Types Of Foundation Settlement
The settlement of the foundation can be defined as the vertical downward movement of the foundation base of a structure into the soil mass. The following common types of settlement are described below
Total Settlement
The vertical downward movement of the base of a structure is called settlement. Settlements in soils are of two types:
- Immediate Settlement (Si).
- Consolidation Settlement (Sc).
The immediate settlement is caused by the elastic deformation of soil mass on the application of a load. The consolidation settlement is taking place over a long period of time due to the gradual expulsion of water from the soil pores. The sum of “immediate settlement” and “consolidation settlement” is termed as “total settlement(S)”.
Thus, S= Si +Sc
Differential Settlement
The relative settlement of the adjacent portions of a structure is termed differential settlement. In other words, when the different parts of the foundation settle at different rates, it is called differential settlement.
Differential settlement can lead to cracks in the walls, beams, floors, and other structural problems. It is most detrimental to the structure and should not be allowed to exceed the permissible limits.
Permissible Settlement
This is the maximum limit of settlement which can be allowed for foundation soil without having any risk of danger to the structure.
Permissible Settlement as Per I.S Code
Uniform Settlement
As the name suggests, this type of settlement occurs uniformly i.e. the entire foundation settles evenly and at the same rate. The probability of structural damage in these cases is relatively low.
Vertical Settlement
When the settlement occurs vertically in a downward direction, it is called vertical settlement. It can be caused by soil erosion, soil consolidation, or the weight of the building itself.
Lateral Settlement
Unlike vertical settlement, lateral settlement refers to the horizontal movement of the foundation. It can happen for the expansion or contraction of soil, slope instability, the presence of a water body near the foundation, or the presence of underground water. Although it is more appropriate to call it a lateral movement of the foundation instead of a lateral settlement of the foundation.
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