Evaluation And Treatment Of Swelling Behaviour Of Expansive Soils In Parts Of Ohafia Southeastern Nigeria
Okoro Lambert Chiedozie
Department of Geology, Federal University of Technology Owerri, Imo state Nigeria
Okeke Osita Christopher
Department of Geology, Federal University of Technology Owerri, Imo state Nigeria
Opara Alex Iheanyi
Department of Geology, Federal University of Technology Owerri, Imo state Nigeria.
Keywords: expansive soil, swelling minerals, plasticity indices, treatment, additives, Ohafia
Abstract
Expansive soils are soils that swell when they are wet and shrink when they are dry. This characteristic nature of swelling and shrinking can cause engineering structures to fail. They can exist anywhere in the world, especially in tropical climates. The swelling of these soils can be attributed to the presence of swelling minerals such as montmorillonite and illite. The study area, Ohafia, lies within the Anambra Basin, Southeastern Nigeria, and is underlain by four different geologic formations (Nkporo, Mamu, Nsukka and Imo Shale) that are known to be shaly, with varying degree of expansion. The engineering structures in the study area show varying degrees of failures expressed as cracks as a result of these expansive soil units. The studied soils derived from different locations in the study area, covering the different swelling geologic formations have liquid limits ranging from 42% - 84%, plasticity indices range from 19.4% - 40%, linear shrinkage values range from 12.1% - 22.1%, free swell value range from 42.9% - 77.1% and have more than 80% passing sieve 75µm. The soils plot as CH and CL soils on the Casagrande plasticity chart and are regarded as inorganic fat and lean clays respectively. X-ray analysis of the soils shows presence of Montmorillonite, Kaolinite, Illite, Chlorite and Halloysite. On treating the soils with cement and lime, a reduction of the swelling characteristics of the soils were observed. The effect of the treatment of the soils with cement showed a reduction of the plasticity indices from 25.6% - 9.3% (Ndiorieke soil, Nkporo), 34.8% - 9.7% (Akanu soil, Mamu), 30.9% - 11.4% (OzuAbam soil, Nsukka), and 40.4% - 12.8 (Amaogbu soil, Imo Shale). On treating with lime, a reduction of plasticity indices from 25.6% - 8.2% (Ndiorieke soil, Nkporo), 34.8% - 10.8% (Akanu soil, Mamu), 30.9% - 7.4% (OzuAbam soil, Nsukka), and 40.4% - 14.7% (Amaogbu soil, Imo Shale) were also observed