Mass-Movement Causes: Overloading

Overloading or the excessive addition of a surcharge load or external load on a hillslope section is one of the external factors influencing slope stability. Although overloading occurs under natural conditions such as vegetation growth, persistent precipitation, and volcanic activity, it is very commonly the result of human activities such as filling for construction works or dumping of waste material. Geotechnical models, generally based on the calculation of the factor of safety ( F ), allow evaluation of the impact of a fill or a cut at different locations on the slope on F . External loading on the upper part of a slope usually decreases slope stability where the slope gradient is higher than the angle of internal friction, whereas external loading on the lower part of the slope stabilizes the slope. However, as parameters controlling the weight resting on a potential surface of rupture affect both shear stress and shear strength, the changes in stability are generally relatively small and decrease with increasing surface of rupture depth. Comparison of the influence of changes in the different parameters on the F by means of a sensitivity analysis indeed shows that changes in the weight on the rupture surface have only a minor impact compared to changes in slope gradient, cohesion, and angle of internal friction. Yet, overloading as a causal factor of landsliding cannot be neglected as it is the cumulative effect of all causal factors that will finally determine the slope stability.