Design of shield tunnel lining taking fluctuations of river stage into account: Fid-Bau Portal

Design of shield tunnel lining taking fluctuations of river stage into account

Lin, Cungang / Wu, Shiming / Xia, Tangdai

Highlights • Two design models for shield tunnel lining beneath the river taking fluctuations in river stage into account are established. • The established design model for impermeable overburden strata of low permeability is verified with field-observations. • The structural safety of the tunnel lining taking impacts of river stage into account is evaluated.

Abstract Fluctuations of river stage are expected to induce changes in loads acting on the tunnel linings and cause readjustments of member forces in the segmental linings subsequently. Therefore, the evaluation of impacts of time-dependent river levels on the loads acting on the tunnel linings is of great importance in design of shield tunnel linings situated beneath the rivers. However, the loads acting the tunnel linings are generally considered as constant in most design methods available, taking no account of the influences of constantly changing river stage. In this study, the influences of river stage on design of shield tunnel linings are evaluated with respect to two common ground conditions: (a) impermeable overburden strata of low permeability and (b) permeable overburden strata of high permeability. Two earth pressure calculation models are correspondingly established. In addition, field observations in the Hangzhou Qiantang River Tunnel are described in detail to present the responses of tunnel linings to fluctuations in river stage and validate the established design model for the former case.