Effects of Fines on Monotonic Undrained Shear Strength of Sandy Soils

Abstract Shear strength of liquefied sands is an important component in seismic slope stability evaluation. Experimental data on a host sand mixed with different amounts of fines content and a careful analysis of other available steady state strength (Sus) data show that fines content and relative density play important roles affecting Sus. Fines content is found to be the major factor affecting Sus. When the Sus data for sands are grouped into (a) relatively clean sands (<12% fines), (b) silty sands (12 to 32% fines), and (c) silts or sandy silts (>50% fines) at the same relative density, relatively clean sands show the highest Sus. Silts show the lowest Sus. Silty sands show intermediate strengths. Based on this data, lower-bound relationships are proposed for Sus as a function of Dr and fines content.