Effect of Moisture Content, Bitumen, Gravel Grain Shape and Density on Shear Strength Parameters of Well-Graded Gravel Materials in Contact with Asphalt Concrete Core

In recent years, the use of embankment dams with asphalt concrete cores has become more popular in comparing with clay core dams owing to its implementation restrictions. Because in this type of dams, asphalt materials form the core of the dam and granular materials are used as a filter around the asphalt core. Therefore, investigation of behavior at the contact surface between these materials is of great importance. In this research, using large-scale direct shear experiment and applying vertical stresses of 1, 3 and 5 kg /〖cm〗^2 in both dry and saturated states, the mechanical behavior at the contact surface of asphalt materials and gravel filters has been investigated. The effect of parameters such as material density, gravel grain shape and bitumen type has been investigated. The results showed that the shear strength at the contact surface of the materials decreases with increasing the moisture content. Changing the shape of the filter material grains to the angular increased the shear strength of the contact surface and the ratio of maximum stress to residual stress at the contact surface for dry and saturated states with different relative densities showed that this ratio increased very little at low densities