Fundamental studies on locating spontaneous combustion of coal by the self-potential method

Self-potential anomalies can be generated by a fluid pressure gradient, by a temperature gradient or by a chemical gradient. On the basis of this principle, the authors propose a self-potential method to locate the fire source of spontaneous combustion of coal, and have performed experiments using models to examine the possibility of this method. The experiments are divided into two groups. The first is to investigate the influence of the heater temperature on potential distribution; the other is to investigate the influence of the heating time. The results of these experiments have shown that the potentials generated by the heat are of measurable magnitude and they become larger with increasing heating time and/or heater power. Moreover, the results of all the experiments have a common feature, namely a potential distribution is always generated corresponding to the conditions of a heat source and there is a centre of potential distribution above the heat source. It is concluded that it is possible, at least at the experimental scale, to locate the heal source by the self-potential method.