Insights on the stability of large excavations from analytical and numerical models

Lack of information on the in-situ deformation and strength properties of the ground mass is one of the major difficulties in the design of underground excavations. As a consequence, design decisions are often made on the basis of empirical decisions developed from the observed performance of both successful and, sometimes, unsuccessful designs in as wide a variety of situations as possible. Increasingly, both technological and economic imperatives are forcing engineers to designs that reach beyond the limits of previous experience, as represented in the empirical data classifications systems. This paper presents examples of approaches to reliable extrapolation of available experience.