Study of the impact of the shear rate on strength characteristics of the soil materials-asphalt concrete interface

Soil shear strength is affected by various factors such as grading, compaction percent of materials, vertical load level, shear rate and other factors. When placing soil and other material in the vicinity , the interaction problem is discussed . Such conditions are observed in embankment dams with asphalt concrete cores, in which determining the mechanical performance of the interfacing materials has great importance. In this research, a laboratory study has been conducted to characterize the interface behavior of soil materials of filter and asphalt concrete in the core, through direct shear test. For this purpose, specimens containing soil materials from classes GC and GP at the same relative density were tested under different shear rates and the strength parameters were determined. On the other hand, for considering the impact of the relative density of the materials on strength characteristics, specimens containing materials from GP class at both medium and high relative densities were tested at different shear rates and the desired parameters were determined. Based on the results, in GC interface materials, the interaction ratio has diminished at small shear rates and increased at elevated shear rates. The amount of increase and decrease of the interaction ratio was equal to 2.36 percent. In GP interface materials, the ratio of interaction has increased by 2.3% with a higher shear rate. Also, for constant shear rates, increasing the compaction percent of materials from GP class in the interface, from medium to high level, has resulted to reduced interaction ratio. Increasing the shear rate in materials with moderate and high relative density also followed, respectively, the increase and decrease of the interaction ratio .