A gravel pit is a type of mine that is left exposed to the surface of the earth. While a great deal of mining is performed deep underground, a gravel pit is used to mine materials located close to the earth's surface. These mines start off as relatively small holes, or voids, and grow larger and larger as more mining is completed. Gravel pits may also be referred to as rock quarries or open-cut mines in some parts of the world.
Gravel consists of small rocks that are used as aggregate in concrete or paving. This material is also used to create a structural base for a roadway, or to aid in soil drainage. Different types of gravel are also placed around planting beds to serve as decoration and as a form of weed control. A gravel pit that provides this type of small stone will generally not include any type of slabs, or larger stones. Some gravel pits, however, may naturally include metals or minerals that can be mined along with the gravel.
To construct a gravel pit, miners start by stripping away topsoil and subsoil layers from the earth, using large stripping machines. This reveals the layers of rock and gravel below the surface so these materials can be easily extracted using front-end loaders and other large machines. Next the gravel is subject to washing and processing before it is shipped to asphalt plants or other manufacturing facilities.
While a gravel pit serves as a simple and effective method of mining gravel from the earth, it also poses a number of challenges for miners. As workers dig down below the local water table, these pits gradually fill with water, which can make mining difficult. In this type of situation, workers may dredge the gravel from below and simply allow the water to fill the pit. Other times, miners rely on large pumps to remove water temporarily to allow the extraction process to continue.
Once all gravel has been removed, these pits are often abandoned by workers. Many communities have attempted to rehabilitate these pits by using them as man-made lakes. Gravel pits that have filled with water often serve as nature preserves or recreation areas, allowing users to take advantage of swimming and boating opportunities. Many communities introduce freshwater fish to these abandoned gravel pits so that the area can serve local fishing enthusiasts. If the gravel pit is located at a high elevation and does not fill with water, mining companies or communities may establish grass and trees on the site to help rehabilitate the land.