The prospective coal-bearing areas of Donbas in Ukraine have been identified. Their development will increase the energy security of Ukraine. It has been suggested that the development of these areas will involve mining the coal seams in a weak roof and floor environment, which are characterized by low compressive strength, lower density and a tendency to plastic deformations. The stability has been assessed of the rocks outcrop on the contour of mine roadways for mines operating in these areas. It has been determined that roof rocks in most of these mines belong to a range of groups from very unstable to moderately stable, and the bottom rocks are, in most cases, prone to swelling. This complicates the intensive prospective areas mining with the use of advanced technologies, as well as secondary support for retained goaf-side gateroads with limited yielding property. The mines have been determined, for which this issue is relevant when mining the seams with further increase in the depth. The mechanism of displacement in the secondary supports and has been exemplified and studied using the numerical method. The obtained results allowed us to substantiate the necessity of developing new technical solutions for the protection of gateroads under conditions of prospective Donbas areas.
Purpose. Evaluate the stability of lateral rocks in the coal massif containing the workings, with introduce count the deformation characteristics of security structures. Methods. To achieve this goal, laboratory studies of the deformation characteristics of security structures located between the simulated roof and the sole of the coal seam, which were subjected to uniaxial compression. Results. It is proved that the deformation characteristics of protective structures affect the stability of lateral rocks in the coal massif containing the workings. The nature of the deformation of security structures under the action of external forces is determined by their rigidity. All other things being equal, when the roof and sole rocks have a constant bending stiffness, their stability depends on the rigidity of the supporting structures and the direction of the load applied in the tangential (wooden cogs, rolling cogs) or radial (riser bushes) direction. For the simulated security structures with an increase in the compressive load, a simultaneous linear increase in their stiffness and deformation modulus is recorded. Moreover, for wooden pillars, when the load is applied across the fibers, the clamped struts of wooden structures are compacted, as a result of which the convergence of the lateral rocks is limited. There is no such pattern for rigid structures in the form of bushes made of wooden risers. After the loss of stability of the protective structure, the modulus of deformation decreases, which is accompanied by an increase in the convergence of the side rocks to the complete destruction of the structure. It is recommended to abandon the rigid and at the same time fragile protective structures designed to support the side rocks. Scientific novelty. The stability of the roof in the carbonaceous massif containing the workings is estimated by the maximum relative deformation of the supporting structures as a result of uniaxial compression using a coefficient characterizing the ratio of the rigidity of the working protective structure and bending stiffness of the side rocks. Practical significance. To ensure the stability of the side rocks in the coal massif and the operational condition of the workings adjacent to the clearing face at the extraction site of the coal mine, it is necessary to focus on the use of flexible structures.
Purpose. To increase the effectiveness of measures to reduce injuries and create safe working conditions for miners in a deep coal mine with steeply inclined coal seams, assess the impact of deformation properties stiffness of secondary support structures of mine gateroads on their stability in the coal-rock strata according to the length of the extraction panel. Methods. To achieve this purpose, the results of in-mine instrumental observations of the stability of haulage roadways under different supporting methods were analyzed, considering the deformation properties of secondary support structures and features of geomechanical processes in the surrounding coal-rock strata during unloading. Results. The conditions for maintaining the mine gateroads within the extraction panel during the methods of supporting practised at the mine were estimated by the magnitude of the convergence of the roof and floor strata on the contour of the haulage roadway and its derivatives. It is determined that in the zone of influence of coal extraction, in the process of deformation of coal pillars or vertical timber sets up to 16-22%, there is a loss of their stability, an increase in the load on the secondary support structure, the intensification of the increase in roof displacements over 0.08 m with a convergence rate of 4.5-5.6 mm/day. In the process of deformation of 4-point chock by 65%, the rate of convergence at the initial stage (30% deformation) increases to 5.1 mm/day, with an average increase in roof displacements to 0.05 m, and then gradually decreases over time, which favourably affects the stability of roof and floor strata and roadways. Reduction of the haulage roadway cross-section when it is supported by coal pillars or vertical timber sets on 45-50% is the result of the destruction of secondary support structures when the rate of convergence of the roof and floor strata along the extraction area is not limited. When supporting the haulage roadway with a 4-point chock reduction of the roadway cross-section by 30% is due to the compression of the secondary support structures, which helps to limit the growth of roof displacements and reduce the rate of convergence of the roof and floor strata behind the working face. Novelty. The estimation of the haulage roadways stability on the steeply inclined coal seams according to the length of the extraction panel is based on the use of regularities of deformation properties of secondary supporting structures of mine gateroads and geomechanical processes in the coal-rock strata when the change in the rate of convergence of the roof and floor strata on the contour of roadways is considered in the zone of influence of coal extraction works. Practical significance. To prevent the collapse of the roof and floor strata in the extraction area of the deep coal mines with steeply inclined coal seams, it is necessary to use yielding secondary support structures of mine gateroads.
The purpose of the article. Studying deformation characteristics of protective structures under the influence of external loads used to maintain lateral rocks in the coal massif behind the production face. Methods. To achieve this goal, laboratory studies of the deformation characteristics of security structures under uniaxial compression were performed. Results. As a result of the research it has been established that at uniaxial compression of wooden protective constructions in the form of rolling fires from sleepers or bushes from risers, change of their rigidity is caused both by differences in properties of wood at action of external force along or across fibres, and design features. In cases where a constant compressive force is applied to the experimental sample across the fibres (rolling fires from sleepers), the change in stiffness is quadratic and reaches minimum values when the deformation of the model by 30-35%, and with a further increase in deformation to 50% stiffness increases. This indicates an increase in the resistance of rolling fires to external loads after their compression, without losing the strength of the structure. Under the action of compressive force along the fibres (bushes of risers), the stiffness of the experimental samples increases until the moment of destruction, when there is a loss of strength of the structure. The change in the stiffness of embedded arrays of crushed rock, if possible, their lateral expansion occurs due to the compaction of embedded material, i.e. recomposition of particles of crushed rock of different fractions in the total volume. Novelty. The nature of the deformation of security structures considered as prefabricated structures can be described by the change in the specific potential deformation energy spent on changing the shape and/or volume of the protective structures. Practical meaning. To ensure the stability of the side rocks in the coal massif containing the workings, it is necessary to focus on the use of flexible protection structures located above the retractable roadway.
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