Control of a Landslide that Occurred at Km 303+800 of the Mianeh-Ardabil Railway

In Mianeh-Ardabil railway, due to the weak geological, a landslide occurred during implementation at km 303+800. In this research, an attempt has been made to determine the cause of the landslide, its surface dimensions and depth, and the geotechnical parameters of the field by means of detailed local investigation and geotechnical tests, as well as a back analysis by computer modeling (EL and FEM). After understanding these parameters, various stabilizing designs were investigated and analyzed, and finally a geogrid reinforced soil wall was designed and implemented for this purpose. In order to determine the depth of the slip’s surface, three small exploratory trenches were excavated and based on the layers displacements that could be observed in the trench walls, an experimental mathematical model was obtained. The model and observations was in good agreement with the results of the study of the changes in shear strength with soil depth. The results of the initial excavation modeling were carried out to reach the elevation code of the reinforced soil wall base with a short-term safety factor (1.25). The experience gained on site indicated the desired stability during the implementation period and the safety factor was sufficient to ensure the temporary slope stability. The stability analysis of the reinforced soil wall along with the railway embankment was done under 8 different states, (drainage and un-drained soil in two static and dynamic conditions with two general states: the stability analysis on the initial landslide’s surface and other possible landslide surfaces).