PROBLEMS OF RATIONAL USE OF THE MINERALS IN THE SUBLEVEL CAVING MINING METHOD

ABSTRACT

This article examines the factors and processes that lead to ore losses and dilution during underground mining of mineral deposits in sublevel caving methods, as well as their impact on the efficiency of a mining enterprise. In the mining method, ore loss and dilution are determined according to the constructive and technological characteristics of the option being used and depend on the organizational and technical factors. Certain measures were recommended to improve mineral production indicators.

АННОТАЦИЯ

В данной статье исследуются ключевые факторы и механизмы, приводящие к потерям руды и её разубоживанию при подэтажном обрушении, а также оценивается их влияние на эффективность работы подземного горного предприятия. Показатели потерь руды и разубоживания рассчитываются с учётом конструктивно-технологических параметров выбранной системы разработки и демонстрируют высокую зависимость от организационно-технических факторов. По результатам анализа предложен комплекс практических мер по повышению извлечения руды и снижению доли разубоживания, что позволит улучшить производственные и экономические показатели горных работ.

Keywords: underground mining, loss, dilution, sublevel caving, ore drawing, physical modelling.

Ключевые слова: подземная разработка, потери, разубоживание, подэтажное обрушение, выпуск руды, физическое моделирование.

Introduction

One of the most widely used mining methods in the world is the extraction of ore minerals by sublevel caving mining method. The main reasons for this is the safety of the method, high work productivity and adaptability to various mining and geological conditions. Nevertheless, high rates of loss and dilution are factors that negatively affect the choice of this method, and are less commonly used in the extraction of valuable ore deposits.

Improving the efficiency of the mining method, rational and insecure use of mineral reserves, normalizing indicators of ore loss and dilution, achieving a minimum cost of ore remain extremely relevant issues for the mining industry in the current complex unstable economic conditions. A notable aspect of these problems is that their solution requires a systemically related and integrated approach.

Materials and methods

The effectiveness of the mining method is mainly characterized by indicators of the extraction of minerals [1]. In the mining method, ore loss and dilution are determined according to the constructive and technological characteristics of the option being used and depend on the following organizational and technical factors: compliance of the selected structure and parameters of the mining method with mining-geological conditions, the procedure for extracting ore, the amount of metal in the ore and surrounding rocks. According to the parameters of the mining and technological conditions and the mining method, the indicators of loss and dilution change [2].

One of the organizational factors affecting ore loss and dilution is the procedure for extracting ore from under the collapsed surrounding rocks. The turn of ore drawing from the panels and the amount of ore extracted is the order of ore extraction. The amount of ore mass emitted represents the volume of ore mass that is extracted from one workings and released continuously or periodically to act as a marginal quantity to initiate the release of ore from a mine working adjacent to it.

To date, the optimal thickness of the collapsible ore layer, the parameters of drilling blasting work, the height of the sublevels and the distances between the drifts have not been proven on the basis of specific laws in order to reduce ore loss and dilution. Only accepted as a recommendation for specific mining conditions. Taking into account the above, the following issues should be studied in more depth and the laws should be developed:

1. The dependence of ore loss and dilution on the scheme of development works for the extraction of the block.
2. Theory of extraction of ore from under collapsed rocks.
3. The dependence of ore loss and dilution on the method of sublevel caving mining.

Ore mining indicators are directly influenced by drilling and blasting operations. Factors affecting these indicators of blasting work are: the completeness of ore breaking within the specified contour, the grinding of ore and surrounding rocks to the desired size, the abundance of ore, the change in the state of tension deformation of the massif. The effectiveness of the blasting works can be increased by changing the length, diameter and distance between the blasthole charges and the simultaneous blasting layers, using stemmings and choosing their optimal length, changing the explosion sequence, short attenuation time and location of cartridges, using an effective explosive type in accordance with the characteristics of ore and surrounding rocks [3,4].

Physical modeling of ore mass extraction in the caving mining method of ore and surrounding rock is one of the main methods for determining the mining indicators. Due to the complexity of experiments carried out directly in mines, the difficulty of organizing work, the need for a lot of time and labor, physical modeling is characterized by its low labor and time consumption, economy of funds and the fact that ore extraction makes it possible to observe the process.

Physical modelling consists of several stages:

1. Development of a research method.
2. Development of a laboratory stand.
3. Experiment based on the research method.
4. Processing of experimental results.

Geometric similarity is ensured if all the dimensions of the studied system in the model and the dimensions of its individual elements are changed by a certain amount in comparison with the dimensions of the system in nature:

                                                      (1)

where l_m and l_n are the linear dimensions in the model and nature.

Kinematic similarity is provided when similar particles moving along geometrically similar trajectories pass through geometrically similar paths at time intervals differing by a constant multiplier:

                                                 (2)

where τ_m and l_n  are the linear dimensions in the model and nature.

Dynamic similarity is provided if the masses of any two similar particles located in space and time, respectively, differ from each other by a constant multiplier:

                                       (3)

where m_m and m_n are the linear dimensions in the model and nature.

The main physical and mechanical properties of materials when modeling ore mass extraction are as follows:

• slope angle;
• the angle of friction of the material;
• volumetric weight and density;
• coefficient of adhesion;
• granulometric content.

Results and discussion

The use of the equivalent materials method in ore extraction modeling has found its practical confirmation in terms of efficiency in the study of complex issues in the technology of mining mineral deposits. The most accurate results in the study of the process can be obtained by conducting a laboratory study in the model [5]. To do this, the following constructive requirements must be met:

• the selected scale of physical models should ensure the exactness and accuracy of the data obtained as a result of the drawing of the ore mass;
• the constructive dimensions of the stand should not prevent the re-study of physical processes of a similar model;
• ensuring visual and documentary control over the processes taking place within the physical model (in this case, over the formation and massive state of the ore drawing indicators).

Among all the studied physical models, the choice and adoption of an option that provides high efficiency indicators for a mining enterprise is carried out by comparing their technical and economic indicators. In addition to the indicators of mining, economic losses caused by loss and dilution are also taken into account in this [6].

Conclusion

The quality of the ore is determined not only by the amount of useful component in it, but also by the presence and quantity of harmful additives in the ore mass, the ripeness of the ore pieces, the constancy of the ore mass component, humidity and other properties. According to the results of studies, these factors have a huge impact on the results of enrichment and metallurgical processes and play an important role in assessing the quality of ore mass. Ore mass quality normalization is the process of ensuring the consistency of the chemical and granulometric composition of the ore mass.

The following basic measures are recommended in order to reduce losses and dilution in the sublevel caving mining method:

1. Determination of the optimal parameters of the mining block.
2. Choosing a rational order of ore drawing.
3. Selection of optimal parameters of drilling and blasting operations.

References:

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