Evolution of stabilised creeping landslides

Abstract

A simple analytical model is proposed to quantify evolution of a creeping landslide stabilised by a retaining wall, or by a natural barrier at the bottom of the sliding mass. Development in time of both the landslide displacements and the earth pressure acting on the retaining structure is obtained in the closed form, with the latter given by the classical Terzaghi expression for the average degree of consolidation. Depending on the value of the long-term safety factor, the landslide either eventually slows down, asymptotically approaching final displacements, or the soil behind the retaining wall comes to a passive failure, followed by a post-failure evolution of the landslide. The model is capable of quantifying both scenarios, with some of its features successfully validated against the monitoring and geotechnical data from the two case studies: the Combe Chopin and Ganter landslides in Switzerland. For the Combe Chopin landslide, which came to a standstill, the model has demonstrated its ability to predict final downhill displacements and their development in time. For the Ganter landslide, which failed and achieved steady-state velocity, the model correctly predicted the long-term landslide evolution and the effects of drainage and erosion on the displacement rates.