Calculation and control of axis deviation for active articulated shield by considering shield-strata interaction

How to accurately reveal attitude variation patterns and thereby achieve efficient control has always been a research focus in both academia and industry. The active articulation effect cannot be accurately characterized in existing mechanics-based studies, and relevant deviation calculation and control methods require further improvement. Therefore, a shield-strata interaction model considering active articulation is proposed and solved using a time- or mileage-incremental process. A theoretical calculation method for axis deviation is then developed via spatial coordinate transformation, and a basic deviation control strategy is further established by designing the optimal correction curve and determining the resultant moment of propulsion forces at each control mileage. The proposed model and methods are validated through a case study in the BinZhong interval of Fuzhou Binhai Express. The effects of active articulation and strata conditions on shield head falling, shield-shell earth pressure, and the actual correction trajectory are carefully discussed, and corresponding deviation control strategies for different strata are established. Some conclusions can be drawn as follows: Attitude angles and axis deviations can be accurately determined by the proposed interaction model and incremental process, and the effect of active articulation is particularly important. Increasing the active articulation angle can effectively alleviate shield head falling. The articulation angle is approximately linear with shield-strata interaction when subgrade coefficients are less than 5 MPa/m, which gradually becomes nonlinear as subgrade coefficients increase. In composite strata, the displacement increment induced by attitude adjustment may cause the actual correction trajectory to deviate from the optimal curve. Increasing the articulation angle can mitigate this deviation, and it is more obvious under larger positive deflections. The collaborative control method by active articulation and resultant moment of propulsion forces can satisfy the optimal correction curve while reducing the resultant moment of propulsion forces, thus achieving efficient control for composite strata. This research can provide mechanical insights into the prediction and timely control of axis deviation during shield tunneling, and lay a foundation for subsequent physics-data-driven modeling.