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| Analysis on the Stability of Shield Underpassing Through Multiple Arch Bridge Repeatedly in Sandy Cobble Stratum |
| JIA Shao-chun |
| （China Railway First Survey and Design Institute Group Co. Ltd, Xi'an, Shaanxi 710043, China） |
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Abstract Abstract：Research purposes： Sandy cobble stratum has significant weak cementation, high sensitivity, and poor self-stability ability after disturbance, and there are few related engineering cases and researches on small clear distance shield tunnel underpassing through multiple arch bridge repeatedly in similar sandy cobble stratum. Based on shield tunnel of Chengdu metro line 5 and line 6 underpassing through multiple arch bridge, three dimensional finite element method is applied to analyze the influence of shield tunnel approaching excavation on displacement and internal force of multiple arch bridge in sandy cobble stratum, and the results are compared with that under condition of ground reinforcement, which provides theoretical guidance for the construction of shield tunneling. Research conclusions：（1）When shield tunnel closely passes through multiple arch bridge which is not reinforced, the unreinforced bridge has large vertical and lateral displacements, the maximum displacement value is 3.92 mm and 0.52 mm respectively. The inhomogeneous settlement of pier and shield tunnel construction cause the axial force, shear force and bending moment of the arch bridge to change, and the maximum internal force occurs at arch foot.（2）For arch bridge foundation and surrounding strata of tunnel, grouting reinforcement can significantly reduce the overall displacement of the multiple arch bridge, the maximum vertical and lateral displacement of the bridge is 2.96 mm and 0.39 mm respectively, with a decrease of 24.5% and 25.0%, respectively. The axial force and shear force changes slightly, the bending moment value decreased significantly, decreasing by 13.1%. （3） The grouting reinforcement method can ensure the operation safety of multiple arch bridge during the shield tunnel construction, and the research results can provide theoretical guidance for the construction of sand cobble stratum shield tunneling.
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Received: 15 November 2017
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2017, Vol. 34 
