Materiały konferencyjne SEP 1993 - tom 2

Underground Exploitation School '93 at Zaporozhie ferro-alloy plant. Ferro-silicon has a shape of spheres with dia 0.001 + 1 mm; volume weight varied 3.8 throught 5.1 g/cm^ depending on the fraction size. AU the sands except Sarmatian sediments were represented by FeSi fractions 0.25+0.001mm and volume mass y = 4.1 g/cm^. The Sarmatian sediments, respectively - 1+O.lmm and y =3.8 g/cm^. According to geołogical data the volume weight of the rocks is, in fact,equal,thus the volume mass scalę is: ^ = 2,41 Yh (6) i.e. the necessary condition of similarity constants is kept. So, due to the increase of the volume masses scalę we managed to bring up the strength characteristics of the equivalent 2.5 times and gave up the idea of using common sand and clay. The simulation scalę is 1:50. The rock layers are simulated down to Quarteriary sdiments with following overload. This is how the model preparation was seąuenced: 4 cm thick materiał was spread , leveled and compressed over the stand bottom, then it was further compacted with the special roli exerting 0.01 MPa pressure. Tłie first layer was covered with the crushed dried chalk to distinąuish between the "sand" and (he "coal". The second layer was conditioned in thermostat, the needed ąuantity of agglomerate and petrolatum beind heated up to 120" C. The mix having been stired, it was again placed into the thermostat for 40-50 min. The second layer formation consisted of seyeral operations: the working sole laying, the working positioning and the roof formation. The layers that followed were formed after the pattem of the Ist one and were separeted by the chalk. The 7th layer surfase was covered with the polyethelene film wit hthe weight over it. As a result the model was obtained which in 12-14 hrs was ready for experiments. This period of time was reąuired for the complete cooling of the "coal layer" and stabilization of all the deformations and strains which were due to appear in course of the model formation. The outbursts was simulated by driving the heading from the side of the stand front. The protective "coal" pack was broken and the crack formed via which the floating mass sprang. At the same time the progress of the outburst could be watched throught the model front wali. The heading having been filled with the "floating mass" to a certain degree, it was stopped and the process interrupted. The rocks shift obtained was taken, geometrical dimentions measured and the heading cleaned like it is done under real conditions. At a certain stage the outburst progressed which looked like an extra inflood of the "floating rock". The shift pattem then looked like the cone widenning. The most characteristic shift and outburst pattens are given in Fig . The data analysis proved; as a rule the protective pack break is not over the total area of the outcroop, but at the local point having dimension 10 x 15 cm (as for reality); the shift engages practically all the floating rocks.At the same time the "cone - pillar" is formed having the shift angles 82-85' at the initial stage of the outburst ,70-75" in progress. Initially, the heading is filled with nearly 30 m^ of floatings and thereafter - over 50-60 m^. The outburst being in progress, the zone of the protective pack break reaches as much 154 Tom II