Effect of activated carbon on hydraulic properties of soil with multi-modal porosity

• Main Author: Wong, Feng Huan
• Other Authors: Harianto Rahardjo
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Civil engineering
• Online Access: https://hdl.handle.net/10356/153833
• Institution: Nanyang Technological University

Slope failures induced by rainfall are not uncommon in Singapore. As pore water pressure builds up in unsaturated soils due to infiltration of water, it reduces the matric suction of the soil. In turn reduces the shear strength and leads to slope failures. Measures to avoid or mitigate these types of failures include holding regular inspections and rectifying defects to prevent soil erosion and water inflow during heavy rainfall as slope protection structures will deteriorate over time. However, there are other effective ways to improve the hydraulic property of the residual soil. One way is to strengthen soil-water retention behavior through the addition of various materials. Hydraulic properties of unsaturated soil above the water table have a major role in slope stability, which are known to be governed mainly by the soil-water characteristic curve (SWCC). Soils such as Sand-Kaolin show multi-modal characteristics in SWCC. Furthermore, the presence of porous materials such as activated carbon significantly affects the hydraulic properties of soils with multi-modal porosity. Therefore, the objective of this study was to investigate the role of activated carbon and in affecting the hydraulic properties of soil with multi-modal porosity. In this study, laboratory tests were conducted on Sand-Kaolin mixtures with varying compositions of 2 types of activated carbon. In total, 18 specimens were made, half using granular activated carbon (SKG) and the other half with powdered activated carbon (SKP). The tests conducted on these specimens included dynamic compaction, index property tests, drying SWCC, shrinkage test and saturated permeability tests. SEEP/W analysis was conducted after obtaining parameters from the drying SWCC and saturated permeability tests. The experimental results show that SKG and SKP mixtures exhibited trimodal SWCCs. A new equation extended from Satyanaga et al. (2013) best fitting equation is proposed to best-fit the trimodal SWCCs. From the seepage analysis and permeability function, it can be seen that SKG3 exhibits the highest permeability compared to the rest of the mixtures. SKP1 has a higher permeability compared to SKP2 for suction ranges up to 30kPa however, when a higher suction is induced, SKP2 is expected to perform better.