Digging, also referred to as excavation, is the process of using some implement such as claws, hands, manual tools or heavy equipment, to remove material from a solid surface, usually soil or sand on the surface of the Earth. Digging is actually the combination of two processes, the first being the breaking or cutting of the surface, and the second being the removal and relocation of the material found there. In a simple digging situation, this may be accomplished in a single motion, with the digging implement being used to break the surface and immediately fling the material away from the hole or other structure being dug.
Many kinds of animals engage in digging, either as part of burrowing behavior or to search for food or water under the surface of the ground. Historically, humans have engaged in digging for both of these reasons, and for a variety of additional reasons, such as engaging in agriculture and gardening, searching for minerals, metals, and other raw materials such as during mining and quarrying, preparing for construction, creating fortifications and irrigation, and also excavations in archaeology, searching for fossils and rocks in palaeontology and geology and burial of the dead.
There are a wide variety of reasons for which humans dig holes, trenches, and other subsurface structures. It has long been observed that humans have a seemingly instinctive desire to dig holes in the ground, manifesting in childhood.
Like other animals, humans dig in the ground to find food and water. Wood-lined water wells are known from the early Neolithic Linear Pottery culture, for example in Kückhoven (an outlying centre of Erkelenz), dated 5090 BC and Eythra, dated 5200 BC in Schletz (an outlying centre of Asparn an der Zaya) in Austria. Humans are unique among animals in the practice of burial of the dead. Intentional burial, particularly with grave goods, may be one of the earliest detectable forms of religious practice since, as Philip Lieberman suggests, it may signify a "concern for the dead that transcends daily life." Evidence suggests that the Neanderthals were the first human species to practice burial behavior and intentionally bury their dead, doing so in shallow graves along with stone tools and animal bones. Exemplary sites include Shanidar in Iraq, Kebara Cave in Israel and Krapina in Croatia. Some scholars, however, argue that these bodies may have been disposed of for secular reasons. Notably, burial of the dead prevents diseases associated with the presence of corpses, and prevents scavengers and other predators from being attracted.
The earliest undisputed human burial, discovered so far, dates back 100,000 years. Human skeletal remains stained with red ochre were discovered in the Skhul cave at Qafzeh, Israel. A variety of grave goods were present at the site, including the mandible of a wild boar in the arms of one of the skeletons.
In construction and civil engineering, a borrow pit, also known as a sand box, is an area where material (usually soil, gravel or sand) has been dug for use at another location. Borrow pits can be found close to many major construction projects. For example, soil might be excavated to fill an embankment for a highway, clay might be excavated for use in brick-making, gravel to be used for making concrete, etc.
In some cases, the borrow pits may become filled with ground water, forming recreational areas or sustainable wildlife habitats (one such example is the Merton Borrow Pit, near Oxford in central England, excavated to provide materials for the nearby M40 motorway). In other cases, borrow pits may be used for landfill and waste disposal.
A regional variation of this is termed "barrow pit" in the western United States (especially the Rocky Mountains). The localism--sometimes pronounced "borrer pit"--describes the ditch along a roadway. These ditches were created to provide the fill to level and crown the roadway and subsequently provided drainage for the road.
An excavation lake (also a flooded gravel pit) is an artificial lake, which usually has its origins in the excavation of gravel or sand for construction materials or in some other kind of surface mining. In many cases, the excavation holes are landscaped according to the land restoration required by law. Because the excavation reached a point below the water table, lakes form naturally. Less frequently excavation lakes are intentionally created, especially as recreation areas.
In Germany the lakes are almost always used for fishing, since a fishery is created by law with every surface water. At some excavation lakes, beaches are added for swimming or other water sports, in particular boating, water skiing or windsurfing. To support these uses, large parking lots, changing areas, and eating areas are also set up. In some cases, the excavation lake serves as a nature reserve, as in the case of the lakes in the Attenborough Nature Reserve.
Although humans are capable of digging in sand and soil using their bare hands, digging is often more easily accomplished with tools. The most basic tool for digging is the shovel. In neolithic times and earlier, a large animal's scapula (shoulder blade) was often used as a crude shovel. In modern times, shovels are typically made of metal, with a wooden handle. Because digging is a cutting process, particularly where the soil being dug contains plant roots, digging is aided by the shovel being sharpened.
Historically, manual shoveling (often in combination with picking) was the chief means of excavation in construction, mining, and quarrying, and digging projects employed large numbers of people. After the Industrial Revolution, mechanization via steam shovels and later hydraulic equipment (excavators such as backhoes and loaders) gradually replaced most manual shoveling; however, individual homeowners still often find reasons to engage in manual digging during smaller-scale projects around the home.
The excavatability of an earth (rock and regolith) material is a measure of the material to be excavated (dug) with conventional excavation equipment such as a bulldozer with rippers, backhoe, scraper and other grading equipment. Materials that cannot be excavated with conventional excavation equipment are said to be non-rippable. Such material typically requires pre-blasting or use of percussion hammers or chisels to facilitate excavation. The excavatability or rippability of earth materials is evaluated typically by a geophysicist, engineering geologist, or geotechnical engineer.
The rippability of an earth (rock) material is a measure of its ability to be excavated with conventional excavation equipment. A material may be classified as rippable, marginally rippable or non-rippable. The rippability of a material is often evaluated by an engineering geologist and/or geophysicist utilizing the seismic refraction equipment (see refraction),. Rippability studies can involve the performance of seismic refraction traverses, the drilling of borings with an air percussion drill rig, the excavation of test trenches with a bulldozer with rippers or backhoe, and by geologic mapping.
Cave-in in an excavation is the detachment of the mass of soil in the side of trench and the sudden displacement inside the excavation which represent a hazard to the person inside. Cave-ins is considered as the most critical risk beside other related hazards within trenches. The reasons that lead to cave-ins fall between pressure on soil, vibration of equipment and excess loads. Cave-ins in excavation is prevented using sloping, shoring and shielding.