Evaluation of the ground forest combustible material ability to ignition and maintaining the combustion process on its surface
Purpose. The article is devoted to the study of the processes of ignition and combustion of ground forest combustible material with the aim of further assessing the possibility of occurrence and spread of forest fires. The object of the research is ground forest combustible material in form of moss, fir-spruce pine needles, spruce needles, bark, foliage and small branches. The subject of the research is the process of ignition and combustion of ground forest combustible material. Methods. The method of experimental study of the processes of ignition and combustion of ground forest combustible material was used; the analysis of the obtained results and their comparison with the data of a natural experiment were carried out. Findings. The experimental data on the rate of flame spread on the layer of ground forest combustible material, the height of the flame front and the thermal load required to maintain the combustion process was obtained, which are important for the theory of forest fires. The scientific novelty of the obtained results is to establish regularity of occurrence and spread of forest fires. Application field of research. Units and subunits for emergences can use the obtained results to predict the conditions of occurrence and spread of forest fires. Conclusions. The research technique and the results of experimental investigations of the processes of ignition and combustion of ground forest combustible material are presented. The values of the rate of flame spread on the layer of moss, pine needles, spruce needles, bark, foliage and small branches and the values of the height of the flame front and the thermal load required to maintain the combustion process were obtained. It was established that the main conductor of ground burning in the forest is moss, the rate of flame spread over its surface reaches 3,13 m/min. Materials that maintain the flame spreading process are moss, pine needles and foliage. Spruce needles, bark and small branches do not form a flame front sufficient to support the combustion process. For these forest combustible materials the heat load required to maintain the combustion process should be more than 5,2 kW/m<sup>2</sup>, 2 kW/m<sup>2</sup> and 1,1 kW/m<sup>2</sup>, respectively.