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Model for preventive recognition of the geodynamic phenomena in coal mines based on geophysical borehole measurements

Development of technology for geophysical measurements in boreholes for preventive recognition of geodynamic events such as gas outbursts during preparation works in the velenje coal mine.

LIGNITE MINE VELENJE is located in SLOVENIA and exploits a thick coal seam with thickness ranging from 20 to 160 metres. The unique exploitation method is called the Velenje mining method. A homogeneous lens shaped seam is 8.3 km long, from 1.5 to 2.5 km wide and lays 200 to 500 metres below underground. The mine provides around 4 million tons of lignite per year for the nearby thermal power plant. Electricity produced in the power plant represents around one third of Slovenian needs and is therefore one of the main strategic suppliers in the country. Because of many tectonic zones that cross the lignite deposit, the excavation process is quite complicated. In tectonically more exposed areas, there is a danger of sudden, unexpected outbursts of gas and coal. Such occurrences are part of geodynamic phenomena. These dangerous phenomena were present at the beginning of excavation more than one hundred years ago and the consequences proved very serious and included fatal accidents. More than 30 years of study into the reasons behind the occurrence of these phenomena have taken place with the aim of trying to understand and describe the key parameters. Based on new understanding, we can define and introduce measures for prevention and protection of miners and mining equipment. Because of the complexity of these sudden and unexpected phenomena, i.e. outbursts of gas and outbursts of coal and gas, we decided to try to solve the problems in cooperation with foreign experts. The results of such interdisciplinary scientific cooperation will substantially contribute to new understanding and progress in explaining the complex reasons for the occurrence of these phenomena. In this context, the results from past research and experience that LIGNITE MINE VELENJE will contribute, are very important. Among the most important knowledge gained so far from research, is the mechanism for describing and explaining coal and gas outbursts. Extensive petrographical research shows a close relationship between the potential danger of coal and gas outbursts and the particular lithotype of the coal. In all parts of the coal seam, where the fine detritic or gelitic lithotypes appear as thick layers of several meters or where the coal is near impermeable roof strata, we can expect an increased danger of coal and gas outbursts. There is potential danger in areas where these conditions are fulfilled and where increased amounts of gas have accumulated. Very crushed and microporous coal mostly appears in tectonically exposed parts of the deposit. Knowledge of the exact location of such zones, where enormous amounts of gas under high pressure can be emitted, is a basic condition for achieving increased safety in developing underground mine structures. In case where the petrography of the area where the planned structures are going to be driven is well known in advance, it is possible to apply the advanced methods that have been developed at the LIGNITE MINE VELENJE over recent years, and to provide a safety passage through such zones in addition to successive degasification. Results from lengthy research and experience related to dangerous geodynamic phenomena represent a good platform that can be upgraded with new knowledge from an international research group. Development work will continue in close cooperation with the development department at the LIGNITE MINE VELENJE and other participating enterprises and research institutions. Activities of all participating parties are subject to the following main objective: The main objective is the development, testing and application of geophysical measuring procedures in long, horizontal, safety-research boreholes that will enable recognition of structures in crushed areas. In addition, the method will enable a reliable 'in-situ' determination of separate coal lithotypes for forecasting dangerous geodynamic phenomena (gas outbursts and coal and gas outbursts). A measuring procedure as a model for preventive recognition of geodynamic phenomena in coalmines is based on geophysical measurements in a borehole and is going to be developed and tested for the conditions in the LIGNITE MINE VELENJE, but it also is expected to have wider general application in other coalmines. The method assists with diminishing risk and increasing safety in mines. For this part, it is very difficult to measure or define the direct economic effects - lives are invaluable. In addition, we expect indirect positive effects related to the stated geotechnical conditions along safety-research boreholes, resulting in the prevention of road-head collapses, faster development of underground structures and first and foremost an optimisation of support systems.
Acronym: 
VELGASPREVENT
Project ID: 
3 556
Start date: 
01-04-2005
Project Duration: 
39months
Project costs: 
920 000.00€
Technological Area: 
Measurement Tools
Market Area: 
Coal mining

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