Tunnelling experiences obtained from projects in Madeira, Iceland and the Faroe Islands will be presented in this paper. These experiences include such as tunnelling conditions in general, support and grouting philosophy and also various types of problems encountered and the solutions found to deal with them, In particular, tile applicability of the most common rock mass classification systems will be discussed in tile paper. Tunnelling in volcanic rock mass have been experienced elsewhere too, however, as a first step in gathering experiences it was considered sufficient to include projects from the countries mentioned above. If this exercise would provide any systematic findings that lead to believe that tunnelling in volcanic rock masses is different compared to other rock masses, a further approach on an increased database would be suggested.
With a rather diversified background the authors of this paper found an interesting interface, namely that related to tunnelling in volcanic rocks. Two of the authors have their experience and background from the Madeira Island, whilst one has his experience particularly from the Nordic countries where tunnelling in volcanic rocks have taken place in Iceland and tile Faroe Islands. On this basis this paper will try to draw the common aspects of tunnelling in volcanic rocks from a number of projects in these countries mentioned above. Common for these is also the fact that they are small groups of islands situated in the Atlantic sea hundreds of kilometres out from the nearest mainland or continent. It was found an interesting exercise to try to draw up the tunnelling experiences from a number of selected projects in these countries and identify common problems and how these were solved. The projects that will be discussed in particular include such as tile road tunnels from Funchal city - Cot a 200 (Marmeleiros: Penteada and Quinta da Palmeira twin tunnels): Porto da Cruz (Cruz da Guarda, Serrado single tunnels); and Água de Pena (Queimada single tunnel). Further, tile water supply and hydropower tunnels of Fajã de Ama, tile connection tunnel of Encumeda to Ribeira Grande São Vicente and in the multipurpose tunnels of Socorridos. From the Nordic countries the experience from subsea road tunnels in Iceland (tile Hvalfjördur tunnel) and the Faroe Islands (the Vagatunnilin tunnel) will be presented together with some general experiences from a wider range of projects. Rock mass classification using various classification systems will also be discussed. In the Nordic countries the Q-system developed by Barton and his colleagues has been the dominating whilst in the Madeira Island the Bienawski geomechanic (Bieniawski, 1989, in Hock. 1997) is most commonly applied. Neither of these two systems were established and developed with particular focus on volcanic rock masses, and are they really applicable as reliable tools these geological circumstances? This paper will discuss these classification systems based on the experiences from the projects mentioned above and specifically focus on the parameters used in the application of quantitative rock mass classification systems in volcanic, basaltic rock types.
