Stiffness characteristics of unsaturated soil

• Main Author: Ong Lay Sah @ Lisa (Wang Lisha).
• Other Authors: Leong Eng Choon
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/39728
• Institution: Nanyang Technological University

Soil is observed to fail at very small strain (0.001% shear strain), hence it is of great importance to understand the behaviour of unsaturated soil at very small strain stiffness and soil stiffness under load. Currently, there are very limited studies on small strain stiffness of unsaturated soil. This report aims to study the very small strain stiffness of unsaturated soil and selected factors such as, net confining pressure and initial matric suction, which are known to have a certain effect on small strain stiffness of unsaturated soil. In order to study very small strain stiffness behavior of unsaturated soil, triaxial cell which allows matric suction to be set to stablise within the soil specimen was used. Transducers that are capable of measuring very small deformation of soil specimens were mounted to measure axial and radial deformation during triaxial compression test. Ultrasonic test was conducted before shearing to obtain the shear wave and compression wave velocity of different specimens set in different conditions. Data were processed and effects of both net confining pressure and matric suction are discussed in the report to investigate the general trends observed. Soil stiffness degradation is touched on in this report to identity the strain at which soil stiffness starts to degrade and the rate of degradation.