A constitutive model for the accumulated strain of unsaturated soil under high-cycle traffic loading

Abstract

The road base is normally situated above the water table and thus in unsaturated state. Experimental results show that the accumulated strains of the unsaturated road base aggregate under high-cycle traffic loads are significantly influenced by the matric suction. To predict the accumulated strain of unsaturated road base aggregate under high-cycle traffic loads, a constitutive model was developed based on the Barcelona Basic Model (BBM) and the shakedown concept. In this model, the shakedown and plastic creep boundaries of the aggregate under cyclic loads were supposed to exist and to have the same shape as the “static” yield surface in BBM. The strain accumulation rates were described as an exponential function of the distance between the peak cyclic stress point and the conjugated point at the current cyclic yield surface. An explicit calculation methodology was adopted to avoid large calculation errors and to improve the calculation efficiency of the model. Comparison between model predictions and testing results proved the accuracy of the proposed model, which can be used as a basic model to predict the long-term deformation of unsaturated road base aggregate under high-cycle traffic loads.