Numerical Analysis of Large Adjacent Caverns for Sydney’s Epping to Chatswood Rail Line

The Epping to Chatswood Rail Line is the NSW Government’s largest publicly funded infrastructure project. It is currently being constructed through the Triassic age sandstones, siltstones and shales of the Sydney Basin. The project consists of twin, 12.5km, 7.2m diameter rail tunnels, 4 new station caverns and numerous shafts/tunnel service buildings. Macquarie Park, Macquarie University and Delhi Road Stations are 3 of the 4 stations along the route. The layout of each of these stations requires the construction of a number of large caverns (20m span) and shafts within close proximity of each other.

As part of the design process, a large amount of numerical modeling has been conducted to investigate the potential interaction between these large adjoining cavern structures. The presence of relatively high insitu lateral stresses has presented a number of challenges for the design process. This paper briefly describes a suite of three dimensional distinct element analyses (3DEC) conducted to investigate the behaviour of these large adjacent excavations. Particular reference is made to how these analyses were used as part of a larger design process.