Characterization and stabilization of an unstable railway cut slope in marl - A case study

Abstract

This paper presents a study of railway cut slope instability at Northeast of Iran. In 1996 the failure occurred at eastern side of the trench, after a long raining period. The trench has been cut in marl, with a well defined weathering profile, from unweathered at depth, to fully weathered at the ground surface. In order to determine the shear strength parameters of the failed ground mass, some back analyses of the failed slope were performed, using a limit equilibrium method by means of CLARA scientific software. By this, the relationship between cohesion and friction angle and also the most probable shear strength values were found. In addition, the change of marly layer with depth was made clear. The main designed stabilization method is, to construct a number of lime columns inside the slide mass and a lime wall at the toe of the unstable slope. The desired configuration of the lime columns was determined by performing some stability analysis, using Finite Element Method by means of PLAXIS 7.2 software. These analyses demonstrate that, by constructing lime columns at 20×20 m grid, the safety factor of the unstable mass will be increased from 1.10 to 1.36 in short-term period, and to 1.50 in long-term period.