Active soils of the Niger Delta

Active or expansive soils of the freshwater area of the Niger delta in southern Nigeria swell and shrink in the rainy and dry seasons respectively together with any structure constructed with and/or on them. In this paper, data on some natural engineering characteristics of these soils derived from previous soil investigation activities within the region were used to identify, characterize and evaluate them for better and more resourceful engineering applications. Also, disturbed samples taken from four locations were chemically stabilized with CaCl2and slaked-lime to reduce swelling potential to tolerable level (i.e. 2.5% for 24-hour free swell index) and with cement to improve strength. 24-hour free swell index was found to diminish with increasing stabilizer content while addition of cement was found to enhance continual increase in MDD, soaked-CBR and durability index such that the soil becomes better compactible, stronger and more durable with increasing cement content. About 2.6% and 14.6% cement contents were found needed to respectively produce sub-base and base-course materials in road works.