Dynamics research on grouping characteristics of a shield tunneling machine's thrust system

Grouped operation of a thrust system has a great effect on the performance of a shield tunneling machine. With consideration of the kinematic constraints from surrounding composite strata, the dynamic model of a grouped thrust system is firstly proposed to investigate the force transmission relationship between external resistances and driving forces. Then, the resistances model is derived based on the parametrized expression of two-layer composite strata. On the basis, the characteristics of each grouping mode for the thrust system are finally studied with variable geologic conditions by an index revealing the overload on segments. Results show that the contours of this index against impacting accelerations are a cluster of quasi-ellipses whose center can help to obtain the optimum grouping mode. Moreover, the adaptability of the thrust system to impacts will change significantly with the variations of the surrounding strata. These findings can serve as helpful instructions for the selection of grouping strategies in future tunneling projects.