Earthworks

The term ‘earthworks’ refers to the removal or placement of soils and other excavated material during construction. This is commonly part of civil engineering works required in the construction of roads, railways, land stabilisation, and land grading to change the topography of a site.

Earthworks: a guide, Second edition, by Paul Nowak and Peter Gilbert, Published by ICE in 2015 states: ‘Earthworks operations include the excavation, transport, placement and compaction of fill materials to construct earth structures, and is a significant element of almost all civil engineering projects. A good understanding of earthworks design and construction enables the delivery of successful projects and avoidance of costly problems.’

Earthwork is one of the earliest and most significant works in the construction process. It involves the removal of topsoil and other material, along with any vegetation, before scraping and grading the area to the finished ‘formation level’. This is usually done using a tractor shovel, grader or bulldozer. Below the formation level, the soil is known as the ‘subgrade’.

Most earthworks are formed by cut-and-fill, and the type of ‘fill’ material must be considered, not only in terms of its physical properties, but on the conditions in which it is to be used, and the methods of compaction. Depending on its quality, compressible subsoil may be removed or stabilised.

In road construction, f the cost of full or partial excavation of subsoil is uneconomical and would be likely to result in consolidation, sand wicks or sand drains may be used. Sand wicks are sand-filled boreholes beneath the road embankment that give greater stability to the soil by decreasing the length that water has to travel in a drainage path, so dissipating water pressure. Sand drains alongside the road are used to intercept ground water. Subsoil drainage should be provided to deal with seepage through pavements and verges, from higher ground and a result of the seasonal rise and fall of the water table.