Mining Thick Seams
Longwall retreating is the primary method of mining at the collieries with more than 98 per cent of the total output.
Coal faces and development headings are equipped with instruments for automatic gas protection and centralized telemonitoring of methane content..
The mining district is usually developed by mine shafts. The mining method is longwall retreating along the strike and down the dip. The mining area is divided into two blocks east and west. The faces are 200 metres long and operate along the strike of the seam. Sandstone forms the immediate roof and floor of the seam.
Each face is equipped with a double-ended drum shearer. The faces are operated on two production shifts and one maintenance shift per day. Each face is supported by shield supports.
In coal face and development operations, use is made of current forecasting of the liability to sudden outbursts that is, establishing dangerous and non-dangerous zones.
Open-cast Mining
Minerals at shallow depths are extracted by open-cast mining which is cheaper than underground mining. Open-cast mining consists in removing the overburden, and other strata that lie above mineral or fuel deposits to recover them.
Opencasts or open-pit mines are in fact quarries for getting coal or metalliferous minerals. In the USA opencasts are called strip mines (strip pits).
An opencast is a long, wide and comparatively shallow working thought it can reach 200 m or even more in depth.
Mineral is usually unloaded at specially equipped permanent stations. Waste rock is dumped at various points which are moved as the work develops.
The aim of such programmers applicable to the mining industry is to control and protect natural resources and regular reclamation and landscape restoration.
Ore mining
As already mentioned, the mining industry is an industry that deals with the extraction of valuable minerals from the Earth.Economic minerals are those that have economic value and include both metal (ore minerals) and non-metallic minerals, such as construction materials (sand, stone, and others).
In selecting work methods of ore deposits, you must consider the following factors: 1)the shape of the field; 2) the sizes of the fields in thickness along strike and down dip; 3) the Type of ore and the distribution of metal in the ore body.
Form ore deposits affects the production method. In addition, a link field with side host rock is of great importance.In the mining industry, as well as in the mining of bedded deposits before production, attract exploration needed to detect, characterize and prove the potential of the ore body. Different types of equipment needed range from small, simple units, such as excavators and dump trucks to the earth-movers, draglines and mechanical shovels.Mining starts with excavation, loading, hauling and lifting rocks to the surface and auxiliary openings.After the ore is mined or dredged, they are usually processed (crushed, concentrated or dry).
Mining and environment
It should be stressed that the effect on the production environment are twofold: First, there are direct effects. Second, there are indirect destructive effects. Mining, especially open cast mining, deforms the surface and creates a lot of waste that contain hazardous substances that pollute water and soil. Water from the mining and processing operations may lead to contamination of the subsoil and the river into which it flows. Most serious of all are the gases formed during melting, which may not only pollute the air in the vicinity of the plant, but the impact on the lake and vegetation hundreds of kilometers through the creation of acid rain.
I must say that land reclamation has emerged as a way to deal with the negative impact after coal and other minerals. Reclamation devoted to the problem of landscape beautification and restoration of its performance, environmental integrity and economic and aesthetic value. In recent years, many industrialized countries have developed and adopted laws, national programs and specific policies for environmental protection.