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).