A cavity type tube well draws water from the bottom of the well where a hollow cavity has formed, rather than from the sides of the well like a standard tube well. The cavity forms as fine sand is pumped out with the initial water, leaving an empty space. This cavity increases the area available to draw water from, allowing more water to enter the well through a reduced velocity. Cavity wells are drilled into permeable unconfined aquifers and do not require a strainer, drawing water from a single stratum where the cavity has formed.

1. TUBE W
ELLS
Cavity Type
Presented by
A . Mounika swathi
Roll.no-13951A0169

2. Tube Well:Tube Well:
A tube well is a type of water well in which a long
100–200 millimetres stainless steel tube or pipe
is bored into an underground aquifer. The lower
end is fitted with a strainer, and a pump at the top
lifts water for irrigation.

5. CAVITY TYPE TUBE WELL:
What is cavity?
It is an empty space within a solid object.
A cavity type tube well draws water from bottom of
the well and not from the sides and is drilled in
alluvial formation.
The flow in a cavity well is spherical.
The area of flow is increased by enlarging the size
of cavity.

6.  The cavity type well do not have a strainer and
draw water from one stratum only.
HOW IS THE CAVITY FORMED?
The tube well is taken down till it
penetrates the impervious or mota
layer and reaches the water bearing
layer. In the initial stages when the
water is pumped out fine sand comes
in the tube well with the water and
consequently a hollow or cavity is
formed at the bottom.

7. After the cavity formation only clear water
enters the tube well. Since the rate of
pumping is more, the velocity of water
entering the coarse sand layer is critical but
when it comes in the hollow the velocity is
reduced. Finally the water enters the tube well
at the bottom with a velocity lower than the

8.  A centrifugal pump is generally adopted for
developing a cavity well.
 Generally the depth of cavity is small (in
centimetres).
Developing a cavity:Developing a cavity:
Air compressors or turbine pumps may not
develop a cavity satisfactorily, unless a small
cavity has previously been created .

9.  The cavity should be developed with utmost
care, otherwise sand is likely to rush into the
casing and choke it.

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