# Research on Grouting Pressure of Earth-Rock Dams Reinforced by Polymer Based on Discrete Elements
## 7 Conclusions  
The technology of PFA-reinforced rockfill materials is of great significance in the reinforcement of rockfill bodies. This study aims to elucidate the reinforcement mechanisms of this technology and to assess the impact of varying grouting pressures on the effectiveness of polymer grouting. Utilizing the DEM, a fluid-solid coupling model for PFA-reinforced rockfill materials was developed. This model simulates the dynamic grouting process and analyzes the slurry diffusion patterns, the extent of slurry diffusion under different grouting pressures, changes in overall and regional porosity, and regional stress variations. The key findings are as follows:  
1. The diffusion of polymer foam within the rockfill body progresses through three distinct stages: the initial slurry is concentrated near the grouting hole, then diffuses rapidly, and finally, the diffusion rate slows down and tends to be stable. During the intermediate phase of grouting, the relatively loose structure and higher porosity of the rockfill surface facilitate easier diffusion of the grout. As grouting progresses to the later stages, the voids available for grout diffusion within the rockfill gradually diminish, imposing certain limitations on the spread of the grout. However, due to the excellent permeability and diffusivity of polymeric foam, a consistent rate of diffusion can still be maintained. This progression exhibits the characteristic features of seepage grouting in polymer foams, aligning with established seepage grouting theories and aiding in understanding the polymer diffusion dynamics within rockfill structures. In practical engineering applications, it is essential to select grouting materials judiciously based on the specific conditions of the rockfill and the reinforcement requirements to achieve optimal grouting and consolidation outcomes;
2. Variations in grouting pressure significantly influence the diffusion extent of the slurry. At low pressures, the diffusion range noticeably increases with rising pressure. The range stabilizes under medium pressure and changes minimally at high pressures. Additionally, the vertical (Z-axis) diffusion consistently exceeds the horizontal (X-axis) diffusion, with the former being more responsive to changes in grouting pressure;
3. There is a direct correlation between grouting pressure and porosity reduction. As grouting pressure increases, the porosity decrease becomes more pronounced, suggesting that higher pressures more effectively compel the slurry to occupy finer pores, thus enhancing material compactness. Across different regions, increasing grouting pressure typically reduces porosity, with the reduction diminishing with distance from the grouting point. At a grouting pressure of 0.9 MPa, the decrease in porosity in regions X2 and X3 is less pronounced, indicating a more uniform polymer distribution and limited pressure influence;
4. The relationship between stress increase and grouting pressure is approximately linear. Both the X and Z directional stresses rise with increasing grouting pressure, exhibiting a linear trend. However, the rate of increase differs between directions, with stress in the Z direction slightly surpassing that in the X direction at lower pressures, and vice versa at higher pressures. These research results can provide a reference for the seismic resistance of earth and rock dams and the reinforcement of rockfill materials, which has certain engineering significance. Meanwhile, because the chemical reaction of polymers is a highly complex process, there are still many difficulties in numerical simulation. Due to the limitations of experimental conditions, research methods, and research tools, there are still many problems that need to be further researched and explored, which can be followed up by further simulations closer to the actual dimensions, the establishment of a more detailed three-dimensional model, and a more comprehensive consideration of the spatial effects of the dam and the flow characteristics of the grouting material.