Abstract:
This case study from the West Gate Tunnel Project, presents an overview of three different piling methods undertaken in soft soils adjacent to existing infrastructure in West Melbourne.
Given the presence of soft soils to significant depth, precast concrete driven piles were considered a cost effective and suitable foundation construction methodology for the proposed bridges as part of West Gate Tunnel Project East Zone. Modelling showed that as large group of new piles were installed the soft soils would displace laterally which may cause impact to adjacent piles in the ground. As the existing piles were ‘ fixed’ at their head by the pilecap, they were subject to additional forces due to this soil displacement. This mechanism was widely debated and not well understood during the design phase leading to further detailed review, field trials and monitoring during the construction phase.
This study presents the methods of predicting ground movement, field trials and monitoring to validate modelling predictions, back analysis of monitoring data and selection of suitable mitigation measures for piling operations.
The field trials and monitoring were shown to validate modelling predictions, leading to selection of a suitable mitigation measures limiting the effects on adjacent infrastructure.