Numerical simulation of freezing effect and tool change of shield machine with a frozen cutterhead

A shield machine with freezing function is proposed in order to realize tool change operation at atmospheric pressure. Furthermore, the transformation project of freezing cutterhead and tool change maintenance method are put forward. Taking the shield construction of Huanxi Power Tunnel as an example, a numerical analysis of the freezing cutter head of the project was carried out. The results show that when the brine temperature is −25 °C, after 30 d of freezing, the thickness of the frozen wall can reach 0.67 m and the average temperature drops to −9.9 °C. When the brine temperature is −30 °C, after 50 d of freezing, the thickness of the frozen wall can reach 1.01 m and the average temperature drops to −12.4 °C. If the thickness of the frozen wall is 0.5 m and the average temperature is −10 °C, as the design index of the frozen wall, the brine temperature should be lower than −28 °C to meet the excavation requirements in 30 d. Analyzing the frozen wall stress under 0.5 m thickness and −10 °C average temperature condition, the tensile safety factor and compressive safety factor are both greater than 2 at the most dangerous position, which can meet the tool change requirements for shield construction.