Impact of Wet-Dry Cycles on the Shear Strength of High Plastic Clay Based on Direct Shear Testing

Cyclic wetting and drying of compacted highly plasticity clays and shales cause volume change through shrinkage and swelling. This eventually may decrease the shear strength to the fully softened state. The objective of the current study is to determine the change in strength as well as physical properties of high plasticity clay due to repetitive swelling and shrinking over time. During this research, the effects of cyclic wetting and drying on the shear strength of the clayey soil were investigated. Soil samples were collected from a slope located on I 35 near Mockingbird, Dallas to prepare test specimens which were subjected to 1, 3, and 5 wet-dry cycle before the direct shear testing. It is observed that the angle of internal friction decreased by 6 degrees and cohesion decreased by 55% of initial compacted stage after the fifth wet-dry cycle.