A new method for determining of parameters simultaneously in the coupled seepage-stress analysis in anisotropic rock is essential for large-scale cavern shape selection

stability analysis

and rock support system design. Based on the Levenberg-Marquit optimization method

a modified method has been put forward by employing a new step factor matrix

in order to calculate both of the parameters of rock mass modulus (E)

the in situ stress (P) and the permeability coefficient (K) in the back analysis. Compared with traditional step factor in optimization algorithm

the new step factor matrix can change the step factors respectively according to the different sensitivities of parameters

with which a new algorithm is established on MATLAB platform. Two case studies show the method’s feasibility and validity in the coupled seepage-stress analysis in a anisotropic rock tunnel engineering; and the results demonstrate that the modified method with new step factor can improve convergence of iterative algorithm obviously which cannot be solved with traditional step factor.