Effect of Sand Content on Cyclic Swell-Shrink Behavior of Compacted Expansive Soil

Alternate wetting and drying of soils arise as a result of seasonal moisture fluctuations which in turn lead to the volume change in soils. An increase in volume caused by an intake of water is termed as swelling, and a reduction in volume occurring due to loss of water is defined as shrinkage. Shrinkage poses a much more serious problem than the swelling and depends on many factors including the sand content. This paper mainly focuses on understanding the role of sand fraction on the swell-shrink pattern of expansive soil. To achieve this objective, the laboratory swell-shrink tests were conducted on both expansive soil (C100) and expansive soil mixed with 50% sand (C50-S50). Digital camera image analyses were performed for identification of cracks during drying cycles. The experimental results show that the vertical, lateral, and volumetric deformations decreased for C50-S50 specimen during each wet-dry (W-D) cycle with reference to the C100 specimen. This is attributed to the reduction in the amount of clay, swelling of clay particles in the inter-void spaces between clay and sand, and encapsulation offered by the sand particles. For C50-S50 specimen, mostly surface cracks were observed and the volume of cracks formed were much lesser compared to C100 specimen.