LARGE-SCALE LANDSLIDE SIMULATIONS - GLOBAL DEFORMATION, VELOCITIES AND BASAL FRICTION

The cause of the apparent small friction exhibited by long runout land slides has long been speculated upon. In an attempt to provide some in sight into the matter, this paper describes results obtained from a di screte particle computer simulation of landslides composed of up to 1, 000,000 two-dimensional discs. While simplified, the results show many of the characteristics of field data (the volumetric effect on runout , preserved strata, etc.) and with allowances made for the two-dimensi onal nature of the simulation, the runouts compare well with those of actual landslides. The results challenge the current view that landsli des travel as a nearly solid block riding atop a low friction basal la yer. Instead, they show that the mass is completely shearing and indic ate that the apparent friction coefficient is an increasing function o f shear rate. The volumetric effect can then be understood. With all o ther conditions being equal, different size slides appear to travel wi th nearly the same average velocity; however, as the larger landslides are thicker, they experience smaller shear rates and correspondingly smaller frictional resistance.