Black cotton soils and other expansive soils have typical characteristics of shrinkage and swelling due to moisture movement through them. Black cotton soils and other expansive soils are dangerous due to their shrinkage and swelling characteristics.
Rich proportion of montmorillonite is found in Black cotton soil from mineralogical analysis. High percentage of montomorillonite renders high degree of expansiveness. This property results cracks in soil without any warning. These cracks may sometimes extent to severe limit like ½” wide and 12” deep.
As per an article on the subject in ‘Sciencedirect.com’, a test taken to make the soil suitable for construction, cement dust from cement plant is found most suited to stabilize the soil to improve the Atterbergs’ Limit and hence Plasticity Index of BC Soil as well as the compressive strength of the soil.
Issues and Problems Faced during the Footing in Black Cotton Soil:
For a project planned by Valfar Architects in Gulbarga, Karnataka, India, while excavating for laying the foundation footing in black cotton soil, a large depth of clay layer was found.
The property of the soil as per test reports had very poor bearing capacity ranging from 5t/m2 to 10t/m2.
Solution: In this condition, the foundation should be prevented from coming in contact with the soil.