Abstract
This study centers on the crucial determination of the mobilized friction angle between soil and various materials, including steel and concrete, to enhance the modeling of soil-structure interaction. The primary objective of the current investigation was to assess the interfacial friction between calcareous and silica sands when interacting with concrete or steel surfaces. To achieve this, direct shear tests were conducted to examine the impacts of relative density (Dr), surface roughness (Rn), and shearing direction. The test results reveal that the shear strength of calcareous sand surpasses that of silica sand when considering a specific Rn. Furthermore, the interface friction of both sand types escalates with an increase in normal stress and Rn, with higher values observed in interactions with steel plates. Notably, the friction angle ratio (the interaction friction angle over the pure sand friction angle) demonstrates minimal dependence on the sand type. The most pronounced divergence in the friction angle ratio is evident at the maximum Rn value, which increases alongside Rn values for both calcareous and siliceous sands. With increasing Rn values, the maximum shear strength, contingent on normal stress and relative density, also rises. The influence of relative density on the interaction friction angle diminishes with escalating surface roughness.