Experimental modelling of debris flow behaviour using a geotechnical centrifuge

Abstract

Physical modelling of debris flows has been carried out in the geotechnical drum centrifuge at ETH Zürich. A new apparatus to model debris flows in the centrifuge is described. The apparatus permits the final reach of a typical debris flow to be modelled within the centrifuge, with unconsolidated material flowing down a slope to deposit as a fan around the drum. Experiments are described for both fixed base conditions and erodible bases. Tests to examine the verification (modelling) of models show that debris flow behaviour is governed mainly by friction and consolidation processes, although some resolution is required between flow behaviour downslope and flow arrest during runout. The results are compared with bulk parameters determined for field-scale debris flows. It is found that some important flow mechanisms, such as contact-dominated behaviour and high pore pressures, are developed that are closer to those developed at field-scale than tests conducted at 1g. Velocity profiles for erodible beds are compared with a semi-empirical expression derived for experimental debris flows at 1g. Normalized velocity profiles are found to be in agreement; however, absolute velocities differ from those predicted. Scaling, the limitations of the apparatus, and potential for future work are discussed.