Displacement back analysis for cross-river tunnel and algorithms comparison

The displacement back analysis model for cross-river tunnel is proposed in this paper according to the nonlinear-least-squares method. In the model, a penalty function is used to translate the constrained boundary into unconstrained. The numerical solutions of the model are carried out by traditional Gauss-Newton-Marquardt (G-N-M) algorithm and improved G-N-M algorithm. The calculation efficiency and accuracy of the two algorithms are compared. The study results show that the calculation results of back analysis are very agreeable with the measured values, indicating displacement back analysis model for cross-river tunnel is valuable in engineering practices. The improved G-N-M algorithm is much more efficient and accurate than the traditional G-N-M algorithm, which is an effective algorithm in solution of the displacement back analysis model for cross-river tunnel and expected to promote in some other engineering fields.