Open-pit mining

Open-pit mines are used when deposits of commercially useful ore or rocks are found near the surface where the overburden is relatively thin.

[not verified in body] It causes significant effects to miners' health, as well as damage to the ecological land and water.

Open-pit mining causes changes to vegetation, soil, and bedrock, which ultimately contributes to changes in surface hydrology, groundwater levels, and flow paths.

It also depends on the amount of structural weaknesses occur within the rocks, such as a faults, shears, joints or foliations.

[8] A haul road is usually situated at the side of the pit, forming a ramp up which trucks can drive, carrying ore and waste rock.

[citation needed] After open-pit mines are closed, they are sometimes converted to landfills for disposal of solid waste.

The main source of air pollutants comes from the transportation of minerals, but there are various other factors including drilling, blasting and the loading and unloading of overburden.

[12] Open-pit nickel mining has led to environmental degradation and pollution in developing countries such as the Philippines and Indonesia.

[17] Open-pit mines operating in an area with heavy groundwater features may eventually face hydrology-related problems.

It is based mainly on an ever-increasing understanding of the rock mass conditions, including groundwater and associated pressures that may be acting within the slopes.

The reduction of groundwater related to pore pressures is a crucial aspect of determining whether or not a geotechnical engineering design for open-pit slopes is attainable.

Because of this, an optimization-based version of the control system is required to ensure that local and regional hydro-geological impacts are within acceptable ranges.

[20] When groundwater pressures cause problems in open-pit mines, horizontal drains are used to aid in accelerating the slope depressurization process.

Horizontal drains are used to lower pore pressure by reducing groundwater head, which enhances slope stability.

Untopping was a feature of Welsh slate workings in the 1930s and 2000s, where Martyn Williams-Ellis, manager at Llechwedd found that earlier Victorian workings could be kept profitable with the newly mechanised techniques for bulk excavation to extract their pillars, and more recently across a number of worked-out mines.

[23] There are no long term studies on the success of these covers due to the relatively short time in which large-scale open-pit mining has existed.

The open pit is then surrounded with a fence, to prevent access, and it generally eventually fills up with ground water.

To mitigate the problem of acid mine drainage mentioned above, flooding is often done with the water of nearby rivers instead of using groundwater alone.

This was achieved by bulk heap leaching at the Peak Hill mine in western New South Wales, near Dubbo, Australia.