Materiały konferencyjne SEP 1993 - tom 2

Szkoła Eksploatacji Podziemnej *93 as 30x40 cm. The rocks shift via the crack formed takes 10-15 min,and when the outburst is in progress it becomes faster: 5-8 min. The "cone" over the heading being the result of the shift leads to the loosening of the rock, distorting its structure and, thus,decreases the strength tens and hundreds of times. So,the initial pressure over the heading can be presumed equal to Y h » the shift cone having been formed in the point of the outburst , the heading will be affected by the concentrated force equal in value to the weight of rocks contained within the "shift cone". The results obtained are important for the perfection of the mining operations. As a result of modelling for the first time ever the qualitative picture of the floatings shift zone which has a shape of a cone with the shift angles 82-85' has been established. The main criteria and constants of similarity for the loose floatings simulation have been given grounds. The equivalents have been selected for the wetted rocks of the DnepropetroYsky brown coal basin. The data obtained served the basis for the investigation of the strain-deformed state of the massif as well as the rocks embracing the horizontal headings with account for the physico-chemical hardening of the roof meterials. 4. The study of the strain-deformed state of the massif embracing the horizontal headings with the roof having floating mass The forecast for the floating outburst into the heading is associated with the study of the strain-deformed state of the rocks embracing the heading. The aim of the study is to evaluate the carryng capacity of the protective (physico-chemically hardened) layer and to determine its thickness sufficient for precluding the floating outburst. It is presumed, that the protective layer is exhausted if its rocks throughout their thickness exceeded the limits of deformation and their greater part ajacent to the heading is broken up to the finał extent of strength . Thus, the preocupation is to determine the parameters of the non-resilient deformation zone in the roof. The solution accounts for, firstly, the presence of the wetted layer in the roof; secondly, the rocks limit characteristics, their ability to gradually lose their carrying capacity beyong the limit of strength. It seems impossible to represent the above factors in the analytical solution. The numeric method (PC, for example) would necessitate the iteration procedures and, conseąuently, considerable computation time. So the solution combined both, namely: method of finite elements to determine the strain concentration coefficients K b i at the background of the hypothesis of the sections fiat deformation which is perpendicular to the longitudinal axis of the heading. The floating mass was presented by the lose rocks layer E^^ /E^^ =0.01 YcA^^kp ^^^ boundaries of which were affected bythe distributed load with the intensity q = yH^ (H^ - the layer depth); Sekcja III 155