Abstract
In this research work, Rock Mass Rating (RMR) was used for the characterisation of rock mass along the tunnel alignment based on physical, geological and geotechnical data of the project area. The deformation modulus was determined using established empirical models for each geotechnical unit of considerations (GTU-4, GTU-5 and GTU-6). The support systems were recommended for all geotechnical units using RMR support chart. Hoek and Brown constants were estimated for numerical modelling using Roclab software. Phase2 software was used for the investigation of redistributed stress conditions and changes in the rock behaviour due to sequential enlargement of the small size rail tunnel. Various design input parameters such as physical and geotechnical properties, in situ stresses, modulus of deformation of rock mass, support systems recommended by RMR were used as input parameters in Phase2 software. The simulated models were analysed for each of the selected geotechnical unit. From the analysis of the simulated models, it was concluded that at GTU-6 there are more chances of instability as compared to other geotechnical unit.
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