[mithun]

What is Soil Bearing Capacity ??

The topmost layer of soil is likely to be loose, unstable and contain organic material. So the topsoil should be removed and the footing trench deepened to provide a level, undisturbed surface for the entire building foundation. If this is not feasible because of a sloping site, the footing will need to be stepped.

Bearing capacity of soil is the value of the average contact pressure between the foundation and the soil which will produce shear failure in the soil.

The bearing capacity of soil is related to the soil type and the expected moisture level.

Soil Type kN/m²

Soft, wet, pasty or muddy soil 27 - 35
Alluvial soil, loam, sandy loam (clay +40 to 70% sand) 80 - 160
Sandy clay loam (clay +30% sand), moist clay 215 - 270
Compact clay, nearly dry 215 - 270
Solid clay with very fine sand 430
Dry compact clay (thick layer) 320 - 540
Loose sand 160 - 270
Compact sand 215 - 320
Red earth - 320
Murram - 430
Compact gravel 750 - 970
Rock - 1700

http://www.fao.org/

[mithun]

Soil when stressed due to loading, tend to deform. The resistance to deformation of the soil depends upon factors like water content, bulk density, angle of internal friction and the manner in which load is applied on the soil. The maximum load per unit area which the soil or rock can carry without yielding or displacement is termed as the bearing capacity of soils.