Probabilistic analysis of ground surface settlement induced by super large diameter shield tunneling based on 3D random finite element method

The accurate prediction of ground surface settlement remains a crucial undertaking in shield tunnelling, particularly for tunnels with super large diameters. Instead of employing conventional deterministic analysis, this study employed 3D random finite element method (RFEM) to probabilistically investigate the longitudinal ground surface settlement induced by super large diameter shield tunneling. Through large quantities of numerical simulations, a new modified Logistic function with parameters of maximum ground settlement S_max, settlement upon face arrival S₀, and settlement speed during face passage v was proposed to represent the longitudinal ground surface settlement curves. The probabilistic distribution of longitudinal ground settlement was transformed into a multivariate Gaussian distribution of S_max, S₀, and v. A randomness transfer coefficient η was innovatively proposed to evaluate the effects of randomness transferred from modulus random field to the ground settlements. It was found that the mean values of S_max, S₀, and v were rarely affected by random field statistics. The randomness transferring coefficient η was determined by the vertical and horizontal scales of fluctuation (δ_v and δ_h). The correlation coefficients between S_max, S₀, and v were only sensitive to δ_h.