Оцінка тримкості литої смуги для охорони підготовчої гірничої виробки

The object of this study is the deformation processes in a protective structure of the preparatory working, maintained in the excavated space of the excavation area. The task addressed was ensuring the stability of the preparatory working in a deep coal mine to improve the safety of miners and coal mining. The assessment of the strength of the cast strip for the protection of preparatory workings in excavation areas has been substantiated. It was experimentally established that in the zone of active influence of mining pressure on the section 0<l<50 m behind the treatment face, there is an exponential dependence between the length of the working l (m) and the relative change in the volume dV of the protective structure. It characterizes the safe deformation resource of the cast strip. Within its limits, the process of gaining strength of the protective structure occurs. At dV<0.18 and the failure rate of the arched flexible support ω<0.2, the losses of the cross-sectional area of the working do not exceed 20 %. Under conditions when dV£0.22, the resistance of the protective structure increases, which makes it possible to limit the movement of lateral rocks on the contour of the working, ensuring its overall dimensions. In cases when dV>0.22, and 0.22<ω<0.68, the losses of the cross-sectional area are more than 40 %. At a distance of l>80 m behind the breakage face, the level of threat of roof collapses approaches a critical state, which is associated with an uncontrolled increase in lateral rock displacements due to the loss of strength of the cast strip. The cast strip performs the functions of a supporting structure only in a certain range of physical, mechanical, and deformation properties. The operational condition of the preparatory working is ensured within the deformation resource of the cast strip. After reaching the rated strength of the cast strip, its strength makes it possible to limit the movement of lateral rocks on the contour of the working and ensure its stability at a distance of l£80 m along the length of the excavation section