We have published many posts regarding black cotton soil. Different types of foundation system are provided in the previous posts. But in this post we will discuss about the economic considerations for designing and placing foundation on this type of expansive soil.
Normally two types of foundation are adopted in broad sense. They are:
a. Deep supporting system
b. Shallow supporting system
Before go through the main topic we will briefly discuss about both system of foundation.
Deep supporting system:
The foundation that has deep component extending well below the active zone of moisture in soil is called a foundation having deep supporting system. The active zone is important as the only enemy to foundation on black cotton soil is moisture. Thus moisture fluctuation does not disturb the foundation system. Plies or drill piers are the ideal example of this type of system.
Shallow supporting system:
The foundation system that does not extend beneath the active zone of moisture is termed as shallow supporting system. As the foundation component remains in moisture zone, the foundation and the structure as well suffer movements as supporting expansive soils get expanded due to activity of moisture.
Now we are ready to discuss the economic considerations. The foundation systems discussed above both have risk of damage due to differential settlement. We have to know about the cost involvement and reduction or increment of risk for particular foundation system. We will finish this topic in next post.