Overview About Excavation

Excavation involves engineering works created through the moving of massive quantities of soil or unformed rock. Engineers need to concern themselves with issues of geotechnical engineering (such as soil fluidity and friction) and with quantity estimation to ensure that soil volumes in the cuts match those of the fills, while minimizing the distance of movement. In the past, these calculations were done by hand using a slide rule and with methods such as Simpson's rule. Now they can be performed with a computer and specialized software, including optimisation on haul cost and not distance (as haul cost is not proportional to haul distance).

Due to the massive amounts of material to be moved-millions of cubic yards in the case of large dams-earthwork engineering was revolutionised by the development of the (Fresno) scraper and other earth-moving machines such as the loader, production

trucks, the grader, the bulldozer, the backhoe, and the dragline excavator.

Excavation initially involves the removal of any topsoil overburden by machine. This material may be examined by metal detector for stray finds but unless the site has remained untouched since its abandonment there is invariably a layer of modern material on the surface of limited archaeological interest. In rural areas, any features are often visible beneath the surface as opposed to urban areas where there may be thick layers of human deposits and only the uppermost contexts will be initially visible and definable through isolation from other contexts

Within the practice of excavation, numerous specialised techniques are available for use, and each dig will have its particular features which will determine the archaeologists' approach. Resources and other practical issues do not allow archaeologists to carry out excavations whenever and wherever they choose. These constraints mean many known sites have been deliberately left unexcavated. This is with the intention of preserving them for future generations as well as recognising the role they serve in the communities that live near them. In some cases it is also hoped that improvements in technology will enable them to be re-examined at a later date, with more fruitful results