Database for dynamic properties of Singapore soils

Soil behaviour is highly non-linear. Under dynamic loading such as earthquake or explosion, the strain experiences by soil can vary over a large range. In order to model the behaviour of the soil correctly under dynamic loading, the stiffness-strain relationship of the soil over a large strain range is needed. Current understanding of soil stiffness also indicated that in many geotechnical engineering problems, the stiffness-strain relationship of soil is important to accurately estimate deformation behaviour. The characterization of soil stiffness over a large strain range for Singapore soils has not been done extensively. This project investigated the stress-strain behaviour of a number of Singapore soils. The small-strain stiffness was obtained using either bender element tests or ultrasonic velocity tests. The intermediate strain level stiffness was obtained using a triaxial apparatus with local strain measurements. The large-strain stiffness was obtained using conventional methods. The effect of degree of saturation on the stiffness of compacted soils was investigated. It was found that confining pressure affects the stiffness-strain relationship of the compacted soil more than matric suction. The effects of void ratio, confining pressure and plasticity index on the stiffness-strain relationship of saturated undisturbed soil samples were investigated. It was found that shear modulus increases with increase in plasticity index and confining pressure but decreases with the increase in void ratio. It was also found that the effect of void ratio and confining pressure is more significant than the effect of plasticity index on shear modulus. The test results provide a small database of dynamic properties of Singapore soils from which further test results can be added to provide a better understanding of the stiffness-strain relationships of Singapore soils.RG81/0