RAPID/Collaborative Research: Investigating the Liquefaction Susceptibility of Calcareous Sand in Hawaii with an Enhanced NHERI@UTexas Large Mobile Shaker

这个快速反应研究（RAPID）奖支持石灰质砂在地震震动液化危险的调查。钙质砂的液化仍然是一个持续的挑战，不仅在夏威夷（2006年Kiholo Bay地震导致Kawaihae港疏浚和自然沉积的钙质土液化），而且在全球赤道地区。包括港口、海运码头和海军设施在内的基础设施的抗震能力是夏威夷和美国本土经济、应急响应和安全的关键组成部分。钙质砂在几个方面不同于石英砂，包括颗粒内孔隙度、研磨表面、可压碎性和可变胶结作用。这些独特的性质意味着，建立的关系，用于评估液化危险的石英砂不能可靠地用于钙质砂没有修改的基础研究。这项研究将提高夏威夷的地震防备能力，并有助于更广泛地从根本上了解这种当地丰富的物质。（1）表征夏威夷钙质砂的基于应变的液化敏感性关系，并将其与石英砂的已建立关系进行比较，（2）研究基于应变的液化敏感性关系对初始土状态和有效应力的依赖性，以及（3）收集特定场地的锥贯入尖端阻力和剪切波速度，以与实验室导出的循环强度相关。将使用NHERI@UTexas T-Rex移动的振动器进行现场循环试验，以研究循环剪切应变与2 m深度以下超孔隙水压力之间的关系。通过将T-Rex应用于螺旋土壤锚（该螺旋土壤锚沿着安装有特殊阵列的颗粒速度和孔隙水压力传感器），可获得深度处的增强震动。现场取样土壤的循环实验室测试将用于表征在现场测试的扩展条件和初始状态下钙质砂的循环行为。该奖项反映了NSF的法定使命，并被认为值得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来支持。

This Grant for Rapid Response Research (RAPID) award supports investigation of the liquefaction hazard of calcareous sands during earthquake shaking. Liquefaction of calcareous sands remains an ongoing challenge, not only in Hawaii where the 2006 Kiholo Bay earthquake caused liquefaction of both dredged and naturally-deposited calcareous soils at the Kawaihae Harbor, but also globally in equatorial regions. The seismic resiliency of infrastructure, including ports, maritime terminals and naval facilities, is a critical component to the economy, emergency response, and security of Hawaii and the US mainland. Calcareous sands differ from quartz sands in several aspects, including intraparticle porosity, abrasive surfaces, crushability, and variable cementation. These unique properties mean that established relationships for evaluating the liquefaction hazard of quartz sands cannot be reliably used for calcareous sands without modifications based on fundamental studies. This research will improve earthquake preparedness of Hawaii and contribute more broadly to a fundamental understanding of this locally abundant material.The specific objectives of this project are: (1) characterize the strain-based liquefaction susceptibility relationship for Hawaii calcareous sand and compare it to established relationships for quartz sands, (2) examine the dependency of the strain-based liquefaction susceptibility relationship on initial soil state and effective stress, and (3) collect site-specific cone penetration tip resistance and shear wave velocity to relate to laboratory-derived cyclic strength. In situ cyclic testing will be performed with the NHERI@UTexas T-Rex mobile shaker to investigate relationships between cyclic shear strain and excess porewater pressure generation below a depth of 2 m. The enhanced shaking at depth will be obtained by applying T-Rex to a helical soil anchor that is installed along with a special array of particle velocity and pore-water-pressure transducers to various depths of interest. Cyclic laboratory testing on site-sampled soil will be used to characterize cyclic behavior of the calcareous sand under an expanded set of conditions and initial states from the in situ testing.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.