Enhancing the adaptability of a mining complex in a dynamic environment by utilizing the technology for the development of a man-made deposit with a mobile ore preparation complex

The paper deals with the issue of the development of man-made deposits of the bulk type, especially that formed during the development of iron ore deposits. An analysis of the actual state of man-made deposits was performed. Based on analysis the technology of man-made deposits mining was proposed. It involves the extraction of technogenic raw materials from the bulk and their separation according to quality characteristics using a mobile ore preparation complex. According to the proposed technology, the conditioned raw materials are sent to the processing place, and the empty rock is laid in layers in the created space. The parameters of the mining system were studied in the paper: the width of the excavator’s cut step is limited on the one hand by the unloading radius of the dragline, and on the other by the turning radius of the dump truck. A significant role is played by the raw material utilization ratio: the larger it is, the narrower the excavator cut step will be. The results of the research can be useful for design organizations and mining enterprises which implement resource-saving technologies.


Introduction
Today's state of open-pit mining operations in Kryvbas iron ore open-pits is characterized by complex mining and geological conditions: the depth of development increases, the geometric dimensions of the working area decrease, water inflows increase, and the strength of rocks increases.All these factors lead to an increase in the cost of extracting minerals from open-pits.The economic conditions of mining operations are also characterized by significant dynamics: the price and demand for the products of mining enterprises changes [1], which leads to a change in the minimum industrial content of a useful component.Due to their inertia, open-pits, as large production systems, cannot adapt their production indicators to economic conditions quickly and efficiently [2][3][4][5].At the same time, its timely increase is possible due to the development of man-made deposits of iron ore raw materials accumulated over the past decades.The conducted studies confirm the perspective, and quite often the economic feasibility of working out such man-made deposits [6].
The tailings of Kryvyi Rih mining enterprises contain dozens of man-made deposits with a significant content of hematite quartzites, which are the condition raw material for iron ore concentrate [7].Manmade deposits, according to the conditions of formation and quality of iron ore raw materials, are divided into the warehouses of coarse-grained sifting of crushing and sorting factories of mines (the content of Fetotal is 40-45%) and massifs of hematite quartzite in the dumps of mines and quarries of mining processing plants (the content of total Fe is 30-45%).Man-made deposits of this product, for example, in the dumps of quarries No. 1 and No. 2 of the MPP "Central", amount to 40 million tons and are the second most important type of hematite raw material in the man-made deposits of the Kryvyi Rih iron ore basin [8].
Dumps of the MPP "Southern" contain 542 million tons of hematite raw material, with a total Fe content of 36%, dump No. 3 of the ArcelorMittal Kryvyi Rih combine -145 million tons of the same raw material with a similar content of the useful component [9,10].
However, technological factors of storage of hematite quartzites with the use of automobile and railway transport determined certain features of their structure, which complicates working out [11,12].
In the sections of dumps that were formed by automobile transport, there is an accumulation of small lenticular ore bodies with a thickness of up to 1-2 m and a length of up to 10-15 m, while the adjacent bodies differ significantly in terms of the mineral and chemical composition of hematite quartzites (figure 1).In sections of the dumps that were formed by railway transport, it is practically impossible to distinguish mineralogically homogeneous hematite quartzite bodies (figure 2), due to the peculiarities of loading, transportation and unloading of hematite raw materials, which is the reason for the high degree of its averaging.Thus, the mineral varieties of hematite quartzites of the Skelevatskyi and Valiavkynskyi deposits are formed randomly, are internally heterogeneous and differ in mineral, chemical composition, structure and texture [13].Not only digital models and databases, but also sufficiently accurate analog drawings are missing for the considered and similar man-made deposits of iron ore raw materials [14].
There is a need for the development of highly effective methods of developing man-made deposits with the provision of a stable flow of iron ore raw materials.The task is complicated by the fact that the man-made deposit consists of man-made raw materialsmixed overburden and poor ore, which is considered as a useful mineral when the man-made deposit is mined.This makes the technology of gross extraction of the rock mass from the pile impractical in solving this problem.It is also not considered possible to ensure the selective extraction of exclusively useful minerals, since the mineral and petrographic features of the man-made deposit during the years of being in the open environment were subjected to physical and chemical processes of migration of useful components [15][16][17].Thus, in the regions where mining complexes operate, most of the man-made mineral raw materials are placed unsystematically.
The purpose of the paper is development of the technology for working out the man-made deposit, which was formed in the process of unsystematic dump formation and definition of operation parameters and conditions of such technology.

Methods
In the domain of conceptual design, the "Functional Decomposition and Morphology" approach is widely acknowledged for its systematic framework, facilitating the translation of a set of technical prerequisites into a concrete product concept.Nonetheless, scholarly discourse has brought to light certain deficiencies intrinsic to this method, primarily in its ability to instigate inventive ideation.Consequently, extant scholarly literature advocates the augmentation of the functional decomposition and morphology process through the integration of tools and methodologies intended to invigorate creative thinking.In this context, the Theory of Inventive Problem Solving appears as a promising and powerful solution that can be effectively solved for the development of technology for working out man-made deposits [18].Thus, to develop technology for developing a technogenic deposit, such principles of the Theory of Inventive Problem Solving were applied as the combination of operations in time and space, the principle of continuity of useful action and the principle of changing object parameters [18].
The task can be solved due to the localized segregation of conditioned and non-conditioned raw materials with the simultaneous rearrangement of the latter in the dump.Segregation by quality and primary grinding is performed using a mobile preparation complex located on the surface of the manmade deposit [3,19,20].

Results and discussion
Excavation and dumping operations are performed using a dragline with gradual transfer of the excavator cut step.As a result, the volume of work on re-excavation and transportation of minerals to the beneficiation factory is reduced, as well as the area of land disturbed by mining operations.In this way, the rock mass is excavated from the body of the man-made deposit with a dragline, its unloading is carried out into the receiving capacity of the mobile ore preparation complex [21], where coarse crushing and segregation of rocks according to physical and mechanical properties takes place, after which non-standard raw materials are placed in the produced space, and useful minerals are placed in the means transport for further processing.
The technological process of working out the bulk deposit with this technological complex is proposed to be carried out as follows.
A dragline (1) is placed on the top of the bench of the man-made deposit, which in reverse works the man-made deposit with a longitudinal excavator cut.After extraction by a dragline, the rock is unloaded into the receiving tank of the mobile ore preparation complex (2), which grinds the rock and separates it according to the content of the useful component (figure 3).The mineral is reloaded by an ore console into a dump truck (3), which then transports the rock to the beneficiation factory.The waste rock is placed in the created space of the first excavator cut step with the help of a dump console.
After the dragline completes the first excavator cut step, it reverses direction and works the second excavator cut step.At the same time, the ore preparation complex is located on the first layer (4) of dumped waste rocks; the mineral using the ore console loads dump trucks fed by the end-to-end transport scheme along the excavator cut step; waste rock is placed with the help of a dump console in the second layer (5) space of the first excavator cut step (figure 4).
Further, after working out the second excavator cut step, the dragline reverses direction and works out the third excavator cut step.At the same time, the ore preparation complex is located on the sole of the man-made deposit layer in the created space of the second excavator cut step; man-made raw materials are loaded with the help of an ore console into dump trucks, that are served by a dead-end supply scheme along the cut step; waste rocks are placed with the help of a dump console in the first layer (4) of the created space of the second excavator cut step.After working out the third cut step, the dragline reverses direction and works out the fourth cut step.At the same time, the ore preparation complex is located on the sole of the layer of the man-made deposit in the created space of the third excavation cut step; the mineral using the ore console loads dump trucks, that are served by a dead-end supply scheme along the cut step; waste rocks are placed with the help of a dump console in the second layer (5) of the created space of the second excavator cut step.
It should be noted that according to the rules of safety technology, during these works, the working bench must be equipped with identification signs outlining the area of mining operations.When choosing the standard size of the dragline, the maximum size of scooping crushed rock should be taken into account.
During developing a man-made deposit, mining works must be carried out in accordance with safety rules and in accordance with the passport for mining a man-made deposit designed at the enterprise.
Development of man-made deposits according to this technological scheme is possible subject to compliance with a number of restrictions.The method of working out the man-made deposit is expedient when more than 25% of raw materials are extracted from the man-made deposit.With the removal of less than 25%, there will not be enough space for the placement of waste rock, and with the removal of more than 50%, the specific land capacity will decrease.Let's define this ratio as the raw material utilization ratio.
The limitation of the parameters of the elements of the development system is related to the specific operating parameters of the existing equipment.According to the proposed technological scheme, the values of the width of the mining and dumping cut step will be equal.Based on this, the height of the dump bench will be inversely proportional to the utilization rate of raw materials: when the utilization rate increases, the height of the dump bench decreases.
The first limitation condition concerns the unloading radius of the dragline and was determined by equation ( 1): where Wthe width of the dump and mining cut step, m; Rp maxthe maximum unloading radius of the excavator, m; Hthe height of the bench of the man-made deposit that developed, m; hbheight of the dump bench, m; αthe slope angle of the mining bench, degrees; For calculation, consider options with a utilization ratio of 0.25; 0.3; 0.35; 0.4; 0.45 and 0.5 and the height of the mining bench is equal to 15 m.For comparison, let's take five draglines from their standard size series.The results of the calculations are summarized in table 1.The studied dependence of the width of the cut step on the raw material utilization ratio is visualized on the graph (figure 5).
The second limitation concerns the road width for turning the dump truck under load.Taking into account the dead-end feeding scheme of the dump truck [22], the width of the cut step was determined by equation ( 2 where Rаthe minimum turning radius of the dump truck, m; Wаdump truck width, m; lаthe length of the dump truck, m; сdistance between the dump truck and the side of the trench, m.Next, the corresponding calculations were carried out for a typical range of dump trucks and the results were summarized in table 2.  The obtained values of the width of the working bench are the minimum values.We imposed the restrictions related to the dump truck on the previously calculated restrictions related to the unloading radius of the dragline and we got the range of possible values of the width of the mining and dumping cut step.We visualize the solution area on the graph (figure 6).On this three-dimensional graph, the possible value range of the width of the cut step is marked in orange, and in bluethe range of values that does not satisfy the condition for the turning radius of the dump truck.

Conclusions
Thus, the paper examines the use of man-made deposits of bulk type as a tool for increasing the adaptability of the mining complex to dynamic economic conditions.A resource-saving technology for the development of man-made deposits is proposed, which ensures efficient land use and a minimum number of re-excavations of the rock mass.The mining and technical limitations of the use of this technological scheme are considered and the range of possible values for the formation of a complex mechanization scheme is proposed.
The results of the research may be of interest to mining and project organizations focused on efficient and resource-saving development of mineral deposits in dynamic economic conditions.

Figure 1 .
Figure 1.The scheme of the internal structure of the automobile dumps of hematite quartzites.

Figure 2 .
Figure 2. The scheme of the internal structure of the railway dumps of hematite quartzites.

Figure 3 .Figure 4 .
Figure 3.The order of working out the first (a) and second (b) cut step of the man-made deposit by dragline using the ore preparation complex: 1dragline; 2ore preparation complex; 3dump truck; 4the first layer of dumped waste rocks; V, P -flow of overburden and ore mass, respectively; Rp -excavator unloading radius.

Figure 5 .
Figure 5. Dependences of the width of the excavator cut step on the raw material utilization ratio during the development of man-made deposits for various models of draglines.

Figure 6 .
Figure 6.Visualization of admissible solutions when determining the width of the cut step: orangeadmissible solutions; bluesolutions outside the range of permissible values.

Table 1 .
Calculation of the cut step width for different values of the utilization ratio for a standard-sized series of draglines.

Table 2 .
Calculation of the width of the cut step for a standard-sized series of dump trucks.