The factors which affect the selection of a method to loosen in situ material in earthworks operations are presented with particular reference to the corresponding contracting pricing structure. The characteristics of rippability classification systems and the requisite exploratory investigations are briefly reviewed. Controlled excavation is discussed in detail in respect of the specification and performance of the machine, the principles of modern tractor mounted rippers and the concepts of economic and mechanical ripping. Layouts, procedures and examples of ripping trials are given. Recommendations with regard to the standardization of specifications for excavation classification are presented in conclusion.
The settlement at the Cape was originally established to safeguard for the Dutch East India Company supplies of fresh water, meat, and vegetables. Subsequent migration into the interior was the result of the evolution of a class of wandering cattle-farmers, extensive rather than intensive users of land, in search of grazing. This trekking was first checked when the vanguard of the black tribes, also pastoralists, were met in the Fish River area.