Finite element study of preliminary design of tunnel support based on RMR and Q-system

Abstract

The main purpose of a tunnel design is to use the rock itself as the principal structural material with little disturbance during the excavation and to provide as little support system as possible. Therefore, the determination of geological and geotechnical conditions in a project area is necessary as to provide the preliminary design of support system. For purpose of this research, secondary data from an island in Singapore were collected. The assessment on the rock mass classification and tunnel support system has been carried out using Rock Mass Rating (RMR) and Q-Index (Q) systems. These two sets of support systems obtained from the RMR and the Q systems will be compared and analyzed using the numerical analysis of Phase2 software. The stress conditions and resulting deformations around the tunnel were monitored to identify the workability of the proposed support system. It was found that, at depth of 50m, the RMR support system appeared to be conservative. However, at the depth of 145m, where the stress is almost three times at which, the proposed of RMR support system provide a satisfactory result compared to the Q system. It is also appeared that total displacement of the tunnel boundary is quite sensitive to the UCSi value. Further parametric study should be carried out on other rock mass parameters to monitor the tunnel behavior.