1. A sandy soil has a porosity of 38% (porosity, n = volume of void/total volume = e/(1+e)) and the grain specific gravity Gs is 2.69. Determine: 
(a) The void ratio;
(b) The dry unit weight;
(c) The saturated unit weight;
(d) The bulk unit weight at a water content of 17%

Q2:
The three common clay minerals are kaolin, montmorillonite and illite.

Kaolin consists of many ‘two layer sheets’, which is made up of a tetrahedral layer and an octahedral layer. These layers are two layer sheets are bonded together quite strongly by hydrogen bonding, leaving kaolin particles very thick. * Specific surface= 20m2/g * Very stable * Very tight lattice structure that prevents water penetration * Not subject to expansion when saturated * High internal friction due to strong silicate structure

Montmorillonite is a three-layer mineral that has weak bonding between the sheets. This allows water to penetrate between individual sheets. This leaves the particle thickness of montmorillinite as just the thickness of a single three-layer sheet. * Specific surface= 800 m2/g * Bonding is weak, therefore unstable * Significant affinity for water, very easily attracts water due to weak connections, therefore water easily penetrates between sheets and particles. * Subject to expansion when saturated (Large volume expansion when water is present) * Low internal friction due to weak connections.

Illite Clay Mineral * Specific surface 80 m2/g * Bonding is intermediate * Water affinity not