Effect of Stone Columns on Strength and Consolidation Characteristics of Black Cotton Soil

One fifth of the land mass in India is covered by black cotton soil (BCS). Due to low permeability, poor strength and high compressibility, they pose huge engineering problems. In the present study, the influence of stone column on the consolidation and strength behaviour of black cotton soil is meticulously studied. Laboratory tests are carried out on both end bearing and floating type stone columns, having diameters (d) 50 mm, 60 mm and 70 mm with l/d ratios 3, 4 and 5 (l being the length of stone column), installed in black cotton soil. The load-settlement and consolidation behaviour of unreinforced and reinforced black cotton soil are compared. It has been found that for d = 60 mm and l/d = 3, the load carrying capacity for reinforced BCS increases by 23% and 20% for end bearing and floating type stone columns, respectively. Moreover the void ratio (e), coefficient of compressibility (av), coefficient of volume change (mv), coefficient of consolidation (Cv), coefficient of permeability (k) and compression index (Cc) of black cotton soils are significantly affected by the l/d ratio and diameter of the stone column. The present study reflects the efficiency of stone columns as suitable ground improvement technique for BCS.