Some characteristics of coarse (granular) and weak rock fill

Naturally occurring granular materials tend to have been derived from a water-borne origin (river, marine or glacial melt-water) or wind-blown origin. Recent materials tend to be uncemented but, in a desert origin, cemented ‘hard pans’ may have formed layers close to the surface.

In the UK, geological strata younger than Permian age tend to be un-cemented although some Cretaceous strata, such as the Greensand, Hythe Beds and Folkestone Beds may contain cemented layers up to 500 mm thick that, historically, were used as building stone locally.

Coarse (granular) soils are normally free draining and easier to handle, in an earthworks context, than fine (cohesive) soils. Apart from uniformly graded sands, silty sands, and some weak rocks, commented on further below, they are relatively trouble free when employed as fill.