SOME DEVELOPMENTS IN SEGMENTAL TUNNEL LININGS DESIGNED IN THE UNITED KINGDOM

Standard all-purpose concrete and cast-iron tunnel linings are discussed with the modifications necessary to suit them for specific purposes and particular types of ground conditions. As well as being designed for ease of fabrication and erection, tunnel lining ring segments also serve as external support for surrounding ground and internal support for roads, railways and services. Although attempts are made to optimise the use of surrounding ground and tunnel lining for mutual support, stresses incurred in handling and construction also must be considered in lining design. In suitable ground conditions the expanded lining has become accepted practice in which a large number of small segments are used to avoid the need for reinforcement. /TRRL/