A model for triggering mechanisms of shallow landslides

L Montrasio,R Valentino

doi:10.5194/nhess-8-1149-2008

Abstract

Abstract. Rainfall-induced shallow landslides, also called "soil slips", are becoming ever more frequent all over the world and are receiving a rising interest in consequence of the heavy damage they produce. At the University of Parma, a simplified physically based model has been recently set up for the evaluation of the safety factor of slopes which are potentially at risk of a soil slip. This model, based on the limit equilibrium method applied to an infinite slope, takes into account some simplified hypotheses on the water down-flow and defines a direct correlation between the safety factor of the slope and the rainfall depth. In this paper, this model is explained in detail and is used in a back analysis process to verify its capability to foresee the triggering instant of rainfall-induced shallow landslides for some recent case studies in the Emilia Romagna Apennines (Northern Italy). The results of the analyses and of the model implementation are finally shown.

Highlights

The literature and various studies performed on shallow landslides or “soil slips” reveal that they have caused heavy damage in different environmental conditions all over the world (Kesseli, 1943; Campbell, 1975; Govi and Sorzana, 1980; Govi and Mortara, 1981; Sidle and Swanston, 1982; Ellen and Wieczorek, 1988)
The results obtained through the application of the simplified model to the four sample sites, on the basis of the geotechnical and pluviometric data relative to each event considered, make it possible to obtain the trend of the safety factor in time
On the basis of the limit equilibrium method, the model defines the safety factor of a slope taking into account the slope geometric features, the geotechnical characteristics and the shear strength of the soil, both in saturated and unsaturated conditions, the drainage capability of the slope, and the way of rainfall infiltration

Summary

Introduction

The literature and various studies performed on shallow landslides or “soil slips” reveal that they have caused heavy damage in different environmental conditions all over the world (Kesseli, 1943; Campbell, 1975; Govi and Sorzana, 1980; Govi and Mortara, 1981; Sidle and Swanston, 1982; Ellen and Wieczorek, 1988). Soil slips are portions of soil of small thickness that, in consequence of rainfalls, detach from the shallow part of a slope and move in different ways. A typical soil slip can be characterised by a first triggering phase and a second evolving phase that may appear as a global translational movement of a few centimetres (Fig. 1A) or several meters (Fig. 1B) or it may turn into a much more evident phenomenon having the characteristics of a mud slick (Fig. 1C and D).

Objectives

Results

Conclusion