EXPERIMENTAL TESTS OF CONCRETE MEANS OF PROTECTION FOR COAL MINES DISTRICT ROADWAYS

Abstract

The current paper is devoted to experimental tests of working protection means in the construction of which concrete in liquid state is used. Such means of protection are most vulnerable to irreversible deformations during the period of their hardening, which coincides with the period of intensive growth of pressure on them from the side of the rock massif. Studies have shown that the pressure of fake rocks on the working protection means depends significantly on the depth of its location and the category of collapse of the roof of the coal seam. The maximum pressure is reached at the moment before the collapse of the roof, that is, at the maximum values of the length of the console of fake rocks, which hangs over the produced longwall space and rests on the working protection means. It was established that the pressure of the fake roof of the coal seam and the relative vertical deformation of the district roadway protection means increase according to the logarithmic dependence of the distance to the longwall outcrop and the time of concrete hardening. With heavy and medium roof collapse, these processes are divided into two stages: in the first stage (the length of which corresponds to the step of the roof collapse), as the longwall moves, the pressure increases intensively, at the moment of collapse it drops by 15-20%, and in the second stage again increases, but 6-8 times more slowly than in the first one, and, provided the relative vertical deformation of the protective device stabilises, passes into a stable mode. With an easily collapsed roof, the step of its collapse does not have a significant effect on the growth and stabilisation of the stress-deformed state of the protective device. The mechanism was revealed and the regularities of loading and deformation of district roadway protection means from a quick-setting mixture depending on the time of its hardening and the distance to the outcrop of longwall, taking into account the category of stability of the roof of the coal seam, were established. Implementation of recommendations for the parameters and technology of the construction of a guard-isolation wall in the conditions of the "Chervonogradska" and "Lisova" mines of the SE "Lvivvugilya" made it possible to reduce the costs of cement-mineral mixture by 27% and save the belt roadways No. 562 and No. 166 for reuse in the production as ventilation during the working out of the adjacent trench column.