The 3D stability analysis of rock mass surrounding Bazoft dam diversion tunnel

Abstract

The Bazoft dam diversion tunnel with length of 450 m and diameter of 9 m is to be excavated in left abutment of Bazoft dam and the currently under study. The lithology mostly comprises of jointed Asmari and Jahrum limestones. The tunnel passes the AS2 zone of Asmari formation belongs to dolomitic limestones of Miocene age. The rock mass discontinuities orientations were studied by a field survey and a statistical analysis. Also the borehole logs and outcrop surveys were used to determine the basic characteristics of the discontinuities. The rock mass surrounding the tunnel is classified using the Q, RMR and GSI methods. The engineering properties and temporary tunnel support systems were determined based on the methods. A series of 3D analytical (stress-strength method) and numerical continuum (FEM) stability analyses were conducted for the rock mass surrounding excavation face based on the excavation scheme proposed by the empirical method based on RMR for supported and unsupported tunnel. Based on the analyses, there is no need for intense support installation. For verification and to determine the influence area of the face, the longitudinal displacement profile values were extracted, drawn and compared with the available literature. © 2010 International Society for Rock Mechanics. All rights reserved.