On Creep Flow of Natural Slopes

ABSTRACT: In this paper a new model for describing creep flow of natural slopes (landslides) is presented. The material in the slope is modeled by a non-homogeneous Bingham model. This new model accounts for the effect of gravitational compaction of the geologic material and allows for the variation of density and yield stress with depth. The yield stress is supposed to be a function of the current density. Although the density could be considered to be linearly dependent on depth, it is shown that a linear variation of the yield stress with depth is physically unacceptable. A procedure for determination of the law of variation of the yield stress with depth from data is outlined. A flow-no flow criterion is formulated. It is shown that the model predicts well the depth at which shear flow initiates and the thickness of the shear zone. All parameters involved in the visco-plastic model are determined from a few in situ measurements. This is an important advantage of the model over existing theories in which the parameters are estimated based on laboratory data on samples taken from the site, thus inevitably disturbed from their natural state. Finally, the model is used to predict the field behavior of several natural slopes in Europe. The predicted displacement profiles correlated well with the field observations.