Controlled Modulus Columns and Shallow Footings for Bridge Foundations on a Western Australian Project

Three bridges in the southwest region of Western Australia were founded on shallow footings located over controlled modulus columns (CMCs). Shallow footings alone were enough to provide adequate bearing performance. The incorporation of CMCs for this foundation solution was rather to ensure settlement and movement were within tolerances for the basis of design requirements, schedule constraints, cost considerations and ground conditions particularly unique to the region. This paper will discuss how the CMCs helped mitigate the potential effects of settlement and rotational movement of bridge abutments and mechanically stabilised earth (MSE) walls. The settlement performance was measured throughout construction and the results showed much less and quicker settlements than predicted. This allowed for corresponding construction on top such as pavements to proceed in a schedule constrained project. The implementation of CMCs also offered advantages in terms of construction efficiency with the installation of CMCs generally faster and less disruptive than other ground improvement methods. Both displacement and replacement methods were used, owing to the ground conditions unique to the region. The challenges of CMC installations and related ground conditions are discussed. This paper will surmise that the use of controlled modulus columns under shallow footings for bridge foundations offers a promising alternative to traditional foundation techniques.