PHYSICOCHEMICAL EFFECTS ON THE BEHAVIOR OF A COASTAL MUDSLIDE

Previous work has shown that the type of clay mineral, the valency sta te of adsorbed cations and the salt concentration of pore-water influe nces the residual strength of clays, Residual strength can therefore b e modified through weathering reactions, clay mineral alterations and fluctuations in groundwater chemistry. This has implications for studi es of the seasonal and long-term behaviour of clay slopes, The paper p resents results from an investigation of a shallow coastal mudslide on the south coast of England which attempts to isolate the influence of physico-chemical processes on mudslide behaviour, Fluctuations in gro undwater chemistry coincided with temporal movement patterns. Low pore -water ion concentrations were apparent immediately before seasonal mu dslide reactivation or periods of high activity, Laboratory tests show ed that low pore-water ion concentrations resulted in low residual she ar strength; higher concentrations observed after movement events led to increases in residual strength.