Mechanics of mudflow mobilization in low-angled clay slopes

Abstract

The Bagnold theoretical method of grain flow is used to explain the mobilization of mudflows formed in clay slopes on low angled surfaces. The reported texture of these mudflows consists of hard pieces of clay or rock in a soft clayey matrix (mud) which can be regarded as a mass of concentrated grains that are dispersed in a fluid medium as assumed by the Bagnold approach. The values of the slope angle at which four cases of mudflow of the reported texture are mobilized in the field, and those obtained using the Bagnold method, are closely in agreement. The Bagnold method provides an alternative to the ‘undrained loading’ and the ‘excess pore water or artesian pressure’ effects which are used to explain mudflow mobilization on flat surfaces but are reported to not be sufficiently comprehensive to explain all cases.