DFI 2017, Melbourne - Design, Construction and Design Validation through High Strength Testing (PDA) of CFA and DD Foundations

Design, Construction and Design Validation through High Strength Testing (PDA) of CFA and DD Foundations

Stefano Pirrello, Keller Foundations, Sydney, Australia, +61 0421 000 127,

stefano.pirrello@keller.com.au (now deepfoundationsolutions@gmail.com)

Sydney’s booming real estate market has pushed property developers to invest in historically “no-go” areas, which were previously too expensive to develop. These areas are usually near rivers where the sites are underlain by deep alluvial and estuarine sediments. In these ground conditions conventional bored pile techniques are often not competitive. Contiguous Flight Auger (CFA) and Drilled Displacement Piles (DD) techniques are on the other hand suitable for these ground conditions. This paper deals with the design and construction challenges encountered with these piling techniques for a series of high-rise towers in Sydney’s West. The advantages of DD over CFA piles such as reduced overall spoil with substantial cost savings and achievable rock sockets in medium strength bedrock are discussed. Design validation through interpretation of real-time data from the piling rigs’ on-board computer data, and low and high strain pile dynamic testing (PDA) is discussed. Testing data is presented as CAPWAP (Case Pile Wave Analysis Program) analyses for different concrete grades.

Keywords: Design of Pile foundations, CFA, DD, PDA, CAPWAP