Deterministic approaches to measure the quality of rock masses do not account for all of the uncertainties that exist. These unknowns can be dealt with probabilistically since the variability of the physical properties of the rock mass that characterize geomechanical quality is unknown prior to tunnel construction. Therefore, probabilistic approaches like Monte Carlo simulation (MCS) can be used to take these uncertainties into account during tunnel support design. The current study investigates the applicability of this approach for a railway tunnel under construction near Srinagar (Garhwal) as part of the Rishikesh-Karnprayag New BG Rail Line Project. The developed excel spreadsheet was validated with Hoek [1]. The method was used to estimate tunnel closure and extent of plastic zone for different probable ground conditions near the construction site. It was observed that installation of a relatively basic support can be quite effective in controlling tunnel closure. However, stiffer supports resulted in higher probability of lower plastic zone radius.