Abstract
The purpose of research
Establishing the scope of reuse of the longwall workings areas
The relevance of the research theme
Ukraine was established as an independent state in 1991. The latest years have seen a long recession in the coal industry.
Modern requirements of a cost-effective and safe mining technology are most completely met by the technology of reserving workings for reuse.
The cost of repairs and maintenance of development workings in the coal mines of Ukraine is about 15% of the total cost of coal mining. Despite the large amount of repair works and their high labor intensity, the length of workings which are in poor condition remains high: around 15-20% of the total length of the maintained workings.
Reuse of excavation development workings leads to a 1.7-1.8 times decrease in the length and cost of excavations required for the preparation of the extraction field. Reuse of zonal mine tunnel (the former transportation tunnel used as an airway) makes it possible not only to get rid of solid blocks between adjacent plots, but also to avoid interruptions during the development of longwall faces. It is also worth noting that it is possible to use direct-flow ventilation with full dilution of methane among the sources of its release. This is good, because often return ventilation does not permit to achieve a high load on the longwall because of air circulation restrictions.
Given the increasing complexity of mining and geological conditions, the increase in cross-section of the workings and their extent, the growth of mining depth, the problem of maintenance of workings in the steady state during the time of their operation is of particular relevance.
Therefore, the aim of this paper is to establish the scope of re-use of the longwall workings areas.
Methods of performance
1. To study the problem, let us consider 2 variants of the longwall method. They are presented in Figures 1 and 2 below.
Figure 1. The longwall method with reuse of the transportation tunnel as an airway.
Figure 2. The longwall method without reuse.
Let us compare the two variants.
Scheme I. The longwall method with reuse of the former transportation tunnel as an airway. The airway behind the longwall is not reclaimed, the haulage roadway is not reclaimed either. Fresh flow goes through the longwall to the solid mass.
Scheme II. The longwall method without reuse. The former airway is reclaimed in advance. Fresh air flow comes through the longwall to the goaf.
2. Let us calculate the costs for the area as follows:
,
where stands for the cost of the construction of the working protection in the third maintenance zone;
R – for the cost of repair of 1m working of a transportation and airway tunnel in the first maintenance zone;
K – for the cost of 1m of an airway working development.
The factors affecting the cost of maintenance:
L – the length of the area wing;
m – seam thickness;
H – the depth of works;
Rc – the resisting power of the solid.
Studying the impact of these factors, we can find the best conditions of reuse of the longwall workings areas.
3. The model of calculating costs when comparing variants of mining methods (mathematical modelling of the costs for each pair of compared variants is made with the help of Microsoft Excel software).
Conclusion
The model of calculating the costs for the considered variants of mining methods will be developed as a result of research work.