Effect of Previous Cyclic Shearing on Liquefaction Resistance of Mississippi River Valley Silt

Abstract

Liquefied silty soil can experience repeated liquefaction as a result of aftershocks or other subsequent earthquake events, which can be considered to be previous cyclic loading. The effect of previous cyclic loading on the liquefaction resistance of low-plasticity silt is investigated in this paper. The experimental program included cyclic triaxial tests conducted on reconstituted Mississippi River Valley (MRV) silt specimens in the laboratory. Two major types of tests were conducted, in which: (1) specimens were loaded until full liquefaction; and (2) loading was stopped before liquefaction occurred. For the specimens loaded until full liquefaction, test results indicated that the rates of development of excess pore pressure and axial strain were greater in extension than in compression during the repeated liquefaction tests. Significant increases in liquefaction resistance were obtained, only as the relative density of specimens approached 100% after more than four liquefaction and reconsolidation tests. For the specimens not loaded until liquefaction occurred, maximum liquefaction resistance was attained when the cyclically induced axial strain was approximately 0.20%. Based on these findings, ground improvement techniques were proposed to improve liquefaction resistance.