Mechanism of Water and Sand Inrush Incident during Deep Buried Coal Seam Mining in Western China
Dong, Shuning (1,2); Guo, Xiaoming (1,2); Wang, Hao (1,2)
1: Xi’an Research Institute of China Coal Technology and Engineering Group Corp, China, People's Republic of; 2: Shaanxi Key Lab of Mine Water Hazard Prevention and Control，Xi’an，China
The water and sand inrush of the roof is showing water and sand flowing into underground working space, which caused considerable economic damage. It is common in shallow coal seam mining, however, a severe water and sand inrush of the roof happened in a deep buried working face of Zhaojin coal mine, Xunyao mining area, proposing a new type roof water hazard of deep buried coal seam mining.
In order to solve this problem, we investigated water source, material source and power source of the accident to study the formation mechanism of the water hazard in Zhaojin coal mine. Moreover, we established the water source identification model considering the evolution of water chemical composition by using hydrochemical, organic compounds in water, and rock dissolution test. This model can be used to determine that the source of inrush water (Cretaceous or Jurassic sandstone aquifers). In addition, we conducted underground drilling, rock mechanical, SEM, and X-ray diffraction test to analyze the source and original structural characteristics of the inrush sand. Furthermore, the breaking regular of the overburden in the soft roof of the coal seam was studied through analyzing and calculating discrete element numerical.
The results showed that the water of the Cretaceous sandstone aquifer flowed into the roof mudstone of the coal seam, which was easy to be muddy-soaked after touching water, resulting in the roof lost stability, then leading to water and sand inrush. Compared to water and sand inrush happening in shallow coal seam mining, the formation mechanism in deep coal seam mining is different: water and sand were separated rather than mixed together; and the incident were caused by mine pressure instead of water pressure.
The results explained the formation mechanism of water and sand inrush in deep coal seam mining. Also, this study provides further evidence for the risk assessment and the control of water and sand inrush in the deep Jurassic coal seam in western China.