Nurul Irah Fazirah Sapar (2023) Study on physicochemical and hydraulic properties of tropical organic soil in Beaufort, Sabah. Masters thesis, Universiti Malaysia Sabah.
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Abstract
Organic soil is a difficult soil to work with in the engineering field due to its characteristics that make it unsuitable for building or highway construction. It is fragile and has low shear strength, a wide deformation range, high compressibility, and a high-water holding capacity. Due to the fact that water is always the primary factor influencing how soil properties behave, this study aims to provide an in-depth understanding of tropical organic soil properties, particularly their hydraulic characteristics, in order to facilitate a better understanding of such soils. Soil water characteristics and hydraulic conductivity are two major components of hydraulic properties. The primary goal of this research is to characterise the physicochemical and hydraulic properties of organic soil in order to establish a relationship between them. Two locations were considered: the Lumadan site and the Klias site, where organic soil samples were collected in Beaufort, Sabah. Field tests such as the von Post test and an investigation of organic soil depth were carried out at the study sites. The scope of the study includes index and chemical properties tests such as natural density, moisture content, organic matter content, fibre content, liquid limit, specific gravity, and pH tests; hydraulic properties tests such as permeability and soil-water retention characteristics; and mechanical compaction properties. The microstructural characteristics and chemical composition of the samples were also determined in this study using the Scanning Electron Microscope (SEM) and Energy-Dispersive X-ray spectroscopy (EDX) tests. As per the findings of the research, Klias and Lumadan organic soils were classified as hemic (pseudo-fibrous), with von Post scales ranging from H6 to H7, indicating a degree of decomposition in the intermediate range. The organic soil depth at Lumadan is 4.5m, while it is 4.0m at Klias. Moisture content, organic content, fibre content, specific gravity, liquid limit, and acidity results indicated that organic soil index properties varied between the Klias and Lumadan sites. The chemical composition of organic soil samples collected at both study sites also demonstrates that the elements present are influenced by the type of cultivation, groundwater level, and local climate conditions. Microstructural analysis reveals that the characteristics of organic soil samples vary slightly. Klias samples are made up of fibres and appear to be woody and porous, whereas Lumadan samples are made up of flaky granular. In terms of hydraulic properties, the average coefficients of permeability of Lumadan and Klias samples are 9.89 x 10-6 m/s and 9.11 x 10-6 m/s, respectively, indicating that organic soil has a low degree of permeability. Four models were used to describe the soil water characteristic curve. Based on the fitting analysis, the Brooks and Corey and Fredlund and Xing models were found to be the best fitted models to represent the soil water characteristic curve for organic soils in Beaufort, Sabah, with a linearity coefficient (R2) ranging from 0.9368 to 0.9978. Organic soils demonstrate a high-water storage capacity, and even at high pressure conditions, such as 1500 kPa, the soil can still store water at a rate of 0.5 to 0.6 residual volumetric water content. Organic soil decomposition alters the hydraulic parameters significantly. In conclusion of this study, soil degradation caused by peatland drainage significantly alters the physicochemical and hydraulic properties of organic soils.
| Item Type: | Thesis (Masters) |
|---|---|
| Keyword: | Organic soil, Tropical soil properties, Hydraulic properties, Soil water characteristics, Hydraulic conductivity, Permeability |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) > TA1-2040 Engineering (General). Civil engineering (General) > TA703-712 Engineering geology. Rock mechanics. Soil mechanics. Underground construction |
| Department: | FACULTY > Faculty of Engineering |
| Depositing User: | DG MASNIAH AHMAD - |
| Date Deposited: | 23 Jan 2025 14:19 |
| Last Modified: | 23 Jan 2025 14:19 |
| URI: | https://eprints.ums.edu.my/id/eprint/42657 |
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