RAPID: Field Investigation of Shallow Ground Improvement Methods for Inhibiting Liquefaction Triggering; Christchurch, New Zealand

2010-2011年，新西兰克赖斯特彻奇市遭受了一系列强烈地震的破坏，其中包括六次重大地震。2011年2月的克赖斯特彻奇地震(移动震级，MW，6.2)产生了该市最大的地面运动，水平峰值地面加速度在0.37到0.52g之间。2010-2011年的地震导致克赖斯特彻奇郊区反复发生液化。一些关键的观察和影响是：(1)沿着现在被指定为红区一部分的埃文河蜿蜒的环流，液化特别广泛和破坏性。(不会重建建筑物的区域)，(2)在红色区域内有6000多处住宅被遗弃？由于经济损失无法修复，(3)估计还有15,000处财产受到液化的影响，(4)总经济损失估计在250亿至300亿新西兰元(或新西兰？S国内生产总值的15%至18%)。克赖斯特彻奇和坎特伯雷地区面临的一个关键问题是在未来地震中仍有液化风险的土地上进行重建。这个问题出现在几乎所有的地震之后，而且几乎没有关于可以用来提高住宅结构和低层建筑在未来地震中的弹性的地基加固方法的信息。面对这一关键的、时间敏感的问题，新西兰当局向一个项目提供了约100万新西兰元，该项目涉及对浅层地基加固方法进行全面的现场试验。其目的是确定是否以及哪些地基改良方法能够达到抑制改良地基中的液化触发的目的，并且是具有成本效益的措施。这一适用于美国和世界各地的新知识迅速被需要，作为重建克赖斯特彻奇和坎特伯雷地区基础设施的前进道路的一部分。新西兰的资金支持该项目的所有技术和后勤方面，液化测试除外。液化测试将使用由NEES@UTexas运营的名为T-Rex的大型移动摇床进行。T-Rex将被用来模拟大范围的受控地震震动水平。这个独特的机会之所以存在，是因为T-Rex已经在克赖斯特彻奇，这是早先涉及深度地震剖面的NEESR项目的结果。这项工作包括收集和解释一个独一无二的数据集，该数据集可用于设计抑制饱和土壤液化触发的浅层地基加固方法。这种知识并不存在，但在美国地震多发地区和世界各地的住宅结构和低层商业建筑中有许多应用。此外，在接近饱和的、易液化的土壤中产生的孔隙水压力将首次在现场收集。这一新知识将有助于更全面地了解这一风险以及缓解风险的方法。这项研究的广泛影响是广泛的。这项研究将通过为超过15,000户家庭开发更坚固的住宅结构设计来影响未来的克赖斯特彻奇社会。此外，还将开发用于设计地面改进以抑制液化触发的新知识，这些改进将直接传输到美国城市，如西雅图、华盛顿州、洛杉矶、加利福尼亚州、孟菲斯、田纳西州和南卡罗来纳州查尔斯顿。新知识还将转移到世界各地的地震多发国家，如中国、智利、海地、日本、台湾和土耳其。这项工作将加强国际研究合作，并将为美国研究生提供有益的国际旅行经历，这些旅行将平衡他们的技术教育，并使他们接触到地震工程中仍然存在的与全球相关的问题

In 2010-2011, the city of Christchurch, New Zealand was devastated by a series of powerful earthquakes, including six significant events. The February 2011 Christchurch Earthquake (movement magnitude, Mw, 6.2) generated the largest ground motions in the city, with horizontal peak ground accelerations between 0.37 and 0.52 g. The 2010-2011 earthquakes caused repeated liquefaction throughout the suburbs of Christchurch. Some key observations and impacts are that: (1) liquefaction was particularly extensive and damaging along the meandering loops of the Avon River, now designated as part of the ?Red Zone? (zone where structures will not be rebuilt), (2) more than 6,000 residential properties are being abandoned in the ?Red Zone? because the damage is beyond economic repair, (3) an estimated additional 15,000 properties were affected by liquefaction, and (4) the total economic loss is estimated to be from 25 to 30 billion NZ dollars (or 15 to 18% of New Zealand?s GDP). One critical problem facing Christchurch and the Canterbury region is rebuilding on land that remains at risk of liquefaction in future earthquakes. This problem arises after nearly all earthquakes and little information exists on ground improvement methods that can be used to increase the resilience of residential structures and low-rise buildings in future earthquakes. Facing this critical, time-sensitive problem, the New Zealand authorities are contributing about $1M (NZ) to a project involving full-scale field test trials of shallow ground improvement methods. The goal is to determine if and which ground improvement methods achieve the objectives of inhibiting liquefaction triggering in the improved ground and are cost-effective measures. This new knowledge, which is applicable in the U.S. and worldwide, is rapidly needed as part formulating the path forward in rebuilding the infrastructure in Christchurch and the Canterbury region. The New Zealand funds support all technical and logistical aspects of the project except the liquefaction testing. The liquefaction testing will be conducted using the large mobile shaker, called T-Rex, that is operated by NEES@UTexas. T-Rex will be used to simulate a wide range of controlled earthquake shaking levels. This unique opportunity exists because T-Rex is already in Christchurch as a result of an earlier NEESR project involving deep seismic profiling. This work includes the collection and interpretation of a one-of-a-kind dataset that can be used in the design of shallow ground improvement methods to inhibit liquefaction triggering of saturated soils. This knowledge does not exist but has numerous applications in earthquake-prone areas in the U.S. and worldwide for residential structures and low-rise commercial buildings. Additionally, pore water pressure generation in nearly-saturated, liquefaction-prone soils will, for the first time, be collected in the field. This new knowledge will help develop a more comprehensive understanding of this risk and ways to mitigate it. The broader impacts of this research are extensive. The study will impact the future Christchurch society at large through development of more robust seismic designs of residential structures for more than 15,000 homes. Furthermore, new knowledge will be developed for designing ground improvements to inhibit liquefaction triggering that will transfer directly to U.S. cities such as Seattle, WA, Los Angeles, CA, Memphis, TN, and Charleston, SC. The new knowledge will also transfer to earthquake-prone countries worldwide such as China, Chile, Haiti, Japan, Taiwan and Turkey. The work will strengthen international research collaborations and will provide U.S. graduate students with rewarding international travel experiences that will balance their technical education and e expose them to the globally-connected problems that still exist in earthquake engineering