Temporary Support Of Deep Basement Excavations In Rock

Deep basements have become common in our modern cities. Whilst the analysis and design of retention systems for deep basements in soil are relatively well established, the same cannot be said for deep basement retention systems in rock. In many instances the design of retention systems in rock are based on a soil mechanics approach and as a result often ignore unique aspects of rock mass behaviour that can significantly impact the performance of these retention systems. It is important that the characteristics of the rock mass are well understood and are quantified during the ground investigation. Some of the aspects of retention system design and analysis that are set out in this paper only became apparent following unsatisfactory performance of a retention system. Due to the sensitivity surrounding such unsatisfactory performance, it has not been possible to include the specific case studies. As a result, this paper provides an overview of the many aspects involved in respect to ground investigations, analysis, design and construction of deep basement retention systems in rock that are required to mitigate against unsatisfactory performance. This paper is restricted to temporary embedded wall retention systems that are installed to allow the construction of the permanent basement structure.