EXAMPLES OF THE BEHAVIOR OF SHOTCRETE LININGS UNDERGROUND

Abstract

The paper presents examples and general observations of the use of shotcrete based on its application in a number of different tunnels and permanent underground openings in Norway. Shotcrete linings of varying lengths are to be found in railway, highway, water supply and sewage tunnels, but first of all in hydro power tunnels. Shotcrete is also used in a number of different underground rooms for lining and supporting. Shotcrete linings are often regarded as an alternative to concrete linings cast in place. Hence these two types of support have to be carefully compared in cost, quality and flexibility. This will often set a limitation on the use of shotcrete. When determining the permanent support of a tunnel one has not only to consider the cost and the type of stability problem, but also different circumstances concerning the prospective use of the tunnel. Furthermore, the physical and mechanical conditions for a tunnel often change after it is in use. Among the applications discussed are underground openings in dry conditions and temperatures above freezing, openings exposed to freezing and thawing, water tunnels in swelling clay and in crushed zones exhibiting squeezing.