INTRODUCTION
The excavation of a borrow pit falls under the engineering discipline known as earthworks. Earthworks projects consist of engineering feats that include transporting large amounts of soil or rock from one area to another. Borrow pit construction may seem relatively easy to accomplish, though this type of digging actually requires an extensive amount of analysis prior to the first dig. Engineers must be sure that the amount of soil dug from a pit area will not disrupt the earth. Since massive quantities of earth must be moved in order to build roads, railways, canals, buildings, and other structures, the invention of various industrial tools has made this task easier. Bulldozers, loaders, production trucks, graders, and many other large pieces of equipment are often used to move soil from one place to another. Without these machines, digging a borrow pit would take years instead of months or weeks to accomplish. A borrow pit’s volume really depends upon the construction project at hand. While major roads and freeways may take multiple tons of gravel to build, small projects may not require much soil. Borrow pits materials such as laterite and granite are one of the most important materials used in earth work engineering construction in the tropics and subtropics where it is in abundance like Nigeria. The use of lateritic soil for construction and civil engineering works is very common. Therefore, Ado the capital city of Ekiti state and its environs have been availed of this wonderful benefit. But when lateritic soil consist of high plastic clay, the plasticity of the soil may cause cracks and damage on pavement, road-ways, building foundations or any other civil engineering construction projects. Lateritic soils are one of important soils and are widespread in tropical areas and subtropical climates. Lateritic soil which is the product of borrow pit excavation is used as a sub-base and base course for construction of highway embankments (Head, 1992). Engineers and Contractors should ensure that the testing and quality control of pavement materials is done before the commencement of earthworks on site and the adequate quality of construction as the construction project is being executed (Owolabi and Aderinola, 2014). Laterite occurs mostly in the tropical and sub-tropical regions with hot, humid climatic conditions. It has been suggested that a mean annual temperature of around 25°C is needed for their formation and in seasonal situations there should be a coincidence of the warm and wet periods. If there is high rainfall during the cold season, laterites do not develop freely. The minimum annual rainfall required for laterite formation is generally at least 750 mm. Laterite as products of tropical weathering with red, reddish brown, or dark brown colour, with or without nodules or concreting and generally (but not exclusively) found below hardened ferruginous crust or hard pan (Ola, 1983).
Unsuitable soils are soils that expand when water is added and shrink when they dry out. This continuous change in soil volume can cause homes built on this soil to move unevenly and crack (Owolabi et al.,2015).