Surface Mining Methods
Near-surface low-grade ore deposits can be mined by using large mechanized equipment to remove ore that typically has been fragmented as a result of drilling and blasting to a size to allow loading onto ore hauling trucks or a conveyer belt system for transport to an area where additional crushing takes place.
An open pit mine has stepped or benched side slopes that will spiral (ramp) down into the ore deposit to allow downward excavation. Typically a planned thickness of ore will be mined as a bench in a horizontal extent until waste rock is encountered. The bench thickness is based on equipment selected to meet the economic objectives of the mine plan. Before the economic extent of the bench is reached, a new bench will be developed by continuing the downward development of access roads. A large open pit may have several benches active at the same time. The size of an open pit will be limited by several factors which commonly include the grade of the ore, the distribution of the ore, the ratio of waste rock to ore that has to be removed to get to the ore, the stability or strength of an excavated slope to stand without collapsing, and the amount of groundwater that may have to be pumped to keep the pit from flooding.
Another factor that now has to be considered for new operations is the extent of reclamation that will be required. This can vary significantly based on regional environmental regulations.
An open pit mine has stepped or benched side slopes that will spiral (ramp) down into the ore deposit to allow downward excavation. Typically a planned thickness of ore will be mined as a bench in a horizontal extent until waste rock is encountered. The bench thickness is based on equipment selected to meet the economic objectives of the mine plan. Before the economic extent of the bench is reached, a new bench will be developed by continuing the downward development of access roads. A large open pit may have several benches active at the same time. The size of an open pit will be limited by several factors which commonly include the grade of the ore, the distribution of the ore, the ratio of waste rock to ore that has to be removed to get to the ore, the stability or strength of an excavated slope to stand without collapsing, and the amount of groundwater that may have to be pumped to keep the pit from flooding.
Another factor that now has to be considered for new operations is the extent of reclamation that will be required. This can vary significantly based on regional environmental regulations.