this PDF file - Archives of Mining Sciences

this PDF file - Archives of Mining Sciences

Archives of Mining Sciences 50, Issue 1 (2005) 49–67
49
WOJCIECH BRADECKI*, JÓZEF DUBIŃSKI**
EFFECT OF THE RESTRUCTURING OF THE POLISH COAL-MINING INDUSTRY
ON THE LEVEL OF NATURAL HAZARDS
WPŁYW RESTRUKTURYZACJI POLSKIEGO GÓRNICTWA WĘGLA KAMIENNEGO
NA POZIOM ZAGROŻEŃ NATURALNYCH
The study of effect of transformations in the Polish coal-mining industry on safety level gives a broad perspective on the natural hazards, revising to some extend the state of the art in the field. The key
issue of this analysis is concentration of production and its effect on the work safety. The complexity
of interrelations, variability of factors and random nature of events make the relation discussed impossible
to express in the form of a descriptive equation. This is because the parameters that describe the level
of hazard are not correlated with the observed accident rate.
The results of the research have practical implication for implementation of innovative technical,
organisational and legal solutions in the mining industry.
Keywords: natural hazards, concentration of production, mining safety
Doświadczenia w zakresie restrukturyzacji polskiego górnictwa węgla kamiennego wskazują, że
są to procesy złożone i trudne, w sposób istotny oddziaływujące także na sferę bezpieczeństwa pracy.
W sposób szczególny uwidacznia się to w odniesieniu do podstawowych zagrożeń naturalnych takich
jak gazowe, tąpaniowe, pożarowe i klimatyczne, z których większość posiada cechy zagrożeń katastrofogennych. Podkreślić należy stosunkowo wysoki poziom potencjalnego stanu powyższych zagrożeń
w polskich kopalniach węgla kamiennego. Aktualnie 12% zasobów przemysłowych zalega w obszarach
o najwyższym ich poziomie,
Analiza wpływu procesów restrukturyzacyjnych na poziom bezpieczeństwa pracy wyróżnia pozytywne
i negatywne elementy tego procesu. Niewątpliwie do pozytywnych należy zaliczyć znaczące uproszczenie
struktury kopalń, zmniejszenie ich liczby, mniej frontów wydobywczych, a także ograniczenie liczby
pracowników zatrudnionych pod ziemią. Powoduje to wyraźnie obniżenie potencjalnego ryzyka wystąpienia zdarzeń wypadkowych poprzez zmniejszenie ilości miejsc zagrożonych i pracowników narażonych
na występujące zagrożenia. Podane dane ilościowe ilustrują wpływ tych zjawisk, który przejawia się,
między innymi, wyraźną poprawą wskaźników opisujących stan wypadkowości, np. liczbą wypadków
śmiertelnych, ciężkich i ogółem.
*
**
WYŻSZY URZĄD GÓRNICZY, UL. PONIATOWSKIEGO 31, 40-055 KATOWICE, POLAND
GŁÓWNY INSTYTUT GÓRNICTWA, PL. GWARKÓW 1, 40-166 KATOWICE, POLAND
50
Niekorzystne oddziaływanie procesów restrukturyzacyjnych na poziom bezpieczeństwa pracy
dostrzega się natomiast w nie zawsze racjonalnie rozumianej i realizowanej ekonomizacji produkcji.
Obserwowano w analizowanym okresie pogarszanie się warunków środowiska pracy. Badanie przyczyn
i okoliczności zaistniałych zdarzeń wypadkowych wskazują, iż często u ich podłoża leży wieloletnie
niedoinwestowanie kopalń, nawarstwiające się nieprawidłowości i zaniedbania w sferze doskonalenia
techniki i technologii górniczych oraz utrzymywania należytego poziomu uzbrojenia kopalń w maszyny
i urządzenia górnicze. Kolejnym negatywnym efektem restrukturyzacji, mającym niewątpliwie istotny
wpływ na aktualny poziom bezpieczeństwa pracy w kopalni, jest odejście od pracy dużej liczby pracowników, zwłaszcza osób kierownictwa i dozoru, o wysokich kwalifikacjach i wieloletnim doświadczeniu
w ruchu zakładów górniczych.
Odnosząc badany problem do relacji pomiędzy procesami restrukturyzacyjnymi a poziomem podstawowych zagrożeń naturalnych szczególną wagę należy zwrócić na zjawisko koncentracji produkcji.
Na pewno powinna ona być ważną cechą nowoczesnego górnictwa i niezbędnym elementem poprawy
wydajności pracy i obniżania kosztów wydobycia. Z drugiej strony, co potwierdzają wyniki badań i doświadczenia praktyczne, jest ona czynnikiem w sposób istotny oddziaływującym na poziom występujących
zagrożeń naturalnych. Oddziaływanie to w przypadku takich zagrożeń jak: gazowe (metanowe), sejsmiczne
i połączone z nim zagrożenie tąpaniami ma charakter negatywny, co oznacza, że istnieje krytyczna wielkość
koncentracji produkcji, charakterystyczna dla danych warunków geologiczno-górniczych, przekroczenie
której wyraźnie zwiększa poziom zagrożenia i ryzyko jego wystąpienia. Należy jednak podkreślić, że
w przypadku takich zagrożeń jak pożarowe, wodne, radiacyjne wpływ koncentracji produkcji może posiadać charakter pozytywny, a dla zagrożenia pyłowego i klimatycznego relacja pomiędzy ich poziomem
a koncentracją nie posiada jednoznacznego charakteru.
Na podstawie uzyskanego materiału obserwacyjnego, obejmującego pełny okres realizacji procesów
restrukturyzacyjnych w polskich kopalniach węgla kamiennego, zestawiono ilościowe charakterystyki
wypadkowości związanej z podstawowymi zagrożeniami naturalnymi o charakterze katastrofogennym
(metanowe, tąpaniami i pożarowe). Określono również kierunki dalszych działań zmierzających do
poprawy stanu bezpieczeństwa pracy w kopalniach węgla kamiennego z uwzględnieniem specyfiki
analizowanych zagrożeń naturalnych.
Słowa kluczowe: zagrożenia naturalne, koncentracja produkcji, bezpieczeństwo górnicze
1. Introduction
Transformation in the Polish mining industry during the last ten years or so, particularly in the coal-mining sector, have been running at a fast pace. This sector of industry
is still under the process of adapting to market economy and the experiences of coal
mining prove that restructuring is very intricate and difficult. The impact of restructuring
processes is becoming more and more evident in the various aspects of mine activities:
technical, economic and social. They have significant effect on the level of occupational
safety in coal mines.
The Polish coal industry is now concentrated in the Upper Silesian Coal Basin. In
many mines of this basin coal resources are nearly exhausted. This forces mine operators to win coal from deeper seams under adverse geological and mining conditions.
The potential for work safety hazards, mainly those associated with natural phenomena
– gas emission, fires, climatic and geodynamic conditions, increases with increasing
depth of mining operations.
51
The growing tendency of these factors and the presence of natural hazards increase
the risk associated with mining operations and creates favourable conditions for the
occurrence of disasters. In order to prevent such events appropriate actions must be
taken as early as at the stage of planning mining operations and appropriate preventive
measures must be taken and special mining techniques must be applied.
A characteristic feature and at the same time the core of the restructuring processes of
hard coal mining is the concentration of production. It contributes to increase in labour
productivity, reduction of production costs and, in the first place, to profitability of mining
operations. However, its adverse effect is manifested by increased level of hazards, both
natural and technical, including general and environmental threats.
Palarski (2004) discusses the problems associated with the restructuring of the mining
industry and indicates that the liquidation of a coal mine should be treated as one of the
stages of the life of a mine, rather than as a social, economic and ecological disaster in the
region. The drawing up of a mine closure programme should be a continuous process that
is carried out during all stages of mining operations, during the design and construction
of the mine, during mineral extraction and shutting down of workings.
The study of experiences gained during the more than 10 years of the restructuring
of hard coal mining industry in Poland has indicated that it had a significant impact on
labour safety. The descriptive and quantitative nature of this impact is described in this
paper.
2. Restructuring of hard coal mining industry in Poland
The process of the reform of hard coal mining industry was initiated in 1989 – parallel
to deep transformations in the political system. The adverse condition of this sector of
economy was at that time the result of:
– most of the mines being located in densely populated and highly urbanised region
of Upper Silesia,
– overproduction (annual output of more than 180 million tonnes),
– high employment rate, leading to low labour productivity,
– reduced domestic demand for hard coal,
– unfavourable coal prices on world markets,
– unsatisfactory level of occupational safety,
– environmental nuisance and damages caused by underground mining.
The reform of the hard coal mining industry in Poland was carried into effect through
several consecutive programmes. The restructuring named as the Hard coal mining: State
and sector policy for the years 1996-2000 did not bring about improvement of economic
and financial standing of the mining businesses. The programme for the years 1998-2002
presented by the Minister of Economy, created legal instruments and indicated the need
52
for financial support from the State, was adopted by the Government on 30 July 1998
(The reform..., 1998). The common feature of the restructuring activities was the adoption of achieving profitability as the principal goal. This goal is also pursued by the
Programme of the restructuring of hard coal mining in Poland in the years 2003-2006 with
the use of anti-crisis acts and initiation of privatisation of some mines. It was backed by
a regulation of the level of an act (Act..., 2003), which defined the principles of financial restructuring, principles of shutting down hard coal mines and indicated sources of
financial means for the restructuring of the hard coal mining industry.
During the course of restructuring processes significant changes in a number of technical and economic indicators were observed. These changes are illustrated in Table 1.
TABLE 1
Hard coal mining indicators 1989-2003
TABLICA 1
Wskaźniki charakteryzujące górnictwo węgla kamiennego w latach 1989-2003
#
1
2
3
4
5
6
7
Indicator
Coal production (millions of tonnes)
Export (millions of tonnes)
Employment (thousands)
Recoverable reserves (billions of tonnes)
Developed reserves
Number of mines
Number of active longwalls
Total number of accidents,
8
of that fatal
Years
1989
177.4
28.9
407
30.7
12.8
70
861
13,365
87
1999
135.4
32.3
272
25.2
9.2
63
415
11,159
36
2000
102.2
23.0
155
18.1
5.8
42
183
2,756
28
2003
99.7
20.0
137
15.9*
5.1*
41
144
2,049
26
* as of 31.12.2002
The data above confirm the continued drop in production and significant decrease in
employment. A marked decrease of balance reserves was observed, including workable
reserves. The number of mines and mining regions dropped significantly.
Turek (2003) studied the changes in the structure of mines and in technical and economic indicators in the restructuring process of hard coal mining and determined that in
the years 1990-2002 the area covered by mining activities was reduced by 721 km2, i. e.
by 37%. A significant drop in daily production was observed – from 452 thousand tonnes
to 370 thousand tonnes. The number of pit shafts decreased from 309 to 207 and the number of production levels decreased from 111 to 75. The total number of active workings
decreased by 48%. The average daily output of one longwall reached 2800 tonnes at the
average longwall length of 222 m. Technical restructuring lead to the simplification of
the hard coal mine model, to increased concentration of coal extraction, to power coal
quality and environmental improvement and to reduction of mining damages.
53
During the reform of the hard coal mining the working safety in mines has improved. The number of fatal and serious injuries has dropped. However, there have been
dangerous events involving multiple casualties the cause of which was associated with
the factors that are intrinsic to production concentration.
Figure 1 shows the locations of mining areas of hard coal mines in the Upper Silesian
Coal Basin and the levels of natural hazards in these areas. Analysis of the distribution
of developed reserves leads to the conclusion that 12% of those reserves lie within the
parts of deposits of the highest hazard level.
Mines being closed
Safe mines
Mines with low hazard level
CZECH REPUBLIC
Mines with medium hazard level
Mines with high hazard level
Fig. 1. Variation of natural hazard level in mining areas of the Upper Silesian Coal Basin
Rys. 1. Zróżnicowanie poziomu zagrożeń naturalnych w obszarach górniczych GZW
3. Effect of restructuring processes on the level of work safety in mines
The factor that is beneficial for the level of work safety in underground coal mines
and is directly associated with the restructuring process, is the decrease of output. It
involves the reduction of the number of people employed in the production processes,
particularly under the ground. It enables reducing coal extraction from hardly accessible
deposits. It allows planning exploitation in a manner that ensures optimum allocation of
coal extraction means in time and space.
54
Adverse effect of the restructuring processes in the hard coal mining industry on the
level of work safety has its source in production economisation. In economic terms work
safety is expressed indirectly in labour cost.
Since 1998 the working environment conditions are deteriorating and the level of risk
associated with mining operations is constantly increasing. This is confirmed by dangerous events that took place in recent years in hard coal mines. The study of causes and
circumstances of these events had proved that their roots originate from many years of
underinvestment in mines, irregularities and negligence in the field of mining technique
and technology improvement and availability of mining machines and equipment. The
current and anticipated future level of work safety in hard coal mines is determined by
three factors:
1) the increasing use of a simplified “sublevel” model of DEPOSIT OPENING,
2) depreciation of the stock of machines and technical equipment in mines,
3) lack of sufficiently efficient and reliable systems for working environment monitoring and for warning people under ground about existing hazards.
In 2003, of the 41 operating hard coal mines, 27 of them applied sublevel mining (in 47
longwalls) and carried out development and preparative work for future sublevel mining
(60 faces). 16 longwalls were worked using the sublevel method at depths of more than
800 metres. Sublevel mining produced 32% of total daily output. Sublevel mining and
the associated concentration of mining operations, together with the increasing depths
at which the operations are carried out, contribute to the rising level of hazards. Operations in 43 faces were performed under the conditions of class B of coal dust explosion
hazard. Methane hazard in half of the open-ends was of the highest categories (III and
IV). Moreover, 27 longwalls were exploited under the conditions of second and third
degree of bump hazard. In all longwalls that were worked with the sublevel method
the temperature of rock exceeded 30°C and hindered ventilation and created a climatic
hazard for people working under ground.
Savings are made by reducing mining investments, departing from equipment modernisation, repair and replacement of worn out machines and devices. In 2003 there were
23028 powered roof support sections in use in coal mines. Of these 4083 were repaired
and further 14352 sections were the product of repair or modernisation of supports
manufactured earlier. It was found that 22% of the total number of roof supports do not
meet the requirements of the Polish standard on passage for people. During the last five
years only 1625 new roof supports were purchased.
Another adverse effect of the restructuring, which undoubtedly has a significant impact
on the current level of work safety in mines, is the quitting of work by a large number of
employees, particularly highly qualified and experienced managers and supervisors.
Szlązak and Szlązak (2003) have studied the effect of restructuring in some coal
mining companies on the accident rate in mines and had not found any close relations
between the phenomena. On the other hand they found that in the years 1993-2001 there
55
was a continuous decline in the total number of accidents and in the number of fatal
and serious accidents, whereas the rate of this decline was much higher than the rate of
employment and production reduction. They have also rejected the argument that restructuring acts as a stressing factor, which contributes to the increase in accident rate.
The general nature of the relations between production concentration and the various
types of hazards is shown in Table 2.
TABLE 2
Effect of production concentration on hazards occurring in mines
TABLICA 2
Wpływ koncentracji produkcji na poziom zagrożeń występujących w zakładzie górniczym
#
1
2
3
4
5
6
7
8
9
10
11
12
Hazard
Gas (methane)
Fire
Climatic
Seismic
Bump
Dust
Water
Radiation
Combined
Mechanical
Electrical
Environmental
Positive
Effect
Negative
x
Ambiguous
x
x
x
x
x
x
x
x
x
x
x
4. Characteristics of changes in the level of basic natural hazards
Natural hazards occurring in Polish hard coal mines include gas hazards, bump
hazards, fire hazards, water hazards, coal dust explosion hazards, climatic hazards and
radiation hazards. In addition to that there are hazards resulting from mining techniques
and technologies, such as noise and vibrations, electric shocks, contact with operating
machines and devices, explosives, etc. In the discussion of the various aspects of the
impact of restructuring, we concentrate on these hazards, which have the greatest effect
on the level of safety and are the cause of fatal accidents and numerous casualties.
Table 3 shows the statistics of fatal accidents associated with the analysed natural
hazards: gas, bump and fire.
The percentage of fatal accidents caused by natural hazards in the total number of fatal
accidents that occurred in coal mines in the years 1989-2003 is illustrated in figure 2.
56
TABLE 3
Statistics of fatal accidents associated with natural hazards in hard coal mines
TABLICA 3
Statystyka wypadkowości śmiertelnej powodowanej zagrożeniami naturalnymi
w kopalniach węgla kamiennego
Number of fatalities
Gas hazard Bump hazard Fire hazard
Total
G
B
F
G+B+F
0
7
0
7
26
6
0
32
0
6
0
6
0
9
0
9
1
10
0
11
4
4
0
8
0
7
0
7
0
3
0
3
0
0
0
0
0
2
0
2
0
1
0
1
0
0
0
0
0
2
0
2
13
3
1
17
1
2
3
6
Year
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
Total
T
82
111
69
52
61
33
33
48
20
30
20
28
22
33
28
Share %
(G+B+F) /T
8.8
28.8
8.6
17.3
18.0
24.2
21.2
6.2
0.0
6.6
5.0
0.0
9.1
51.5
21.4
% of total fatal accidents rate
60
51,5
50
40
28,8
30
24,2
21,4
21,2
20
10
0
17,3
8,5
8,6
18
6,6
6,2
0
9,1
5
0
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Fig. 2. Rate of fatal accidents caused by natural hazards in coal mines
Rys. 2. Wypadkowość śmiertelna powodowana zagrożeniami naturalnymi w kopalniach
węgla kamiennego
57
The share of basic natural hazards in the causes of fatal accidents has varied since
1996. However, it always remained low. This changed in 2002, when two mining disasters associated with gas and dust hazards occurred and caused 13 fatalities. Fire hazards
in general did not inflict fatal accidents and their destructive nature manifested itself in
heavy material damage, production loss, and destruction of machines and equipment.
4.1. Gas hazards
Gas hazards in Polish hard coal mines is associated exclusively with the presence of
methane in the strata and with its release during mining operations. Data on that hazard
is presented in Table 4.
TABLE 4
Gas hazards in coal mines in the years 1989-2003
TABLICA 4
Charakterystyka zagrożenia gazowego w kopalniach węgla kamiennego w latach 1989-2003
Year
No. of mines with
methane-bearing
seams
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
55
55
54
54
54
52
48
44
43
43
43
41
38
38
36
Share of production from methanebearing seams
w/o methane
with methane
extraction
extraction
39
37
38
36
32
38
40
36
47
33
39
35
34
38
39
38
36
40
39
44
37
42
36
48
35
48
36
48
36
50
Absolute
methane capacity
(m3/min)
1989,6
1881,5
1577,7
1613,6
1483,9
1431,0
1418,0
1400,2
1504,7
1453,6
1436,1
1470,0
1440,2
1455,6
1522,5
When analysing the effect of restructuring processes on the level of gas hazard in
Polish hard coal mines, we must point out the insignificant changes in the percentage
of coal extraction from methane-bearing seams (37% on the average) in spite of the
substantial decline (nearly 50%) in total coal production. Incommensurate with the
reduction of the number of mines was also the decrease of the number of mines where
coal is extracted from methane-bearing seams. This indicates that the potential gas hazard
58
has been increasing in the years 1989-2003. This confirms that the absolute methane
capacity of mines varies with time. The advantageous phenomenon is the increase of coal
production from methane-bearing seams in mines where methane extraction is applied.
This is also evidenced by the stability in the quantity of methane produced this way.
The number of mines extracting coal from methane-bearing seams is shown in fig. 3.
number of mines
60
50
55
55
54
54
54
52
48
44
43
43
43
41
40
38
38
36
30
20
10
0
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Fig. 3. Number of mines where coal is extracted from methane-bearing seams
Rys. 3. Ilość kopalń eksploatujących pokłady metanowe
Restructuring processes, due to the simplification of the structure of mines, provide
opportunities to attain better efficiency of ventilation systems, and should therefore
alleviate the methane hazard. This, however, is not the case. On the contrary – we can
speak of significant increase of the potential methane hazard if we relate the absolute
methane capacity to the number of active longwalls, which had decreased six-fold during
the analysed period. The reasons for such a state of things include:
– large share of methane-bearing seams of increasing absolute methane capacity in
the overall number of mined seams (this is also the result of the increasing depths
of workings, which is associated with increased methane capacity, increased gas
pressure and reduced methane permeability of coal seams),
– decreasing efficiency of preventive methane extraction – resulting from the properties of coal seams,
– increasing concentration of production (amount of methane released to the workings
is proportional to coal output),
– failure to adapt the model and structure of mines (because of shortage of means)
to gas conditions.
Results of studies indicate that faster daily advances of faces mean not only larger
quantities of methane released from the worked coal seam, but also further reach of
stress-relief zone, which often leads to significantly larger space from which methane
is released. They confirm that the methane hazard forecasts made until now were not
59
adequate and that there is a need to apply dynamic forecasts, which take into account
the rate of face advance and the new phenomena resulting from the variation of this rate.
There is the problem of determining the permissible safe coal output from individual
longwall sections under the conditions of methane hazard, particularly in the case of
high potential hazard (III and IV category). Experience shows that this output depends
on anticipated absolute methane capacity, efficiency of the ventilation system and of
preventive measures applied.
The often applied sublevel method of mining is highly inadequate from the viewpoint
of methane hazard when undertakings in the field of improving ventilation system operation and cost reduction are assessed. Moreover the sizes of headings, including longwall
headings, are such that air in quantities sufficient to maintain safe and permissible methane
concentration cannot be provided when gas emission from active headings is high.
In all, the restructuring processes are not beneficial in terms of gas hazard in the Polish
hard coal mines. Further operations and the undisputed need to concentrate production
require the development and implementation of new technologies, which would ensure
safe mining under the conditions of increasing methane hazard.
4.2. Fire hazard
Fire hazard, due to its characteristics (gases and smoke proliferated in workings), may
be dangerous to larger groups of workers. We may differentiate between endogenous
fires, which result from the tendency of coal to ignite spontaneously, and exogenous
fires the source of which is not associated with the coal seam.
Data on fire hazard in Polish hard coal mines during the restructuring of the mining
industry is presented in Table 5.
The variation of fire index with time is shown in figure 4.
number of fires
per output of 1 mln tor
0,18
0,16
0,16
0,14
0,12
0,12
0,1
0,08
0,11
0,1
0,09
0,09
0,07
0,07
0,07
0,06
0,06
0,05
0,05
0,04
0,04
0,03
0,02
0,01
0
1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003
Fig. 4. Fire index
Rys. 4. Wskaźnik pożarowości
60
TABLE 5
Fire hazards in Polish hard coal mines in the years 1989-2003
TABLICA 5
Charakterystyka zagrożenia pożarowego w polskich kopalniach węgla kamiennego w latach 1989-2003
Year
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
No. of under-ground fires
endo-genous
13
11
16
11
10
7
9
7
4
5
3
2
1
4
exo-genous
4
6
6
2
5
5
0
2
2
2
3
1
0
3
Fire index (no. of fires
per 1 million tonnes
of coal produced)
0,09
0,11
0,16
0,10
0,12
0,09
0,07
0,07
0,04
0,06
0,05
0,03
0,01
0,07
Depth (m)
above 500 m below 500 m
6
7
2
9
7
9
1
10
4
6
1
6
4
5
2
5
1
3
1
4
0
3
0
2
0
1
2
2
When assessing the effect of restructuring processes on fire hazard we must state that
this hazard has been decrasing, as measured by the number of fires and also by the fire
index, although these parameters show certain degree of variability in some years. The
restructuring of the mining industry has in the case of this hazard a beneficial effect.
This beneficial effect seems to have its sources in the group of mining factors: in the
reduction of coal headings and in faster rate of longwall advance.
The former factor reduces the number of spots of potential hazard of endogenous
fire, whereas the beneficial effect of the latter factor is associated with the relation between the period of incubation of an endogenous fire and the longwall advance rate.
This period, usually lasting from 5 weeks to about 5 months, is very short in relation to
the time of working the given panel. For this reason any idle time in longwall working,
especially longwall with caving, or any slowdown in longwall advance is dangerous from
the viewpoint of fire hazard, as it creates stable conditions favourable for air infiltration
into the gob and formation of fire sources. Ensuring safety and continuous working in
longwalls of high output in seams with high tendency to spontaneous combustion requires
increased spending on fire prevention. Fire prevention in this case must not only include
appropriate mining technology, but also modern hazard monitoring systems, particularly
for detecting spots of possible spontaneous coal temperature rise.
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4.3. Climatic hazard
Climatic hazard results from the adverse effect of air temperature and humidity on
human organism. It has no destructive features. However, it creates an unfavourable
working environment under the ground. It is associated with heat and moisture sources
in the form of rocks and electrical and mechanical equipment. The mining regulations
distinguish three temperature ranges:
– below 28°C, where normal working time is possible,
– 28 to 33°C, or where the cooling intensity of air is below 11 Kata moist thermometer degrees, where working hours have to be reduced to 6,
– above 33°C, where work is forbidden.
The study of climatic hazard in Polish coal mines indicates that the concentration
of coal production from longwall faces associated with the restructuring of the mining
industry is the cause of on-going increase of the number of headings where air temperature exceeds 28°C. This is illustrated in Table 6.
TABLE 6
Climatic hazards in coal mines in the years 1989-2003
TABLICA 6
Charakterystyka zagrożenia klimatycznego w kopalniach węgla kamiennego w latach 1989-2003
Year
1989
1992
1995
1998
2000
2001
2002
2003
Standardised hazard parameters
No. of headings No. of headings where hazard No. of headings where hazard
where hazard exists exists per 1 million tonnes
exists per number of active
of coal output
longwalls
110
0,62
0,13
159
1,21
0,30
152
1,12
0,37
188
1,62
0,71
164
1,60
0,90
218
2,12
1,35
234
2,28
1,55
143
1,43
0,47
The extraction of deeper coal seams leads to increased heat flux from the rock mass
to the mine air. The concentration of production, involving the use of high power coal
winning machines and transport equipment, has similar consequences. The widely adopted sprinkling systems in longwall cutter loaders contribute to increased humidity of
air. Tests have shown that heat from technological processes may constitute 50 or more
62
percent of total heat balance. Coal production concentration has some advantageous
effects. One of them is the possibility of more efficient use of the ventilation system
through:
– simplification of the ventilation network and shortening of the distance fresh air
has to pass to reach the mining area,
– increase of the quantity of fresh air due to lower number of mining areas that have
to be provided with fresh air.
Increasing the lengths of longwalls, while failing to develop sufficient structure of
headings, leads to the deterioration of climatic conditions.
Figure 5 shows the number of headings where climatic hazards occurred.
250
234
number of headings
218
200
188
159
150
164
152
143
110
100
50
0
1989
1992
1995
1998
2000
2001
2002
2003
Fig. 5. Number of headings operated under the conditions of climatic hazard
Rys. 5. Ilość wyrobisk prowadzonych w warunkach zagrożenia klimatycznego
4.4. Bump hazard
Bump hazard has the characteristics of a hazard of catastrophic nature. Geological and
mining conditions of the Upper Silesian Coal Basin promote seismic phenomena induced
by mining operations. At present coal is extracted in 29 mines where bump hazard exists
and annual coal production from these seams exceeds 40 million tonnes.
The adopted measure of potential bump hazard is the level of seismic events that
accompany mining operations. Of significance are seismic events of adequate intensity
expressed as seismic energy of the tremor. In Poland it is accepted that this threshold
seismic energy is E = 105 J, which is equivalent to seismic magnitude of about 1.5. Physical parameters of these phenomena, characterising both the tremor epicentre and the
63
rock mass where the tremor is generated, provide information in this field. However, the
real level of bump hazard is characterised by actual symptoms of the impact of seismic
phenomena on mine headings. Sensing these phenomena, and above all their effects
in the headings, including accidents, is the basic feature of the real hazard. Miners are
exposed to serious injuries and loss of life during bumps. Relevant statistical data are
presented in Table 7.
TABLE 7
Potential and real bump hazards in Polish coal mines in the years 1989-2003
TABLICA 7
Charakterystyka potencjalnego i faktycznego zagrożenia tąpaniami w polskich kopalniach
węgla kamiennego w latach 1989-2003
Real hazard
Year
Potential hazard
(no. of tremors
E ≥ 105J)
no. of
bumps
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
1076
1038
863
833
932
752
465
564
547
663
1135
1088
1137
1324
1524
15
16
8
10
18
12
7
2
2
5
2
2
4
4
4
No. of fatal No. of other
accidents
accidents
7
6
6
9
9
4
6
3
0
2
1
0
2
3
2
56
30
16
36
28
40
34
19
6
14
2
0
19
13
16
Length
of caved
headings
(m)
121
102
16
23
1220
199
251
140
0
0
0
0
0
0
110
Length of
damaged
headings
(m)
1564
1472
838
646
1739
903
651
38
169
463
199
72
723
540
145
Figure 6 shows the distribution of one of the parameters that describe real bump
hazard – length of headings damaged as a result of bumps.
Despite the decrease in total coal production during the restructuring of the coal
mining industry, the share of seams where bump hazard exists in that production is not
changing proportionately, it is even rising. Resources of seams where bumps do not
occur are being exhausted and in consequence miner operators have to turn to seams
where that hazard exists. It is obvious that going down deeper under the ground, which
happens in most of the mines, adds to this problem.
meters
64
2000
1739
1564
1500
1472
1000
903
838
723
651
646
540
463
500
199
169
72
38
0
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
Fig. 6. Length of mine headings damaged by bumps
Rys. 6. Długość wyrobisk uszkodzonych w wyniku tąpań
Since 1996 a reduction in the number of bumps is observed. This does not correlate
well with the reduction in coal production, but it can be related to the changes that are
taking place in the structure of the mines, including those that extract coal from seams
liable to bumps. This structure is being substantially simplified, mainly by reducing the
number of mining areas and longwalls (six-fold in relation to 1989). In the case of mines
operating on seams where bump hazard exists this fact provides new opportunities for
planning underground working in space and time and for rarefying it, which is beneficial
from the viewpoint of bump hazard.
Restructuring processes in the Polish coal mining industry have distinct effects on
the level of bump hazard. On the one hand these are advantageous effects, and rational
use should be made of them. On the other hand they bring about disadvantages, which
are above all the result of the relationship between production concentration and seismic
activity and bump hazard.
5. Future undertakings aimed at work safety improvement
Detailed study of changes in the level of basic natural hazards that took place during the period of the restructuring of the Polish coal mining industry, supported by the
analysis of dangerous events that occurred in recent years and were caused by these
hazards, enables the formulation of the following main areas of activities leading to the
improvement of safety:
– with respect to hazards determined by the atmosphere in mines:
• planning mining operations in seams of high gas hazard with account taken
of dynamic forecasting and criteria defined by gas-ventilation balances in the
various mining areas,
65
• improvement of ventilation efficiency by enlarging the cross sections of headings
and their maintenance, particularly near longwall faces,
• development of more efficient technologies of preventive methane extraction
from the strata,
• implementation of continuous measurements in gas hazard monitoring systems,
• implementation of gas measurements to warn about spontaneous heating of
coal,
• implementation of climate improvement techniques, including central air conditioning;
– with respect to seismic and bump hazards:
• planning mining operations in seams of high bump hazard with account taken
of the level of production concentration and its adaptation to anticipated seismic
activity,
• application of the principle of diffusing production within the area of the mine
and in boundary regions of the mine,
• implementation of measures that increase the dynamic strength of longwall
roof supports,
• pursuit of solutions for increasing the stability and strength of road supports,
• development of new techniques for disintegrating the structure of large rock
blocks, particularly rocks in the roof,
• development of seismic monitoring systems by implementing new interpretation
procedures, particularly with respect to geophysical methods,
• implementation of technical and organisational solutions that would enable
reduction of workforce in areas of potentially high hazard, by mechanising
operations, use of closed circuit TV, etc.
• use of more efficient personal protection equipment.
One important area of activities, related to overall problems of occupational safety
and health in the mining industry, is the implementation of solutions that cover entire
systems, in particular the occupational safety and health system. An important component of such a system is the improvement of training methods, which should include
simulation of situations that lead to the occurrence of hazard effects. It is necessary to
study, adapt and improve regulations concerning natural hazards in the aspect of the
changing natural and technological conditions.
Implementation of innovative technical, organisational and legal solutions in the
mining industry must be performed under the close supervision of mining authorities.
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6. Conclusions and comments
1. Experience gained during the long years of the restructuring of the coal mining
industry indicates the existence of a number of relations between the range of transformation made and the level of natural hazards occurring in mines. Undoubtedly
one of the significant factors is the concentration of production that is associated
with the restructuring process. The complexity of interrelations, variability of
factors and random nature of events make the relation discussed impossible to
express in the form of a descriptive equation. This is because the parameters that
describe the level of hazard are not correlated with the observed accident rate.
2. The directions of the effects of processes that are part of the restructuring programme on the level of hazards in mines are of differing nature. A beneficial effect
is observed in the area of fire, water, radiation and mechanical hazards. Adverse
effect is exhibited in the sphere of gas, seismic and bump hazards. The effect on
the level of climatic and dust hazards is not unambiguous.
3. The control of natural hazards, the level of which rises with the increasing depth
and concentration of mining operations, calls for the implementation of an efficient
and reliable system for detecting and monitoring the events occurring in the strata
and in the working space and for warning workers about the existing danger. This
applies in the first place to these areas of mines where various hazards coexist:
methane, fire, dust explosion and geodynamic hazards. The methods of performing
actions in this field should take into account the specific features of the hazard,
variability of its parameters in time and space and automation of preventive measures.
4. An automatic methanometric system should provide continuous measurements
of methane concentration in the air of mine. Safeguards must be installed in mine
headings to protect against local concentration of methane. Equipment for on-site
use for assessing the risk of coal dust explosion must be developed and applied.
Mines must be equipped with improved geophysical equipment for recording
geodynamic events in order to determine the stress in the strata and forecast bumps
and tremors.
5. The provision of safe working conditions in coal mines will require the application
of alternative solutions, consistent with the increased level of hazards. This needs
more spending on research, experimental and design work. The expenses required
are higher than those affordable to a single mine operator. Co-ordination of actions
and cumulation of means is essential.
6. The sub-level model of opening out operations should not be applied on a large
scale. Sub-level working can only be applied in exceptional instances upon making
comprehensive checks of the correctness of the proposed solution. Mining operations carried out below extraction levels should always be verified with respect
to safety requirements.
67
7. The experience gained in recent years, as well as the results of research, show that
there are distinct restrictions of production concentration in seams where bump
hazard exists. One may think of a coal production limit which can be attained in a safe
manner with respect to bump hazard in the given conditions of rock mass stress and
strain, which are defined by local geological and mining situation. Exceeding this
limit causes rapid increase in seismic activity and in the number of bumps.
8. Apart from natural hazards, there are other causes of dangerous events and accidents
in coal mines Those that occurred in 2003 include non-compliance of workers with
principles of occupational safety, work under unsupported roof or walls, riding
on conveyors, working too close to moving equipment, improper co-ordination of
team tasks, lack of personal protection equipment and lack of work supervision.
The effects of these factors may also be indirectly associated with concentration
of production.
9. The characteristics of the discussed effects in the aspect of changes brought about
by the restructuring processes enable identification of the main factors that define
the current level of the various hazards. The most important technical, organisational, supervision and inspection activities may be formulated to create safer labour
conditions in the coal mines being restructured.
10. Mining supervision authorities play the leading role in ensuring proper level of
safety in mines being restructured or shut down. Long term strategy of the activities
of mining authorities, work programmes of the State Mining Authority and the
plans of district mining offices include the tasks associated with that role.
REFERENCES
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D u b i ń s k i , J. et al., 1999. Concentration of production and mining hazards. (in Polish) Wyd. Główny Instytut Górnictwa. Katowice,
K o n o p k o , W. et al., 2003. Annual report on the status of basic natural and technological hazards in coal mining.
(in Polish) Wyd. Główny Instytut Górnictwa. Katowice.
P a l a r s k i , J., 2004. Problems accompanying the processes of restructuring the mining industry and the shutting down
of mines. (in Polish) Wiadomości Górnicze 1/2004
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of coal mining industry. (in Polish) Prace Naukowe GIG. Katowice.
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2037).
REVIEW BY: PROF. DR HAB. INŻ. JANUSZ ROSZKOWSKI, KRAKÓW
Received: 03 November 2004