Rock-fall Hazard Investigation on Chalus Road

Description

    Project Manager: M.J.Bolourchi E-mail: mjbolourchi@gsi.org.ir Editors: M.J.Bolourchi; I.Entezam Soltani; M.Mahmoudpour; F.Ansari 2006   Contents: Chapter one: "climate and hydrology" A.Shemshaki Chapter two: "Geomorphology, Geology, Engineering geology and Structural geology" A.Sadeghi; A.R.Sayareh; M.Mahmoud Pour; S.Karim Nejad Tari; A.Dadsetan Chapter three: "Rock-Fall Hazard Rating System (RHRS)" I.Entezam Soltani Chapter four: "Slope Mass Rating (SMR)" M. Mahmoud Pour; S. Karim Nejad Tari Chapter five: "Conclusion" I.Entezam Soltani; M. Mahmoud Pour; M.J.Bolourchi     Abstract Chalus road is one of the most beautiful country roads and a major lifeline between North and Central part of Iran. Due to active tectonic of the area and lack of modern engineering design in constructing of this old road it is susceptible to stability problems especially rock-fall. The event of 28th May 2004 earthquake triggered a lot of rock-fall along the road and caused human casualties and heavy damage to the road. Following this event engineering geology department of GSI started a project to investigation rock-fall hazard along the Chalus road from pole-zangole to Marzan-Abad (almost 50 km of road). This study used two different methods: Rock-fall Hazard Rating System RHRS (Pierson et al., 1993) and Slope Mass Rating SMR (Romana, 1985, 2003) to evaluate rock-fall hazards. The preliminary rating of the road according to RHRS, shows that nearly 20 km of road come under C category ( High estimated potential for rock-fall in this study) and 20 km under B category ( Moderate estimated potential for rock-fall). Detailed rating on 47 slopes in C section of the road shows following results, 7 slope receive score between 400-500, 18 slopes 500-600, 14 slopes 600-700 and 6 slopes receive score more than 700. The SMR classification of 40 slopes shows that highest value (SMR= 76) belong to Kahar formation (almost stable) and lowest value (SMR= 35) belong to sandstones of Doroud Formation (need the complete support system). This study is intended to assess the rock slopes conditions adjacent to road, to identify where rock-fall remediation is needed and prioritize the work using these approaches, and also may be able authorities to make informed decision on whether to take a total correction approach or only reduce the rock-fall hazard according to each slope condition and give a coast estimation and understanding of benefits associated with each of their choices. It should be mention that this result is valid for normal and static condition, more detailed work is necessary in case of probable earthquake occurrence and other extreme conditions.