CONSOLIDATION BEHAVIOR OF COLLAPSIBLE CLAYEY SOILS IN SATURATED AND UNSATURATED CONDITIONS

The eect of suction on consolidation behavior has a dominant role to play in the constitutive modeling of unsaturated soils, and, therefore, has received the researchers attention in this eld. In this paper, the eect of the initial conditions of compacted specimens of a clayey soil on their consolidation behavior, under saturated and unsaturated states, is investigated. After determining the compaction curve of the soil, the samples were statically compacted at dierent initial suctions and void ratios (moisture content, dry densities). In order to investigate the volume change behavior of collapsible soils, the cylindrical samples were loaded to a denite stress in conventional oedometer apparatus. Then, while keeping the vertical stress constant, the volume changes of samples due to wetting were measured. After completion of the collapse settlements, the stepped loading of the samples was continued and the end of the primary consolidation line of the samples were attained. The saturated normal consolidation lines of samples with dierent initial water contents and dry densities are compared. It is shown that the normal consolidation line is almost unique and its position is not aected by the initial condition of the samples. This result suggests a simple method for predicting the collapse potential under dierent conditions. The method can be described as follows: The eective stress after saturation is calculated. The initial void ratio (before saturation) subtracted from the void ratio of the soil in a saturated normal consolidation line, corresponding to the eective vertical stress at saturation, would be the change of void ratio due to saturation. The collapse settlements could then be easily calculated. Since determination of the saturated normal consolidation line is a conventional and inexpensive procedure, the proposed method can be regarded as a versatile and inexpensive technique for forecasting the collapse potential.