Experimental Research on the Transverse Effective Bending Rigidity of Shield Tunnels

Gang Zheng,Jibin Sun,Tianqi Zhang,Yawei Lei,Tao Cui,Yu Diao,Xuesong Cheng

doi:10.1155/2019/2174562

Abstract

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 ratio η with a concentrated force, which is notably different from realistic loading patterns. To obtain more reasonable η values, 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 the η values of the stagger-jointed assembly mode were clearly larger than those of the straight-jointed assembly mode under both loading patterns. η increased as the load increased under the realistic loading conditions, whereas η decreased as the load increased under the concentrated load. More importantly, the η values 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 relating η to the ratio of the cover depth to the tunnel diameter were proposed for sandy soil.

Highlights

Association (ITA) combined and summarised the design methods utilised in different countries [2, 6, 7]
In the multihinge ring approach, the surrounding pressure and soil resistance have substantial impacts on the stress and deformation of the linings. is model is applicable only to hard strata and straight-jointed assembly patterns, and it may lead to a small bending moment. e beam-spring model method appears to be the most sophisticated approach, and it is generally applicable for evaluating the influence of joint stiffness on the mechanical properties of segmental rings under different ground conditions
Transverse Deformation Characteristics under the Concentrated Loading Conditions. e results indicate that the three tests for each mode provided similar results, which indicates the repeatability of the test results

Summary

Introduction

Association (ITA) combined and summarised the design methods utilised in different countries [2, 6, 7]. E elastic foundation approach is the most frequently utilised design method because of its conciseness and convenience This method can classify the types of joints of segments using the universal rigidity ring method [8, 9], the average uniform rigidity ring method [10,11,12,13], the multihinge ring method [14], and the beam-spring model method [15,16,17]. E beam-spring model method appears to be the most sophisticated approach, and it is generally applicable for evaluating the influence of joint stiffness on the mechanical properties of segmental rings under different ground conditions. The value and influence of η have been studied by several researchers, using different methods, such as theoretical analyses and model tests

Methods

Results

Conclusion