Kravchenko A. The effect of physical properties of coal bearing rocks on coal seams inclination to sudden extrusions

Dissertation is devoted to issues of rock massif condition estimation us-ing physical, mechanical, and microstructural properties of coal bearing rocks for the purpose of substantiating the more reliable criteria to predict a coal seam inclination to sudden coal extrusion during coal production from flat seams occurring in complicated mining and geological conditions. Experimental studying the physical properties variability in various coal seam roof rocks under complicated mining and geological conditions had re-vealed the rock heterogeneity effect on the manifestations of gas dynamic ac-tivity in coal seams, sudden coal extrusions being dominating dynamic con-stituent. It was established in this work that the phase state of quartz and hy-drogenous constituents content in the basic roof sandstone of a coal seam exert influence on manifestations of sudden coal extrusions. Experimental studies had shown that the hydrogenous constituents' content in the basic roof sand-stone depends on concentration of iron compounds in this sandstone. A crite-rion for prognosis of sudden coal extrusions was substantiated based on ob-tained results, subject to specific changes in phase state of rock forming quartz, hydrogenous constituents' content, and ferrous compounds content in the basic roof sandstone of a coal seam. Similar criterion of sudden coal extrusion prognosis was first substanti-ated for coal seams with the roof formed by argillic minerals. This criterion is based on properties (activation energy of fluid escape) and microstructural fea-tures of the rock forming quartz in argillites of immediate roof. Results of ex-perimental studies allow forecasting sudden coal extrusions in faulty coal seams.