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Until recent centuries, all artificial wells were pumpless dug wells of varying degrees of formality. Their indispensability has produced numerous literary references, literal and figurative, to them, including the Christian Bible story of Jesus meeting a woman at Jacob's well (John 4:6) and the "Ding Dong Bell" nursery rhyme about a cat in a well.<a href=http://www.cnpumps.com/deep-well-pump.html></a>
Such primitive dug wells were excavations with diameters large enough to accommodate men with shovels digging down to below the water table. <a href=http://www.cnpumps.com/swimming-pool-pump.htm>swimming pool pump</a> They can be lined with laid stones or brick; extending this lining into a wall around the well presumably served to reduce both contamination and injuries by falling into the well. A more modern method called caissoning uses reinforced concrete or plain concrete pre-cast well rings that are lowered into the hole. A well digging team digs under a cutting ring and the well column slowly sinks into the aquifer,whilst protecting the well digging team.
Hand dug wells provide a cheap and low-tech solution to accessing groundwater in rural locations, with a high degree of community participation. Hand dug wells have been successfully excavated to 60m. Hand dug wells are cheap and low tech (compared to drilling) as they use mostly hand labour for construction. Hand dug wells have low operational and maintenance costs. Even if the hand pump is broken, water can still be extracted. In many cases, hand dug wells are similar to traditional abstraction methods and are readily accepted by the host community. <a href=http://www.cnpumps.com/jet-pump.htm>jet pump</a> The construction of hand dug wells can incorporate a high degree of community participation (e.g. pre-fabrication of concrete rings). Hand dug wells can be easily deepened, if the ground water level drops, by telescoping the lining further down into the aquifer. The yield of existing hand dug wells may be improved by deepening or introducing vertical tunnels or perforated pipes.
Hand dug wells are not suited to hard ground formations and take time to dig and line. <a href=http://www.cnpumps.com/deep-well-pump.html>deep well pump</a> Construction of hand dug wells can be dangerous due to collapsing soils, falling objects and asphyxiation. Hand dug well construction generally requires the use of a trained well construction team. Construction of hand dug wells can require large capital costs for equipment such as concrete ring moulds, heavy lifting equipment, well shaft formwork, motorized de-watering pumps, and fuel.<a href=http://www.cnpumps.com/submersible-sewage-pump.html>sewage pump</a> Since most hand dug wells exploit shallow aquifers, the well may be susceptible to yield fluctuations and possible surface contamination.
Safety during hand dug well construction is paramount due to the risk of collapse, <a href=http://www.cnpumps.com/submersible-sewage-pump.html>submersible pump</a> falling objects and suffocation from exhaust fumes from dewatering pumps.
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- 2010/03/11(木) 13:53 -