Disaster-causing mechanism of roof 'toppling-slumping' failure in a horizontal sublevel top-coal caving face

摘要

To reveal the disaster-causing mechanism of roof collapse in horizontal sublevel top-coal caving faces for steeply inclined thick seams, a mechanical model is proposed based on the engineering background of the Jiangcang #1 coal mine in China. It is indicated that there is a "toppling-slumping" roof failure mode in horizontal sublevel top-coal caving faces, and the impact load generated by roof topping and slumping is the main cause of disasters. The impact load increased with the increase in impact height and the decrease in top-coal fragmentation degree. The experimental results of granular top-coal impact experiments showed that the impact load decreases with the increase in top-coal laying thickness. The top-coal layer acts as a cushioning in the process of roof collapse, and the cushioning correction coefficient is between 0.40 and 0.65. The cushioning correction coefficient increases as the impact height, top-coal fragmentation degree and laying thickness increase. A method is proposed to calculate the impact load in this study, and it is validated by field measurements.