Characterisation of ground conditions to reduce risk for building footing design in Melbourne, Victoria

Footing systems for many of Melbourne’s tall buildings are rarely governed by their ultimate capacity, rather, the allowable displacement of the footing system is likely to be the primary consideration. An appropriate geotechnical investigation must therefore assess the stiffness characteristics of the in situ ground, and in particular the founding materials that support these footing systems. In order to further characterise ground conditions and better manage ground risk, in situ pressuremeter testing can be used in conjunction with more traditional investigation methods and verification activities during construction to provide prudent yet not overly conservative geotechnical advice and design for these developments. This paper discusses two case studies comprising historical geotechnical investigations for buildings in Melbourne, where the use of pressuremeter testing in conjunction with traditional investigation methods have provided greater confidence on the deformation behaviour of founding conditions. This paper sets out how the results from the investigations were used to inform footing solutions to be designed and subsequently constructed, as well as discussing the value of verification activities to confirm design assumptions, further reducing the ground risk during construction and realising efficiencies in the footing design.