Materiały konferencyjne SEP 1992

Szkoła Eksploatacji Podziemnej * 92 375 2. Description of the phenomena The mentioned phenomena differ from "typical" outbursts of gas and coal łn the following main patterns: - bursted coal is crushed and prevailing dimension of coal płe- ces is in centłmeters, - the araount of fine coal powder is negligible, - bursted coal remains in the vicinity of the face, - the amount of released gas is remarkably lower, - the after - burst - cavity is filled by crushed coal ajid with- out "typical" shape (Fig, 1) Such outburst phenomena occur in coal faces in specific geomechanical conditions which could be schemat ically described by fig. 2: - sandstone bed of the thickness bigger than 10-15 m is signifi- cant in the roof, - generał goaf has not been developed yet, it happens that face support is heavy loaded. sometimes the floor is broken, - the depth Is greater than 500-600 m below surface, In case of the roadways such phenomena are observed: - in subhorizontal seams in the areas with increased tectonic stresses» - in inclined or steep seams due to gravity forces. "Normal" outbursts of gas and coal occur in zones formed by primarily highly disturbed coal, something like tectonic breccia (types III or IV according to the author's classif ication, Rakowski, 1983). In conditions being under consideration such a coal structure is not the regularity. But the presence of very thin (1-5 cm) layers of finely granular coal (mylonite) in the seam profile is typical. The origin of these specific layers Is explained as the result of differential lateral movements during orogenic processes. The areas with tectonic structures of thrust or fold type are characterized by them. Contact planes of the roof aind the floor with the seam are usually slickenslides. SE