Appropriate Intrusive Site Investigations Save Our Clients’ Money

This paper demonstrates how a supplementary, targeted ground investigation has the potential to considerably reduce construction cost, program and ground related risks. A case study is presented based on the draft final earthworks design of a proposed metro trains stabling facility which was first conducted based on limited site investigation (SI) data and then revised based on a targeted ground investigation. The earthworks design required site levels of a low-lying brownfield site to be raised by up to 3m. The site is underlain by significant depths of superficial deposits and long-term consolidation settlements pose an operational risk. The limited extent of the initial SI led to a large uncertainty in key design parameters and settlement predictions exceeded operational tolerances. This raised the requirement for potentially prolonged and expensive ground improvement works. A targeted SI was designed to reduce parameter uncertainty and the subsequent analysis reduced the settlement estimate magnitude and uncertainty negating the need for ground improvement works.