11. Earthmoving

Abstract

This chapter follows on from the design, planning, performance and use of clay in the construction of fills and in the quarrying of clay as a mineral for use in construction presented in Chapter 10 by considering the practical aspects involved in the excavation, loading, transportation, modification, placement and compaction of clays in construction and mineral extraction projects. The various operations involved in the excavation, loading, transportation, modification, placement and compaction of materials in or on the ground are termed ‘earthmoving’. The structures that are formed as the result of these operations are known as ‘earthworks’. Some earthworks are constructed to carry out a particular function, such as cuttings and embankments for roads or railways, whereas others, such as quarries and borrow pits, are formed as a consequence of the removal of materials for other uses. Some quarries may be re-used as landfill sites for the disposal of waste materials. In recent times, landfill sites have become engineered structures in their own right and quarries in clay are especially valued owing to the low permeability of the underlying clays, which serve to limit the movement of leachate or liquid wastes away from the site. In earthmoving practice, clays may be considered as those materials containing predominantly clay- and silt-size materials (i.e. fine-grained soils); however they also include materials that contain sufficient fine material that cause them to behave as fined-grained soils and weak rocks, including clayey sands, glacial till and some highly to completely weathered rocks. They may vary considerably