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Concept
Slug test
Résumé
In hydrogeology, a slug test is a particular type of aquifer test where water is quickly added or removed from a groundwater well, and the change in hydraulic head is monitored through time, to determine the near-well aquifer characteristics. It is a method used by hydrogeologists and civil engineers to determine the transmissivity/hydraulic conductivity and storativity of the material the well is completed in.
The "slug" of water can either be added to or removed from the well — the only requirement is that it be done as quickly as possible (the interpretation typically assumes instantaneously), then the water level or pressure is monitored. Depending on the properties of the aquifer and the size of the slug, the water level may return to pre-test levels very quickly (thus complicating accurate collection of water level data).
A slug can be added by either quickly adding a measured amount of water to the well or something which displaces a measured volume (e.g., a long heavy pipe with the ends capped off). An alternative object is a solid polyvinyl chloride (PVC) rod, with sufficient weight to sink into the groundwater. The objective here is to displace water, not merely be "heavy". A slug of water can be removed using a bailer or pump, but this is more difficult to do since it must be done very quickly and the equipment for removing the water (pump or bailer) will likely be in the way of getting water level measurements.
A slug test is in contrast to standard aquifer tests, which typically involve pumping a well at a constant flowrate, and monitoring the response of the aquifer in nearby monitoring wells. Often slug tests are performed instead of a constant rate test, because:
time constraints (quick results, or results for a large number of wells, are needed),
the well does not or cannot have a pump installed on it (slug tests do not require pumping),
the transmissivity of the material the well is cased in is too low to realistically perform a proper pumping test (common for aquitards or some bedrock monitoring wells), or
the general size (order of magnitude) of the aquifer parameters is all the accuracy that is required.
Source officielle
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