Abstract
Shallow landslides in nearly saturated uncohesive to slightly cohesive soils are triggered by high intensity, short duration rainfall which infiltrates into soil and changes intergranular friction and effective stresses. For this, the especially developed Soil–Water Interaction Modelling System (SWIMS) was used with CL-ML type soils. For simplicity, rainfall intensity and duration were kept constant. Results showed that (1) All 35° slopes were failed by translational failure. For the other (15°,25°) slopes, no failures were observed; (2) For all slopes, FOS increased with increasing compaction degree and decreased with increasing slope angle; (3) Other parameters, such as soil density, porosity, saturation degree, water contents, and water permeability may also affect shear strength/slope stability, especially for low degrees of saturation (S<95%), compared to high degrees of saturation (S=,>95%). (4) A correlation of SWIMS tests observed that average wetting band depths (hobser), with the calculated wetting band depths from the Lump Equation (hLE), were poor, as hobser values were much higher than hLE values. Differences increased for very low degrees of saturation (S), compared to S>95%. This meant that the Lump equation underestimated wetting band depths. Further, if the Lump equation is still considered valid, this would imply either water-permeability increases, porosity decreases or both occur towards full saturation; a process where the last possibility is the most probable occurrence.
Highlights
Slope stability problems of shallow landslides are among the most commonly encountered problems in geotechnical engineering
A number of landslides in unsaturated soils usually occur during the wet season
Results of the Soil–Water Interaction Modelling System (SWIMS) tests and slope stability analyses are combined in Table 6 to show soil types, initial water content, proctor’s maximum dry density results, factors of safety obtained from the FEM analyses and the degrees of relative compaction obtained [67]
Summary
Slope stability problems of shallow landslides are among the most commonly encountered problems in geotechnical engineering. Due to the practical importance of the subject, assessing the stability of a natural or man-made slope has received great attention across the geotechnical community, for many decades. The first question that must be answered is: Why does a natural slope suddenly move/fail after a long period of existence? Doi:10.1016/j.scient.2011.09.010 duration) is one of the most important factors in this question. Slope failures triggered by rainfall cause considerable property damage with loss of life, every year throughout the world. A number of laboratory, numerical and field studies have been conducted to understand interrelations between soil stability and rainfall. A number of landslides in unsaturated soils usually occur during the wet season
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