Influence of mixture composition in the collapse of soil columns

The collapse and consequent spreading of a column of granular or cohesive material is a simple experiment used by many research groups to collect data on the rheological behavior of the materials and for calibrating numerical propagation models. This paper deals with the results of a comprehensive experimental program carried out with mixtures of sand, kaolin and water: the main aim of the program is the understanding of how the composition of the mixture influences the collapse and run-out mechanisms. In particular, the run-out length and the maximum height of the final deposit are the two fundamental characteristics taken into consideration to distinguish each test and to find a relation with the mixture composition. Various materials are taken into account: four percentages of kaolin and water are considered for the experiments and different amounts of sand are added to these matrices. The main aim is the comprehension of the role of the coarse grain content in a cohesive collapsing mass. Finally, some considerations about the dependency of the final runout on the aspect ratio of the initial column are dealt with.