Experimental Research on the Transverse Effective Bending Rigidity of Shield Tunnels

The uniform rigidity ring model is commonly used to design the segmented structures of shield tunnels. However, model tests have been primarily used to study the transverse effective rigidity ratioηwith a concentrated force, which is notably different from realistic loading patterns. To obtain more reasonableηvalues, in this study, tests were performed with a concentrated load on an experimental bench and with a realistic loading pattern in sandy soil in a rigid steel tank. Three types of segmental ring models were designed and tested: straight-jointed, stagger-jointed, and uniform rings. The test results indicated that theηvalues of the stagger-jointed assembly mode were clearly larger than those of the straight-jointed assembly mode under both loading patterns.ηincreased as the load increased under the realistic loading conditions, whereasηdecreased as the load increased under the concentrated load. More importantly, theηvalues derived from the realistic load tests were considerably larger than those derived from the concentrated load tests for both assembly modes (i.e., 0.423–0.672 and 0.587–0.761 for the straight-jointed and stagger-jointed assembly modes, respectively), and the former should be recommended for practical engineering applications. Furthermore, formulas relatingηto the ratio of the cover depth to the tunnel diameter were proposed for sandy soil.

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