In order to study the correlation of key construction parameters for slurry balance shield and their correlation mechanism, based on the excavation data of 863 rings in shield section 3#~2# of Qinghuayuan Tunnel, normality of key parameters in different strata were judged through statistical methods and their relationships were systematically explored. Based on common machine learning algorithms such as random forest and BP neural network, the prediction model of cutterhead torque in complex interbedded stratum was established to reflect the priority of the model input characteristic quantity. The results show that the difference between the stratums has a significant effect on the correlation strength of excavation parameters, which can be changed from very weak correlation to strong correlation. The study indicates a strong correlation among cutterhead torque, slurry pressure and shield thrust in multiple strata. The input of weakly correlated parameters in the prediction model has a limited effect on the improvement of the prediction accuracy and the quality of the prediction model can be guaranteed by selecting some strongly correlated parameters.

The cutterhead is prone to mud cake problems when the shield is tunneling in the cohesive stratum. In severe cases, the cutterhead is blocked to reduce the shield tunneling efficiency and affect construction safety. During the process of the slag adhering to the cutter head, it is accompanied by the solidation and hardening of the mud cake. To find out the influencing factors of consolidation and hardening of mud cake in shield cutterhead, laboratory tests are carried out by using a self-made cutter head tunneling simulation device. The relationship between soil properties, temperature, cutterhead earth pressure, and consolidation and hardening characteristics of mud cake is studied. The experiment of soil conditioning is carried out to explore the influence of different soil conditioners on the degree of consolidation and hardening of mud cake. The results show that the water content and cone penetration depth of mud cake can characterize the consolidation and hardening characteristics of mud cake. The properties of the soil have the greatest influence on the degree of consolidation and hardening of the mud cake formed by the cutterhead after excavation, followed by the temperature, and the cutterhead earth pressure has stratigraphic differences on the degree of consolidation and hardening of the mud cake. The foam agent has an obvious effect on the consolidation and hardening of pure clay and sand-containing clay cake, while the dispersant only has an obvious effect on pure clay.