Drainage and Dewatering | Building Construction

Introduction to Drainage and Dewatering


What is drainage?


Drainage can be classified into two categories:

  1. Surface drainage
  2. Sub-surface drainage

What is Surface drainage?


Sub-surface drainage


What is dewatering?


  • when it is situated below the ground water table or
  • when it is surrounded by a coffer dam.

Why is dewatering done?

Only understanding the definition of dewatering is not enough. It is essential to know the reason as to why it is done.

Some times in some areas, the water table is high. This causes trouble and discomfort during construction. The water is pumped out so as to keep the excavation dry. Excavation has to be kept dry so that concreting can be done.

Sometimes temporary dewatering may suffice. Temporary dewatering is draining out the water at the time of construction and it is then followed by restoration to its original water level as soon as the construction is complete.

What is permanent dewatering and why it is done?

Permanent dewatering is removing the subsurface gravitational water throughout the life of the structure. This is done to protect the structure from moisture and dampness.

Check out: Causes of Foundation Damage | Moisture

Advantages of Subsurface drainage

It helps in improving the properties of the soil

Helps in the stabilization of soils

Let us consider the case of “Fine grained soil”

The water removed from fine grained soil is not much but the improvement in the properties of the soil is significant.

Helps in reducing hydrostatic pressure acting at the base of the structure

Methodology to be adopted for Sub-surface drainage:

The methodology adopted at a site would depend on various factors. They are as follows:

  • Characteristics of the soil
  • Position of the water table
  • Time period

Also check out:

Inceptor Ditches

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  1. #1 by Joseph on February 14, 2012 - 5:55 am

    carry on such nice posts…

    • #2 by BenzuJK on February 27, 2012 - 11:02 pm

      Thank you Joseph. Will definitely do.

  2. #3 by gaurav on March 19, 2012 - 11:15 pm

    what is meant by coffer dam ?

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