Search

The mining in seams with a high methane content by means of a longwall system, under conditions of high extraction concentration, results in exceeding methane concentrations allowed by the regulations at workings of the longwall environment, with the effect of mining machines' standstill periods. The paper is a part of a study supporting the development of a system for shearing cutting speed control at the longwall, which should substantially reduce the production standstills due to exceeded limits and switching off the supply of electric equipment. Such a control system may be appropriate for longwalls ventilated using "Y" and "short Y" methods. Efficient Computer simulations of the 3D airflow and methane propagation may assist the design and initial evaluation of the control system performance. First chapters present studies that are necessary for a proper formulation of the properties of the longwall model. Synthetic analysis of production during the period of longwall operation allowed one to choose the input assumptions to carry out ventilation-methane computations in a CFD numerical model of longwall Z-11. This study is followed by a description of the model that is used for a case study, considering three variants of the shearer position. Finally, initial simulation results and directions of further studies are discussed. [ABSTRACT FROM AUTHOR]

The use of computer techniques at the design stage of industrial facilities is essential in modern times. The ability to shorten the time required to develop a project and assess the safety of the use of assumptions, often enables the reduction of the costs incurred in the future. The possibility to skip expensive prototype tests by using 3D prototyping is why it is currently the prevailing model in the design of industrial facilities, including in the mining industry. In the case of a longwall working, its stability requires the maintenance of the geometric continuity of floor rocks in cooperation with a powered roof support. The paper investigates the problem of longwall working stability under the influence of roof properties, coal properties, shield loading and the roof-floor interaction. The longwall working stability is represented by an index, factor of safety (FOS), and is correlated with a previously proposed roof capacity index ‘g‘. The topic of the paper does address an issue of potential interest. The assessment of the stability of the roof in longwalls was based on the numerical analysis of the factor of safety (FOS), using the Mohr-Coulomb stress criterion. The Mohr-Coulomb stress criterion enables the prediction of the occurrence of failures when the connection of the maximum tensile principal stress σ1 and the minimum compressive principal stress σ3 exceed relevant stress limits. The criterion is used for materials which indicates distinct tensile and compressive characteristics. The numerical method presented in the paper can be utilized in evaluating the mining natural hazards through predicting the parameters, which determine the roof maintenance in the longwall working. One of the purposes of the numerical analysis was to draw attention to the possibilities that are currently created by specialized software as an important element accompanying the modern design process, which forms part of intelligent underground mining 4.0. [ABSTRACT FROM AUTHOR]