Support pressure assessment in arched underground openings through poor rock masses

Himalayan tunnels provide challenging opportunities for working on the problem of assessment of support pressure in tunnels. A resume of the efforts by Indian researchers on this topic is presented in this paper, with a brief review and comparison with the approaches of Bieniawski (1979) and Barton et al. (1974; Analysis of Rock Mass Quality and Support Practice in Tunnelling, and a Guide for Estimating Support Requirements, Report by NGI, June). It is noted that Goelʹs classification of tunnelling conditions (Goel, 1994; Correlations for Predicting Support Pressures and Closures in tunnels. Ph.D. Thesis, Nagpur University, India, p. 308) is complementary to the Q-system. Contrary to Terzaghiʹs theory, support pressures are observed to be independent of opening size.