Undrained behavior of silt-clay transition soils with varying degrees of overconsolidation

The influence of silt content on the stress-strain, pore pressure change and strength characteristics of silt-clay transition soils is presented. One-dimensional consolidation tests and consolidated-undrained triaxial compression tests on three soils of similar base clay but with different silt contents were performed. The undrained triaxial tests were carried out on specimens of the silt- clay soils with different overconsolidation ratios. It was observed that the tested silt-clay soils were less compressible when consolidated in the vertical direction as the silt content increased. During triaxial shear, the silt-clay soils exhibited stiffer stress- strain response with increasing silt content. The pore pressure changes increased with the amount of non-plastic silt in the soils, particularly at low overconsolidation ratio (OCR). The undrained shear strengths and effective friction angles significantly increased with the amount of silt. It was observed that the degree of overconsolidation significantly influenced the undrained shear strengths of the silt-clay soils but less so for the effective friction angles.