ABSTRACT:

This paper presents a case study of the uplift capacity of rock socketed grout injected piles used along a section of the Eastern Distributor Project in Sydney. A significant component of the Eastern Distributor is a 600m long tunnel underpass on South Dowling Street constructed using cut and cover techniques in water bearing sands. Along this section the motorway was lowered below surface level, requiring piles subject to both compressive loads and uplift loads due to buoyancy effects. This paper discusses the geotechnical model and the design procedures developed for auger grout injected piles socketed into Hawkesbury Sandstone. Procedures were developed to account for uncertainties with variations in the buried sandstone topography and constraints of the chosen construction method. Results of full-scale pile uplift tests are discussed. Comparisons are made between measured load capacity, and uplift capacity predictions using published design methods.

INTRODUCTION

The six kilometre long Eastern Distributor is a privately funded $A700 million transport link and is part of Sydney's orbital road network. It connects the eastern side of Sydney's CBD with Southern Cross Drive and Sydney Airport, and will link the M5 East (under construction) to the Harbour Bridge and Harbour Tunnel. Leighton Contractors constructed the Eastern Distributor during the period August 1997 to December 1999. Maunsell McIntyre Pty Ltd (Maunsell) was the Principal Design Consultant. A significant component of the Eastern Distributor includes a tunnel underpass on South Dowling Street from 100m south of the O'Dea Avenue / Todman Avenue intersection in Zetland to 100m north of the Lachlan Street / Dacey Avenue intersection. In this "Dacey-Todman" section the road pavement is about 5m below adjacent ground level and is constructed within a 600m long cut-and-cover tunnel. Precast concrete beams in the tunnel roof support the southbound and northbound surface road.

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