Suction Stress Characteristic Curve for Compacted Silty Sand from Suction-Controlled Triaxial Testing

In general, most of the soils encountered all over the world that support engineering structures are in unsaturated conditions and they undergo repeated wetting and drying due to ingress of rainfall, seasonal fluctuations in water table and temperature changes in environment. Recent studies have demonstrated that the suction characteristic curves (SSCCs) can be used to describe the state of stress in unsaturated soil. However, limited experimental data is available to verify the trend of suction stress variation that is typically experienced by soils around the world. The purpose of this study is to present SSCC for compacted silty sand in light of the experimental data obtained from suction-controlled triaxial testing over a matric suction range varying between 0-750 kPa. In this paper, the method proposed by Lu and Likos (2006) was used to indirectly calculate the experimental values of suction stress corresponding to each level of matric suction. The experimental suction stress was found to increase non-linearly with increasing suction. Furthermore, the soil water characteristic curve (SWCC) parameters were obtained on test soil and used to estimate the SSCC using the predictive model proposed by Lu et al. (2010). However, the suction stress values were mostly underpredicted using this model. On the other hand, a simple exponential equation was found to best fit the suction stress over the matric suction range of 0-750 kPa for compacted silty sand.