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.
