6.5. Design and construction of water wells

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6.5.1. Main elements of water well

Main elements of water well

The figure shows the typical elements of a well. A well may have all or only some of these elements.

  1. Riser pipe
  2. Grouting cement.
  3. Perforated Filter (screen)
  4. Gravel pack
  5. Sump
  6. Level recorder (Monitoring Line)
  7. Pump typically submersible

Ccasing ή riser pipe: It is the inner lining of the well. Stabilize the walls of the well and protect it from sloping due to soil instability. Depending on the soil and the diameter of the drill, it can be a metal or plastic pipe. For shallow and large diameter drillings (D> 50 cm) can consist of pieces of cement pipe. The diameter of the shield is always slightly smaller than the diameter of the borehole.

Question: When do you not need shielding?
Question: When is multi-diameter shielding needed?

Screen: In combination with the layer of gravel they retain the soil material, prevent coagulation and do not fill the well with materials from the soil tissue of the aquifer

Sump: Area where any inflows of soil material settle so as not to block the perforated filter

Grouting: In combination with the shielding, it holds the walls of the drilling and protects it from possible contamination.

γεωλογική τομή γεώτρησης

6.5.2. Well design

Question: What do we control / plan about drilling a well?

  1. That we will have an adequate supply of Q
  2. Effects on water quality and quantity in the aquifer
  3. Mining and shielding costs (depth, soil types, etc)
  4. Operating and maintenance costs (pumping depth, soil geology, distance from the end user)
  5. Static stability and operational reliability.

6.5.3. Well drilling

(1) Hand drilling

Limited Depth (10-20 m), Large diameter (over 50cm)
Question: Watch the video below. How does the well fill with water? Where was the gravel placed and why

(2) Drilling with an auger drill

(3) Drilling with a rotary-impact drilling rig

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