The impact of cyclic wetting and drying on the swelling behaviour of stabilized expansive soils

Black cotton soil(BCS) deposits, stabilized with waste materials-wood-ash and organic matter (leaves, grass, etc.) exist in BCS areas of North Karnataka. India. These ash-modified soils (AMS) are apparently stabilized by hydrated lime produced by biochemical, dissolution, and hydration reactions. The influence of cyclic wetting and drying on the swelling behaviour of wood-ash-modified BCS and laboratory lime-treated BCS specimens are examined in this study. Such a study is required to assess the long-term behaviour of chemically stabilized soils in geotechnical applications. Cyclic wetting and drying caused the AMS specimens to become more porous and less saturated. Consequently, the cyclically wetted and dried (or desiccated) AMS specimens collapsed significantly at the experimental flooding pressures. The beneficial effects of lime-stabilization of the BCS specimens were also partially lost in cyclically wetting and drying them. The clay contents of the lime-treated BCS specimens increased on cyclic wetting and drying. The increased clay contents in turn, affected their Atterberg limits and swell-shrink potentials. Partial loss of inter-particle cementation, increased porosity, and reduced degree of saturation, also imparted small to moderate collapse potentials to the desiccated lime-treated BCS specimens. (C) 2001 Elsevier Science B.V. All rights reserved.