ESTIMATING THE RADIAL DISPLACEMENT ON THE TUNNEL BOUNDARY BY ROCK MASS CLASSIFICATION SYSTEMS

Abstract

RMR classification of rock masses was developed based on a great number of practical cases in tunneling by Bieniawski in 1973. RMR illustrates instructions of the design of support and stand-up time of the tunnel. In Russia, there is a rock classification for the stability of rock masses surrounding the horizontal tunnels that have been developed by VNIMI and are included in design standards (SNiP II-94-80 Underground Mine Workings). In this paper, the relation between RMR, VNIMI’s classification, and Radial Displacement (RD) was surveyed by using RS2 software (Rocscience). Geology conditions of Ialy Hydropower Plant Expansion Project, Viet Nam for D shaped circle and horseshoe tunnel is adopted as a reference case. The tunnel stability was estimated by the Radial Displacement (RD) determined at some vital points of the typical tunnel boundaries that allow predicting the stability of the tunnel after being supported.