Integral criterion of coal seam breakability
Abstract
The integral index of coal breakability is currently accepted as its cuttability which is a weighted mean value of cuttability of coal, dirt bands and hard mineral inclusions but it is weakly reflective of presence of hard mineral inclusions and hard dirt bands that to a great extent condition dynamic characteristics of coal cutting as well as reliability and productiveness of coal cutter-loaders. Ignoring properties of inhomogeneities in coal results in considerably inaccurate choice of coal cutting machine performance, especially in complex structure seams. In connection with this, a problem was formulated such that its solution would, on the one hand, allow estimating coal cutting machine conditions not by a set of characteristics but by an integral criterion perceptive of hard inhomogeneities in coal and, on the other hand, permit using this index in calculating performance and productivity of coal cutter-loaders and production data of coal faces and coal mines. The article describes studies into strength characteristics and geological structure of coal seams (cuttability of coal, interbeds and hard inclusions, specific content of hard inclusions per coal seams). By the results of the studies and based on the physical views on influence exerted by these characteristics on serviceability and life of cutting tools, the authors put forward an integral criterion of coal breakability—equivalent cuttability index Аe. In the capacity of a reliability criterion for cutting tool, the authors assume failure rate—the value that is inverse to basic overhaul time. The practical importance of Аe is its ability to estimate operating conditions of a cutter–loader not with a set of characteristics but with an integral critertion, considering presence of hard heterogeneities in coal, first, and second, Аe is applcable in calculation algorithms for parameters of cutter–loaders, their output, serviceability, basic overhaul time and, on the whole, performance of production faces and coal mines.