Abstract: Objective: To address the unclear grout diffusion mechanism and the insufficient understanding of geoelectrical response characteristics during grouting in saturated sand strata, indoor grouting simulation experiments were conducted to investigate the grout diffusion behavior and its geoelectrical response characteristics in saturated sand layers, so as to provide a theoretical basis for real-time monitoring and performance evaluation of grouting-based water control and strata reinforcement in underground engineering. Methods: A saturated sand layer was constructed in a three-dimensional physical model with dimensions of 82 cm × 82 cm × 82 cm, and grouting experiments were carried out under a grouting pressure of 0.3 MPa. Based on the indoor three-dimensional model and a parallel electrical monitoring system, the exciting current, self-potential, primary field potential, and apparent resistivity were dynamically monitored throughout the entire grouting process. The spatiotemporal evolution characteristics of these electrical parameters during grout diffusion and consolidation were then systematically analyzed. Results: The experimental results showed that the exciting current was a sensitive electrical parameter for characterizing the grout diffusion and consolidation processes, effectively reflecting the advance of the grout front and the evolution of conductive pathways. At the initial stage of grouting, the exciting current decreased from approximately 0.75 mA to 0.65 mA. Subsequently, with the displacement and mixing of grout and pore water, the electrical conductivity increased, and the exciting current rose to approximately 0.80 mA before gradually stabilizing. Both the self-potential and primary field potential exhibited pronounced fluctuations and increasing trends during grouting, which effectively revealed the migration pathways and diffusion range of grout at different strata levels. Owing to the heterogeneity of the weathered zone, the variations in electrical parameters were more complex, with stronger spatial differences and instability, whereas the responses in the saturated sand layer were relatively consistent. The three-dimensional inversion results of apparent resistivity indicated that the resistivity generally decreased first and then increased during the grouting process. During the grouting stage, grout entered the formation and mixed with pore water, forming a low-resistivity zone of approximately 50 Ω·m. During the consolidation stage, as cement hydration intensified and pore spaces were progressively filled, the free water content decreased and the conductive pathways within the pores were weakened, resulting in a gradual increase in resistivity to above 150 Ω·m. Conclusions: Grout diffusion and consolidation in saturated sand strata induce significant geoelectrical responses during the grouting process. Among the monitored parameters, the exciting current is the most sensitive to the advancing grout front and consolidation evolution, while the self-potential, primary field potential, and apparent resistivity can characterize grout migration and consolidation features from different perspectives. Grout consolidation in saturated sand strata exerts a pronounced weakening effect on conductive pathways, leading to significant electrical property variations. The results of this study can provide a reference for the real-time monitoring, dynamic identification, and engineering evaluation of grouting-based water control and reinforcement effects in underground engineering such as coal mines.