Volume change and collapse potential of unsaturated residual granite soil
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Date
2014
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Publisher
Universiti Teknologi Malaysia
Abstract
Tropical residual soils are generally unsaturated and attain strength from capillary stresses as well as cementation of soil particles. The strength however decreases significantly upon saturation due to the collapse of capillary stresses. Recently, a large number of modified pressure plate-type devices have been developed to study hydro-mechanical behaviour of unsaturated soils using axis translation technique. Despite the progress in experimental methods, there are still some problems related to the axis translation technique application, e.g. evaporation and condensation of water on the cell wall. This study focuses on the effects of suction changes on volume change behaviour and collapse potential of an unsaturated residual granite soil. A modified oedometer was developed and successfully employed to perform various experiments on unsaturated soils by controlling vertical net stress, suction and temperature simultaneously as well as minimizing the problems related to water condensation. Soil-water characteristic curve (SWCC) for a residual granite soil at different densities was then established based on results obtained from experiments using the modified oedometer. It was found that the empirical equation suggested by Fredlund and Xing (1994) was the best relationship to describe SWCC of the granite residual soil. Results from unsaturated consolidation tests showed a unique volume change behaviour for the residual soil before air entry value, between air entry value and residual suction, and beyond residual suction. The results also indicated higher collapse potential with higher level suction so that the soil was classified as trouble soil. The amount of collapse under a constant suction increases with increasing vertical net stress until reaching a maximum value, and then decreases at the high stress level
Description
Thesis (Ph.D (Civil Engineering))
Keywords
Soil absorption and adsorption, Soil capillarity, Shear strength of soils—Testing