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

2010年至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（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0.52 g之间。2010-2011年的地震导致基督城郊区不断出现液化现象。一些关键的观察和影响是：(1)液化在埃文河蜿蜒的环线沿线特别广泛和具有破坏性，现在被指定为？红色区域?（不重建构筑物的地区）；(2)超过6,000个住宅物业被遗弃在？红色区域?由于破坏超出了经济修复的范围，(3)估计还有15,000处房产受到液化的影响，(4)总经济损失估计在250亿至300亿新西兰元（或新西兰的15%至18%）之间。s GDP)。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进行重建。这个问题在几乎所有的地震之后都会出现，而且关于地面改善方法的信息很少，这些方法可以用来增加住宅结构和低层建筑在未来地震中的恢复能力。面对这一关键且时间敏感的问题，新西兰当局正在为一个项目提供约100万新西兰元（NZ），该项目涉及对浅层地面改善方法的全面现场测试试验。目的是确定哪些地面改善方法能够达到抑制改善后地面液化触发的目标，并且是具有成本效益的措施。这种新知识适用于美国和世界各地，是制定克赖斯特彻奇和坎特伯雷地区基础设施重建道路的一部分。新西兰的资金支持该项目的所有技术和后勤方面，除了液化测试。液化测试将使用名为T-Rex的大型移动振动筛进行，该振动筛由NEES@UTexas操作。霸王龙将被用来模拟大范围的可控地震震动水平。这个独特的机会之所以存在，是因为T-Rex已经在基督城了，这是早期NEESR项目涉及深层地震剖面的结果。这项工作包括收集和解释一个独一无二的数据集，该数据集可用于设计浅层地面改善方法，以抑制饱和土壤的液化触发。这种知识并不存在，但在美国和世界各地的地震多发地区，住宅结构和低层商业建筑中有许多应用。此外，在接近饱和、易液化的土壤中，孔隙水压力的产生将首次在现场收集。这一新知识将有助于更全面地了解这种风险以及减轻这种风险的方法。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个家庭开发更坚固的住宅结构抗震设计，在很大程度上影响未来的基督城社会。此外，将开发用于设计地面改善以抑制液化触发的新知识，这些知识将直接转移到美国城市，如华盛顿州西雅图、加利福尼亚州洛杉矶、田纳西州孟菲斯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联系问题

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