Current Conditions of Open Mining of Mineral Fields of Kazakhstan

The paper contains the review of issues of completeness and quality of mineral mining at the opencast mines and creation of geomechanical justification of systems with internal p iling. Current mining production is characterized by the increase of share of open mining of mineral resources, the ratio of which in the world mineral mining is nearly 70%. Capacit ies of mining companies keep on g rowing, production processes are being intensified; depth and periods of operation of open mines are being increased. In these cond it ions , issues of increase o f economic efficiency and env ironmental safety o f min ing operat ions become of more importance; one o f the most rad ical ways o f solut ion o f th is p rob lem is the maximum use fo r locat ion o f overburden rock and p roduct ion waste from the waste quarry area as a vo lume man-caused resource. The work contains the analytical rev iew of the current state of open mining of mineral resources of Kazakhstan, sequence of mining operations with internal piling, sequence of format ion and development of internal dump, optimal parameters of dumps (volume, height, stratification, angles of d ips) as well as the stability of inactive pit edge before and after its loading with embankment.


Introduction
Open method of mineral field develop ment (OMFD) that has been mainly developed since the middle of ХХ century keeps on remain ing the basic one in the majority of mining countries.
At present time the specific weight of the open method of mineral field development proves that this general direction of development of mining branches is still saved for the purpose of provision of fuel and minerals needed to satisfy the needs of power system, ferrous and non-ferrous metallurgy, chemical industry, and construction branch.
The source of raw materials and minerals for coal industry with open method of their development in CIS is based on the fields situated in the eastern regions of the country (main ly Kansko-Achinskiy, Ku znezk and Ekibastuz basins), where nearly 98% of geological reserves of coal suitable for open min ing is situated.
Iron ore mining with open method is concentrated at the fields of Ukraine (Krivorojskiy basin), Center (Kursk magnetic anomaly), Kazakhstan (Soko lovsko-Sarbaiskoye, Kacharskoye, Lisakovskoye, Ayatskoye fields) and Ural. Mining of non-ferrous metals with open method is main ly realized in Siberia and Kazakhstan.
Increasing demands of Kazakhstan in fuel and minerals are satisfied due to the open method of min ing and characterized by the application of highly productive equipment and new technological solutions in the production.
In view of depletion of ore reserves buried at accessible depth, the main direction of develop ment of mining industry will be further development and improvement of open method of minerals development that is related to the need of operation of fields with complex mining and geological conditions, large (down to 700 m) depth of development and significant (mo re than 40-50 years) life time of pit walls.
Today in the Republic 35% of copper-containing ores are developed with open mining, in 2012, the share of open method will be increased up to 65 %, in 2015 -up to 76 %, in 2020 -up to 79 %, and in 2025 it will reach 84 % due to the development of the largest fields of the corporation "Kazah mys", "Aktogai" and "Boschekul". In Aktogay it is planned to mine 50 million tones of ore per year, in Boschekul -fro m 8 to 14 million tones/year. The depth of the open mine "Aktogai" in final contour will be 700 m, open mine "Boschekul" -up to 400 m. The volu me o f rock mass will be: for A ktogai -30 mln.m 3 /year, for Boschekul -15 mln.m 3 /year.

Discussion
Recently the basic research on the issues of open pit mining is directed at the solution of various environ mental aspects, at the same time the issues of development of resource saving technologies of piling require further research.
Wastes of mineral mining represented by the overburden are mainly placed on the surface of the open mine or in its open area. External waste dumps alienate significant land resources deforming the relief and negatively affecting the environment.
In Kazakhstan more than 26 b illion tones of production wastes have been accumulated at the dumps, which are increased by 1 billion tones every year. Out of these waste, the most part (58%) includes the wastes of ferrous and non-ferrous metallurgy. Non-ferrous metallurgy of Kazakhstan is represented by 24 companies of three main segments of industries: copper and aluminum, lead and zinc, gold and rare metals.
Develop ment of open mines is accompanied with constant increase of distances of transportation of the overburden to the external dumps and therefore the costs for piling. In particular, this is typical for railway du mps which, in view of low values of gradients passed by this transport, are made at significant distances from open mines by low layers and on large areas. In other words, technical characteristics of the railway transport predetermine the two-d imensional construction of dumps for the overburden and large areas of disturbed lands several times exceeding the land allotment of open mines.
To smaller degree th is is referred to the most popular at present time vehicle and bulldozer du mps, however in this case also the distance of rock transportation to the dumps along the surface is often much more than at the open mine itself, and land areas allocated for du mps are co mpared to the area of the open mine over the surface or exceeds it several times. By construction, external vehicle and bulldozer du mps can be called height-two-dimensional ones. They are formed in one layer or several layers the total height of the dump (layer) is 100-120 m and more.
Along the deepening and enlargement of open mine, the cost for format ion of t wo-dimensional (railway) and height-two-dimensional (vehicle and bulldozer) dumps, besides, land areas under them will be increased, in view of which the issue of improvement of piling technology will be crucial.
At  [4]. At that, traditionally the area of application of technologies with the use of the open area in both domestic and foreign practice is mainly refers to horizontal and flat (up to 10-12 0 ) fields. The ways of increase of volu me of internal piling must be searched by means of creating the mining methods ensuring stability of internal dumps on more inclined grounds.
At that geological characteristics of rocks, mining and technical conditions, technology of operations at the working place, safety requirements and time of operation are determined by the basic parameters of internal du mps such as quantity and height of layers, min imal sizes in the plane. Besides, the applied parameters of the du mp should ensure the opportunity of its setting out in case of temporary storage of the rock.
At the development of flat and steeply inclined fields much experience was gained in the field of piling in various mining and technical conditions (stable and unstable ground, plain, undulating land and high land relief, layering), at various location relat ive to contours (external and internal) and various methods of safety provision (conservation of stability and controlled shifting).
The classification of dumps developed by the member of Academy N.V. Melnikovа contributes to the selection of rational process charts of piling for steeply inclined fields of certain mining and technical conditions and correct organization of du mp ing operations in open mines [5].
Further solution of the problem requires the development of scientific grounds of technologies of open pit mineral mining with maximu m possible internal piling in wide range of mining and geological and min ing and technical conditions.
Sequence of mining operations with internal piling determines the progressive advance of the dump along with the progress of field develop ment.
However the fo rmation of internal dumps requires the thorough study of issues related to the proper stability of internal p it walls loaded with embankments of internal dumps. At that, geomechanical justification of the piling place, sequence of piling, its parameters (volu me, height, layers, angles of dips) is needed. Since the disturbance of stability of the system can lead to emergencies (collapse of pit wall, landslides) and to temporary shutdowns or reductions of min ing in the period of emergency liquidation.

Results
Thus, analysis of experience of mineral field develop ment proves that the rational use of open area, ensuring the optimal location of the overburden at the least costs for their transportation and storage as well as the search for reduction of adverse environmental impact of mining production, is one of the main reserves of increase of econo mic efficiency and mining safety.
Another factor, that is worthy of consideration, is the technology of mining operations in the Kazakh oil fields, worked by open method, yielding counterparts overseas in terms of mine technical and environ mental efficiency and safety. At present, due to the ever increasing demands for greater economic efficiency and environmental safety of mining operations, it is important and urgent to find solution to maximize space for the waste of mining fields. Search fo r solutions to mentioned problems is main ly in the direction of creat ing a method of mining to ensure the sustainability of internal piles on more sloping grounds, as well as increasing the use of the mou ldboard in min ing fields. To address the problem, a series of scientific work is, currently, underway. One of them is the development of a scientific basis for the further exp loration of resource-saving technologies and open min ing with ma ximu m internal stacking. It is important to consider such tasks as: • Geo-mechanical study of min ing development; • Optimization of the parameters of the min ing field's spacer; • Analytical calculat ions of volumes of overburden; • Justification quarry transport and all processes; • Sustainability-p it dumps and sides; • Calculat ion of the environ mental risks.
One of the main parameters in the security of these conditions is the stability of pit walls, which provides optimu m angle side. The Kazakh mines, such as asbestos 'Zhitikara', sections of JSC "Shubarkol", " Bogatyr Coal", LLP "Karazh ira Ltd» and others can skip the internal stacking. Positive aspect in this case is the fact that such a resource-mining system reduces the cost of transportation of overburden, reduces the cost of land reclamation fro m external piles, wh ich consequently leads to lower production costs. This raises the issue of geo-mechanical character that is the sustainability of pit slopes and internal du mps. For each particular field it is necessary to study sustainable geo-mechanical parameters of boards and benches.