Investigating the reactivation potential of an ancient landslide in the second lot of the Miyaneh-Ardabil railway

In this study, a huge old landslide located at the chainage of ۳۷۰ km of the second lot of the Miyaneh-Ardabil railway has been investigated. What makes this old landslide important is the presence of large bridge (# ۱۲) on the railway route at the toe of this landslide. This landslide has occurred in geological units which consist of volcanic and pyroclastic rocks, mainly tuffs, andesitic tuffs, and andesites. In some parts of the study area, these geological units are geotechnically very weak and do not have favorable quality due to weathering of rock masses and occurrence of fault zones. The results of studies show that the main cause of landslides is the saturation of geotechnical materials due to long-term precipitations and the occurrence of medium to high magnitude earthquakes in the surrounding areas (according to high seismicity of the area). This study aims to investigate the engineering geological features of this large and old landslide and to provide solutions to reduce its risk. For this purpose, after evaluating the geotechnical parameters of materials, through laboratory and field tests, field surveys, experimental and analytical methods, engineering judgment and back analyses, the stability of the slope has been analyzed using limit equilibrium methods by considering appropriate failure criteria for the involved materials. The effect of the two main parameters of groundwater level fluctuations and seismic accelerations on the stability of the slope has been investigated. Based on the analyses results, the construction of drainage galleries for removing underground waters and surface drains for collecting surface waters, are suitable methods to increase the safety factor and reduce the risk of landslides.

Keywords:

landslide , limit equilibrium , reversal analysis , safety factor , stabilization