Engineers Australia

Class A prediction of a relieving slab using uncoupled models

David Oliveira, Dan Gorman and Frances Badelow

Abstract

Construction of the new Windsor Road on/off ramps, part of the M2 Upgrade project, required limiting the loads and movements imposed on existing precast concrete walls so that no additional pressure was applied as a result of the new construction works. This was necessary due to possible structural deficiencies of some of the existing reinforced concrete elements. A piled relieving slab was adopted as the final solution to support the reinforced soil wall ramps and a comprehensive soil-structure interaction assessment was carried out in order to predict the pile head deflections and assess potential loading of the existing walls.

A Class A prediction was carried out of the piled relieving slab performance using simplified uncoupled models which accounted for all likely loading mechanisms, including structural loads and induced soil movements. As the models were uncoupled, i.e. two distinct models, the interaction between them was assessed by plotting the load-displacement curves of both piles and the RSW/slab models, then identifying the equilibrium point. Instrumented piles confirmed the Class A prediction of very small pile head deflections indicating that the solution had successfully achieved the objective of limiting the applied loads onto the existing walls.