Laboratory Study Phenomenon of Coal and Gas Outburst Based on a Mid-scale Simulation System

Shoutao Hu,Junqing Meng,Baisheng Nie,Yankun Ma

doi:10.1038/s41598-019-51243-4

Shoutao Hu, Junqing Meng + Show 2 more

Open Access

https://doi.org/10.1038/s41598-019-51243-4

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Abstract

Outburst simulation experiments facilitate understanding coal and gas outburst in underground mining. With the help of the mid-scale simulation system, a model based on similitude principle, coal seam sandwiched by roof and floor, was constructed to conduct an outburst experiment. It had a three-dimensional size of 1500 mm × 600 mm × 1000 mm with 0.5 MPa gas pressure. The experimental procedures include specimen preparation, moulding, sealing, gas charging and adsorption, and completion. The outburst process was investigated by analyzing the gas pressure variation, temperature variation, outburst propagation velocity, particle size of outburst coal and energy transformation. During the experiment, each gas charging was accompanied with gas pressure or temperature fluctuation because of coal behavior of gas adsorption-desorption. The outburst propagation velocity was 17.2 m/s, obtained by a mass-weighted calculation of velocities of outburst coal. The small-size coal particles have a higher desorption rate and tend to participate in outburst process. According to energy conservation law, the energy forms of the outburst included elastic strain energy (Ee), gas expansion energy (Ep), internal energy of coal (ΔU), breakage work (W1), throwing out work (W2) and gas-flow loss energy (ΔE), and each was calculated respectively. Gas potential energy, including gas expansion energy and internal energy of coal, registered a larger percent and was far greater than the strain energy. And it can be the main factor influencing the occurrence of low-threshold outburst. The experimental system provides a feasible way to study the initiation and evolution of coal and gas outbursts.

Highlights

In the process of coal exploitation, coal and gas outburst is a dynamic disaster without any conspicuous precursor
An experimental apparatus was constructed by Tu et al.[5] to simulate the outburst related to gas-rich areas, and the tension effect of gas on coal was observed
A Mid-scale simulation system for outburst experiment developed by Nie et al.[16] can accommodate specimen with dimensions of 1500 mm × 600 mm × 1000 mm, simulating the coal seam sandwiched by roof and floor and local stress concentration ahead of work face

Summary

Introduction

In the process of coal exploitation, coal and gas outburst (hereinafter referred to as “outburst”) is a dynamic disaster without any conspicuous precursor. Wang et al.[11] analyzed the contributions of in situ stress and gas pressure to the outburst process, using the test system of one-dimensional outburst. Yin et al.[12] developed a comprehensive simulation device with large-sized coal samples It satisfied the outburst experiments with non-uniform distribution of loadings, a certain size of outburst port and 2 MPa gas pressure[12,13]. Based on the Mid-scale simulation system, this paper conducted the investigation on the outburst occurrence and propagation by analyzing the variation of gas pressure and temperature, velocity attenuation of outburst coal and distribution of pulverized coal. This work may help understanding of the outburst mechanism and provide some implications on outburst prevention in underground mining

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