Causes of failure in foundation

i.    Unequal settlement of subsoil: All soils, except rock and murum yield under the load of the structure. Uniform yielding and within a particular limit is harmless, but unequal yielding creates cracks in the building and ultimately results in failure of the structure.

ii.   Unequal settlement of masonry: It is caused by shrinkage and compressibility of mortar joints and the poor quality of material used in foundation.

ii.    Withdrawal of subsoil moisture: This occurs in wet soil.  As the moisture of the soil evaporates in dry weather, the soil becomes compressed and cracks thereby causing failure of the foundation.

 iv. Volumetric change in soil: Black cotton soil has the property to shrinks while dry and swells while wet. This character makes it unsuitable for building construction as during the seasonal changes its volumetric composition changes in a large extent. A foundation on such soil condition is detrimental as the change in volumetric composition greatly impacts the foundation.

v.   Lateral pressure on super structure: When the structure is subjected to lateral pressure due to wind or the lateral thrust of arches or a sloping roof or wide cantilever projections, which causes eccentricity of the loads, a tendency of tilting or overturning is developed, resulting in failure of the foundations.

vi.  Lateral escape of subsoil: When the building is situated near a deep cliff or a river, the soil below the foundation may escape laterally and cause settlement of the foundation. Similarly, if the depth of the foundation is small or the subsoil below the foundation is of a sliding nature, it may slip away under the loads and cause the failure of the foundation.

 vii. Action of atmosphere: Atmospheric action also contributes in the deterioration of the existing foundation.  Rain is the main element that should be kept away from reaching anywhere near the foundation.  A proper drainage system is prescribed. The foundation should be constructed at a sufficient depth, beyond the reach of surface water.