Research On The Influence Of Mining Width On Controlling Mining Subsidence With Grouting Backfill Into Isolated Areas Within Overburden

The technique of grout injection into bed separation of overburden that have the ability to protect surface buildings during longwall mining under populated areas without the removal are widely used in Huai Bei mining areas for it can achieve high extraction rate while producing low capital cost and little interference to coal mining. The thought of this technique was designing subcritical panel width and leaving stable pillars between adjacent panels to reduce surface subsidence from the source. On this basis, the support area that is formed by isolated grout injection(IGI) during mining, in conjunction with the pillars reduces surface subsidence so as to meet the requirements for mining under populated areas without the removal. The width of working face was a key factor in the process of the implementation of this technique. For coal mines, the width of working face was related to coal production and practical benefits. The cost of coal mining per ton would decrease with a wider working face, and the benefits would go up at the same time. However, it would increase the difficulty for subsidence control. On the contrary, although we can meet the requirements of subsidence control with a narrow working face, the benefits of enterprise would be poor. And we can not achieve grout injection into overburden of isolated longwall panels. So the study of the influence of working width in subsidence control with IGI is significant.This thesis made full use of analogy number as the basic approach combined with actual data to analyze the influence of working width in subsidence control with IGI. The real basis have showing that if we make the ratio of filling volume and grouting layer the same, the increasing of working width will influence the surface subsidence. With wider working face, the surface subsidence was more easily influenced by the ratio of filling volume. In details, the higher ratio of grouting, the quicker the speed of surface subsidence.Numerical simulation of IGI under the different widths show that maximum subsidence is 92.3mm, 166.4mm, 342.7mm, 416.5mm, 572.9mm, 626.6mm and the maximum horizontal movement value is 33.4mm, 58 mm, 113.2mm, 134.7mm, 155 mm, 165.7mm, when mining width is 90 m, 120 m, 160 m, 180 m, 200 m, 240 m. With the increase of mining width, surface subsidence, inclined value, horizontal movement value are all increased. Taking the model in the paper as an example, we can obtained the limit mining width with IGI is 200 m under the condition of the overlying strata structure and grouting.This thesis also analyzed the influence of the height of grouting layer in the control of surface subsidence. The result shows that, for the single working face, if we make the ratio of filling volume the same, the height of grouting layer has little influence on the control of surface subsidence, if the width of digging is relatively narrow. But with the increasing of digging width, the influence of the height of grouting layer on the control of surface subsidence was more obvious so that we can find out the best mining width based on grouting layer.