Dear Friends, Soil exploration depths for structure foundations can not be generalized. The designer/ approving authorities has to suggest such depths. For gravity principle design (self weight resist stresses), it is advisable for soil exploration upto hard strata. For less important structure, normally twice the height of structure is criteria for soil exploration. For Hydraulic & irrigation structures, soil exploration 2 M below impervious strata met with is the general criteria. Importance, magnitude, type of structure viz., multi storeyed building, bridge, dam, barrage, CM&CD works of canals, and underground water storage tanks/liquid-petrolium product tanks etc will be the deciding factor for soil exploration. Just sharing my views.
For tall buildings,After the rock is met we have to drill upto 10 metres into rock.as per tall buildings latest code.
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