Open pit mining
Surface mining

The process of producing useful minerals from open surface mines. Also known as open pit mining. When the ore body is buried shallow or the surface has an outcrop, the application of open pit mining is the most advantageous. Compared with underground mining, the advantages are sufficient resource utilization, high recovery rate and low depletion rate. It is suitable for large-scale machinery construction, rapid mine construction, high output, high labor productivity, low cost, good working conditions and safe production. However, it is necessary to strip the rock and soil, and to abandon a large number of rocks, especially the deep open pit mines, which often occupy more farmland, and the equipment purchase cost is higher, so the initial investment is larger. In addition, open-pit mining is affected by the climate and has a certain impact on equipment efficiency and labor productivity. With the development of mining technology, the scope for open pit mining is increasing, and it can be used to mine low-grade deposits and some underground mined mines. For flat deposits (generally the dip angle of the ore layer is less than 12° ), the method of reversing, traversing or longitudinal mining is adopted. For inclined deposits, a combination of steps, transverse mining or sub-stage mining is used.

Liaoning Grand Arc Mountain iron ore panorama

Open pit mining operations mainly include piercing and blasting, mining, transportation and dumping. The quality of these four tasks and the cooperation between them are the key to open pit mining. Perforated blasting is to drill a directional blasting hole of a certain diameter and depth in the open pit rock to break and loosen the rock. The perforating equipment mainly includes impact drilling rig , down-the-hole drilling rig and roller rig, etc., and more commonly used ammonium explosives, slurry-like water-resistant explosives, emulsion explosives and granular emulsion explosives. The loading work is to manually or mechanically load the ore into the transportation equipment. , or directly to the job at the designated location. Commonly used equipment is excavators (multiple buckets and single buckets), wheel shovel and front loaders, and are widely used as single bucket excavators. Transportation job is to open pit mining, rocks were transported to the unloading point (or beneficiation plants) and waste dump, while the transport to the mining field production personnel, equipment and materials. The main modes of transport are railways, roads, conveyors, hoists, as well as hydraulic transport and ropeway transport in rugged mountains. The transportation mode must be comprehensively considered in terms of topography, geology, climatic conditions, open pit production capacity, mining depth, physical and mechanical properties of ore and surrounding rock, and after a comprehensive technical and economic comparison, determine a reasonable mode of transportation. Dumping work refers to the removal of a large amount of topsoil and rock covering the mineral deposit and its surrounding area from the open pit, and transporting it to a specially set site (such as a dumping site or waste rock yard) for disposal. According to the different earth-laying equipment, the method of earth-moving is divided into bulldozer bulldozer, bulldozer dumping, front-loading machine dumping and dragging scraper or rope bucket dumping. The excavation site should be selected as close as possible to the mining site and occupy less farmland. If conditions permit, it should be placed in the valley and in the depression, pay attention to environmental protection and land and return to the field.