Development and Validation of Performance Based Design Procedures for Kinematic Loading of Pile Foundations During Lateral Spreading

在大多数大地震事件中，松软饱和砂的液化会对建筑物、交通系统和生命线造成重大破坏。液化通常会导致横向扩散，通常会影响桥梁和港口，在救援工作和震后恢复最需要的时候破坏这些关键的运输环节。尽管在过去的20年中，在理解横向扩展和桩响应机制方面取得了重大进展，但校准和验证工作在很大程度上仅限于小规模的离心机试验和地震期间非常小的现场案例历史。为了在工程实践中获得广泛的认可，这些方法现在需要使用包括全尺寸结构（如2010年智利Maule 8.8级地震中损坏的结构）在内的充分记录的案例进行校准或验证。作为本研究的一部分，岩土工程现场调查将在2010年智利Maule地震期间经历了不同程度横向扩散破坏的三个桥墩场地进行，包括钻孔、SPT测试和地震CPT探测，以开发和记录新的横向扩散案例历史。这些新案例的数据，包括岩土力学特性、码头上部结构和基础设计方案，以及地震性能数据，随后将在杨百翰大学和GEER网站上公布，供地震危害社区查阅。随着新的横向扩展案例历史的发展和记录，传统的确定性方法将用于计算每个案例历史的自由场横向扩展位移以及桩基位移和旋转。将与实测的现场表现进行比较，并评估程序中可能出现的变化，以提高对这一大震级事件的一致性。最后，将开发一个基于性能的概率设计（PBD）程序，并将其用于计算自由场横向扩展位移和桩位移作为年超越率的函数。智利天主教大学的合作者将协助实地工作并进行他们独立开发的平行概率程序。本研究的技术影响包括：(1)编制了新的大震级横向传播病例史，这是大多数横向传播数据库所缺乏的；(2)开发和校准横向扩散土中桩的确定性和基于性能的设计程序，这些设计程序有可能在地震发生时显著减少破坏和随后对社会的经济损失；(3)提高地震事件中生命线的可靠性，减少直接和间接损失；(4)使用本研究中开发的经过验证和校准的程序将减少不必要的缓解成本，同时确保满足安全和代码性能要求。这项研究的更广泛影响和教育效益包括：(1)通过已建立的网站为世界各地的研究人员提供充分记录的案例历史；(2)通过研究合作和圣地亚哥地震研讨会向智利工程师传授基于性能的设计方法的技术；(3)与研究生和本科生进行指导活动；(4)通过杨百翰大学巴尔沙木桥测试项目向高中生进行推广。

Liquefaction of loose saturated sands results in significant damage to buildings, transportation systems and lifelines in most large earthquake events. Liquefaction commonly leads to lateral spreading which often impacts bridges and ports, damaging these critical transportation links at a time when they are most needed for rescue efforts and post-earthquake recovery. Despite significant advancements in understanding the mechanics of lateral spreading and pile response during the past 20 years, calibration and verification efforts have largely been restricted to small-scale centrifuge tests and a very small set of field case histories during earthquakes. To gain widespread acceptance in engineering practice, these methods now need to be calibrated or verified using well-documented case histories involving full-scale structures such as those damaged during the Mw 8.8 Maule, Chile earthquake in 2010. As part of this study, a geotechnical site investigation consisting of drill holes, SPT tests, and seismic CPT soundings will be performed at three pier sites that experienced various levels of damage from lateral spreading during the 2010 Maule, Chile earthquake in order to develop and document new lateral spreading case histories. The data from these new case histories, including geotechnical properties, pier superstructure and foundation design plans, and earthquake performance data will then be published on BYU and GEER web sites for access by the earthquake hazard community. Following the development and documentation of the new lateral spreading case histories, conventional deterministic methods will be employed to compute free-field lateral spread displacements along with pile foundation displacement and rotation for each case history. Comparisons will be made with measured field performance and possible variations in the procedure will be evaluated to improve agreement for this large magnitude event. Finally, a probabilistic performance-based design (PBD) procedure will be developed and employed to compute the free-field lateral spread displacements and pile displacement as a function of annual rate of exceedance. Collaborators at the Pontificia Universidad Catolica de Chile will assist in field work and conduct parallel probabilistic procedures which they have developed independently. The technical impact of this study includes: (1) the compilation of new lateral spread case histories from a large-magnitude earthquake, for which there is a scarcity in most lateral spreading databases; (2) the development and calibration of deterministic and performance-based design procedures for piles in laterally spreading soil that have the potential to significantly reduce damage and subsequent economic losses to society in the event of an earthquake; (3) improvement in the reliability of lifelines during seismic events that will reduce both direct and indirect losses; and (4) use of the verified and calibrated procedures developed in this study will reduce unnecessary mitigation costs, while assuring that safety and code performance requirements are satisfied. The broader impacts and educational benefits of this study include: (1) the development of well-documented case histories available to researchers world-wide through the established web sites, (2) technology transfer of performance based design methods to Chilean engineers through research collaboration and a earthquake seminar in Santiago, (3) mentoring activities with graduate and undergraduate research students, and (4) outreach to high school students through the well developed BYU balsa wood bridge testing program.