Abstract: Stochastic calculations, by combining the random field theory with the finite difference analysis and Monte Carlo simulation, are used to conduct reliability analysis on the surrounding soil deformation induced by twin tunneling in multi-layer soils considering the spatial variability of soil parameters. The effects of scales of fluctuation (SOF) of Young’s modulus in both vertical and horizontal directions on deformation reliability index are investigated and discussed in detail. Results demonstrate that the reliability index of maximum deformation (surface settlement, vault settlement, and surrounding rock convergence) obtained by stochastic analysis decreases with the increase of SOF, and the comprehensive reliability index of deformation increases with the increase of allowable value of deformation. Additionally, the entropy weight coefficients of deformation indices are objectively determined by using the entropy theory. Combining the reliability design method and the engineering risk analysis theory, the comprehensive reliability of deformation is analyzed, and the deformation control index system of shield tunnel suitable for Xiamen area is put forward.

Key words: twin tunneling, elastic modulus, spatial variability, random field theory, entropy theory, comprehensive reliability, deformation control index system