Module 6 : Design of Retaining Structures
Lecture 30 : Dewatering [ Section 30.3 : Design steps for dewatering systems ]
   
  Design steps for dewatering systems
   
 

Design of a dewatering system requires the determination of the number, size, spacing, and penetration of wells or well points and the rate at which water must be removed from the pervious strata to achieve the required groundwater lowering or pressure relief. The size and capacity of pumps and collectors also depend on the required discharge and drawdown.

The essential steps involved in the designing of the dewatering system are given below:

   
Subsoil investigation
  The characteristics of the soils adjacent and beneath the excavation should be investigated well. Grain size distribution and permeability are the two parameters to be determined. Indian Standard recommends a field pumping test for this case.
   
Source And Water Table Details
  Source of seepage and knowledge of the water table at a particular site are the most important factors to be considered while designing a dewatering system. The source of seepage depends on the geological features of the area, nearby streams or water bodies and amount of drawdown. A flow may be from an aquifer being drained the distance to which is known as the radius of influence. It can be estimated from the draw down curve established from a field pumping test.
   
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