The origin of the rocks of Chalus road, active tectonics or Quaternary climate

Chalus Road, as one of the main axes of communication between the north and south of Central Alborz, has always witnessed the occurrence of numerous rockfalls and this causes countless damages. In this article, the method of dispersion and the reasons for the occurrence of these spills are investigated. For this purpose, the method of risk zoning of rock fall using rock engineering factors has been used. The results show that between the Karaj Dam and the beginning of the urban area, there are at least nine main areas where rock falls affect the road axis. Asara shales, middle tuff member, and Quaternary units respectively have the highest amount of rockfall origin. Except for some areas, there is no defined connection between the tectonic fracture zones and the starting points of rockfalls. Statistical studies show that most landslides occur at the end of winter and the beginning of spring. Regardless of the fact that tectonics has caused the fragmentation of the rock units of the region, the time of occurrence of the events shows their direct relationship with the Quaternary climate. It is suggested that the road department implement stability systems and rockfall control in identified high-risk areas in order to prevent future disasters