10. Earthworks

Abstract

Ever since man began establishing settlements in prehistoric times, he has been reshaping his built environment. The placement of clay has been used to form embankments, dams, quarry tips, mounds or levelled areas. This process is referred to as ‘filling’ and the final structure is known as a ‘fill’. By excavating clays, engineering structures such as cuttings, ditches and moats have been constructed. Clay has also been excavated as a raw material in manufacturing, for example for the pottery and building industries. The resulting fill structures and excavations are collectively referred to as earthworks. Horner (1988) and Trenter (2001) provide a thorough summary of British practice and the somewhat dated ‘ Earth Manual ’ (US Bureau of Reclamation 1974) describes American practice. A particular useful reference on the use of soil and rock in construction with an emphasis on Australian experience is given by McNally (1998) and Fookes (1997) covers tropical residual clay soils in terms of characteristics, description and engineering properties. It is likely that the earliest earthworks were for the purpose of living and defence but as populations increased water supply and irrigation became important. Although many of the earliest earthworks have become obscured with time, canals have been dated from about 4000 BC in Iran and earth dams in Jordan from about 3200 BC (McFarlan 1989). Clays have been excavated for the production of pottery for thousands of years and the occurrence of kaolin-rich clays probably led to the development of porcelain in China.