Tunneling and support systems of the Selahaddin Tunnel

This thesis emphasizes the major factors which controls rock mass properties and thereof stability. Some of them are bedding and layering which are major types of discontinuity, mineralogical properties, and rock substance properties of both dry and 72 hours soaked samples. Clay minerals, particularly smectite group clay minerals, are the most governing factor when the medium is moist to wet. 5% of smectite clay mineral in a rock might be enough to turn the uniaxial compressive strength (Uc, MPa) of 5 to zero upon soaking for 72 hours. Reinforcement design is a dependent function of (a) attitude of bedding and in places fault, (b) tectonically induced in-situ stresses, and (c) rock mass and rock substance properties. The innovative approaches proposed herein contributed appreciably to Salahaddin, Shaqlawa, and Mirawa tunnels which have already been completed within extremely weak to moderately weak sedimentary rock units without any failure in the same region. The trinity water, discontinuity, and clay (WDC), is the main causative behind all geotechnical problems. In this sense model study of geology, hydrogeology, engineering geology, geotechnics, and geoenvironment in four dimensions (x, y, z, and t) comes first to locate and orient the alignment of a tunnel properly and complete the project at a desired level of confidence. It is not difficult to envisage and foresee inevitable failures, if a tunnel is located along an active fault.