Aquifer

1
(No Transcript)
2
Aquifer

• Properties Porosity, specific yield, specific
  retention.
• Potential Transmissivity, storativity.
• Types confined, unconfined.
• Hydraulic conductivity, Physical Laws controlling
  water transport.

3
Porosity

• Porosity is percent of rock or soil that is void
  of material.
• n 100 Vv/V
• n porosity (percentage)
• Vv volume of void space (L3, cm3, m3)
• V unit volume of material including voids and
  solids.

4
How to measure porosity
5
Density of a fluid

• ? m/v (M/L3)
• m mass (M)
• v volume (L3)

6
Total Porosity

• n 100 1 (?b/?d)
• n porosity (percentage).
• ?b bulk density of aquifer material.
• ?d particle density of aquifer material.

7
Factors affecting porosity

• Packing
• Grain-size distribution - sorting

8
(No Transcript)
9
Grain packing, grain size, and porosity

• Cubic packing n 47.65
• Rhombohedral packing n 25.95
• Grain size mixture gt porosity lowered.

10
(No Transcript)
11
Processes affecting grain sorting

• Well-sorted sediments
• gt wind, running water, wave action
• gt higher porosity.
• Poor sorting
• gt glacial action, landslides
• gt lower porosity.
• Grain shape
• gt sphere, rod, disk, book

12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)
18
Sediment Classification

• Sediments are classified on basis of size of
  individual grains
• Grain size distribution curve
• Uniformity coefficient Cu d60/d10
• d60 grain size that is 60 finer by weight.
• d10 grain size that is 10 finer by weight.
• Cu 4 gt well sorted Cu gt 6 gt poorly sorted.

19
d60
d10
d60
d10
20
d60
d10
d10
d60
21
(No Transcript)
22
Porosity of sedimentary rocks

• Diagenesis gt compaction, removal or addition of
  material, transformation of minerals by
  replacement or phase change.

23
(No Transcript)
24
Porosity of sedimentary rocks

• Diagenesis gt compaction, removal or addition of
  material, transformation of minerals by
  replacement or phase change.
• Primary porosity pores between grains.
• Secondary porosity fractures in rock.
• Clastic rocks n 3 - 30.
• Limestones and dolomites n 1 - 30.

25
Porosity of plutonic and metamorphic rocks

• Weathering and fracturing increase overall
  porosity.
• Tectonic stresses - fracturing, faulting,
  folding.
• Fracturing increases porosity by 2 - 5.
• Weathered plutonic rocks can have porosities of
  30 - 60.

26
Depth 100 (meters)
27
Porosity of volcanic rocks

• Degassing products gt holes in the rock.
• Shrinkage cracks -gt joints
• Basalt 1-12.
• Pumice glassy rock formed from a magma with
  high gas -gt can be as high as 87.
• Pyroclastic deposits Tuff 14 - 40
• Ash 50.

28
(No Transcript)