Tuesday, February 14, 2012

Deep Well System | Civil Engineering Projects

In our series of articles regarding wells and well Points, we have discussed the following:

Now we will move on with our further discussion on "Deep Well System".

A deep well is about 30 to 60cm in diameter, bored to a depth of 15 to 30m. It is provided with a casing which is perforated one in the previous zones penetrated. Coarse filter material is placed in the annular space between the casing and the walls of the hole. The spacing of deep wells varies between 10 to 30m, depending upon the area to be dewatered and the location of the water table.

A submersible pump is placed inside the casing near the bottom. The pump is driven by a motor mounted on the top of the casing through a vertical shaft. However, if the motor is submersible, it can be directly attached to the pump.

As the pump is  placed at the bottom, there is no restriction on the height to which the water can be lifted, unlike a shallow well system.

Deep wells are located on the outer periphery of the area to be excavated. A row of well point is also installed at the tow of side slopes is also installed at the toe of side slopes of the deep excavation ti intercept seepage between the deep wells and to prevent sloughing of the slopes near the toe.

As in the case of well point systems, pumping once started must be continued until the entire excavation work is completed. If the pumping is stopped in between, there would be a rapid development of hydrostatic and seepage pressure in the excavation, which may prove to be disastrous.

We will discuss "Horizontal Wells" in our succeeding article.