Deformation modulus of rock mass is an important parameter for all geotechnical applications. However, its determination is a difficult task. For this reason, rock engineers and engineering geologists have proposed numerous empirical equations for estimation of deformation modulus based on rock mass and intact rock properties. In the present study, validation of existing empirical equations in case of biotitic gneiss rock mass, a metamorphic rock of the Proterozoic age (2500My – 544My) of Indian Himalaya has been undertaken. Data of uniaxial jacking tests, rock mass rating (RMR), rock tunnelling quality index (Q) and geological strength index (Qc) were used for determination/estimation of deformation modulus. Estimated values from empirical correlations are much higher in comparison with the actual in-situ results as well as the average results of the laboratory tests performed on selected core samples of biotitic gneiss. Further, in this study, the influence of geological features on deformability characteristics has also been studied
