# Grouting Process Simulation Based on 3D Fracture Network Considering Fluid-Structure Interaction
## 4 Conclusions  
The purpose of this study is to investigate the grouting process in fractured rock mass and the influence of grout on the fracture network; thus, a grouting simulation approach considering fluid-structure interaction based on the 3D fractured network model is developed, and the hydropower station X is taken as a case study to do some in-depth analysis using the proposed approach. The results show that the grouting simulation considering fluid-structure interaction is more realistic and can simultaneously reveal the grout diffusion and fracture deformation, which indicated that it is necessary to consider the effect of fluid-structure interaction in grouting simulation. The main conclusions of this study are as follows:  
1. In fracture network modeling studies, fracture aperture values are often ignored or inaccurate, which will affect the authenticity of grout simulation. Combined with the exposed surface fracture catalog data, we use the relationship between fracture apertures and trace lengths to obtain a more realistic value of fracture aperture and to establish a more reliable model for numerical simulation of grouting.
2. During the grouting process, the filling of the primary fractures is influenced by the number of intersecting secondary fractures, whilst the filling of the secondary fractures is related to the fracture aperture, and the length of the intersection between the secondary fracture and the primary fracture. Fracture aperture and dip angle have a significant effect on the grout diffusion rate, while the fracture aperture is the major influencing factor. Moreover, the effect of fluid-structure interaction between the grout flow and the rock mass has a certain influence on the grout diffusion length and neglecting this effect will cause an underestimation of the grouting performance.
3. When the fractures in a certain region intersect with each other and are close to other fractures in the surrounding area, the rock mass between such fractures will be the least rigid and prone to deformation during the grouting process.
4. Grouting pressure, grout water-cement ratio and rock mass elastic module all have effects on the grouting process. Therefore, in the grouting construction process, the appropriate grouting pressure and grout water-cement ratio should be selected according to different geological conditions.
5. The effects of fluid-structure interaction between the grout and the rock mass will affect the grout diffusion process and the rock mass deformation. Therefore, the grouting process simulation considering the fluid-structure interaction can better analyze grout diffusion and rock deformation, and hence explore the grouting mechanism under real conditions.  
These results can provide an important theoretical basis and valuable information for grouting construction, and in future research the grouting performance considering the effect of underground water can be further studied.  
**Author Contributions:** Conceptualization, Y.Z., X.W. and S.D.; Formal analysis, Y.Z. and W.C.; Methodology, Yu.Z. and S.D.; Writing--original draft, Y.Z.; Writing--review and editing, X.W., S.D., W.C., Z.S., L.X. and M.L.  
**Funding:** This research was funded by the National Key R&D Program of China, grant number 2018 YFC0406704; the Science Fund for Creative Research Groups of the National Natural Science Foundation of China, grant number 51621092; and the National Natural Science Foundation of China, grant number 51439005.  
**Conflicts of Interest:** The authors declare no conflict of interest.