Studying the effect of coal strength parameters on coal and gas outburst: a case study of Tabas coal mine

Abstract

Coal has been used for centuries as a energy source, and it remains a vital fuel for electricity generation in many countries. However, the risks of coal mining are high, and outbursts and gas emissions are two significant hazards associated with underground coal mining. Coal and gas outbursts are sudden and violent ejections of coal, gas, and rock from the working face of an underground coal mine. They occur when high gas levels, such as methane, accumulate in the coal seam and are released rapidly due to the stress and pressure caused by mining activities. Numerical simulation is one of the most powerful methods to study this complex phenomenon. The purpose of this article is to investigate the effect of coal strength parameters on the occurrence of the desired phenomenon in underground coal mines using the finite element numerical method. For the study, the sub-tunnel of the E4 workshop of the Parvade 1 Mine of Tabas, which is located at a depth of 472 meters from the ground, was investigated in the Phase2 simulation software and the possibility of an outburst in this layer assuming the existence of a pocket with a pressure of 0.6 MPa and crushed rock. The unstable failure index has been used to determine outburst-prone areas. In general, the application of UFI is to detect areas prone to brittle failure in phenomena such as Spalling, Rockburt, and Outburst. When this index is greater than 1, there is a possibility of this phenomenon because there is excess energy in the rock. According to the results of this research, strength parameters such as cohesion, angle of internal friction, and modulus of elasticity have a significant effect on the severity of outburst, at the same time the probability of this phenomenon is estimated independently of the tensile strength of coal. Considering that the UFI index used confirmed the results of previous researchers about this phenomenon, it can help predict this phenomenon. For the first time, this criterion is written based on energy components instead of stress and was able to show the effect of different parameters on outbursts.