Black cotton soils also other expansive soils own typical characteristics of shrinkage including swelling due upon moisture movement within them.
When moisture enters between the soil particles under some hydrostatic pressure, the particles separate out, resulting in an increase in the volume.
This increase in volume is commonly called as swelling. If this swelling is checked about restricted high swelling pressure, acting within this upward direction, will be induced.
This would result in several cracks in the walls and may sometimes damage the structures such as lintels, beams, slabs, etc.
Shrinkage cracks are formed on the ground surface. This shrinkage cracks some time also known as tension cracks, maybe 10 to 15 cm wide on the ground surface.
Black cotton soil and other expansive soils are dangerous due to their shrinkage and swelling characteristics.
Besides, these soils have a very poor bearing capacity, ranging from 5 t/m2 to 10 t/m2.
Types of foundation in black cotton soils.
Foundation into black cotton soils someone of the subsequent types
Strip foundation:For medium loads, strip foundation someone provided, along with including special design features.
Strip Footing
Strip foundationsare applied where the soil is of great bearing capacity. The key areas of astrip foundation for concrete hole wall construction also timber frame cavity wall construction do similar. The size and position of the strip are directly related to the overall width of the wall.
Pier foundation
Piers are dug at regular intervals andfilled with cement concrete. The piers may hold on stable bearing strata.
Pier foundation is a lot of individual posts dug inside some ground. It is sometimes called “post foundation”. Primarily these poles are located at the intersections of the walls of the house.
Under-reamed pile foundation
An under-reamed pile is a pile of shallow depth (1 to 5 m ) having one tube at its deeper end.
A structure built about expansive soils often cracks due to this differential change caused by the other swelling also shrinking of soil. under-reamed piles provide a satisfactory solution to the above problem.
The principle of this type of foundation is to transfer the load to hard strata which have sufficient bearing capacity to take the load.
Single also double under-reamed piles may further be provided to foundations of structures into poor soils overlying firm soil data. In unusual soils, if repeated under-reamed piles turn provided, both this under-reams shall rest within each firm soil data.
