Prediction and optimization of fracture behavior and fracture angle in key strata under roof-cutting blasting

To address the challenges of difficult caving of thick and hard roofs in deep coal mining, excessive cantilevered roof lengths that easily induce intense strata pressure and rockburst events, and the reliance of conventional roof-cutting blasting parameters on empirical design, this study investigates the prediction of fracture behavior and parameter optimization of key strata under roof-cutting blasting conditions. Based on elastic and material mechanics, a coupled mechanical model of a cantilever beam–voussoir beam system for key strata was established, and an analytical expression for the roof fracture angle was derived. The controlling mechanism of the fracture angle on overburden movement patterns and the distribution of abutment pressure in the working face was revealed. Integrating field borehole exploration and microseismic monitoring, an integrated method for roof behavior prediction and dynamic parameter optimization–comprising ‘theoretical calculation–borehole exploration–microseismic monitoring–numerical simulation’ –was proposed and validated. The results show that, after parameter optimization of roof cutting in Panel 3106 of a particular mine, the actual fracture angle of the key stratum increased significantly, the cantilever length was reduced by 46%, and the intensity of microseismic energy release decreased effectively. Moreover, the peak abutment pressure in the working face shifted deeper into the solid coal, leading to a shift from ‘passive pressure resistance’ to ‘active pressure relief.’