Effectiveness of PV Drains for Mitigating Earthquake-Induced Deformations in Sandy Slopes

Abstract

This paper considers the effectiveness of a Pre-fabricated Vertical (PV) drain array for mitigating the earthquake-induced permanent ground deformations of a water-fronting loose sand fill based on results of numerical simulations. The numerical simulations are performed using the OpenSees finite element framework to represent the non-linear coupled ground deformation and transient pore pressures with customized 1-D finite elements to describe flow in the PV drains. Soil behavior is modeled using an advanced elasto-plastic effective stress soil model ("DM" for Dafalias & Manzari, 2004). The analyses focus on the performance of an 18.3m high sand fill, representative of many west-coast port facilities, and compare the response with and without the PV drain mitigation system for a suite of 58 reference seismic ground motions. The computed permanent slope deformations are well correlated with the peak ground accelerations (PGA) and especially the Arias intensity (I[subscript a]). The PV drain mitigation system is effective in reducing permanent lateral deformations at the crest of the slope by a factor of 1.2 - 3.5. The system effectiveness is largely independent of the characteristics of the ground motions. The damage results have been incorporated in slope fragility curves that can be used to quantify the expected costs from earthquake damage.