Disposal overburden

Many waste-rock or overburden disposal systems result ia compacted dumps having uncontrolled distribution of fines. In such dumps, solution distribution is poor and there is Htde oxygen for reaction with the sulfides. Methods for managing these dumps to maximize copper recovery have been actively pursued. 

Another important implication is that highly permeable soil liners generally have defects, such as cracks, macropores, voids, and zones, that have not been compacted properly. One opportunity to eliminate those defects is at the time of construction. Another opportunity arises after the landfill is in operation, and the weight of overlying solid waste or of a cover over the whole system further compresses the soil. This compression, however, occurs only on the bottom liners, as there is not much overburden stress on a final cover placed over a solid waste disposal unit. This is one reason why it is more difficult to design and implement a final cover with low hydraulic conductivity than it is for a bottom liner. Not only is there lower stress acting on a cover than on a liner, but also the cover is subjected to many environmental forces, whereas the liner is not. 

Problems at the mining stage center around overburden and waste rock disposal and the potential contamination of surface water courses from... 

Disposal of the overburden can be a significant operation. Top-soil should be handled and stored in such a way as to preserve its fertility and permit its later use in landscaping schemes [4.7,4.8]. Sub-soils and over-lying rock may be tipped, in which case the tips must be designed to be stable and have adequate drainage [4.9, 4.10]. In some situations, it may be possible to sell part of the overburden as in-fill. 

The amount of overburden that has to be removed is an important factor in quarrying operations, for if this increases and is not useable, then a time comes when quarrying operations become uneconomic. The removal of weak overburden is usually undertaken by scrapers and bulldozers, the material being disposed of in spoil dumps on site. Unfortunately, in the case of weathered overburden, weathered profiles are frequently not a simple function of depth below the surface and can be highly variable. Furthermore, in humid tropical areas, in particular, weathered horizons may extend to appreciable depths. Consequently, assessment of the amount of overburden that has to be removed can be complicated. Indurated overburden... 

Open-pit mine In this type of surface mines, the overburden is removed from the mine and dumped to a disposal area. The desired material is worked from stepped horizontal benches. Each bench is separated from the adjacent benches by vertical shelves. The slope angle ranges 50°-70°. Since clay layers are softer than most materials and the exposed parts become very shppery in rainy season, a smaller slope angle is required to maintain stability of the mine. 

Open-cast mines They are surface mines in which the stripped overburden is not removed from the mine to be dumped in a separate disposal area, but is cast (i.e. hauled and dumped) inside the mine from where the desired material is already worked. 

In any mining operation, overburden materials and tailings are disposed in the waste dumps. Many construetion works necessitate excavation and removal of soil and sediment layers from a large area and dumping them to a nearby place. Clays are the major components of these waste dumps. Clays may also be present in some types of industrial wastes. Different components of the waste dump may have different impacts on the water, soil and air of the surrounding regions. The impacts of clays of the waste dump on the environment are given below. 

The volume of unsuitable overburden and intersecting layers or lenses that need to be removed prior to or during borrowing. These materials may have to be removed and disposed of at significant costs. 

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