Probabilistic analysis for twin tunneling-induced longitudinal responses of existing shield tunnel

Abstract

This paper performs a probabilistic-based analysis for evaluating the longitudinal responses of the existing shield tunnel to the twin tunneling underneath. A deterministic model based on the two-stage analysis method is proposed for calculating the twin tunneling-induced deformations of existing tunnels. An efficient metamodel is built using sparse polynomial chaos expansions to surrogate the deterministic model and carry out the sensitivity analysis. Afterward, the metamodel and Monte Carlo simulation method are combined to assess the failure probabilities of the tunnel deformations exceeding allowable thresholds under given volume losses. The analysis results show that uncertainties of the random parameters lead to a significant effect on the tunnel responses and failure probabilities, indicating the necessity of probabilistic analysis on this problem. The uncertainties in the greenfield soil settlement dominate the assessment of the tunnel settlement, and the parameters associated with the soil-tunnel interaction influence the curvature radius and joint deformations more remarkably. An approximately linear increase in the allowable volume loss can be seen with increasing horizontal distance between twin tunnels. The reduction in the skew angle strengthens the influence of the failure mode of the tunnel settlement on the probabilistic evaluation of the system.