U.K. Tunnelling Costs Halved by Use of Unbolted Concrete Lining Segments

Britain now has more than 25 years experience in the development of precast tunnel linings, for tunnels in clay. These linings are expanded directly against the ground. Under suitable circumstances, these linings show a marked savings in cost compared to the methods of tunnel lining which they have replaced. Savings in several instances have amounted to more than 50%, in conjunction with more rapid rates of construction. While these linings were originally studied for tunnels in London soils, they have been adapted to several other stiff and firm clays and marls for roads, railways, electrical services and water. Several analytical and experimental studies have been necessary in developing these linings, including trial lengths of tunnel to familiarize contractors and to confirm expectations.