Residual strength of kaolin and bentonite: the influence of their constituent pore fluid

The residual strength of clays is affected by their mineral composition and by the nature of their constituent pore fluid. In principle, both factors may influence either strength parameters or stresses, but it is not yet completely clear how this influence works. Previous publications have elucidated some aspects of clay residual strength behaviour. This Paper investigates further the roles of minerals and pore fluid composition on the residual strength of clayey soils. It describes and analyses tests on kaolin, bentonite and their mixtures exposed to distilled water and sodium choride solutions with given concentrations. The results show that the shear strength of kaolin is not affected by the solutions used, whereas the residual strength of bentonite varies greatly because of the inward salt diffusion towards the clay. Further, for the clay mixtures with any of the pore fluids considered, the weaker component has the greater influence on the behaviour of the mixture.