Use of micro-pile inclusions to enhance foundation rocking isolation

A preceding experimental study carried out at the University of Dundee, as well as independent experimental and numerical research results, have shown the improved seismic performance of rocking shallow foundations in comparison to conventional, conservatively designed foundations. By properly reducing the size of the footing, rocking behavior due to seismic loading can occur about the footing base. It has been shown that rocking foundations can reduce seismic ductility demand on bridge columns and improve bridge performance so much so as to enable them to safely resist very strong seismic motions which lead to collapse of alternative conventional systems. Yet, key concern is the potential for significant settlement accumulation, especially in relatively poor soil conditions. Therefore, current research objectives focus on exploring possible innovative foundation systems that will optimize the seismic performance of rocking foundations. Centrifuge model testing and 3D numerical modelling was employed to investigate the performance of various hybrid foundation systems. This paper presents preliminary results for one of the investigated alternatives: a rocking-isolated footing standing on top of soil reinforced with a grid of micro-pile inclusions.