Dilatancy in the analysis of interlayer cyclic shear test results

Dilatancy measurements of double-layer specimens were recorded during cyclic shear tests to derive information on the interface fatigue behavior. Two direct shear testing devices, representing the two most common types of guillotine and inclined configurations, were used. The results clearly highlight a dilatancy variability from the random aggregates distribution at the contact plane, even for specimens prepared in the same way, A saw-chain model is introduced for useful schematization of volumetric expansion during the shear test. Moreover, a new interpretation of the interface fatigue event is presented, based on the trend of dilatancy speed, which shows three stages: (1) important movement perpendicular to the sliding plane; (2) insignificant increase in dilatancy; and (3) crisis and detachment. The number of loading cycles at the beginning (Noverride) and end (Ncrisis) of the dilatancy is introduced as significant moments of the interface fatigue evolution. © 2016 American Society of Civil Engineers.