Failure Mechanism of Grouted Floor with Confined Aquifer Based on Mining-Induced Data

Grouting in the key region is a preferred method to prevent the water inrush in underground engineering. Based on the special geological structure of complex aquifer in Huainan mining area of China, an evaluation method of grouted floor was proposed based on mining-induced microseismic (MS) data. A numerical model with complex aquifer was established, and the fracturing zone and stress distribution were studied under different grout radius. The water inrush coefficients were discussed based on a mechanical model. The results show that the floor failure calculated by the aggregation degree of 55% similar to 65% in depth was consistent with the drill core. In the case project, the source parameters changed abnormally after the action of ground pressure. Larger radius grouting has reduced the extension of mining failure and hydraulic fracturing zone, and the failure depth is significantly less than that of the original state. The relative tensile strength increases in the deep grouted floor, which reduces MS events. Moreover, the grouting hindered the concentrated destruction of the floor in the longitudinal direction. The rock failure with high connectivity only occurs in a narrow horizontal area instead of longitudinal propagation. The diffusion radius has great interference on the mining stress of the upper and lower layers in grouted zone, and also in the surrounding rock at both ends of the working face. The water inrush coefficients are determined by grouting horizon and diffusion radius, which should rely on a threshold value of 1.5 times of the layer thickness. This study is helpful to understanding of MS and numerical simulation in the engineering application, and can provide some reference for the grouting and failure mechanism of floor with confined aquifer to realize disaster prevention. Highlights The highlights of this study are as follows: center dot An evaluation method of grouting effect in the key region based on mining-induced data is proposed. center dot Microseismic aggregation degree and damage connectivity characterize the floor failure and conductivity. center dot Grouted cement increases the rock tensile strength to reduce the hydraulic fracturing from confined water. center dot The grout radius is controlled by the key grouting layer and original aquiclude properties.