In response to the surface moraine collapse and debris flow incidents resulting from the natural caving method at the Pulang copper mine in Yunnan Province, this study undertook laboratory experiments on moraine grouting. The objective was to investigate the fundamental mechanisms and developmental processes of cement slurry diffusion within moraine, as well as to analyze the diffusion characteristics and solidification effects of cement slurry under varying grouting pressures. The experiments utilized undisturbed moraine with a stone content of 50% and a moisture content of 11.83%, employing five grouting pressure gradients of 0.4, 0.8, 1.2, 1.6, 2.0 MPa. Utilizing a self-developed grouting apparatus, the study systematically examined the impact of grouting pressure on grouting volume, diffusion radius, formation of splitting channels, and the solidification effect. The findings indicate that:(1)Due to the percolation effect, the diffusion of cement slurry within the moraine is primarily governed by compaction and splitting diffusion, rather than permeation diffusion. During the initial phase of grouting, the slurry compacts the moraine proximate to the grouting port, forming a spherical slurry bubble, which characterizes the compaction diffusion stage. As the pressure escalates to the splitting threshold, the slurry propagates along the moraine’s weakest surfaces, resulting in the formation of primary and secondary slurry vein structures, marking the splitting diffusion stage.(2)Quantitative analysis reveals a positive correlation between grouting volume, diffusion radius, splitting crack width, and channel length with grouting pressure. Notably, the diffusion radius and splitting crack width exhibit a nonlinear growth trend as grouting pressure increases.(3)Furthermore, throughout the grouting process, the cement slurry exerts a significant lifting effect on the moraine. By compacting and splitting the moraine, the slurry generates an upward lifting force, which effectively mitigates moraine settlement.(4)Scanning electron microscopy reveals that the C-H crystals, C-S-H gels, and ettringite minerals formed during the cement hydration process occupy the pores within the moraine and interact with the moraine particles, resulting in a dense mass structure that significantly enhances the mechanical properties of the moraine.(5)The solidification effect of cement slurry grouting on moraine is primarily characterized by two mechanisms: compaction effect and skeleton support effect. For the compaction effect, the grouting process increases the density of the moraine, thereby enhancing its strength. For the skeleton support effect, the cement slurry veins provide structural support and constrain the deformation of the surrounding moraine, functioning as a skeletal framework. This study aims to elucidate the diffusion behavior and solidification effects of cement slurry in moraine, offering theoretical insights for moraine grouting reinforcement projects and the prevention and management of collapse pit geological hazards.