ABSTRACT
This chapter discusses the fundamentals of permeability of soils and rocks, including different scales of permeability. Natural materials can have a very wide range of permeability values, and the factors controlling permeability are different in, say, a sedimentary sequence of glacial deposits from those in a weathered and fractured rock. The use of Darcy’s law and the concept of permeability is justified by a macroscopic approach and treating blocks of soil as being relatively homogeneous porous media, but it is important to realize that groundwater flow in soils can be very complex at small scale. The Darcy permeability of these soils is so low that even if large head differences are applied, the water flow rates that can be generated are infinitesimally small. Groundwater flow can therefore be modelled by the same methods as used in soils, based on values of permeability determined from pumping tests and other methods.
