Electromagnetic radiation signal monitoring and multi-fractal analysis during uniaxial compression of water-bearing sandstone

Abstract

Rockburst disasters seriously threaten the safety of deep coal mining. Electromagnetic radiation (EMR) is a powerful means of rockburst monitoring and early warning. However, the current related research often ignores the fact that the rock mass in engineering is frequently in a water-bearing state. Therefore, in this paper, the EMR signals of sandstone samples with different water contents were monitored under uniaxial compression. The experimental results showed that with the increase of water content, the EMR signals of sandstone weakened as well as the mechanical strength. Compared with dry samples, the total EMR energy and peak EMR energy of saturated samples decreased by 71.41% and 76.06% respectively. Moreover, higher moisture content would lead to lower dominant frequency and amplitude of EMR signals under various stress levels. Through multi-fractal analysis, it is found that with the rise of moisture content, the non-uniformity of signal (Δα) and the frequency diversity of minimum and maximum signals (Δf) decreased. These reflect some changes in the generation mechanism of EMR signal. The abrupt changes of Δα and Δf can be regarded as precursors of rock failure. The research results can provide guidance for the frequency band selection and precursor identification of rockburst monitored by EMR.