INJURIES FREQUENCY OF EMPLOYEES IN UNDERGROUND COAL MINES IN SERBIA

: The work in underground coal mines is one of the most difficult activities. General characteristic of working condition these mines are contained in the fact that all coal mines are in the low mechanized level which produce heavy manual work, low productivity and high financial costs. High risk level of injuries and occupational diseases are special problems in these working conditions. The workers disability is also huge problem. All of these produce a production and financial loses. Based on a comprehensive overview of the natural and geological conditions in the coal seams, technical and technological solutions for exploitation in active mines and injuries analysis in this paper, the frequency of injuries with the basic influencing parameters for the period 2014-2016 is given. In the analysis of this topic, the methods of analysis and synthesis were mainly used, and real parameters were obtained and from them high quality conclusions were coming out.


INTRODUCTION
In underground coal mines in Serbia, which are organized as a state-owned company PE PEU -Resavica, exploitation of quality anthracite, bituminous coal and lignite is carried out.Currently, eight coal mines are active with 11 underground productive units which are located in western, central and eastern parts of the country.The main characteristic of underground coal mining is the mutual coherence and cohesion in time and space of the main working processes starting from exploration, opening, development, excavation hauling and hoisting to the following processes such as ventilation, dewatering etc. Human work is included in all of these phases and high risk level of injury is also attendant.
The general characteristics of underground coal mines, including working conditions and high risk level of injuries during the working processes, are (Ćurčić et al., 1981): • Working operations of coal excavation process are performed in the underground mining drifts with limited work space; • The mining drifts and crosscuts are exposed to constant influence of mine pressure and the employees are also exposed to potentially dangerous of working space collapses, the fall of coal and overburden from the sides and roof; • Geological conditions of exploitation and applied technical solutions cause separation of congestion, toxic and explosive gases and dangerous and harmful concentrations of coal dust.• Potential possibilities for irruption of large amounts of water and sludge into underground mining facilities that can cause sinking of mines and employee injuries.
• The possibilities to provide and changing clean air are difficult in mining drifts; • The employees in the coal mines are exposed to the influence of higher temperature differences in different parts of mine and other unfavorable ergonomic conditions; • There are potential possibilities for the occurrence of endogenous and exogenous fires in the coal mines, which can lead to mining disasters, group or individual injuries; • Limited lighting possibilities of mining drifts may be potential causes of injuries; • Exposure of workers to the harmful effects of noise and vibration, which is the cause of occupational diseases.
These characteristics make work under conditions of underground exploitation particularly harmful and dangerous to the life and health of workers, resulting in personal and collective cases of injuries and occupational diseases.The most important research on the topic of injuries in coal mines in Serbia was done by Stojadinović et al. (2012).
Injuries for a 10 years period in PE PEU were analyzed in this paper.
This work will result from the fact that in the meantime, the mines have introduced new legal acts and measures that have been implemented based on them, among which the most important Risk Assessment Workplace Act.This led to a significant reduction in the number of injuries on mines.

INJURIES OCCURENCE IN COAL MINES
When solving the problem of protection and safety of work in underground coal mines it is necessary to analyze in detail the natural and technical-technological conditions and to evaluate the possible negative effects on the functioning of the work process and the emergence of potential hazards to the safety and health of employees.
According to the current law dealing with occupational safety and health at work, accidents at work are any injury caused by immediate and short-term physical, chemical or mechanical action, as well as injuries caused by sudden changes in the physiological state of the organism, when this injury is causally related to the performance of work on specific workplace.Related to the concept of an accident at work is the concept of an mishap at work, and he represents an unplanned, unforeseen, unwanted and uncontrollable events, which may result in injury or property damage, or both.
A dangerous event is the unsafe contact of a man with a material factor, or the harmful effect of a material factor on man, which occurred in connection with the performance of the work during which the employee was injured.Knowing the type of dangerous event determines the immediate causes or circumstances related to the site where the injury occur, which directly acted on its occurrence.
In the case of mining accidents, there are usually several causes that have occurred in some order, so that at least one immediate and a number of indirect causes are affected by the injury.

FREQUENCY ANALYSIS OF INJURY AND CHARACTERISTICS OF INJURIES
In order to show the frequency of injuries of employees in underground coal mines in Serbia, numerous documentary sources have been used: reports on injuries in mines, annual reports on the state of safety and health at work, expert analysis of serious and fatal injuries, reports on the work of the mines (monthly and annual), both in underground mining units and mines, as well as in total for all mines in the company JP PEU -Resavica.The data (JP PEU, 2016;Ivković, 2010Ivković, , 2012) ) were selectively collected, and then systematized by key factors and then analyzed in detail and calculated the basic parameters of the injuries.In addition to the presentation of the key parameters of the frequency of injuries, the causes and sources of injury were specifically addressed, with a correlation with the locations of the injuries.
The cause of the injury is the irregular procedure, that is, the action of workers in the conditions of existence of a particular danger, while the source of the injury is defined as an objective or subjective factor (object, matter, person, place, which occurs at the place of the injury or in its adjacency and contains defects, etc.) which resulted in an injury to the employee.In practice, sources or cause of the injuries are wrong identified or incorrectly stated, and the quality of the injury analysis depends on the experience of the person who performs the analysis and its knowledge of the technological process and theoretical knowledge of the occurrence of the injury.
The paper also presents the working day losses due to sickness, both caused by injuries and illnesses, and a comparison with the productive working days.The largest number of injuries, in the observed period (table 1), occurred in RMU "Rembas", considering that in this mine, mining works are performed in 3 underground mining units, and this mine has the largest number of employees.After Rembas, in Aleksinac mines there is also a high number of injuries.This is the result of more intensive work and the application of a drilling and blasting system of making drifts, because their workers work exclusively in the drifts making.Out of the total of 1,336 injuries that occurred in the observed period, 1194 injuries were categorized as light, with a percentage share of 89.3% in the total number of injuries.Interesting is the analysis of the number of injuries according to the age structure where the highest number of injuries was recorded to the workers who have over ten years of work experience, Table 4.This generation of workers relaxed and without fear accessing to the working activities, therefore they are less cautious and therefore exposed to the highest risk of injury.Workers with a working experience of up to five years approaching with their work tasks with great care, so the number of injuries in this category is lower.Workers who have several years to retire are also behaving the same way.From the Table 5 can be seen that the day of the week does not have any effect on the occurrence of injuries.The number of injuries in the 1st shift is the largest (44.4%), considering that the most of service jobs are carried out in the 1st shift, and that in the first shift works the most workers.The first and last two hours in shift are for hours with the lowest number of injuries.In these parts of the shift there preparatory and final operations are performed at the work sites.Therefore, the number of injuries is the smallest, while in the production part of the shift from the third to the sixth working hour the greatest number of injuries is occurred.It is extremely high number of injuries of extremities (hands, feet) in percentage 73% in the total number of injuries.According to the source of the injuries, the largest number of injuries occurred after fall pieces coal or overlaying rocks.Also, injuries from heavy objects carried through the mine are also dominant (arched support segments, segments of chain conveyor) as well as parts of rope driven monorail to which the cargo is delivered to the mine, table 9. Tables 11 show the days lost due to injuries and illness.In state-owned enterprises, illnesses and injuries are often used for longer absence from work than necessary, so the data in these tables are based on existing data, but do not represent a realistic picture of absence from the work as a result of occupational illness or injury.The methods which are used for coal mining in Serbia's mines are at a very low technological level with a large part of manual work.This is also shown by this analysis (Tables 12 and 13) where a large number of injuries can be noticed in relation to the amount of coal excavated.The introduction of mechanization in the development of the mine and preparation drifts and for coal excavation, as well as the additional training of workers would lead to a reduction in the number of injured workers.

CONCLUSION
On the basis of the conducted research it follows that injuries at work are a constant companion of exploitation work in underground mines in Serbia, and that their cause is related to natural and technological solutions for the works on coal excavation.The frequency of injuries is expressed and a special problem is the high level of serious injury, which results in a longer sick leave and a certain degree of disability.
As the injuries have multiple negative impacts, it is imperative that mandatory safety measures are applied and consistently control their application in order to reduce the number of injuries.In addition, it is inevitable to modernize the technological phases of the underground exploitation process by strengthening the introduction of mechanized equipment, devices and plants in order to reduce the contribution of hard physical work and lead to a secure and safer work.The fact arising from the analysis is that injuries are caused mainly by carelessness and insecurity, which again indicates a low level of technological discipline and training of workers.The high frequency of injuries caused by excavation activities requires the modification and changing of existing excavation methods, ie the reduction of the share of manual work on excavation, the development works and the delivery of materials.This can be effectively solved by the introduction of continuous miners or by introducing longwall excavation in parts of the deposit, where natural -geological conditions allow it.

Table 1
Injuries by mines that are the subject of analysis

Table 2
Summary view of injuries by category

Table 3
Injuries rates according to qualification structure According to the qualification, the highest number of injuries is recorded in qualificate workers group, with a share in the total number of injuries of 44.4%, table 3.Such a trend of injuries is expected given that coal excavation is done by qualified miners, and they are exposed to the highest risk of injury.Unskilled workers are mainly engaged in the delivery of the necessary material, which is usually performed manually in the excavation area and preparation crosscuts.

Table 4
Injuries rates according to workers age structure

Table 5
Injuries by days of the week

Table 6
Injuries by working shifts

Table 7
Injuries according to hours of work in shifts

Table 8
Injuries according to the injured parts of the body

Table 9
Injuries by source of injury

Table 10
Injuries by causer of injury

Table 12
Days lost due to injuries vs. works shift which were done

Table 13
Indicator of injuries