Justification for the parameters of safe undermining of the rocks the soil working carried out by the outburst sandstones

Abstract

Abstract. The authors provide a justification of the parameters for safe bottom rock ripping in the working driven by drilling and blasting operations through the prone-to-outburst sandstones and by forming an unloaded (with no outburst hazard) zone that is created from the previously driven working. For the conditions of the Pokrovskoe Mine of the 1st northern belt road No. 11, a nomogram of numerical values of the stresses is given. From the reduced calculations, radius of the unloaded, with no outburst hazard zone in the vertical and horizontal planes around the experimental entry of the 1st northern belt road in the block No. 11 was obtained with taking into account an anisotropy, depth of mining operations and deformation rate. The analysis of the material set out in this paper allows to conclude that the unloading effect of the mined working predetermines the safety of mining operations carried out through the prone-to-outburst sandstone, and drilling and blasting operations can be carried out within the calculated protected area in the same way as in zone with no outburst hazard. During the research, the patterns of unloading effects of the working were established, as well as dependences for determining boundaries of the unloading zones in specific mining geological conditions, which should be determined in each working for conducting blasting operations. The above justifications are reduced to the fact that the drilling and blasting operations for ripping the prone-to-outburst bottom rocks in the working floor are carried out in already unloaded (i.e., with no outburst hazards) zone, which is created from the same working previously driven. This implies that drilling and blasting operations will be carried out in the sandstone with no outburst hazard. This makes it possible to conduct the drilling and blasting operations without performing any predictions and with no shaking blasting, which will reduce time cost and labor intensity providing significant savings of material and technical means. The further research is needed, which should establish the interdependence between the size of the unloaded (with no outburst hazard) zone around the working in the sandstones and depth of the mining operations, section of the working and time period passed after this working has been driven. Keywords: working, ripping, prone-to-outburst sandstone, drilling and blasting operations, safety.