# An Experimental Study on the Sealing Mechanism of a Karst Pipeline by Dynamic Water Grouting
## 5 Conclusions  
This paper takes the pipeline water burst in the karst area as the research object. WEMS was developed, and the orthogonal test of magnetic self-polymerization slurry plugging was carried out using the self-developed visual karst pipeline water burst grouting plugging simulation test system. Finally, the shear mechanism of magnetic slurry magnetization plugging was analyzed. The specific conclusions of this study are as follows:  
1. Experiments show that when the water-cement ratio of the new WEMS is 0.35-0.55 and the amount of Fe\({}_{3}\)O\({}_{4}\) powder is 20-40%, the grouting sealing performance is the best.
2. The orthogonal test was carried out on the plugging law of the magnetic self-polymerizing slurry under high flow velocity and dynamic water conditions. The water plugging pressure, dynamic water flow rate, and slurry retention rate were selected as evaluation indexes, and the primary and secondary relationships of the influencing factors of each evaluation index were obtained by range analysis.
3. In the indoor experiment, the primary and secondary relationship between various factors and slurry plugging pressure was determined as plugging length > Fe\({}_{3}\)O\({}_{4}\) power ratio > water-cement ratio. The water plugging pressure is positively correlated with the length of water plugging and the amount of Fe\({}_{3}\)O\({}_{4}\) powder, and the water plugging pressure increases with its increase.
4. In the analysis of the dynamic water flow rate and the dynamic water anti-scouring effect, the dynamic water flow rate and slurry retention rate are most affected by the amount of Fe\({}_{3}\)O\({}_{4}\) powder, followed by the plugging length, and the water-cement ratio has a minor effect. The new WEMS can effectively complete the long-distance plugging of karst pipelines.
5. The relationship between the shear strength and magnetic field strength, plugging length, and slurry ratio was established by analyzing the force of WEMS in the process of grouting plugging.  
Introduction, J.L. and S.L.; materials and methods, J.L. and S.L.; results, B.P. and M.W.; discussion and conclusions, S.L.; writing--original draft, S.L. and M.W. All authors have read and agreed to the published version of the manuscript.  
The authors gratefully acknowledge the financial support provided by the National Natural Science Foundation of China (52079071), the Natural Science Research Project of Yichang (A22-3-003), the Fund for the Opening of key Laboratory of Geological Disaster in the Three Gorges Reservoir Area by the Ministry of Education (2020 KDZ08) and the Research Fund for Excellent Dissertation of China Three Gorges University (2021 BSPY016).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Magnetic Field Strength** & \multicolumn{3}{c}{**14,000 GS**} \\ \hline Fe\({}_{3}\)O\({}_{4}\) power ratio & 20\% & 30\% & 40\% \\ \hline Plugging length (mm) & 100 & 200 & 300 \\ Water plugging pressure (kPa) & 6 & 11.4 & 17.7 \\ Shear strength (kPa) & 2.69 & 7.62 & 13.71 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Weak anti-shear parameters of magnetic grout under different plugging lengths.  
Data Availability Statement: The research data are included within the article, and further data are available from the first and corresponding author upon request.  
The authors declare no conflicts of interest.