In recent years, due to population growth, urban and inter-urban traffics are increasing, while the use of road tunnels and railway tunnels has reduced traffics, consumption fuel and etc. Koohin railway tunnel located in the Qazvin-Rasht route in western part of the Alborz mountains is one of the great sections inter-urban tunnels in Iran. It is of clear importance that preventing financial losses and casualties requires the structures to withstand the static loads such as in-situ stress and dynamic loads such as earthquakes. Due to the dynamic loads on the structure, several risks can be created in different
sections of tunnel. In this paper, the sections with 6, 15, 30, 40, 60, 80 and 100 meters of overburden along the Koohin tunnel alignment were investigated in order to determine the maximum risk. This section in outset was analyzed by analytical methods under conditions of full-slip and no-slip caused by dynamic loads triggered by Zanjan earthquake-prone fault and north Qazvin earthquake-prone fault, respectively. Next, the risk of sections was examined by impact-probability matrix method. The results show that the highest risk created in sections with 6, 80 and 100 meters of overburden.