Investigation of the Centers of Endogenous Fires at the Rock Dumps of the Coal Enterprises

Abstract

The formed rock dumps of sections, mines and washing plants are composed of carbonaceous rocks and are capable of spontaneous combustion when the required amount of air is supplied. The conducted studies evaluated the efficiency of detecting a center of spontaneous combustion at the rock dumps of sections by measuring the temperature of rocks in the wells with a depth of 2.5 m, drilled at the distance of 20 m from each other, according to the current normative documents. For the landfill, a dump site with a long-existing center of spontaneous combustion was selected. The experiment showed the impossibility of drilling wells on the slopes of the dumps, as well as the need for casing the wells with pipes along the entire length. The temperature of rocks in the wells at a depth of 2.5 m varied from 69 to 773 °C. It was found that in the heated zone there are sharp temperature drops in the rocks, which cannot be detected with an interval between the measurement points equal to 20 m. With such a distance between the control wells, the places with a diameter of 1–10 m may remain undetected at the initial stage of spontaneous combustion. Measurements showed that in all the wells the rock temperature increases with depth. At the same time, the recommended well depth of 2.5 m does not allow determining the size of the heated zone deep into the rock dump. The upper layer of rocks above the center of spontaneous combustion exceeds the ambient temperature, so remote temperature measuring devices can be used to detect endogenous fires in the rock dumps. The use of thermal imagers installed on the unmanned aerial vehicles will significantly reduce the cost of detecting spontaneous combustion centers on the rock dumps and increase the efficiency of detecting fire centers not only on the dump sites, but on the slopes of the dump side and in other hard-to-reach places. Moreover, with a decrease in the atmospheric air temperature, the efficiency of remote thermal photography does not decrease. To clarify the parameters of the center of endogenous fires, it is advisable to use the temperature measurement of rocks with a contact thermometer at a depth of 0.5 m.