Robustness analysis of shield tunnels in non-uniformly settled strata based on fuzzy set theory

Abstract

This study presents a robustness analysis of shield tunnels in non-uniformly settled strata based on the fuzzy point estimate method (FPEM) and geotechnical structural robustness analysis methods. The uncertainties of key geotechnical parameters and loads were characterized using the fuzzy sets and the influence ofdifferentfuzzy membership functions andboundary values on the robustness index of shield tunnel was investigated. The structural design of the shield tunnel cross-section in non-uniformly settled strata were optimized by considering the reliability and robustness indices of the shield tunnel under the ultimate limit states, serviceability limit states, and economic costs. The results indicate that compared with the traditional Monte Carlo simulations, the FPEM is computationally efficient with favorable accuracy, and is suitable for the robustness analysis of shield tunnels. Increase of the segment thickness, reinforcement ratio and diameter of the joint bolts can efficiently improve the design robustness of the shield tunnel. Besides, the boundary values and distribution characteristics of the membership function of the random variables in the FPEM have significant effects on the errors of the calculation results.