Rock-socketed pile design and construction: a better way?

Piles socketed into rock are often used to support heavy loads from buildings and infrastructure. Piles typically of up to 1·8 m diameter carrying safe working loads of up to 40 MN are utilised in Australia. Their design has traditionally been based on conservative, empirical rules. GARSP (Golder Associates Rocket field Socket Procedure) is a recent design innovation that provides a serviceability approach to design, and allows socket lengths to be optimised during the drilling process, often resulting in significant savings. It also provides better control of the risks associated with unexpected ground conditions and with construction of the pile. GARSP has been used in collaboration with Wagstaff Piling on several large-scale socketed pile projects in Melbourne, Australia, including the second hotel for Crown Casino, the new grandstand at the Melbourne Cricket Ground, the redevelopment of Spencer Street Station, and several residential towers. The adoption of this approach for these projects in conjunction with best practice construction techniques has resulted in significant cost savings in terms both of materials and of construction time. This paper briefly describes the traditional design approaches and the basic components of GARSP, and then presents some recent projects where it has been used.