Effect of coconut shell ash on pore water pressure changes in sand

• Main Author: Lim, Gabriel Jose G.
• Format: text
• Language: English
• Published: Animo Repository 2020
• Subjects: Soil amendments; Organic wastes as soil amendments; Pore water; Shear strength of soils; Civil Engineering; Geotechnical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/6413; https://animorepository.dlsu.edu.ph/context/etd_masteral/article/13498/viewcontent/Lim_GabrielJose_11772603_Effect_of_Coconut_Shell_Ash_on_Pore_Water_Pressure_Changes_in_Sand_1b_Redacted.pdf
• Institution: De La Salle University

Previous studies showed that addition of coconut shell ash (CSA) to soil improved the soil’s strength parameters, like California Bearing Ratio, Maximum Dry Density, Unconfined Compressive Strength, Plasticity Index, Angle of Internal Friction, and Cohesion. But the effect of CSA in decreasing soil susceptibility to static liquefaction has yet to be investigated. Static liquefaction is a major concern because it is defined when soil loses its strength and behaves like a fluid. This causes settlements, damages to buildings, and endangers lives. The loss in soil strength is attributed to the increase in pore water pressure. Pore water pressure buildup is more likely to happen in loose and saturated sands. This study hypothesizes that the particle size and the chemical property of CSA can reduce the liquefaction susceptibility of sands by decreasing pore water pressure buildup when the sand is subjected to vertical loads. For the experiment, the consolidated undrained (CU) triaxial test was conducted to determine the necessary parameters like the volume change, major principal stress, minor principal stress, and pore water pressure at failure. Samples are subjected to consolidating pressures of 25kPa, 50kPa, and 100kPa at a target relative density. The Cam-Clay Model was used to analyze soil behavior between the control samples and the samples mixed with CSA. Results show that administering five (5) percent CSA expanded the soil’s yield surface, improving soil’s ability to respond elastically to deformations. Five (5) percent CSA decreased pore water pressure buildup in the samples subjected to 50kPa and 100kPa consolidating pressures by 6.53% and 5.55%, respectively. However, for the sample subjected to 25kPa consolidating pressure, five (5) percent CSA caused an adverse effect by increasing pore water pressure buildup by 10.73%.