Snowmelt Water Breakthrough into Coal Mine in Sub-Artic Region
Miletenko, Natalia Alexsandrovna; Odintsev, Vladimir Nikolaevich; Fedorov, Evgeny Vyacheslavovich
Institute of Comprehensive Exploitation of Mineral Resources Russian Academy of Sciences, Russian Federation
Paragraph 1. Abundant snowmelt water causes damage mainly to engineering constructions on earth surface. However, snowmelt water may jeopardize safety of underground mining. There are various mechanisms responsible for this effect that are associated with water filtration process. The paper addresses a specific case of the snowmelt water effect characteristic of highly frozen ground and related to generation of frost cracks in the rock mass. The frost cracks going up to ten meters in depth are characteristic of subarctic regions.
Paragraph 2. This phenomenon is illustrated with an example of snowmelt water breakthrough at the Yun-Yaga mine. The paper is the first to demonstrate that frost cracks may cause spontaneous hydrofracture of rock mass in the technogenic area of the influence of underground excavation during spring-summer defrosting.
Paragraph 3. Computer modeling was made for rock hydrofracture from a 3m deep sinkhole on the earth surface to a ventilation excavation situated at a 30m depth under the effect of rock pressure and hydrostatic pressure of water in crack. The modeling involved the finite element method and a stepwise approach using a calculation procedure based on Griffith-Irwin theory of cracks. Calculations were also made for water filtration from the water conducting crack into the ventilation excavation.
The modeling explained some characteristic details of water breakthrough at the mine not understood previously: (1) development of a long water conducting crack at the border of the mine influence zone; (2) crack arrest near the roof of the ventilation excavation; (3) development of local intense filtration in the roof of the ventilation excavation; (4) rocks washout and falling from the zone of influence of the crack tip. It also explained the cause of the major water conducting crack development at the moment when snowmelt water reached the maximum level.
Paragraph 4. The conclusion was made that subjective factors of water breakthrough into the mine involved existence surface sinkhole at the mine influence zone and insufficient effectiveness of anti-snowmelt water measures. The objective factors of water breakthrough include the presence of frost cracks and talik in frozen ground. Therefore these objects (as concerns size and location) should be mandatorily taken into account in geophysical study within the system of measures to prevent snowmelt water breakthrough.