Materiały konferencyjne SEP 2023

2 Roadway districts in the coal mines are in particularly difficult conditions. This is due to technological features of their functioning. These roadways are bordered with the mining longwall. Therefore, after its passage, a cavity is formed in the walls of the roadway district. Replacement of the mined-out coal seam on the connection of the face with the roadway is carried out by constructing protection means - various structures made of wood (chocks, clustered chocks, rows of breaker supports, stacked walls, etc.) or concrete walls. Concrete protective walls feature greater rigidity, which positively influences on the state of the roadwaydistrict. Among them, concrete cast and packed walls have become the most widespread [2-5]. These types of protection means, in addition to improvement of the stress-strain state of the roadway districts and surrounding rocks, prevent the leakage of fresh air from the roadway into the mined-out space of the longwall and, conversely, the leakage of methane from the mined-out space into the roadway. That is, cast and packed walls are protective-insulating, which helps to improve ventilation of the mining area, increase permissible load on the longwall by the gas factor, and improve working conditions and safetyof miners. A peculiarity of technologies for constructing these types of protection means is the use of quick-hardening mixtures in a liquid state. Most often, the basis of these mixtures is cement with sand as filler and various additives to accelerate its hardening. Sometimes mixtures based on anhydride are used. 2. THE MAIN PART When a longwall has been passed, the undermined roof rocks of the coal seam are separated and load the protection means. In this case, rate of the load growth depends on the category of cavability of the coal seam roof and the speed of the longwall face advancing. The maximum loads on concrete wall are reached at the moment before the roof fall, that is, at maximum length of the cantilever of rocks hanging over the wall. Therefore, the harder are the roof rocks (the lower is the category of the roof cavability [6]), the longer they hang over the wall. This increases the maximum loads on the wall that can be achieved. And, conversely, with weak roof rocks, the maximum loads on the wall are smaller, due to the smaller dimensions of the cantilever of overhanging rocks. On the other hand, weak rocks are deformed faster, therefore, the rate of growth of loads on the wall increases. The weaker is the roof and the more intensive are the stoping operations, the faster the protection means are loaded. In the case of a delay in gaining strength by concrete relative to the increased loads on it, cracks occur and spread in the concrete, which leads to the loss of the load-bearing capacityof the protection means of the roadway. Therefore, when calculating the parameters of cast or packed walls, an important criterion is the correspondence of the rate of gaining strength by concrete to the mining and geological conditions of the location of the roadway district and technological parameters of the coal seam mining. This research is devoted to the solutionof this problem. The purpose of the research is to substantiate the correspondence of the intensity of the mixture hardening to the growth of loads on the protective-insulating wall over time with taking into account the speed of the longwall face advance. Based on the results of the performed work, the rational parameters of the mixture were substantiated, namely the intensity of growth of its uniaxial compressive strength over time. Samples of mixtures were tested in laboratory conditions according to standard requirements. In order to take into account the mine conditions of protective-insulating walls working, a physical simulation of the processes of their deformation and destruction under the action of rock pressure was carried out [2]. For calculating parameters of the protective-insulating walls, it is proposed to use the coefficients of the influence of mine conditions: the geometric structure of the wall k str , the unevenness of the relief of underworked and overworked rocks k w