Abstract: To address the challenges of non-uniform grout diffusion and the difficulty in forming a continuous water cutoff curtain in water-rich muddy silt layers of open-pit coal mines, a novel method combining high-pressure pulsed gas pre-splitting for soil layer with pressure grouting was proposed and implemented in a pilot project of Chaoyang Open-pit Coal Mine in Heilongjiang Province. A discrete element method (DEM) model based on fluid-solid coupling theory was developed to investigate, from a mesoscopic perspective, the influence of pulsed gas parameters (pressure and frequency) on soil fracture propagation. By integrating the geological characteristics of the stratam, the optimal pulsed gas parameters were determined. Field grouting tests were conducted using a self-developed pulsed gas pre-splitting grouting control system, and the grouting effectiveness was systematically evaluated through field monitoring data, core sampling tests, and water pressure tests. The results demonstrate that high-pressure pulsed gas significantly enhances fracture density in muddy silt layers, with the fracture growth process categorized into three distinct stages: rapid growth (Stage I), slow growth (Stage Ⅱ), and stabilization (Stage Ⅲ). The effective fracture propagation range exhibits a positive correlation with gas pressure, while showing an initial increase followed by a decrease with the increasing of gas frequency. The optimal gas parameters were identified as a pressure of 2 MPa and a frequency of 2.5 Hz. The pulsed gas pre-splitting grouting technology effectively reduces grouting pressure, increasing grout volume by 24% in loose sand layers and 92% in silty sand layers, with a maximum diffusion radius of 2 meters in open-pit mine strata. This method significantly improves the injectability of low-permeability silty sand layers and achieves exceptional anti-seepage and water cutoff performance.