Experimental study on evolution law for particle breakage during coal and gas outburst

Abstract

Coal and gas outburst is a dynamic phenomenon in underground mining engineering that is often accompanied by the throwing and breakage of large amounts of coal. To study the crushing effect and its evolution during outbursts, coal samples with different initial particle sizes were evaluated using a coal and gas outburst testing device. Three basic particle sizes, 5-10 mesh, 10-40 mesh, and 40-80 mesh, as well as some mixed particle size coal samples were used in tests. The coal particles were pre-compacted at a pressure of 4 MPa before the tests. The vertical ground stress (4 MPa) and the horizontal ground stress (2.4 MPa) were initially simulated by the hydraulic system and maintained throughout. During the tests, the samples were first placed in a vacuum for 3 h, and the coal was filled with gas (CH 4) for an adsorption time of approximately 5 h. Finally, the gas valve was shut off and the coal and gas outburst was induced by quickly opening the outburst hole. The coal particles that were thrown out by the outburst test device were collected and screened based on the particle size. The results show the following. (1) Smaller particle sizes have a worse crushing effect than larger sizes. Furthermore, the well-graded coal particles are weakly broken during the outburst process. (2) As the number of repeated tests increases, the relative breakage index grows; however, the increment of growth decreases after each test, showing that further fragmentation becomes increasingly difficult.

Influence of Deformation and Instability of Borehole on Gas Extraction in Deep Mining Soft Coal Seam

“…Many scholars both at home and abroad have studied the deformation and instability disciplines of coal rocks around the extraction boreholes [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. Tezuka and Niitsuma [6] proposed some borehole stability models and conducted theoretical analysis on the stability of borehole wall based on such models.…”

Influence of combination forms of intact sub-layer and tectonically deformed sub-layer of coal on the gas drainage performance of boreholes: a numerical study

“…Tectonically deformed coal is the coal whose chemical and mechanical properties have been dramatically altered by tectonic movements (Cheng and Pan 2020;Ju et al 2014). Different from intact coal, it is usually characterized by a higher gas content, a higher gas desorption rate, a lower mechanical strength and a lower permeability (Black 2019;Wang et al 2015;Wu et al 2019;Zhao et al 2015Zhao et al , 2019Zhi and Elsworth 2016). Tectonically deformed coal is widely distributed in China, specifically, in the west of Henan Province, the south of Shanxi Province and the middle and north of Anhui Province, etc., where intense tectonic movements occurred during coal formation.…”

Near-source characteristics of two-phase gas–solid outbursts in roadways

“…These have defined the principal characteristics of shock wave propagation in roadways (Miao et al 2013) including the influence of the gas phase (Wang et al 2012(Wang et al , 2011Zhou and Wang 2017). The outburst shock wave is known to result from the mobilization of a large amount of pulverized coal carried by gas (Wu et al 2019;Xue et al 2015). However, none of the prior studies considered the interaction between the pulverized coal and gas flow.…”