1-D settlement characteristics of unsaturated soils

• Main Author: Li, Bing.
• Other Authors: Leong Eng Choon
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/15946
• Institution: Nanyang Technological University

As demonstrated in urban and industrial developments, many conditions may cause the moisture content in the foundation soil to accidently increase, for example, by excessive irrigation or broken water pipes. Problem will arise if the existence and extent of this collapse is not recognized prior to construction. This study has investigated the compression behaviour of six types of residual soils and one type of volcanic soil, Shirasu, under one-dimensional loading. Single point multiple specimens tests were conducted by oedometer apparatus to study the wetting-under-load behaviour of residual soil specimens of various void ratios, water contents, initial matric suctions and pore structure. A family of consolidation curves was obtained for each soil upon wetting under different loading. Empirical compression equation was employed to estimate the potential settlements. Based on this study, the following important conclusions can be drawn: 1. The settlement upon wetting behaviour of unsaturated soils is path-dependent. Wetting under loading yields much lower settlement than wetting prior to loading. 2. Compacted soils with lower compaction effort (and lower dry density) collapse more upon wetting. This observation is also noted by Houston and Huston (1997). 3. Compressibility of soils undergoing single point multiple specimens test after wetting is neither path-dependent (this observation is also noted by Houston and Houston, 1997), nor dependent on initial suction before wetting. 4. Soils with dry-of-optimum water content will experience less settlement than those with wet-of-optimum water content under the same compaction effort upon the application of loading, due to their higher suction. This observation was also noted by Alonso et al. (1994) 5. Compressibility increases with corresponding increase in the degree of saturation (decrease in matric suction), and vice versa. 6. The equation proposed by Widiastuti (2005) yielded good estimation of settlement of unsaturated soils.