Numerical analysis of seismic performance of inclined piles in liquefiable sands

Previous post-earthquake damage investigations have indicated that inclined piles have either performed satisfactorily or poorly during seismic events; hence their effectiveness is still questionable. This paper aims to clarify the performance of inclined piles installed in the liquefiable ground during earthquakes. To this end, a three-dimensional finite element model has been developed using the OpenSees program. The effects of soil-pile interaction have been evaluated by applying interface elements between the soil and the pile. Subsequently, the behavior of sand is described with the help of a multi-yield-surface plasticity constitutive relation. By changing the pile configurations and the amplitude of loading patterns, a series of parametric analyses are conducted, and the system responses (i.e., soil, cap, and pile responses) are compared. The results clearly illustrate that the presence of inclined piles has a beneficial effect on the dynamic response of the soil-pile-cap system in nonliquefied soils and of the cap response in liquefied soils. However, highly detrimental effects of inclined piles on the soil and pile responses have been observed as the soil liquefies. Based on the results, the conditions wherein inclined piles may perform satisfactorily or poorly are highlighted.