Lateral Stress in Sands During Cyclic Loading

Abstract

Laboratory data are presented of lateral stress (expressed in terms of the coefficient of lateral stress K) changes in dry sand in response to cycling of vertical and shear loads. The data demonstrate the variation of K with initial void ratio, vertical loading history and shear loading history. Tests were performed on dry samples of the ASTM grade C-109 Ottawa sand (mean particle size is 0.36 mm, coefficient of uniformity is 1.8, maximum void ratio is 0.75 and minimum void ratio is 0.41) in a simple shear apparatus. Cylindrical sand samples were confined laterally by a wire-reinforced rubber membrane and vertically between roughened end plattens. Vertical load application and the action of horizontal stresses are described. The stress path of a typical test is illustrated, and details are given of the initial loading, the second test phase when vertical stress was held constant, and the third phase which consisted of cycling the vertical stress between two values. Experimental values of the at-rest lateral stress coefficient are plotted against initial void ratio. It is concluded on the basis of these studies that under the conditions operating in this study, the coefficient of lateral stress is a function of vertical loading history, shear loading history and initial void ratio. Other conclusions are presented which relate to the relationship between the at-rest coefficient of lateral stress and the initial void ratio; the production of stress paths with hysterisis loops by the cycling of vertical loads; and the increase of the coefficient of lateral stress with shear strain amplitude and cycle number during repeated shear straining.