Piezoelectric Effect and Ignition Characteristics of Coal Mine Gob Roof Collapse

Existing studies of coal self-ignition and impact frictional sparks do not provide valid support for the analysis of ignition sources in all cases of methane explosions in the gob. In this paper, the explosion in the gob of the Renlou coal mine is used to investigate the piezoelectric effect and ignition characteristics of roof collapse in identifying a new ignition source of gas explosion. Experimental and theoretical analyses conclude that the piezoelectric effect is produced by quartz, which is the main constituent of the roof sandstone. During the loading process, the piezoelectric effect and compressive strength are key factors in the gathering of free charges on rock tips. During rupture, the rock tip retains a large number of charges, forming a point-surface effect, which triggers an electron avalanche accompanied by an orange-yellow spark lasting over 22 ms, far exceeding the ionization energy and ignition induction period of methane-air mixtures. The piezoelectric effect and compressive strength of the rock cause the generation of electrical sparks, which is the ignition source of the explosion in the gob of Renlou mine II7322.

Automated summary

Existing studies on coal self-ignition and impact frictional sparks do not fully support the analysis of ignition sources in all cases of methane explosions in the gob. This paper investigates the piezoelectric effect and ignition characteristics of roof collapse in the Renlou coal mine to identify a new ignition source of gas explosion. The experimental and theoretical analyses reveal that the piezoelectric effect and compressive strength of the rock are key factors in generating electrical sparks, which serve as the ignition source in the explosion at the Renlou mine II7322.