Residual shear strength of clayey soils: the influence of displacement rate

This paper reports the results of some laboratory shear tests aimed at evaluating the influence of the displacement rate on the residual shear strength of a natural clayey soil and of kaolin-sand mixtures at various percentages. Some results relative to a bentonite are also reported. The tests were performed by means of various types of shear apparatuses in a wide range of displacement rates. The results show that the residual shear strength increases with the displacement rate for the considered kaolin and bentonite, whereas it remains constant for the sand. The influence of the percentage of kaolin on the shear behaviour of the mixtures is not linear. No influence of the displacement rate was observed on the shear strength of the natural clayey soil. However, an influence of pore fluid composition on the residual shear strength on this latter, as well as on the shear creep behaviour was observed.