Lateral Spread Displacement and Bridge Foundation Case Histories from the 1991 Magnitude 7.6 Earthquake near Limón, Costa Rica

Abstract

This paper presents four liquefaction and pile response case histories associated with highway bridges from the April 22, 1991 7.6 magnitude (M) earthquake near Limón, Costa Rica that were analyzed more than 20 years after the earthquake. Details regarding observed soil layering, measured soil properties, site geometries, structural details, and damage are presented. Back-analysis of lateral spread displacements, liquefaction triggering, and kinematic pile response are performed to assess methods and models commonly applied in modern engineering design. Results of the liquefaction and lateral spread back-analysis show that conventional empirical methods for estimating lateral spread displacements can yield reasonable displacement predictions if multiple models are used and averaged. Empirical models tend to underestimate displacements in cases where considerable fines were encountered in the liquefiable soil. Simplified Newmark-type slope displacement models significantly underpredict the ground displacements observed at the bridge abutments of the four case histories. Results of the kinematic pile response back-analysis demonstrate that simplified conventional superpile methods closely replicate the observed pile response from the four case studies, particularly when using a simplified hybrid p-y model for the liquefied soil. Additional important lessons regarding the resilience of damaged infrastructure, the contribution of the bridge deck in the kinematic loading of piles, and the importance of considering void-ratio redistribution and the potential development of water films in kinematic pile response are discussed.