Experimental study of the role of interface element in earth dams with asphalt concrete core - Case study: Mijran dam

In recent years, the tendency to use asphalt concrete cores in earth dams is very common and is increasing. In such dams, the interaction between asphalt concrete core and soil materials has an important role in dam stability. The present study, as a case study of Mijran Dam located in Ramsar area in Iran, has evaluated experimentally the mechanical behavior of the interface between the filter soil material and the asphalt concrete core in the laboratory. In this regard, the samples were tested using large-scale direct shear machine in different normal stresses and in dry and saturation conditions. Also, tests have been performed on samples with different percentages of bitumen and relative density of filter materials at different shear rates and under different freeze-thaw cycles. In all the above conditions, the shear surface has been considered as the interface and the shear rate used in different tests varied in the amounts of 0.5, 1, 1.5 and 3 mm/min. The results of this study show that different percentages of bitumen used do not have such an effect on the shear strength parameters of interface. As the relative density increases, the values of the shear parameters increase. If the sample is dry or saturated, parameters such as dilation angle and shear stiffness increase with increasing density, but the interaction ratio increases in the dry state and decreases in the saturated state. As the shearing rate increases, the dilation angle and interaction ratio in the interface materials increase by about 2–3%. On the contrary, increasing the freeze-thaw cycles reduces the mentioned strength parameters.