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

2010-2011年，新西兰基督城遭受了一系列强烈地震的破坏，其中包括六次重大事件。 2011年2月的基督城地震（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和0.52 g之间。2010-2011年的地震导致整个基督城郊区反复液化。一些关键的意见和影响是：（1）液化是特别广泛和破坏沿着蜿蜒的埃文河，现在指定为部分？红区？(zone（二）区内有六千多个住宅物业被弃置？红区？由于破坏是不经济的修复，（3）估计额外的15,000财产受到液化的影响，（4）总的经济损失估计为250亿至300亿新西兰元（或15%至18%的新西兰？s国内生产总值）。 基督城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重建。几乎所有的地震后都会出现这个问题，并且几乎没有关于可用于增加住宅结构和低层建筑在未来地震中的恢复力的地基加固方法的信息。 面对这一关键的、时间敏感的问题，新西兰当局正在为一个涉及浅层地基加固方法的全面现场试验的项目捐款约100万美元。 其目的是确定地基加固方法是否以及哪些地基加固方法能够实现抑制加固地基液化触发的目标，并且是具有成本效益的措施。 这种新的知识，这是适用于美国和世界各地，是迅速需要的一部分，制定前进的道路，重建基础设施在基督城和坎特伯雷地区。 新西兰的资金支持该项目的所有技术和后勤方面，但液化测试除外。 液化试验将使用大型移动的振动筛进行，称为T-Rex，由NEES@UTexas操作。 T-Rex将用于模拟各种可控地震震动级别。 这个独特的机会存在，因为霸王龙已经在基督城作为一个早期的NEESR项目涉及深地震剖面的结果。这项工作包括收集和解释一个独一无二的数据集，可用于浅层地基加固方法的设计，以抑制饱和土壤的液化触发。 这方面的知识并不存在，但在美国和世界各地的地震多发地区的住宅结构和低层商业建筑中有许多应用。此外，孔隙水压力的产生，在近饱和，易破裂的土壤将首次在现场收集。 这些新知识将有助于更全面地了解这一风险以及减轻风险的方法。 该研究将通过为15，000多户住宅开发更稳健的住宅结构抗震设计，对未来的基督城社会产生广泛影响。 此外，将开发新的知识，用于设计地面改良，以抑制液化触发，这些知识将直接转移到美国城市，如华盛顿州的西雅图、加利福尼亚州的洛杉矶、田纳西州的孟菲斯和南卡罗来纳州的查尔斯顿。新的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验，这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全球相关问题

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