Abstract
The compound dynamic disaster of coal and gas outbursts and rockburst is a typical hazard jeopardizing the mining of the high gas content coal seam under a hard roof condition. In this study, the hard roof’s mechanism inducing this hazard is analyzed. Physical analog modeling experiments and in situ monitoring of mining-induced stress were performed during coal seam mining under a hard roof condition. The pattern of hard roof breakage effect on the stress-fissure field evolution was revealed. The elastic energy was released and propagated on both sides immediately after the hard roof breaking, leading to energy accumulation. Meanwhile, expansive roof collapse resulted in the intense weighting of the working face and rockburst. Thus, the coal and gas outburst occurred under the joint action of the impact energy generated by breaking the hard roof and gas expansion energy. In other words, the compound dynamic disaster happened. Synergistic stereoextraction integrating cross-seam drilling and along-seam drilling was combined with deep hole advanced presplitting blasting technology to cope with the compound dynamic disaster in the high gas coal seam under a hard roof condition.
Highlights
Rockburst and coal and gas outbursts are the most severe dynamic disasters occurring in coal mining
In China, coal seams are usually featured by complex geological conditions and faced with the challenge of severe coal and gas outbursts and rockburst disasters [1]
There are some common features between the coal and gas outburst and rockburst, and they cannot be plausibly explained by the conventional theory of coal and gas outburst or rockburst [4]
Summary
Rockburst and coal and gas outbursts are the most severe dynamic disasters occurring in coal mining. The compound dynamic disaster in the coal mines results from the joint action of high ground stress in deep positions, high gas pressure [6], hard roof, low-permeability coal bodies, and other engineering [7] and geological factors. The primary mechanism, by which a hard roof induces rockburst, is related to the stress concentration due to a hanging roof and coal and rock failure caused by shock bump under roof breaking Such failure can directly lead to rockburst and other types of disasters, such as water bursting in mine, coal and gas outburst, and roof caving [14,15,16]. To reveal the compound dynamic disaster’s occurrence mechanism, we need to study the stress evolution and the deformation and failure features of the surrounding rocks under a hard roof condition. The hard roof’s stress distribution and deformation features upon breaking and the hard roof mechanism inducing the compound dynamic disaster were analyzed in detail
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