<p>Clogging of the cutterhead presents a significant challenge in shield tunnelling, particularly in clayey ground. While adhesion between clayey soil and metal is the primary cause, existing adhesion mechanisms and assessment criteria, predominantly established for non-immersed or Earth Pressure Balance (EPB) shield conditions, cannot be directly applied to slurry shields where the excavation chamber is fully immersed in slurry. This study investigates the adhesive characteristics between clayey soil and metal specifically under slurry immersion. A series of normal adhesion tests were conducted on artificial clayey soils with varying compositions and initial consistency indices, both before and after immersion in different fluids (deionized water and bentonite slurries). Beyond quantifying adhesion stress, the study systematically analyzed the post-immersion water content distribution to reveal the underlying mechanisms. The results demonstrate that the slurry immersion environment profoundly alters the adhesive stress, which can either increase or decrease depending on the initial water content, water absorption rate, and immersion duration. A key finding is the introduction of the “Adhesion-Active Layer” concept, indicating that adhesion is governed by the dynamically changing state of a thin surface layer rather than the bulk soil property. Furthermore, an “Adhesion Evolution Path Model” is developed, categorizing adhesion trends under immersion and highlighting the critical role of immersion time. This study provides a fundamental mechanistic understanding and a predictive framework for assessing clogging potential in slurry shields, moving beyond static models and offering direct experimental insights for risk assessment and mitigation strategies.</p>