EAPSI: Achieving seismic resilience by understanding liquefaction effects in Christchurch, New Zealand

地震是发生在世界各地的自然灾害，会引起地面震动，并有可能造成重大破坏。在地面震动过程中，周围土壤中的水压力会增加。当水压力超过一定的阈值时，土壤就会坍塌，变成液体，通过地面向上流动。这种现象被称为液化，导致地面沉降，对地上和地下结构都有影响。在2010-2011年坎特伯雷地震序列期间，新西兰克赖斯特彻奇附近在16个月的时间里发生了几次大地震。这些地震造成的液化破坏影响了克赖斯特彻奇周围的大片地区，破坏了建筑物、基础设施网络和关键的生命线系统。这种广泛反复的液化程度在现代城市环境中几乎是前所未有的。通过克赖斯特彻奇的现场采样和岩土实验室测试计划，这项研究将有助于目前对液化的理解。这项研究将在坎特伯雷大学与米斯科·库布里诺夫斯基博士合作进行。在克赖斯特彻奇的地震后工程调查期间，发现了一个重要的观察结果：实践状态方法错误地预测了许多细粒(粉质)土壤场地液化的发生和严重程度。目前评估液化势的实用方法主要是基于干净的沙子；对于细粒土壤是否会液化以及采用适当的评估程序，仍有相当大的争议。本研究旨在提高细粒土液化的认识水平，同时评价现有液化评价方法的保守性程度。液压固定活塞土样将从克赖斯特彻奇各地的现场获得，循环应力比(CSR)曲线将通过循环三轴试验得到。实验室结果将与震后现场观测和既定的液化评估程序进行比较，以评估细粒土壤的液化性质。这些结果的影响将提高面临类似液化灾害的城市的地震复原力。该NSF EAPSI奖是与新西兰皇家学会合作资助的。

Earthquakes are natural hazards that occur throughout the world, causing ground shaking and the potential for significant damage. During ground shaking, water pressure in the surrounding soil increases. When the water pressure exceeds a certain threshold, the soil collapses, becoming fluid and flowing up through the ground surface. This phenomenon, called liquefaction, causes ground settlements that affect both above- and below-ground structures. During the 2010-2011 Canterbury Earthquake Sequence, several large earthquakes took place over a 16 month period near Christchurch in New Zealand. Liquefaction damage from these earthquakes affected a significant large area around Christchurch, damaging buildings, infrastructure networks, and critical lifeline systems. This degree of extensive repeated liquefaction was virtually unprecedented in a modern urban setting. Through field sampling in Christchurch and a geotechnical laboratory testing program, this research will contribute to the current understanding of liquefaction. This research will be conducted at the University of Canterbury, in collaboration with Dr. Misko Cubrinovski.During the post-earthquake engineering investigation in Christchurch, an important observation was made: state-of-practice methods incorrectly predicted the occurrence and severity of liquefaction for many sites with fine-grained (silty) soils. State-of-practice methods for assessing liquefaction potential are largely based on clean sands; there remains considerable debate as to whether fine-grained soils will liquefy and the appropriate assessment procedure to employ. This research aims to advance the state of knowledge on liquefaction of fine-grained soils, while evaluating the level of conservatism in current state-of-practice liquefaction assessment methods. Hydraulic fixed-piston soil samples will be obtained from sites throughout Christchurch and cyclic stress ratio (CSR) curves will be developed through cyclic triaxial testing. Laboratory results will be compared with post-earthquake field observations and established liquefaction assessment procedures to evaluate the nature of liquefaction in fine-grained soils. The implications of these results will advance seismic resilience for cities faced with similar liquefaction hazards. This NSF EAPSI award is funded in collaboration with the Royal Society of New Zealand.