Spiling bolts and reinforced ribs of sprayed concrete replace concrete lining

Abstract

This article discusses how and when spiling bolts and reinforced ribs of sprayed concrete should be used to achieve safe progress in poor rock mass conditions. It is discussed when bolting and reinforced ribs of sprayed concrete can replace cast in place concrete as permanent rock support. Examples from the challenging Froyatunnel illustrate how this was achieved in poor to extremely poor rock mass conditions. Numerical models comparing sprayed concrete and cast in place concrete are briefly reported.