Landslide Mitigation

Landslide mitigation refers to lessening the effect of landslides by constructing various man made projects on slopes which are vulnerable to landslides. Landslides can be triggered by many often concomitant causes. In addition to shallow erosion or reduction of shear strength caused by seasonal rainfall, causes triggered by anthropic activities such as adding excessive weight above the slope, digging at mid-slope or at the foot of the slope, can also be included. However, often individual phenomena join together to generate instability, also after some time has elapsed, which, other than in well-instrumented limited areas, do not allow a reconstruction of the evolution of the occurred landslide. It is therefore pointless, for the purpose of planning landslide hazard mitigation measures, to classify the work as a function of the phenomenon or of more important phenomena, renouncing any attempt to precisely describe all the causes or the conditions which, at different times, contribute to the occurrence of the landslide. Therefore, slope stabilisation methods in rock or in earth, can be collocated into three types of measure:

• Geometric methods, in which the geometry of the hillside is changed (in general the slope);

• Hydrogeological methods, in which an attempt is made to lower the groundwater level or to reduce the water content of the material;

• Chemical and mechanical methods, in which attempts are made to increase the shear strength of the unstable mass or to introduce active external forces (e.g. anchors, rock or ground nailing) or passive (e.g. structural wells, piles or reinforced ground) to contrast the destabilising forces.

The different type of material conditions the engineering solution adopted, although It always comes back, in principle, to the previously introduced classification.