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A box cut serves as the first step in the excavation of most mining areas. It consists of a single rectangular cut made in the surface of the earth, forming a box shape. Box cut mining is primarily used for extracting coal, but may also be applied to other types of materials ranging from metals to minerals. Depending on where these materials lay in relation to the surface of the earth, a box cut may be the sole excavation method used on a project, or may be the first of many methods employed.
In basic strip or surface mining, workers start by using a dragline excavator to create a box cut along the length of the site. The earth and rocks removed from this cut are set aside above ground for later reuse. Workers then enter the trench created by the box cut and mine all available minerals and ore. Once the trench has been stripped, the soil and rocks are used to refill the box cut. Workers may continue this process across the land, cutting and filling one strip at a time before moving on to the next.
The box cut may also be employed for mining coal that is located at a steep slope to the surface of the earth. During this process, workers start by creating a box cut deep enough to reach the start of the coal deposit. This box cut serves as an access point for deeper mining. For example, a shaft may be drilled from inside the trench to the base of the coal deposit. Working out of this type of trench puts workers closer to the materials they are mining, and often results in increased soil stability and safety compared to working from the earth's surface.
In order to support the trenches created by these cuts, workers rely on a variety of shoring techniques. Rock bolts are used to pin the walls of the trench into the surrounding rock or soil, which helps to prevent cave-ins. Wire mesh may be used to cover these walls to reduce the risk of rock or dirt sliding onto workers below. On long-term mining projects, the walls of the trench may be covered with shotcrete to provide maximum strength and stability. On very deep box cuts, the walls of the trench must be sloped out to further mitigate risk.
Compared to other mining techniques, box cutting is relatively fast and easy. Unlike more complex methods, it requires only a large excavator and basic shoring supplies. It also serves as an effective method of subsoil exploration prior to investing in other equipment.
Despite its many benefits, box cut mining is also associated with a number of potential risks or limitations. Even on very shallow trenches, a cave-in could easily kill workers. Shoring and support must be employed to reduce this risk. Ventilation is also a major concern, particularly as these trenches grow deeper and deeper.
I think when people criticize the practice of strip mining, the first thing that bothers them is the box cut. The entire mine really does look like an ugly box cut out of a natural mountain. I can understand from an engineering standpoint why mining companies would want to start from the edges and work their way in and down, but it does emphasize the fact that resources are being systematically pulled out of the ground.
I think it would help ease tensions if the strip mines were eventually back filled and landscaped after all the coal or whatever was excavated.
When I was growing up, there was a coal strip mine near our town, and we could always tell we were getting close to it when we saw the huge rectangle in the side of a mountain. I didn't know it was called a box cut, but it makes sense. It was always straight and flat, like someone ran a giant scraper straight across the top of a hill.
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