Experimental Study on Influence of Borehole Arrangement on Energy Conversion and Acoustic Characteristics of Coal-Like Material Sample

Chuanbo Hao,Gang Liu,Fukun Xiao,Zhiyuan Hou

doi:10.1155/2020/4790587

Abstract

This paper examines the effects of borehole arrangement on the failure process of coal-like materials based on its energy conversion and acoustic characteristics from the perspectives of energy, AE energy, AE spectrum, and frequency band. Findings from the study revealed that the presence of borehole can significantly reduce the conversion ratio and growth rate of elastic energy during the loading of coal-like material sample and delay the release of internal energy of the sample. Also, it can reduce the frequency band energy of the main frequency of acoustic emission signal but has little effect on the size and richness of the peak frequency of acoustic emission signal. The practice that makes drilling diameter and depth increase stepwise can minimize the elastic energy conversion ratio, the growth rate, and the main frequency band energy of acoustic emission signal of coal-like material sample and postpone the internal energy release of the sample to the greatest extent, so as to enrich the richness of the secondary frequency of acoustic emission signal. The results of this study have certain guiding significance for the layout of pressure relief boreholes in the production process of coal mines.

Highlights

Increment in mining depths results in an increase in the crustal stress of the coal body, making the occurrence of rock burst a restricting factor in the safe and efficient production of coal in China [1, 2]
To study the speed at which the elastic strain energy increases in the coallike material sample, we introduce a new variable, the elastic strain energy growth rate Ws’, which is calculated as [25]
This paper studied the effect of structural defect on the internal energy conversion of coal from the perspective of the growth in elastic energy rate

Summary

Introduction

Increment in mining depths results in an increase in the crustal stress of the coal body, making the occurrence of rock burst a restricting factor in the safe and efficient production of coal in China [1, 2]. E previously mentioned scholars have carried out theoretical research, numerical calculations, and laboratory experiments mainly on the mechanism and parameter optimization of pressure relief drilling, but there are few experiments on the combination process of pressure relief borehole from the perspective of energy conversion process and acoustic emission characteristics. For this reason, from the perspective of the energy accumulation and dissipation in coal mine rock burst, this paper discusses the effect of pressure relief drilling on energy conversion and dissipation of coal-like materials and the effect of drilling arrangement on pressure relief effect. Based on the first law of thermodynamics, from the perspectives of energy conversion, AE energy, AE frequency spectrum, and AE frequency band energy, the effects of drilling arrangement on the energy conversion and acoustic characteristics of coal-like materials are discussed and analyzed

Test Scheme and Condition

Findings

Discussion

Conclusion