# A State-of-the-Art Review on the Study of the Diffusion Mechanism of Fissure Grouting
## 6 Conclusions and Prospects  
We systematically reviewed the current development status of fissure grouting in terms of theory, numerical analysis, and experimental aspects. In future research, a combination of theoretical analysis, numerical simulation calculations, and on-site experimental monitoring could facilitate a better understanding of the slurry diffusion mechanism in fissure grouting. We drew the following conclusions based on their previous research:  
1. The current research on fissure grouting flow and diffusion theory faces several challenges and unresolved issues. Firstly, the interaction between the grout and the rock mass during the grouting process is complex and influenced by various factors such as fissure morphology and distribution, grouting materials, grouting pressure, and flow rate. This complexity makes it difficult to accurately describe fluid flow and diffusion. Secondly, existing research lacks guidance for practical engineering applications and mostly focuses on idealized conditions without considering diffusion in actual engineering porous media and the heterogeneity of pore channels. 2. The diffusion theory of polymer grouting tends to focus on fissures and small pores, neglecting the influence of large-pore gravel media and water flow on diffusion. Moreover, in engineering practice, the diffusion mechanisms and layout parameters of multiple grout holes need to be considered, but there is currently a lack of a mature theoretical basis and comprehensive methods that account for the filtration effect caused by grout particle movement. Therefore, further research is needed to address these issues and improve the accuracy and practicality of the fissure grouting flow and diffusion theory. 3. The numerical simulation study of rock fracture grouting is of great significance for engineering projects such as mines and tunnels and can provide guidance for grouting design and construction. It improves efficiency, quality, environmental protection, and safety. Future research should focus on optimizing grouting methods, considering phase transition characteristics of high polymers, comprehensively analyzing factors like fissure characteristics, and developing advanced detection and simulation methods for accurate prediction and simulation of grouting in real fissured rock masses. 4. Experimental research on grouting in fractured rock masses forms the basis for the engineering design and practical implementation of rock mass grouting projects. Thisresearch includes studying the properties of fractures and grouting characteristics, the influence of grouting parameters on grouting effectiveness, deformation, and stress characteristics of rock masses after grouting, and exploring the spatiotemporal evolution of slurry characteristics and porosity in fractures. Future research will focus on developing more efficient and accurate experimental methods, advanced grouting technologies, comprehensive and precise rock mass models, and improving the control and monitoring capabilities of grouting processes. Additionally, in-depth analysis can be conducted on the mechanisms and treatment methods for poor grouting in rock masses, distribution patterns of fractures, exploration of optimization methods for grouting parameters, and grout quality testing techniques. The development and application of new materials also hold the potential to enhance grouting efficiency. X.D. : conceptualization and writing--original draft. Z.L. : writing--review and editing. H.F. and B.L. : supervision, validation, and writing--review and editing. X.Z., K.Z., B.X. and S.W. : conceptualization, supervision, validation, and writing--review and editing. All authors have read and agreed to the published version of the manuscript. This work was supported by the National Key Research and Development Program of China (No. 2022 YFC3800039), Sponsored by Natural Science Foundation of Henan (No. 232300421064), the National Natural Science Foundation of China (Nos.