Building Construction
Raft foundations are used for:

Providing increased area of foundation over poor bearing capacity of soil
Spanning over small soft or loose pockets
Counter acting the hydrostatic effect
All listed here

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Building Construction
During percussion drilling

Caving or mixing of strata are caused in soft soils or cohesion-less soils
Ground water observations are hindered due to entry of the slurry in the soil below the bottom of the hole
All listed here
The soil to a considerable depth below the bottom of the hole gets disturbed

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