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Rib spalling is one of the main factors restricting the safe and efficient production of the fully mechanized mining face in gangue-bearing coal seams, and the gangue has significant influence on the occurrence of rib spalling. In this study, the instability process and mechanical mechanism of rib spalling in gangue-bearing coal seams were studied, and the sensitivity of gangue parameters to rib spalling was analyzed. The simulation test of rib spalling under different gangue parameters was carried out by orthogonal tests. The width and depth of rib spalling were taken as evaluation indexes, and the influence of gangue parameters on the rib spalling was analyzed by variance analysis and significance tests. The results show that the failure process of rib spalling is characterized by the fracturing failure of the lower coal body, shear failure of the gangue layer, and the falling off of the upper coal body caused by the gravity; the gangue parameters (thickness, density, joint inclination, and internal friction angle) have an important influence on the sliding instability of the coal wall. In the sensitivity analysis, the influence of gangue parameters on the width of rib spalling is ordered as gangue density > joint inclination > gangue thickness > internal friction angle; the influence of gangue parameters on the depth of rib spalling is ordered as gangue density > joint inclination > internal friction angle > gangue thickness. Besides, the greater the gangue density, the less damage caused by stress concentration, and the lower the risk of rib spalling. [ABSTRACT FROM AUTHOR]

Volatile halogenated hydrocarbons (VHCs) attracted many attentions due to its toxicity and persistence in the environment. In this research, a novel in situ ecological restoration reactor was applied to the degradation of VHCs in polluted river water. The optimized working condition adaptation of the in situ restoration technique was evaluated through orthogonal tests. The experiments showed that when the water depth was 0.4 m, the HRT was 5 days, and the current velocity was 1 m/s, the optimal removal efficiency of VHCs in the reactor was achieved. And the removal rates of CHCl3, CCl4, C2HCl3, and C2Cl4 reached 70.27%, 70.59%, 67.74%, and 81.82%, respectively. The results showed that both HRT and water depth were significantly related to the removal efficiency of reactor. The physiological state of the plants was analyzed by fitting rapid light curve (RLC) model, which showed that the accumulation of VHCs inhibited the photosynthetic performance of plants. Moreover, the microbial community structures of fillers were tested by high-throughput sequencing, and the findings supported that the microbial community made a great response to adapt to the changes in environment of the reactor. The relative abundance of Rhodocyclaceae increased slightly, which hinted that it had good adaptability to VHCs in polluted river water. The research results confirmed that in situ ecological restoration reactor was a potential approach for removal VHCs in polluted river water. [ABSTRACT FROM AUTHOR]