The Dez-Qomroud Tunnel Project lot No. 6 is situated along the Zagros Mountains in west-central Iran. A comprehensive engineering geological study was conducted to determine geomechanical characteristics of the rock masses along the tunnel route. Rock mass classification systems such as rock mass rating (RMR), Q-tunneling index, rock quality designation (RQD), geological strength index (GSI) and rock mass index (RMi) were all employed to classify and characterize the rock masses in order to provide a basis for estimating deformation and strength properties, to supply quantitative data for the design engineering team, and to provide a platform for communication between exploration, design and construction groups. Results obtained from applying different rock mass classification systems for the different rock masses exposed at the QTP6 tunnel path are shown and interpreted in this article.
Supplying sufficient water for both drinking and irrigation purposes to vast arid areas in central Iran that have limited local supplies is one of the great challenges that the Iranian water supply industry faces. The Dez-Qomroud water tunnel project will convey water from the adjacent Dez Highlands to a central Iran watershed known as Qomroud in order to address these needs; it involves four tunnels (total 50 km), three small dams and a large dam. The Qomroud Tunnel Project lot No. 6 is situated along the Zagros Mountains in west central Iran. The tunnel depth (overburden thickness) ranges from 20 to 165 meters. Comprehensive engineering geo-logy and rock mechanics studies were conducted in the study area to assess the geologicalgeomechanical characteristics of the rock masses along the tunnel route. Based on geotechnical drilling reports, the main stratum along the tunnel is a weak mud-supported conglomerate: the Bakhtiari conglomerate formation. The physical and geomechanical properties of the conglomerate exposed in the study area were determined in the laboratory based on ASTM standards and ISRM suggested methods. In order to characterize the rock masses along the tunnel axis, rock mass classification systems such as rock mass rating (RMR), Q-tunneling index, rock quality designation (RQD), geological strength index (GSI) and rock mass index (RMi) were employed to classify and characterize the rock mass. The goals were to provide a reliable and proper basis for estimating deformation and strength properties, to supply quantitative data to design engineers, and to provide a quantitative platform for communication between exploration, design and construction groups. The rock mass constants mb, s and a, GSI values, uniaxial compressive and tensile strengths, cohesion and internal friction angle, global strength and the Young's modulus of this rock mass at the tunnel site were determined from GSI values using RocLab freeware. Results obtained from different rock mass classification systems for the conglomerate rock mass are shown and interpreted in this article.
The Qomroud water Tunnel Project lot No. 6, known as QTP6, is a nearly 1.80 km long tunnel, located 45 km south of the Aligoudarz-Isfahan 500 road (Fig. 1).
