Objective For coal mining areas in the middle reaches of the Yellow River basin, sealing mining-induced fractures via grouting serves as an effective approach to preventing water inrushes from coal seam roofs while also protecting groundwater resources. However, accurately identifying the migration paths of grouts remains a bottleneck for the further application of grouting modification technology to fractured rock masses.

Methods This study investigated a coal mine threatened by both water inrushes from the coal seam roof and a short supply of water resources within the Jurassic coalfield in the middle reaches of the Yellow River basin, focusing on the magnetic tracing of the migration paths of grouts in fractured rock masses within the coal seam roof. Employing a range of techniques, includ-ing laboratory tests and analysis, physical simulations using similar materials, and theoretical calculations, this study ana-lyzed the performance, microstructures, and magnetic responses of magnetic grouts. Furthermore, using magnetic particles as a tracer, this study carried out tracing experiments on the migration paths of grouts in fractured rock masses and exam-ined the distribution of magnetic intensity along the paths.

Results and Conclusions The performance test results indicate that the optimal mix ratios of the magnetic grouts included a water-cement ratio of 1.0∶1.0, along with a mass fraction of 15% and a particle size of 0.2 μm for magnetic particles. The grouts prepared using such mix ratios exhibited both the magnetic properties of solid magnetic particles and the properties of ordinary cement grouts. The analytical results reveal that the migration paths of grouts in the specimens of fractured rock masses, as plotted in the magnetic intensity monitoring diagrams, were roughly consistent with the fracture locations and shapes in the physical diagrams and the fracture localization maps derived using acoustic emission tests. Such consistency demonstrates that the magnetic intensity monitoring can be used to characterize the migration paths of grouts in fractured rock masses. Using the proposed method for calculating the magnetic intensity of grouts migrating in fractured rock masses, the magnetic intensity at various points of the centers of the fractured rock masses was determined. Furthermore, the calculated migration paths of grouts were largely consistent with the actual flow paths observed in the grouted specimens, further verifying that it is relia-ble to characterize the migration paths of grouts in fractured rock masses based on magnetic intensity. The results of this study help address the challenge of accurately identifying the migration paths of grouts in fractured rock masses, providing a basis for the parameter design and performance evaluation of grouts for these rock masses.