Dilation Angle and Liquefaction Potential

Abstract

Its proposed that the dilation angle or expansion rate of the sand during shear is a measurement describing the initial state of the sand which could be obtained in both the laboratory and the field and which could give a measure of liquefaction resistance. The dilation angle can be readily obtained in the laboratory from drained triaxial or simple shear tests and in the field it can be obtained from self-boring pressuremeter tests. A liquefaction resistance chart based on dilation angle rather than on corrected blow count is presented. From this chart an estimate of the field liquefaction resistance of saturated sands can be obtained from dilation angles from self boring pressuremeter tests. Details are given of the analysis procedure in which the dilation angle was obtained as a function of relative density by performing drained static simple shear tests on the same sand over a range of relative densities and observing volume change characteristics. The relations between liquefaction resistance, relative density and dilation angle are discussed. Liquefaction resistance can be correlated with relative density, corrected dilation angle or corrected blow count and a chart showing liquefaction resistance in terms of these three parameters is shown. The latter indicates that liquefaction is not likely to occur regardless of the stress level provided the relative density is in excess of 75%, the corrected dilation angle is greater than 16 degress or the corrected blow count exceeds 20.