Evaluation of Liquefaction Potential of Saturated Granular Soils under Partial Drainage Conditions

美国和世界上其他地震活跃地区因地震引起的场地液化而遭受了相当大的破坏，这对港口设施、桥梁、水坝、地下管道和各种类型的建筑物造成了非常昂贵的破坏。地震工程研究所报告说，袭击主要城市地区的大地震造成的建筑环境损失的直接成本和间接经济成本很容易超过1000亿美元。如果能够可靠地预测土壤系统的性能，并改进当前的设计和补救措施，就可以大大减少这种损失。该项目解决了与评估实际排水条件下土壤沉积物液化潜力有关的工程知识的关键空白。这项工作将有助于减少与现场液化危险有关的不确定性和大笔费用。研究和教育活动符合国家利益。它们有可能通过更好地评估液化潜力来提高经济竞争力。从这项研究中获得的知识将防止未来的生命损失，并有助于美国公众的福利。该研究将为地震工程和地震科学的进步作出贡献。这些活动还将使美国的STEM劳动力具备全球竞争力，并配备高性能计算建模的最新发展。液化是由于快速地震加载过程中孔隙空间的挤压而产生的水压积聚的结果，反过来又降低了土壤的强度。将全排水条件下砂土的循环收缩与不排水条件下孔隙压力的产生进行类比，主要解释了循环加载过程中孔隙压力发展的机理。然而，根据外部加载速率、土壤渗透性和原位孔隙压力边界条件等因素，预计在现场会出现不同的排水条件。这些条件可能导致剪切过程中孔隙体积和孔隙水压力同时发生变化的部分排水情况。在这种情况下，原本被认为是不可液化的土壤，如致密的沙子，实际上可能会经历不稳定。该项目旨在提供地震作用下孔隙流体运移的准确表征，并评估实际排水条件下的液化潜力。nsf支持的NHERI的网络基础设施组件的高性能计算（HPC）资源使开发能够以前所未有的分辨率无缝建模土壤系统的通用预测工具成为可能。利用并行计算的高保真全耦合微力学计算模拟计划在此努力中提供急需的答案，以了解地震加载过程中控制孔隙压力演变的力学过程。

The U.S. and other seismically active areas around the world have sustained considerable damage resulting from earthquake-induced site liquefaction that was associated with very costly damage to port facilities, bridges, dams, buried pipes, and buildings of all types. The Earthquake Engineering Research Institute reports that the direct cost of losses in the built environment and the indirect economic cost of a major earthquake that strikes a major urban area could easily exceed 100 billion dollars. Such losses could be significantly reduced if the performance of soil systems could be reliably predicted and current design and remediation measures improved. This project addresses a critical gap in engineering knowledge related to the evaluation of the liquefaction potential of soil deposits under realistic drainage conditions. This undertaking will help in reducing the uncertainty and large costs associated with site liquefaction hazards. The research and education activities fall within the national interest. They have the potential to achieve increased economic competitiveness through better assessment of liquefaction potential. The knowledge gained from this research would prevent future loss of lives and contribute to the welfare of the American public. The research will contribute to the progress of earthquake engineering and science. The activities would also lead to a globally competitive American STEM workforce equipped with the latest development in high-performance computational modeling.Liquefaction is a result of water pressure build-up due to squeezing of pore space during rapid earthquake loading that, in turn, reduces soil strength. The mechanism of pore-pressure development during cyclic loading has been mainly explained based on the analogy between cyclic contraction of fully drained sands and pore pressure generation in undrained conditions. However, depending on several factors such as external loading rate, soil permeability and in-situ pore-pressure boundary conditions, different drainage conditions are expected in the field. These conditions may lead to a partial drainage situation in which simultaneous change in pore volume and in pore water pressure may occur during shearing. Under these conditions, soils originally believed to be non-liquefiable such as dense sand, may actually experience instability. This project aims at providing accurate characterization of pore fluid migration during seismic loading of a soil deposit and assessing liquefaction potential under realistic drainage conditions. The high-performance computing (HPC) resources of the cyberinfrastructure component of the NSF-supported NHERI enable the development of a universal predictive tool capable of seamless modeling of soil systems at an unprecedented resolution. High-fidelity fully-coupled micromechanical computational simulations utilizing parallel computing are planned in this effort to provide much-needed answers to questions related to understanding the mechanical processes that control the evolution of pore pressure during seismic loading.