The Port of Miami Tunnel project in Miami, USA, included twin bore 12.9m diameter, 1.2km long tunnels driven beneath a shipping channel to form a road connection between the highway network on Watson Island and the port on Dodge Island. The tunnels pass through challenging and variable ground conditions comprising layered carbonate sedimentary formations of highly permeable coralline limestones and sand with high groundwater pressures. The tunnels were constructed using a modified EPB-TBM which was the largest soft ground TBM ever used in North America at the time. Due to the difficult ground conditions and construction risks involved, the Design and Build Contractor undertook an exceptionally detailed ground investigation to characterise and understand the materials to develop an appropriate construction methodology for the tunnels.
GCG were engaged as a specialist sub-consultant to provide an independent interpretation of the ground conditions and advise on the bored tunnel construction methodology. GCG performed a holistic interpretation of the ground investigations to confirm the contractor’s ground model and in particular the characteristics of a highly porous, variably cemented coralline limestone layer located at a critical section of the tunnel alignment.
GCG also advised on soil conditioning treatments for EPB tunnelling on the project. This involved designing and performing a series of laboratory tests to assess the feasibility of conditioning the different materials to be encountered for successful EPB tunnelling and informed the selection of appropriate tunnelling methods for the ground encountered at different sections along the alignment. GCG were also involved in field monitoring of the TBM spoil properties and the machine operations throughout the tunnel construction.
Merritt, A., Jefferis, S., Storry, R. & Brais, L. (2013). Soil conditioning laboratory trials for the Port of Miami Tunnel, Florida, USA. World Tunnel Congress 2013 Geneva, Underground – the way to the future! G. Anagnostou & H. Ehrbar (eds).
Storry, R. B., Pina, R. M., Hochart, A. & Hight, D. W. (2013). Ground investigation challenges at the Port of Miami Tunnel Project, Miami, Florida, USA. Rapid Excavation and Tunneling Conference & Exhibit 2013, Washington DC