Single-layer load-bearing tunnel lining structure in hard rock masses

Abstract

The paper presents some of the observations made during tunnel construction with a single-layer load-bearing lining in hard rocks. The load-bearing elements of one such lining were observed, as were measures to improve the quality of the material, as well as other required actions to guarantee its stability throughout its lifespan. An extremely important measure is to limit the water inflow into the tunnel, by pressure grouting contemporary grout mixtures into the fractures, commonly referred to as pre-grouting. This paper also shows the construction time and cost of single-layer lining compared to the traditional two-layer lining. The construction expenses of single-layer tunnel lining are slightly lower compared to two-layer tunnel lining. Nevertheless, the main benefit is construction time-savings. The observations are presented using a practical example: a tunnel in the limestone rock near the Mratinja dam, between Plužine and Šćepan polje in Montenegro.