Collapse of granular-cohesive soil mixtures on a horizontal plane

The collapse test with granular or cohesive materials known as ‘slump test’ is a simple, small-scale experiment. It can be used to study the rheology of soil masses involved in flow-slides and to calibrate the numerical models used for analyzing the propagation of soil-flows. This study presents the results of an extensive, experimental program carried out with this type of test, using different amounts of granular and cohesive soil fractions with different percentages of water. The experiments aim at evaluating how the mixture composition influences the flow behavior. In particular, the runout length and the profile of final deposits can be correlated to the composition of a mixture and its behavior. Moreover, the time taken to complete the collapse and the slumping velocity are also taken into account. The results of 71 tests are considered all together to formulate different predictive models based on regression between the geometrical and kinematic features of the slump test. Different sets of predictors, i.e. the material composition, the initial diameter and height of the sample, are included in these regression models. The accuracy of the models is then evaluated, based on some performance coefficients.