engleski

Impact of gravity retaining wall on the stability of a sandy slope in small-scale physical model

Physical modelling of landslides by analysing the behaviour of small-scale landslide models subjected to artificial rainfall can be divided into modelling under 1g conditions and under increased acceleration (n times gravity) in a centrifuge. Physical modelling of landslide initiation began in Japan in the 1970s on scaled natural slope models. After initial experiences with field and laboratory researches, small-scale landslide modelling has found wide application around the world in various aspects of landslide investigations, analysing different types of landslides, different types of slope materials and landslide movements. The main task of landslide physical modelling has been to study the initiation, motion and accumulation of fast flow- like slides caused by infiltration of surface water. Studies that have included landslide mitigation measures in the small-scale physical model are rare and have not established correlations with the behaviour of on-site mitigation structures. This paper discusses the behaviour of a small-scale sandy slope supported by a gravity retaining wall in the foot of the slope, during artificial rainfall in 1g loading conditions. Two models of sandy slopes, with and without retaining wall applied, were exposed to identical intensities of artificial rainfall. The results of the simulations indicated that the slope supported by the gravity retaining wall at the toe remained stable under the same conditions under which the sandy slope collapsed. The supported slope also remained stable under much longer rainfall. At the end of the simulation, the supported slope was subjected to much higher rainfall intensities, well above the infiltration capacity of the sandy material, and surface runout was affected. The combination of surface erosion and saturation of the superficial layer of the slope led to the initiation of a debris flow, while the complete saturation of the slope at the moment when the ground water level reached the surface of the slope caused the soil strength to be exceeded and the formation of a surface of rupture and consequently movements of the formed landslide body. Although the landslide movement caused displacement and longitudinal deformation of the gravity wall at the slope foot after local shear failure in front of the wall foundation, in general the gravity wall significantly improved the stability of the slope. The results of the measurements carried out with the installed geodetic and geotechnical monitoring system allowed a comprehensive understanding of the whole process of infiltration of precipitation and reduction of soil strength until the development of the fracture surface in the slope, as well as the process of incremental load development on the retaining structure until the limit resistance of the structure.

landslide, physical modelling, sandy slope, remedial measures, monitoring

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