Soil-water characteristic curves of compacted soils

• Main Author: Ng, Keith Rui Kang
• Other Authors: Leong Eng Choon
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/67431
• Institution: Nanyang Technological University

The definition of residual soil refers to soil like material that comes from the result of in situ weathering of rocks. In Singapore, residual soils are from the Bukit Timah Granite and the Jurong Formation, each covering around one third of Singapore. In the construction of engineering structures, loose soil need to be compacted to increase their unit weight. The process increases the soils’ strength characteristics, which in turn increases the bearing capacity of the foundations over the soil. Compaction also prevents settlement and increases slope stability. In this project, soil samples of height 30mm and diameter 50mm were cut from soil compacted at different water contents. Both the standard and modified Proctor efforts were used. The soil water characteristic curves (SWCCs) were obtained using the pressure plate test and the chilled mirror test. The objective was to compare the SWCCs of soil compacted at different water contents to observe if there is a difference in the soil fabric. The results showed similarity between soils compacted at same dry density with one water content at the dry optimum and the other at the wet of optimum. The chilled mirror was able to produce SWCC at higher suctions than the pressure plate test to give a more in depth analysis. The pressure plate test was able to show the drying and wetting SWCCs but the chilled mirror was only able to show the drying SWCC. The time taken for the samples to reach an equilibrium of no significant weight loss around 8 days. The results showed that soils at the same density but different water contents have a higher AEV for soils compacted at the dry of optimum. For the same density, the hysteresis was also smaller for soil compacted at the wet of optimum. As the degree of saturation increase, the hysteresis decreases.