Q1: Which one of the following statements is true ?

ANS:D - All the above.

Porosity is a measure of pore spaces in soil. It is a volumetric ratio. It is ratio of total volume of voids (filled with water or air) to the total aggregate volume of soil mass.

It is dependent on so many factors like texture, structure, arrangements of particles and organic content.

Clays have particles size below 2 microns and these small particles have small pores and the interconnected pores gives more voids which makes it more porous.

Sand have particles size greater than clay and these particles have small pores compared to same volume.

Hence clays is highly porous than sand. However, clays are not permeable (water can't flow easily through them because of these small pore size) and sands on the other hand offer excellent drainage properties.

When it comes to porosity, then clay is more porous than sand. This is because the grain size of clay is much smaller than sand. So inter-granular space between the individual grains is much more in case of clay than sand. But all these pores are not interconnected so the permiability of clay is poor. However the intergranular space in sand is more so it has greater perbiability.

But then again everything can happen depending on the degree of compaction and lithification.

Porosity (n) is the percentage of void (Vv) in the total volume+void (V) of a solid of earth material. According to Fetter, pg 75, in table 3. 4, Porosity ranges for sediments.

Well-sorted sand or gravel = 25-50%.

Mixed sand and gravel = 20-35%.

Clay = 33-60%.

This is according to Meinzer (1923a) ; Davis, 1969; Cohen, 1965; and MacCary and Lambert, 1962.

So, Clay should be much porous than sand thou not pretty much.

As mentioned 'the dispersive effect of the electrostatic charge present on the surface of certain book-shaped clay minerals causes clay particles to be repelled by each other resulting in relatively large proportion of void space.