The mechanism of a railway landslide caused by rainfall

This paper presents the study of a landslide induced by rainfall above a railway line in terms of site investigations, laboratory tests, finite element, and limit equilibrium analyses. The purpose of the study is to identify the cause and failure mechanism so as to prevent the recurrence of such failure. The slope concerned was composed of 3 similar to 4 m thick fissured clay overlying highly weathered mica marble interbedded with quartz schist. The slope was cut into two steps and was protected by a masonry revetment and a thin masonry retaining wall at the toe. The region concerned suffered a whole month's light drizzle in September, after which a rainfall of an intensity of 80 mm (in 48 h) occurred 5 days prior to the failure that happened on October 5, 2004. The rainfall infiltration and a failed drainage system behind the retaining wall resulted in high saturation of the clay and finally led to an undrained failure. The short-term slope stability using total stress parameters was examined by the finite element and limit equilibrium analyses. The factors of safety of the slope obtained by the finite element and limit equilibrium analysis were 0.935 and 0.854, which are in agreement with the occurrence of failure. Since the slide took place through the interface of the soil and rock, the exposure of rock has significant effect on the stability.