Framework for mapping liquefaction hazard–Targeted design ground motions

Journal of Geotechnical and Geoenvironmental Engineering
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Abstract

Liquefaction-induced ground failure poses substantial challenges to geotechnical earthquake engineering design. Current approaches for designing against liquefaction hazards, as specified in most seismic provisions, focus on estimating a liquefaction factor of safety (𝐹⁢𝑆𝐿) and typically characterize earthquake loading using design parameters based on probabilistic or deterministic ground motion levels. Because 𝐹⁢𝑆𝐿 is estimated deterministically, this basis of design neglects considerable uncertainties for estimating liquefaction triggering and its consequences and results in a lack of liquefaction-specific design criteria, particularly as structural design has advanced toward risk-targeted performance objectives. This study presents a framework for developing liquefaction-targeted design criteria based on a minimum acceptable return period of liquefaction, informed by probabilistic liquefaction hazard analysis (PLHA). PLHA quantifies annualized rates of liquefaction by considering contributions from (1) the full ground-motion probability space, and (2) uncertainties in liquefaction triggering using probabilistic models. PLHA is used in this study to characterize the current, effective return periods of 𝐹⁢𝑆𝐿 (𝑇𝑅,𝐹⁢𝑆) obtained from conventional liquefaction hazard analysis (CLHA) using uniform-hazard ground motions. 𝑇𝑅,𝐹⁢𝑆 is evaluated in a parametric study of nearly 100 sites throughout the conterminous United States. The results indicate large geographic variations in acceptable liquefaction hazard levels, with implied 𝑇𝑅,𝐹⁢𝑆 ranging between approximately 1,000 to 3,000 years. To address these inconsistencies without the computational demands of full PLHA, a framework is proposed for developing a liquefaction-targeted design peak ground acceleration, 𝑃⁢𝐺⁢𝐴𝐿, for use in liquefaction models that result in consistent liquefaction design levels across all geographic locations. The mapped 𝑃⁢𝐺⁢𝐴𝐿 is shown to be somewhat sensitive to site-specific properties, and adjustment factors are developed and presented. The proposed 𝑃⁢𝐺⁢𝐴𝐿 mapping procedure produces 𝐹⁢𝑆𝐿 estimates that are consistent with those obtained from full PLHA at a target 𝑇𝑅,𝐹⁢𝑆, providing a promising roadmap to incorporating PLHA concepts into current liquefaction design methods.

Suggested Citation

Makdisi, A.J., and Kramer, S.L., 2024, Framework for mapping liquefaction hazard–Targeted design ground motions: Journal of Geotechnical and Geoenvironmental Engineering, v. 150, no. 12, 04024123, 13 p., https://doi.org/10.1061/JGGEFK.GTENG-12804.

Publication type Article
Publication Subtype Journal Article
Title Framework for mapping liquefaction hazard–Targeted design ground motions
Series title Journal of Geotechnical and Geoenvironmental Engineering
DOI 10.1061/JGGEFK.GTENG-12804
Volume 150
Issue 12
Year Published 2024
Language English
Publisher American Society of Civil Engineers
Contributing office(s) Geologic Hazards Science Center - Seismology / Geomagnetism
Description 04024123, 13 p.
Additional publication details