The traditional and the most common method

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PASSAGE 3- Questions 28-34
Hand-dug Wells
ECAVATION BELOW
WELL
The traditional, and the most common method, of obtaining
groundwater in rural areas of the developing world is by means of hand-
dug wells. However, because they are dug by hand their use is restricted
to suitable types of ground, such as clays, sands, gravels and mised soils
where only amall boulders are encountered. Some communities use the
skill and knowledge of local well-diggers, but often the excavation is
carried out, under supervision, by the villagers themselves.
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water
The volume of the water in the well below the standing water table acts
as a reservoir, which meets demands during the day and replenishes
itself during periods when there is no abstraction. Depths of hand-dug
wells range from shallow wells, about five metres deep, to deep wells
over 20 metres deep. Wells with depths of over 30 metres are sometimes
constructed to exploit an aquifer that has already been located. It is
impractical to excavate a well which is less than a metre in diameter. An
excavation of about 1.5 metres in diameter provides adequate working
Choose NO MORE THAN TWO WORDS OR A NUMBER from the passage for each
answer.
space for the diggers and will allow a final internal diameter of about 1.2
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metres once the well has been lined.
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Digging with the sides of the excavation supported
There are several methods of supporting the sides of the excavation
while digging proceeds. The safest is to excavate within pre-cast
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concrete rings which later become the permanent lining to the sides of
the well. The first ring has a cutting edge, and additional rings are placed
on it as excavation proceeds. As material is excavated within the ring, it
sinks progressively under its own weight and that of the rings on top of
it. This method should always be used in unstable ground. When
construction has been completed, the joints between the rings above