Tunnel lining design — do the theories work? : Schmidt, B Proc 4th Australia-New Zealand Conference on Geomechanics, Perth, Western Australia, 14–18 May 1984V2, P682–693. Publ Barton: Inst of Engineers, 1984

Abstract

Continuum mechanics models using closed solutions are fine tools for parametric studies and, when properly calibrated, can be an aid in detailed lining design. Continuum mechanics models using finite element methods go one step further allowing layered soils to be analyzed and providing a method of taking into account the vertical in-situ stress gradient. However, these methods require the use of data input that is elusive, including representations of equivalent soil modulus and presumed initial lining loads. The variability of natural deposits along a length of tunnel, and the a priori unknown details of construction, make a fine-tuned of all parts of the lining infeasible. The impossible task of designing tunnel linings is made possible by the forgiving character of the problem, as demonstrated by thousands of successful tunnel linings throughout the world. The fact is that tunnel linings only provide a helping hand; most of the tunnel support is provided by the soil itself. A circular lining made of conventional materials is capable of considerable compression and distortion without losing its integrity, providing considerable reserve beyond the nominal design load. Although rational analyses, such as those provided by reasonable structural or continuum mechanics models, should not be ignored, the most successful tunnel lining is one that properly considers practicality of construction as well as the final functional requirements of the tunnel. (TRRL)