Australian Geomechanics Vol. 60(3) September 2025 p. 79-92
Ison Road Overpass bridge with high approach embankment at each abutment has been proposed to carry the existing Ison Road over Geelong to Melbourne rail corridor, extending the road south towards Browns Road in Werribee, Victoria. The high approach embankment behind each abutment requires a retaining structure to retain its earth fill. At the same time, collision protection shall be considered in accordance with AS 5100.1 for all structures within 20 m adjacent to existing or proposed rail track centrelines. An innovative hybrid retaining system consisting of L-shape wall, reinforced soil structure (RSS) block and required ground improvement works has been progressively developed through value engineering process as part of design development which was then built successfully. This paper commences with a brief description of geological conditions along the proposed project alignment and then discusses the optioneering process to develop the innovative and cost-effective retaining system to support the high abutment approach. The paper moves further to discuss key geotechnical issues and challenges encountered in design, basis of design, design approaches and assumptions, ground improvement works needed, subsequently presents key observational views from construction of the retaining system and finally presents some technical insights for future design and construction of similar retaining system as conclusions.
