Frictional resistance between organic soil and construction materials

Organic soil is a mixture of fragmented organic material formed in wetlands under appropriate climatic and topographic conditions and it is derived from vegetation that has been chemically changed and fossilized. This type of soils has low shear strength and high compressive deformation which often result in difficulties when construction work is undertaken on the deposit.In this study, interface friction between organic soil and some of construction material used in pile foundation was investigated. Construction materials used in this work are rough and smooth concrete, corrugated and painted metal, and wood. Soil used in this experiment was obtained from Sakarya region, Turkey. Four different water contents were used for organic soils. These are %0, %25, %50 and 75%. Interface friction angle was measured using direct shear test device. Tests were performed with locating construction material at lower part of the shear box and filling the upper part with organic soil. Three different normal forces were used 5kg, 10kg, 20 kg and shear stress at 5% strain rate was taken as maximum shear stress to determine interface friction angle.Test results showed that water content of the organic soil, surface roughness and material type effect interface frictional coefficient.