Assessment of Stabilized Silt Clay Sand with Oil Palm Fibre Bunch (OPFB) Local Fibre for Slope Foundations: A Case of Coastal Soils of Mombasa, Kenya

Improvement of shear strength parameters is essential for designing the OPFB fiber mix with silt clay sand for slope stability. The objective of this study was to assess the stabilized silt clay with oil palm fibre bunch (OPFB) local fibre for slope foundation. Series of laboratory tests were conducted on various materials under study and the results revealed that, OPFB mix can be used as an additive to cement for purpose of improving engineering properties of the Silt Clay sand to cut down costs without compromising the set standards. It was established that, the shear strength parameters of the soil-fibre mixture (φ and C) can be improved significantly up to an optimum and reach a certain point where it starts to decline. The shear stress–strain curves obtained from the CU triaxial tests for reinforced sands with 30 mm fibre length together with those for unreinforced silty sand were compared; the result indicated that, fibre-reinforced specimen showed higher deviator stress at 0.25% fibre and reduces at 0.5% fibre. The strain corresponding to the peak deviator stress was increased by fibre content. Patterns of stress–strain curves for all reinforcedsamples indicated improvement in the deviator stress for all compositions and fibre content. Deviator stress of fibre-reinforced soil showed a slight increase with increasing pore pressure. The increase of the fibre content caused an increase in pore water pressure due to inclination of specimens to decrease the volume. Changes in the shear strength of fibre-reinforced soil indicated that soil strength parameters (internal friction angle φ’ and cohesion C’) increase as the internal friction surface increases between fibre and soil at certain point.