Stefanovich L.І., Sobolev V.V., Rudakov D.V. ,Bilan N.V. The analysis of fracture development in the gas-saturated fossil coal for different conditions of the coal seam unloarding

Details
Parent Category: Geo-Technical Mechanics, 2019
Category: Geo-Technical Mechanics, 2019, № 149

Geoteh. meh., 2019, 149, 26-37

https://doi.org/10.15407/geotm2019.149.026

 

THE ANALYSIS OF FRACTURE DEVELOPMENT IN THE GAS-SATURATED FOSSIL COAL FOR DIFFERENT CONDITIONS OF THE COAL SEAM UNLOARDING

1StefanovichL.І.,2SobolevV.V., 2Rudakov D.V. ,2BilanN.V.

1Institute for Physics of Mining Processes, NAS of Ukraine, 2National Technical University Dnipro Polyteсhnic

UDC 622.831.2:531.391.5

Language: Russian

Annotation.

Development of fracturing of gas-saturated coal seam under conditions of its slow and fast unloading was considered. The situation when great proportion of cracks in the coal seam are oriented parallel to the bottom of the face was studied. Curves of crack initiation at fast and slow unloading of coal seam were constructed. Basing on the analysis of these curves, a three-stage process of major crack evolution in the marginal part of the coal seam was theoretically investigated. Influence of various factors on the proneness-to-outburst of gas-saturated coal seams was analyzed, namely: rates of the coal seam unloading and modulus of the coal substance adhesion. On the basis of comparison of the curves of crack initiation, which describe the process of main crack propagation at different conditions of coal seam unloading, it is shown that slow unloading of the coal seam leads to a greater spread of transverse cracks in the marginal part of the formation in comparison with the sharp (adiabatic) unloading of external mechanical stresses. This phenomenon is especially characteristic for the small initial cracks. A series of cracking curves was constructed for various coal grades with different moduli of the coal substance adhesion. Having analyzed these crack initiation curves, influence of the coal adhesion modulus on the occurrence of a sudden outburst was determined. It is established that in case of gas-saturated coal seams containing a system of cracks parallel to the bottom of the face, the outburst hazard of the coal seam increases significantly with decrease of the coal adhesion modulus. This means that the range of sharp "shooting" of cracks at the second stage of their evolution is significantly expanding. Moreover, this danger is more significant at slow unloading of the external load. The theoretical analysis shows that tin order to reduce risk of outburst in gas-bearing coal seams, especially with a small adhesion modulus, it should be taken into account that outburst danger increases with increases of the rate of the working driving. The aim of the work is to study effect of the speed of mining operations and strength characteristics of the coal seam, such as modulus of the coal substance adhesion, on the coal seam fracturing .

Keywords: fracturing, gas-saturated coal seam, crack initiation curves, rate of coal seam unloading , adhesion modulus of the coal substance, outburst hazard.

References

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About the authors

Stefanovich Leonid Illich, Doctor of Physics and Mathematics (D.Sc.), Deputy Director of the Institute for Scientific Work, Institute for Physics of Mining Processes NAS of Ukraine (IPMP, NAS of Ukraine), Dnepr, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

Sobolev Valerij Victorovich, Doctor of Technical Sciences (D.Sc.), Professor of the Department of Construction, Geotechnics. and Geomechanics,. National Technical University “Dniprovskaya politechnica” (NTU “DP”), Dnepr, Ukraine, This email address is being protected from spambots. You need JavaScript enabled to view it. .

Rudakov Dmitrij Victorovich, Doctor of Technical Sciences (D.Sc.), Professor, Department of Hydrogeology and Engineering Geology, National Technical University “Dniprovskaya politechnica” (NTU “DP”), Dnepr, Ukraine,, This email address is being protected from spambots. You need JavaScript enabled to view it. .

Bilan Nataliya Valerievna Candidate of Geology and Mineralogy (Ph. D), Associate Professor of Department of Hydrogeology and Engineering Geology, National Technical University “Dniprovskaya politechnica” (NTU “DP”), Dnepr, Ukraine, bilanatan@gmcom.