Palm biodiesel contaminated sand-steel interface testing with direct simple shear apparatus

This paper describes the use of a laminar-ring direct simple shear apparatus that was employed to test interface properties with the soil specimen contained in a stacked metal rings. A series of interface tests between steel and palm biodiesel contaminated soils were conducted using the developed apparatus. The mining sand samples contaminated with different palm biodiesel contents were tested on relatively smooth and rough steel surfaces. Parameters investigated include palm biodiesel content, surface roughness and normal stress. The experimental results show that the contribution of palm biodiesel content to interface shear strength is significant. Interface shear strength increases with the increase of palm biodiesel content. Applied normal stress and surface roughness have remarkable influence on the interface shear strength. The decrease in interface shear strength due to an increase in palm biodiesel content is observed. Soil dilatancy is observed for clean mining sand but as the palm biodiesel content is increased, higher soil dilatancy is obvious in lower normal stresses. The rate of increase of soil dilatancy is greater in higher palm biodiesel content than in lower palm biodiesel content. They also indicated that the surface roughness has a significant effect on the interface shear strength at a given palm biodiesel content and normal stress level. With respect to surface roughness and palm biodiesel content, three shearing modes are likely to take place: shearing at the interface, shearing within the soil and an intermediate mode involving these two types of shearing. For the second mode, the shear strength at the soil-rough steel interface is likely to be greater than the shear strength of the sand, particularly for sand with higher palm biodiesel content.