Monday, February 27, 2012

Dewatering Systems Design | Civil Engineering


Dewatering Systems Design
In the design of dewatering systems, well points or wells play a significant role. While designing a dewatering system, the number, size, spacing and penetration of the well points or wells have to be determined.

The above mentioned parameters depend on the following:
  • Expected rate of discharge
  • Soil type
  • Drawdown in the wells

There should be a proper arrangement made. Collectors and pumps having sufficient capacity are to be installed on the site for the intended purpose.
Darcy’s law is used to compute the rate of discharge. It is of utmost importance to establish a fundamental relationship between the discharge and the corresponding drawdown.

Assumptions:
The stratum is homogenous and isotropic in nature.
The flow of water is continuous and steady.
Equations for the rate of discharge and corresponding drawdown for different types of wells are developed in the following sections.

The well may be either gravity well or artesian well. A gravity well penetrates a homogenous, pervious stratum aquifer in which the water table is located. An artesian well penetrates a homogenous, pervious stratum which is bounded by impervious strata above and below and in which the piezometric surface is an artesian well falls below the top of the pervious stratum.

The equations developed may also be used for the determination of discharge from wells for irrigation and other purposes. However, such wells are constructed for supplying water and not drainage. In this text, the use of wells for drainage is of main concern.

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