Department of Civil Engineering, Zanjan Branch٫ Islamic Azad University٫ Zanjan, Iran
This paper presents the results of engineering geological studies of rock blocks along a road tunnel in NW Iran. The tunnel is to cross the Western Alborz Mountain Range through 530 m in length with 11.2 m span and 8 m height. Eocene tuffs and andesites crop out in whole of the tunnel route. Numerical analyses are done using, a 3D stability analysis and visualization program, called Unwedge that studies pyramidal blocks and supplies an easy-to-use, graphical environment for data entry and visualization. The analysis of support pressure and the sensitivity analysis are done in the different units of the tunnel and the most critical mode of joints combination and the most optimal excavation direction in each of the units is determined. From this analysis, it is possible to ascertain the support pressure for stabilize the rock blocks as a function of the trend and plunge of the tunnel axis. Three-dimensional diagrams have been used to illustrate how the support pressure assembly might affect the design of an excavation.