Thrust allocation method for shield machines under synchronous propulsion and assembly mode incorporating segment damage constraints

To address the tunneling axis deviation and segment damage caused by thrust imbalance due to missing hydraulic cylinders in shield tunneling machines, a nonlinear thrust allocation method incorporating segment damage constraints is proposed. A segment plastic damage model is established via ABAQUS finite element analysis to determine the ultimate load under maximum principal stress, which is incorporated as an explicit constraint in thrust allocation. The minimum mean square deviation of partition thrust is employed as the objective function, combined with the physical limitations of hydraulic cylinders, to formulate a constrained nonlinear optimization model. This model is transformed into quadratic programming subproblems through Taylor expansion, and an improved sequential quadratic programming (IQP) algorithm is developed by introducing a second-order correction function to ensure global convergence. Simulation results demonstrate that IQP reduces the mean square deviation by 13% compared to the least-squares method and improves computational efficiency by 32% compared to standard SQP. A case study confirms that partition thrust is primarily influenced by tunneling posture, verifying the feasibility of the proposed method in achieving balanced thrust distribution while ensuring segment structural safety.