Application of response surface methodology to geotechnical parameter estimation in tunneling

摘要

The present study proposes a back analysis method for estimating the geotechnical parameters of the surrounding rock mass in tunneling. This method takes a direct search approach based on a successive response surface method, where the size of the region of interest is adjusted to facilitate a fast convergence of the parameter estimation process. Using a software tool developed in this study, the response surface method is combined with a numerical code, FLAC2D, which has been popularly used in numerical simulations of underground problems. Based on a railway tunnel example, the computational accuracy and efficiency of the proposed method are investigated. The back-calculations between the algorithm, which considers the adjustment of the region of interest, and the non-adjustment algorithm are compared to understand how the adjustment affects the back analysis results. In addition, the effect of different locations of measurement points at the tunnel roof and sidewalls on parameter estimation is investigated. The results of these investigations show that the adjustment algorithm can produce better results in computational accuracy and efficiency than the non-adjustment algorithm. Back-calculated solutions for different locations of measurement points agree well with the exact solution, suggesting there are no significant differences between converged parameter values.