Investigation of soil-steel interface behavior of Iraqi soil by direct shear apparatus

Soil - structure interaction is an important theme observed in many civil engineering structures like fondations. The interface shear strength plays a significant role in the analysis and design of many structures constructed above or under the ground. In this study, a total of 28 specimens were tested at vertical stresses of 100, 200, and 400 kPa using direct shear apparatus under consolidated drained condition. A silty sand soil, as per USCS classification system was prepared in the laboratory at different water contents (4.5%, 8.8%, and 12.5%) and voids ratios (0.4, 0.6, 0.8, and 1). The frictional resistance of this soil was measured. The soil samples were also sheared against three steel surfaces of different textures (smooth, moderate-rough, and rough). The experimental results showed that the steel surface texture is an effective factor in soil-steel interface shear strength. The interface shear strength of the rough steel surface was found higher than smooth and semi-rough steel surfaces. In addition to the surface roughness, the water content and void ratio also play important roles in interface shear strength