Abstract: Frequent mud-caking is one of the primary challenges limiting efficient shield tunneling in cohesive strata. Based on an extensive review of existing literature, this study discusses and summarizes the research progress and technology development of shield mud-caking globally from three key perspectives: causes, risk prediction, and prevention techniques. Limitations of existing studies are highlighted, and future research directions and development trends are proposed. At a macro level, the mud cake formed on the shield results from the combined influence of geological conditions, equipment, and construction factors. However, its precise formation mechanism during tunneling is yet to be fully understood in a scientifically rigorous manner. Adhesion at the soil-to-metal interface has emerged as a critical breakthrough in explaining the causes of mud cake formation and has become a research hotspot in recent years. However, existing adhesion tests lack standardized procedures and a unified evaluation system for soil-to-metal adhesion. Current risk prediction models based on soil-to-metal adhesion research still have limitations, with suboptimal performance in practical applications. In future, expert knowledge should be integrated with real-time construction data to develop a knowledge- and data-driven risk prediction models. The prevention and mitigation of mud-caking in shield tunneling should follow the principle of "geology as the foundation, equipment as the key, and management as the core". However, existing control measures often lack theoretical guidance, leading to a degree of uncertainty in their application. To address this, it is essential to integrate theoretical research with engineering practice and establish a scientifically robust and comprehensive control system for mitigating mud cake formation.

Key words: shield tunnel, mud cake, mud-caking mechanism, prediction methods, prevention techniques