Identification and Prediction Method of Working Face Water Inrush of Isolated Overburden Grout Injection

ABSTRACT Isolated overburden grout injection (IOGI) is an economical and efficient green mining technology. During the grout injection process, a large amount of slurry bled water will enter the underlying rock strata below the grouting layer. Under certain conditions, the slurry bled water may seep along the overlying rock layer into the water‐conducting fractured zone (WCFZ), resulting in the increase of water inrush in the working face, which affects the production safety and the grouting effectiveness. Therefore, it is urgent to establish the prediction model of working face water inrush and establish a safe grouting layer selection method to prevent the grouting water from entering the working face in the process of grouting filling. In this article, a new identification and prediction method of working face water inrush of IOGI were proposed. According to the characteristics of seepage boundary, a “semi‐ellipsoid” theoretical model of seepage boundary of slurry bled water was established, and a dimensionless Formula of the model parameters was constructed. The dimensionless Formula was solved based on the experimental results of influencing factors of seepage boundary. Based on the distribution characteristics of free water in grouting filling, the identification and prediction method of working face water inrush of IOGI were established. The prediction method was analyzed to the actual mine, and the correctness of the prediction method was verified. Using the proposed prediction method, a selection method of grouting layer (the distance between grouting layer and coal seam roof > seepage boundary | c | + the height of WCFZ H d ) was given to ensure that the slurry bled water will not enter the working face during the grout injection process. So as to ensure the effective implementation of grout injection work.