Open Pit Mining Methods
Open pit mining is the process of extracting ore, rocks or any valuable material from the ground by digging. Some people call open pit mines quarries. Most open pits are designed in a step-like structure, with each step (sometimes called ledge or bench) dug deeper into the earth to reach the area to be mined. The steps include access roads, and as more material is removed, new steps can be built. The goal is to remove the valuable material, but that involves first removing large quantities of rock at the lowest possible price.
Other People Are Reading
Things You'll Need
- Backhoe and haul trucks
- Trained workforce
- Required permits and licenses
Instructions
-
-
1
Design a detailed plan. Any mining design should anticipate environmental or public relations issues involved with the site. Environmental regulations should be reviewed and compliance included as part of the overall design. Impacts to the environment include air and noise pollution, dust suppression, water discharge and runoff, and waste disposal.
-
2
Gather data and request permits. Core holes are drilled and samples taken before full-scale open pit mining begins. All sites require permitting for local and national standards.
-
-
3
Dig the pit at an angle. Excavation of the area to the first step should be at an angle rather than straight down. This is to minimize falling rock, but depends mainly on the size and structural weakness of the rock. The horizontal surface of the step is called the bench or ledge, and the wall is known as the batter.
-
4
Continue digging steps. Several steps may be needed for ore that is deep underground. For small mines or quarries, a V-shape without steps may be sufficient.
-
5
Create a haul road from the bottom of the pit to the surface. This is essential for removing the overburden and waste rock in order to expose the ore. The haul road is essentially a long ramp that trucks and other excavation vehicles can use.
-
6
Pile the waste rock at the surface. This has the double benefit of keeping the waste rock out of the pit and preventing erosion near the edge of the pit. The waste rock should also be stepped, as in the pit, to reduce the likelihood of erosion and rockfall.
-
7
Rehabilitate the land after mining. When the mine is exhausted the pit should be backfilled with a combination of rock and clay to stabilize the soil.
-
1
Tips & Warnings
The public should be protected from open pits by adequate fencing, even after the pit has been rehabilitated.
Resources
- Photo Credit Christian Holzner (Wikipedia Commons - Public Domain)
