Abstract: To address the issue of insufficient real-time monitoring and refined analysis of the cutterhead′s mechanical loading and temperature distribution during earth pressure balance (EPB) shield tunneling, this study explores the thermo-mechanical coupling mechanism and its evolution in the cutterhead under the influence of foam conditioning. Firstly, direct shear tests and interface shear tests were conducted to determine the shear strength parameters of the soil and the soil-cutterhead interface friction coefficient, both before and after conditioning with dispersed foam. On this basis, a thermo-mechanical coupled numerical model capable of reflecting the dynamic soil-cutterhead interaction was established using three-dimensional finite element method, and transient simulations of the cutterhead excavation process were performed. Influence of foam conditioning on the spatiotemporal evolution of the stress and temperature fields on the cutterhead is systematically investigated, revealing the influence mechanisms of key construction parameters such as muck discharge efficiency and cutterhead rotation speed on the thermo-mechanical response of the cutterhead. The results indicate that: (1) Foam conditioning considerably reduces the peak equivalent cutting stress and peak temperature on the EPB shield cutterhead by 22.3% and 19.8%, respectively, and effectively suppresses thermal stress and uneven expansion by improving muck discharge and heat exchange efficiency. (2) At a high rotation speed of 1.8 r/min, the peak stress and temperature on the cutterhead in untreated ground reach 66.89 MPa and 133.3 ℃, respectively. Foam conditioning effectively mitigates temperature rise and stress concentration under high-speed excavation, with the effect being particularly significant when the rotation speed exceeds 1.5 r/min, the stress reduction can reach 11.12 MPa and the temperature reduction can reach 16.9 ℃ when the rotation speed reaches 1.8 r/min. It is recommended that the cutterhead rotation speed be controlled within 1.5 r/min in combination with soil conditioning technology during actual construction to enhance cutterhead operational safety and excavation efficiency.

Key words: EPB shield cutterhead, heat transfer efficiency, cutting stress, thermo-mechanical coupling, foam-conditioned effect