Strength of soft clay reinforced with crushed coconut shell columns / Ieszaliana Binti Ali

Faculty of Civil Engineering Technology

Thesis (Master of Science) -- Universiti Malaysia Pahang – 2024

Include bibliographical reference

Stone columns could be used as a ground improvement technique by replacing a portion of soft soil with granular material such as stone or sand. The benefits of using stone columns in lowstrength soil have been proven to be an efficient method in improving the bearing capacity and reducing the settlement of soft soils. This research used the laboratory scale model to investigate the role of crushed coconut shell columns in enhancing the shear strength of the soft reconstituted kaolin clay. The shear strength characteristics can be obtained by determining the effect of area replacement ratio, height penetration ratio, and volume replacement on crushed coconut shell columns. Reinforced kaolin samples were tested with an Unconfined Compression Test (UCT) and an Unconsolidated Undrained Triaxial Test (UU). The specimens used were 50 mm in diameter with a height of 100 mm and weights 312.4 g. The research variables were height penetration ratios of 0.6, 0.8, and 1.0 with crushed coconut shell columns with diameters of 10 mm, 12 mm, and 16 mm. The kaolin sample without reinforcement of crushed coconut shell columns was the controlled sample. The highest improvement of shear strength of crushed coconut shell columns on area replacement ratio of 4.00% at 10 mm diameter columns was at 0.8 height penetration ratio with 73.42%, whilst for area replacement ratio of 5.76% at 12 mm diameter columns, the highest was also at 0.8 height penetration ratio with 66.82%. Meanwhile, the highest improvement of shear strength of the crushed coconut shell column for the area replacement ratio of 10.24% at 16 mm diameter columns was at 0.8 height penetration ratio with 22.32%. The maximum shear strength improvement was at 0.8 height penetration ratio for all crushed coconut shell columns. The Unconsolidated Undrained (UU) test showed a significant improvement in cohesion, c, which was recorded to be from 22.3% to 66.23%. Meanwhile, the friction angle, ϕ, increased from 0% to 50.15%. The UU test results were almost identical to the UCT results, where the highest improvement occurred at 0.8 penetration height ratio for a 10 mm diameter column. The correlation obtained the coefficient value of determination ranging from 0.8 to 1. The very strong correlation between area replacement ratios against shear strength proved that the most controlling parameter the in the shear strength of soft clay is area replacement ratio. In conclusion, crushed coconut shell columns positively increase the shear strength and can be implemented to reduce dependence on natural materials, maximize the potential for renewable materials, and minimize waste.