The violent failure of rockmass exhibited around the head race tunnel in Parbati (Stage-II) hydroelectric project is the key example of subsequent and repetitive rockbursts observed in any deep underground excavations. The rockbursts occur under very high in situ stress and in massive rocks of high brittleness index. To estimate the effect of geometry and speed of excavation, varying rockmass and such a high in situ stress has on the intensity of rockburst observed in a tunnel, the headrace tunnel of Parbati (stage-II) project is taken as an example. A comparison of varying stresses, deformation and strength factor on the tunnel boundary with the progressing excavation is drawn between sections of the tunnel with a recorded history of rockbursts. The first section consists of the 6 m Ø horse-shoe tunnel excavated with drill and blast method (DBM) and the second section consists of the 6 m Ø circular tunnel excavated with tunnel boring machine (TBM). To make the comparison fair, almost same overburden depth in similar Manikaran quartzite rock along the tunnel with constant inclination are chosen. Thus, the objective of the paper is to observe, compare and conclude the failure expected based on stresses generated, deformations possible and rockburst potential using numerical and empirical classification methods along both the tunnel sections as the excavation progresses. In conclusion, the tunneling experience, observations made, and mitigation methods thus adopted serve us to prepare for future projects in the Himalayas.