Significance of Interface Nonlinearity on the Seismic Response of a Well-Pier System in Cohesionless Soil

Interaction between a well foundation (caisson) and the surrounding soil during earthquake shaking involves complicated material and interface nonlinearities such as soil inelasticity, separation, sliding, and uplifting. It is often perceived that the interface nonlinearity has appreciable effects on the seismic response of the well foundation. This paper studies soil-well interface behavior during ground shaking and evaluates the significance of interface nonlinearity on the seismic response of the soil-well-pier (SWP) system. Seismic analysis of the soil-well-pier system was performed using the two-dimensional finite element model considering soil and interface nonlinearities, under both full- and partial-embedment conditions of the well foundation. Soil was assumed to be cohesionless and analyzed under both saturated undrained and dry conditions. Results of this model were compared with those of a model with perfectly-bonded interface. The design displacement and force resultants were found to be marginally overestimated and were on the conservative side in absence of nonlinear interface.