Chapter 14: Soils as particulate materials

Soil comprises countless particles of different shapes and sizes which are in frictional contact with each other and are acted on by gravity. This chapter illustrates the key features of mechanical behaviour that stem directly from the particulate nature of soils. A simple base friction apparatus is described that demonstrates some of these features. In particular the importance of self-weight and microfabric are illustrated, together with the phenomena of contractancy and dilatancy. The apparatus is used to study particle movements associated with active and passive earth pressures, settlement and bearing capacity. A simple mechanistic approach is presented to illustrate the importance of pore water pressure, leading to a demonstration of Terzaghi's effective stress principle. A similar mechanistic approach is used to introduce some key features of unsaturated soil behaviour.