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

迫切需要调查在2010-11年新西兰坎特伯雷地震期间受到强烈震动但没有表现出液化证据的粉质土的地震反应，尽管最先进的液化程序表明应该已经发生了重大的地面破坏。目前的程序对液化引起的地面破坏的高估可能会在克赖斯特彻奇恢复期间浪费数百万美元，此外还会在全球范围内招致成本，因为工程师们需要昂贵的地基改善或建筑基础，这些程序表明这些程序可能会液化。新西兰政府热衷于资助这一重要课题的研究，并渴望国际社会的参与。新西兰已经制定了一项全面的建议，以进行额外的测试，以促进他们对粉尘在液化触发和地面破坏中的作用的理解。他们渴望在这一努力中与美国研究人员合作。已建立的程序对液化触发的过度预测似乎是由于它们无法捕捉粉质土壤的响应。用于开发这些程序的经验数据库主要由来自清洁沙场的触发数据组成。经验液化触发过程的保守性也导致了对液化的过度预测。要最终评估低塑性粉质土的液化势，需要进行先进的实验室测试。随着克赖斯特彻奇恢复的继续，工程师们面临着一个两难境地--如何才能用已建立的液化触发程序预测这些粉质土壤中的显著液化，与在多次强烈震动期间几乎没有观察到液化损害的矛盾观察相一致？这个问题对于开发在风险和可负担性之间取得合理平衡的实际工程解决方案具有重要意义。这项研究利用新西兰已经开展的大量工作来指导克赖斯特彻奇的重建。新西兰政府资助机构只对这一努力感兴趣，前提是它能迅速执行，以便在重建期间帮助工程师和规划者。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日程期间参与。这项工作利用了由国家科学基金会资助的克赖斯特彻奇先前和当前的研究，不会重复正在进行的工作。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有关粉质土壤液化的正在进行的研究，并使世界各地普遍受益。记录和学习设计级地震后的观测对于增进我们对地震工程的理解是非常宝贵的。研究粉质土液化的发生或不发生，评估液化对建筑物和生命线的影响，为我们理解土壤液化提供了宝贵的信息。该项目将向全球研究界提供来自震后观测、岩土调查和实验室测试的高质量数据。这些数据可以合并到现有的国际数据集中，以帮助改善关于土壤参数、液化触发和相应影响的经验相关性。现有的研究数据大多与砂性土有关，因此增加粉质土的这些信息将大大有助于扩大经验设计方法的适用性。最后，拟议的研究支持一个国际研究伙伴关系，该伙伴关系将在全球范围内促进液化工程方面的知识，同时在新西兰工程师紧急重建期间向他们提供关键信息。

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.