Abstract: The widespread use of the shield method has raised the challenge of economically and environmentally managing shield waste muck, which is a crucial factor limiting its efficient implementation of the shield method. In this study, a case study is conducted on an airport shield tunnel project at the Nanning International Airport Comprehensive Transportation Hub Urban Rail Transit Airport Line, and the feasibility of employing shield waste muck for insitu absorption in the production of raw materials for karst grouting is discussed. An L16(44) orthogonal test design is employed to perform indoor tests on karst grouting materials made from shield muck. Herein, the impact of various factors on the slurry′s performance index is examined. The optimal slurry mixing ratio is determined using the multitargetideal point method. Finally, the research findings have been successfully put into practice at an engineering site. The results demonstrate the following: (1) Shield waste muck is a viable raw material for karst grouting, partially resolving the issue of shield muck treatment. The resulting grouting material satisfies the safety and efficiency requirements for subsequent shield tunneling. (2) Under the optimal mixing ratio (watercement ratio, shield waste muck content, quicksetting agent content, and expansion agent content of 1.41, 35.80%, 0.48%, and 0.31%, respectively), the slurry′s performance parameters comply with the karst filling and grouting standards. (3) Examination of the core sample post grouting reveals a strong bond between the slurry and karst filling, ensuring a smooth subsequent shield tunneling process without any unexpected deviations. The grouting and excavation effects align with expectations, and onsite preparation of shield waste muck after simple treatment results in material cost savings of approximately 30%. The economic and environmental benefits of this approach are noteworthy and merit widespread adoption.

Key words: shield tunnel, karst grouting material, shield waste muck, resource utilization, orthogonal test