Determination of the sensitivity index and its critical value for outburst risk prediction: A case study in Fuxiang mine, China

Fakai Wang,Yunpei Liang,Lei Li,Xuelong Li,Zhongguang Sun

doi:10.1177/0263617420963735

Abstract

Gas occurrence in coal seams shows zonation, and the outburst risk prediction index is significantly affected by coal seam gas. For different coal mine, the sensitivity of prediction index of outburst risk is inconsistent, and the different area of the same coal mine can present different sensitivities to the same index. In this study, we measured the industrial analysis of coals and determined the degree of outburst risk of each coal seam using coal samples with the particle size of 1 ∼ 3 mm. The relationships between the equilibrium gas pressure and gas desorption index of drill cuttings, between the desorption index of drill cuttings and the adsorption pressure, and between the critical values of the indexes of drill cuttings were also analyzed using the fuzzy clustering method. Based on the analysis of the particle size distribution of coal samples, the influence of grain size on the critical value of the drill cuttings desorption index was studied. The results showed that the critical values of the desorption index of drill cuttings were different under different adsorption equilibrium gas pressures, and those critical values increased with increasing adsorption equilibrium gas pressure. The desorption index of drill cuttings and adsorption equilibrium gas pressure had a linear relationship, and the higher the degree of outburst risk was, the greater the slope of the fitting function and the smaller the intercept; under the same gas pressure of adsorption equilibrium, there was a linear relationship between Δh2 and K1, and the higher the outburst risk of coal seam was, the smaller the slope of the fitting function and the greater the intercept. The drill cuttings desorption index Δh2 was more sensitive than the index K1. Under the same test pressure, the smaller the particle size of the coal samples was, the greater the value of desorption index of drill cuttings and the higher the outburst risk of coal seam. The research results have significant theoretical importance and practical value for the prediction and prevention of coal and gas outbursts in coal mines with similar occurrence conditions of coal seams.

Highlights

Coal is the main nonrenewable energy resource consumed in China
The desorption index of drill cuttings had the characteristics of short measuring time and accurate results, and it was the key parameter for predicting coal and gas outburst risk in the mining face
The results show that under the same pressure conditions, the smaller the particle size of coal samples were, the greater the desorption index value of drill cuttings (Beamish and Crosdale, 1998; Zhou et al, 2020)

Summary

Introduction

Coal is the main nonrenewable energy resource consumed in China. Due to the advancement of coal mining in recent years, mining depths have reached 1,300 m and are estimated to reach 1,500 m within the 20 years (Fan et al, 2019a; Hasiah et al, 2013; Levine, 1986). Coal and gas outburst accidents occur frequently during the process of uncovering coal in deep mines (Fan et al, 2019c; Feng et al, 2020; Tian et al, 2016; Wang et al, 2018). The accident occurred at a point 956 m down the main shaft, where an operation to uncover coal was located. It could be regarded as a typical outburst accident while uncovering cross-cut coal in a deep mine. This is because inaccurate validation of the outburst prevention effect leads to outburst accidents. The accurate validation of the outburst prevention effect is a necessary method to ensure the safety of deep coal mine operations

Methods

Results

Discussion

Conclusion