复工作的继续，工程师们面临着一个两难的境地--如何使用已建立的液化触发程序预测这些粉质土壤中的严重液化，与在多次强烈震动期间观察到很少或没有液化损害的矛盾观察结果相协调？ 这个问题对于开发在风险和可承受性之间取得合理平衡的实际工程解决方案非常重要。本研究利用新西兰已经完成的大量工作来指导基督城的重建。 新西兰政府资助机构只对这项工作感兴趣，如果它可以快速执行，以便它可以帮助工程师和规划师在他们的重建。 因此，这项工作是紧迫的，美国研究人员必须在压缩的新西兰工作时间表中参与。 这项工作利用了由NSF资助的基督城先前和当前的研究，并没有重复正在进行的努力。 通过这项研究开发的高质量案例研究和相关的实验室测试和分析将推动正在进行的关于粉土液化的研究，并使全球范围内的广泛利益。 记录和学习设计级地震后的观察是非常宝贵的，以促进我们对地震工程的理解。 调查粉质土液化的发生或不发生以及评估液化对建筑物和生命线的影响提供了宝贵的信息，这些信息将作为我们理解土壤液化的基准。 该项目将向全球研究界提供来自震后观测、岩土工程调查和实验室测试的高质量数据。 这些数据可以被纳入现有的国际数据集，以帮助改善经验的相关性，土壤参数，液化触发，和相应的影响。 目前可用的大多数研究数据与桑迪有关，因此增加有关粉质土的信息将大大有助于扩大经验设计方法的适用范围。 最后，拟议的研究支持一个国际研究伙伴关系，这将在液化工程领域推动全球知识的发展，同时为新西兰工程师在紧急重建期间提供关键信息。

There is a pressing need to investigate the seismic response of silty soils at sites that were strongly shaken during the 2010-11 Canterbury, New Zealand (NZ) earthquakes but did not exhibit evidence of liquefaction, although state-of-the-art liquefaction procedures indicate that significant ground failure should have occurred. The overestimation of liquefaction-induced ground failure by current procedures could potentially waste millions of dollars during the Christchurch recovery in addition to costs incurred worldwide, because engineers are requiring expensive ground improvement or building foundations where these procedures indicate that liquefaction is likely. The NZ government is keen to fund research on this important topic and desire international participation. A comprehensive NZ proposal has been developed to perform additional testing to advance their understanding of the role of fines in liquefaction triggering and ground failure. They are eager to partner with US researchers in this effort. The over-prediction of liquefaction triggering by established procedures appears to be a result of their inability to capture the response of silty soils. The empirical database used to develop these procedures consists primarily of triggering data from clean sand sites. Conservatism of the empirical liquefaction triggering procedures also contributes to the over-prediction of liquefaction. To evaluate conclusively the liquefaction potential of low plasticity silty soils requires advanced laboratory testing. As the Christchurch recovery continues, engineers are faced with a dilemma - How can the prediction of significant liquefaction in these silty soils using established liquefaction triggering procedures be reconciled with the contradictory observation that little or no liquefaction damage was observed during strong shaking on multiple occasions? The question is of great importance for developing practical engineering solutions that strike a sensible balance between risk and affordability. This research takes advantage of the substantial work already performed in NZ to guide the rebuilding of Christchurch. The NZ government funding agencies are only interested in this effort if it can be performed quickly so it can assist engineers and planners during their rebuild. Thus, the work is urgent, and U.S. researchers must participate during the compressed NZ work schedule. This work leverages prior and current research in Christchurch funded by the NSF and does not duplicate ongoing efforts. The high-quality case studies and associated laboratory testing and analysis developed through this research will advance ongoing research regarding the liquefaction of silty soils and enable widespread benefits worldwide. Documenting and learning from observations after design level earthquakes are invaluable to advancing our understanding in earthquake engineering. Investigating the occurrence or nonoccurrence of liquefaction of silty soils and evaluating the effects of liquefaction on buildings and lifelines provide invaluable information that will serve as benchmarks to our understanding of soil liquefaction. This project will provide high-quality data from post-earthquake observations, geotechnical investigations, and laboratory testing to the worldwide research community. These data can be incorporated into the existing international dataset to help improve empirical correlations regarding soil parameters, liquefaction triggering, and consequential effects. Most of the research data currently available relates to sandy soils, so addition of this information regarding silty soils will assist greatly in broadening the applicability of empirical design methods. Lastly, the proposed research supports an international research partnership that will advance knowledge worldwide in liquefaction engineering while providing critical information to NZ engineers during their urgent rebuild.