Geotechnical Challenges For Construction Of Diaphragm Walls And Foundation Of Sydney’s Tallest Building, Crown Sydney Hotel Resort

Crown Sydney Hotel Resort is the Stage 1C component of Barangaroo South and is being developed as a single high rise mixed use tower of 72 stories (271m high), rising over a multi-level podium and a 3 level basement car park (total 75 levels). The Crown Sydney Hotel Resort basement retaining wall comprised 33 diaphragm wall (D-wall) panels and 36 barrettes for the foundation of the main tower and more than 130 bored piles (including bored compression piles, bored tension piles, bored sleeved piles and permanent plunge column piles). AECOM were engaged as designers of the foundation works by Piling Contractors Bauer Australia Joint Venture (PCBAJV) who constructed the foundation works as the D&C foundation contractor. The depth of foundation elements varied from 25 m to 50 m below ground level.

AECOM provided an initial concept design followed by a detailed design services and then, during construction, full time on-site geotechnical inspection of the basement diaphragm walls and foundations. This paper will focus on the challenges of geotechnical verification of diaphragm wall panel, barrette and pile foundation construction and how these challenges were met. During fulltime site inspection, hydraulic trench cutter penetration rates various sandstone rock classes have been measured and compared with the borehole data. Rate of penetration of the piling rig into the various sandstone rock classes, rock quality and rock apparent temperature were closely monitored and recorded as part of verification of the socket requirements. Monitoring, data collection and comparing the data with available boreholes, allowed AECOM to develop a method to reliably check the rock socket compliance with requirements across the site. Other geotechnical observations and lessons learned during the inspection of the pile, diaphragm wall and barrette construction are also presented in this paper.