Abstract

For the pertinent use of NMT method, both characteristics of jo ints (JRC, JCS and ф r) and characteristics of rock mass(Q-Value) must be investigated carefully. The main objective of the study presented is to investigate how sensitive thepredicted behaviour of an underground excavation is to various realistic assumptions about some input parameter for thejointed rock mass. Joint pattern in the tunnel is predicted by statistical approach (chi-square test). In this paper,sensitivity studies involving in joint characteristics were car ried out. The parametric studies involving change in Barton-Bandis joint model have shown that JCS is relatively insensitiv e to JRC and ф r. An increase in JRC value may not,according to the Barton-Bandis model, necessarily lead to a dec rease in displacement. The importance of dilation inpredicting the behaviour of a rock mass around an excavation is emphasized from a comparison of the Barton-Bandisjoint behaviour model with the Mohr-Coulomb model. The Barton-B andis model predicted higher stress, which allow forthe build-up of stress caused by dilatant behaviour.