Role of Spatial Variability in Liquefaction Consequence Severity

当强烈的地面震动导致饱和、松散的沙子和淤泥沉积物失去支撑建筑物、桥梁、港口和港口基础设施等结构的强度和能力时，就会发生地震引起的液化。不幸的是，人口中心往往建在易受土壤液化影响的沉积物之上和内部。发生在地震活动区的周期性地震往往会造成大范围的破坏，影响住房、关键基础设施、公用事业和应急服务网络。例如，2010-11年新西兰坎特伯雷地震序列造成的土壤液化造成了150亿美元的损失。在日本东北和关东地区，超过2.5万所房屋遭受了与液化有关的破坏。如果液化危险没有得到充分的探索和减轻，地震易发地区居民受到的破坏和破坏的广度将造成重大的经济后果，影响社区从地震事件中恢复的能力。该项目旨在利用新西兰岩土工程数据库（NZGD）中收集的重要数据集，确定液化易感土壤沉积物的空间变异性对液化诱发后果严重程度的作用。通过将这些可探测到的地貌特征与现有的液化触发和严重程度模型的性能以及2010-11年坎特伯雷地震序列期间观测到的实际反应联系起来，可以更好地理解液化现象及其后果。在NZGD中确定的有足够数量的土壤勘探来确定可液化土壤沉积物的垂直和水平固有变异性的地点将构成这项工作的基础。一名博士生和一名本科生研究助理将在首席研究员的指导下，与新西兰坎特伯雷大学的研究人员合作开展该项目。评估土壤固有空间变异性所需的分析程序将被提炼成一个广泛和自由分布的用户友好框架，以促进更多地将随机场方法应用于可液化土壤场地的评估。本研究将通过考虑利用随机场理论（RFT）量化的土壤空间变异性测量推断出的潜在可液化土壤的地质和地貌特征，解决现有评估液化严重程度技术的潜在缺陷。坎特伯雷地震序列后的震后液化严重程度观测提供了一个现成的观测来源，通过它可以检验空间变异性的知识是否可以减少液化严重程度测量的不准确性。土的自相关和固有变异性的测量将直接量化使用锥贯试验数据在NZGD使用严格的统计方法，以提高我们对液化易感土壤空间变异性的垂直和水平测量范围的理解。此外，这项工作将评估量化随机场模型参数和地貌控制对液化严重程度测量的相对准确性或不准确性的相关性。这项工作将为未来的研究奠定基础，通过显著增加RFT框架内的特征站点数量，特别是水平变化的测量，以及通过与nsf赞助的岩土极端事件侦察协会合作，培训当前和未来的地震工程教育工作者和学生，以提高对RFT解释框架的认识。该奖项反映了美国国家科学基金会的法定使命，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。

Earthquake-induced liquefaction can occur when strong ground shaking causes saturated, loose sand and silt sediments to lose their strength and ability to support structures, such as buildings, bridges, and port and harbor infrastructure. Unfortunately, population centers are often founded above and within the kinds of sediments that are susceptible to soil liquefaction. The periodic earthquakes produced in seismically-active zones tend to lead to widespread damage that can affect housing, critical infrastructure, utility, and emergency service networks. For example, $15B of damage was attributed to soil liquefaction resulting from the 2010-11 Canterbury Earthquake Sequence in New Zealand. More than 25,000 homes experienced liquefaction-related damage in the Tohoku and Kanto districts in Japan. The breadth of damage and disruption to the residents of earthquake-prone areas pose significant economic consequences if the liquefaction hazard is not sufficiently explored and mitigated, impacting the ability of communities to recover from an earthquake event. This project aims to leverage the significant dataset gathered within the New Zealand Geotechnical Database (NZGD) to identify the role of spatial variability of liquefaction-susceptible soil deposits on the severity of liquefaction-induced consequences. An improved understanding of the liquefaction phenomenon and resulting consequences may be obtained by linking those detectable geomorphological signatures to the performance of existing liquefaction triggering and severity models and the actual responses observed during the 2010-11 Canterbury Earthquake Sequence. Sites identified in the NZGD that have a sufficient number of soil explorations to establish the vertical and horizontal inherent variability of liquefiable soil deposits will form the basis for this work. One doctoral student and one undergraduate research assistant will work on this project, under the supervision of the Principal Investigator and in collaboration with researchers from the University of Canterbury, New Zealand. The analytical procedures necessary for evaluating the inherent spatial variability of soils will be distilled into a broadly-, and freely-distributed user-friendly framework to spur greater application of random field methods to the evaluation of liquefiable soil sites. This study will address potential shortcomings in existing techniques to assess liquefaction severity by considering the geologic and geomorphological signature of potentially-liquefiable soils deduced from measures of soil spatial variability quantified using random field theory (RFT). Observations of post-earthquake liquefaction severity following the Canterbury Earthquake Sequence provide a ready source of observations by which to test whether or not knowledge of spatial variability can reduce the inaccuracy of liquefaction severity measures. Measures of soil autocorrelation and inherent variability will be directly quantified using cone penetration test data in the NZGD using rigorous statistical methods to improve our understanding of the range in vertical and horizontal measures of spatial variability of liquefaction susceptible soils. Furthermore, this work will evaluate the potential for correlation of quantified random field model parameters and geomorphologic controls to relative accuracy or inaccuracy in liquefaction severity measures. This work will lay the groundwork for future studies by significantly increasing the number of sites characterized within the RFT framework, particularly measures of horizontal variability, as well as train current and future earthquake engineering educators and students in RFT to promote awareness of this interpretational framework by teaming with the NSF-sponsored Geotechnical Extreme Events Reconnaissance Association.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.