Abstract: The permeability of clayey silt is between that of clay and silty sand. The coefficient of permeability obtained by the conventional permeability test does not consistent with the field performance which might result in an adverse effect on the dewatering for the deep excavation. This paper presents a case history of permeability tests on undisturbed clayey silt soils in consolidometers and triaxial cells. The coefficients of permeability obtained under different seepage pressures, consolidation pressures and seepage paths are evaluated, and their effects are compared. The results indicate that the magnitude coefficients of permeability in the vertical and horizontal directions reduces with the increase of consolidation pressure. When the consolidation pressure is greater than the effective overburden pressure, the coefficient of permeability demonstrates a strong relationship with the consolidation pressure and the impact of seepage path is relatively small.

Key words: Clayey Silt, Coefficient of Permeability, Seepage Pressures, Consolidation Pressure, Seepage Path