How porous is sand?

Question

How porous is sand?

Answer 1

Typical porosity of some common sediments and rocks :

- Soil: 55%

- Gravel & sand: 20-50%

- Clay: 50-70%

- Sandstone: 5-30%

- Limestone: 10-30%

- Fractured igneous rocks: 10-40%

Answer 2

Don't confuse spatial porosity (how much space there is between -particles in a medium) with effective porosity (how easy it is for water to pass through the medium).

Although clay may be more porous than sand, it has a much lower effective pore space, and can be compacted to prevent water passing through it.

The porosity of sand and clay is very similar in the table; but note the much lower effective porosity of the clay.

Here is a reference that tabulates various materials:

http://web.ead.anl.gov/resrad/datacoll/p...