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Module 6 : Design of Retaining Structures

Lecture 30 : Dewatering [ Section 30.2 : Methods of Dewatering ]


	Deep Well Drainage
	Deep well drainage system consists of deep wells and submersible or turbine pumps which can be installed outside the zone of construction operations and the water table lowered to the desire level. Deep wells are usually spaced from 8-80 meters depending upon the level to which water table must be lowered, permeability of the sand stratum, source of seepage and amount of submergence available.

	Fig. 6.49 Deep well dewatering
	Deep well system is suitable for lowering the ground water table where the soil formation is pervious with depth; the excavation extends through or is underlain by coarse-grained soils. This method is also suitable when a great depth of water-lowering is required or where a head due to artesian pressure has to be lowered in permeable strata at a considerable depth below the excavation level. Deep wells may be combined with the well point system on certain field conditions for lowering the ground water tables.