The Qomroud Long Tunnel (QLT) project will convey water from the adjacent Dez Highlands to a central Iran watershed known as Qomroud to address water needs in central Iran. Laboratory tests on core samples were carried out to delineate the physical and geomechanical properties of the intact rock along the tunnel axis. Physical and geomechanical properties such as dry density, saturated density, porosity, uniaxial compressive strength (UCS), shear and compressional wave propagation velocity (VS, VP), and water absorption ratio were determined for each rock unit, based on ASTM standards and ISRM suggested methods. Results from these laboratory tests are presented and discussed in this article.
Numerous examples exist in the engineering geology literature of poor engineering geological investigations or unexpected ground conditions which led to severe construction problems in tunneling and underground excavations, imposing large delays in construction time and notable increases in tunnel advance costs. Tunneling activities are perhaps the most geologically dominated civil engineering projects undertaken. However, even a well-designed, comprehensive geotechnical study can directly examine but a negligible portion of the rock mass along the tunnel axis. Thus, there is always substantial uncertainty associated with the engineering geology data collected, even with a comprehensive site investigation program. Supplying sufficient water for both drinking and irrigation purposes to a growing population is one of the great challenges that the Iranian water supply industry faces. The Qomroud Long Tunnel (QLT) project will convey water from the adjacent Dez Highlands to a central Iran watershed known as Qomroud. It is part of the Qomroud Tunnel Projects (QTP) which involves four tunnels, three small dams and a large dam. The QLT, the longest tunnel in the QTP project, is situated in the geologically-defined Sanandaj- Sirjan metamorphic zone along the Zagros Mountains. This zone is one of the most tectonically active areas in Iran and has experienced several metamorphic, magmatic and tectonic phases in the pre-Cenozoic era. From the initial geological investigations along the first 10 kilometers of the QLT, known as QLT1, the main tunnel-axis strata appeared to be schistose rocks such as pelitic schist, calcareous schist, and graphitic phyllite alternating with interlayers of meta-dolomite and meta-quartzite. The lithomechanical characterization of the rocks included comprehensive rock mechanics studies conducted in the study area. In this article we highlight results from laboratory tests on core samples carried out to delineate the physical and geomechanical properties of the intact rock at the tunnel site. For the different rock units exposed in the study area, physical and geomechanical properties such as dry density, saturated density, porosity, durability index, uniaxial compressive strength (UCS), shear and compressional wave propagation velocity (VS, VP), and water absorption ratio were determined in the laboratory based on ASTM standards and ISRM suggested methods. Also, engineering and mechanical properties of the soil sections along the tunnel were characterized and tested.