Ground behaviour and rock mass composition in underground excavations

Underground excavations like tunnels, caverns shafts, are located in a vast variety of rock mass and ground conditions with different modes of behaviour. The paper describes the main parameters and features determining the behaviour of the ground surrounding an underground excavation, namely: (1) the ground conditions (rock mass, stresses and water) and (2) the project related features, (size and shape of the opening and excavation method). Based on this a simple, qualitative division of the rock masses is presented, which together with the influence of stresses, ground water and dimension of the excavation, is used to find the probable behaviour. This may help the user to select appropriate rock engineering tool(s) for the geotechnical design as has been described by the two authors in an earlier paper.