MRI: Acquisition of a Confined Bi-Directional Cyclic Shear Apparatus for Research and Education on Earthquake-Resilient Infrastructure

液化是在重大地震事件中造成广泛破坏的主要原因之一，威胁到建筑物、基础设施和生命线（如水管和煤气管、水坝和港口设施）的基础系统的完整性。该主要研究仪器（MRI）奖支持获得有限双向简单剪切装置，以模拟代表现场实际土壤应力状态的条件-允许更有效的结构设计，以减轻地震灾害。PI还将开发一个独特的附加系统，以控制土样的饱和排水，从而首次在实验室研究中采用真实的边界和荷载条件，研究部分排水对砂的响应的影响。该设备将促进加州州立大学洛杉矶分校的教师与他们在学术界和工业界的合作伙伴之间的研究合作。该仪器还将为南加州代表性不足的少数民族学生提供培训机会，否则他们将无法接触到先进的动手实验室研究。虽然已经进行了大量的研究，对砂土的循环响应，以了解液化现象，一些基本的问题仍然没有答案，特别是在实验室结果与现场性能。所研究的测试程序可以确定解释实验室和现场之间差异的因素，从而允许开发更强大的预测工具来补充经验关系，以评估在预期的地震激励期间地面是否会发生地震，从而实现更有效的结构设计和减轻灾害。该仪器将使研究人员能够表征土壤对独特应力路径和部分排水条件的反应。这些数据将被用来研究使用边界控制试验来模拟土壤局部排水试验的可行性。新仪器亦会协助研究斜坡的土壤反应及桩柱漂移现象。试验结果将用于提高对循环后粘土再固结和应力-应变特性的理解，以及在不同剪切方向的横向荷载下的土-桩相互作用。使用该仪器进行的研究将为数值建模人员在校准和验证其本构模型时生成有价值的数据集。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。

Liquefaction is one of the major causes of extensive wide-spread damage during major seismic events, threatening the integrity of foundation systems for buildings, infrastructure and lifelines such as water and gas pipes, dams, and port facilities. This Major Research Instrumentation (MRI) award supports the acquisition of a confined bi-directional simple shear apparatus to simulate conditions that represent the actual soil stress state in the field-- allowing more effective design of structures to mitigate earthquake hazards. The PI will also develop a unique add-on system to control saturation drainage of the soil specimen enabling, for the first-time, laboratory research with realistic boundary and loading conditions on the effect of partial drainage on the response of sands. The device will promote research collaborations between faculty at Cal State LA and their partners in academia and industry. The instrument will also provide training opportunities for underrepresented minority students in Southern California who otherwise would not be exposed to advanced hands-on laboratory research.Although much research has been carried out on the cyclic response of sands to understand the phenomenon of liquefaction, a number of fundamental questions remain unanswered, especially in relating laboratory results to field performance. The researched testing program can identify factors that explain the discrepancies between lab and site, allowing the development of more robust prediction tools to complement empirical relationships to assess whether the ground will liquefy during the expected seismic excitation, thus enabling more effective design of structures and mitigation of the hazard. The instrument will enable researchers to characterize soil response subjected to unique stress paths and partial drainage conditions. The data will be used to investigate the feasibility of using boundary-control tests to simulate soil partial drainage tests. The new apparatus will also support investigations on soil responses in ground slope as well as the pile drift phenomenon. The test results will be used to advance understandings in post-cyclic clay reconsolidation and stress-strain behavior, and soil-pile interaction under lateral loading with varying shearing directions. Studies using the instrument will generate valuable data sets for numerical modelers when calibrating and validating their constitutive models.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.