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摘要
Research purposes: Upside surcharge is an important external reason for which induces excessive settlement, large elliptical variation and disease of subway shield tunnels. This paper introduces the settlements and diseases during the two soil stacking loading and unloading processes of an actual project in details. Through the investigation of the current status of tunnel diseases, combined with the analysis of tunnel settlement and ellipticity monitoring data, the safety status of the shield tunnel structure is estimated by using three-dimensional finite element detailed model to calculate the structural stress of shield tunnel. Research conclusions:(1) There is a significant correlation between the settlement rule, ellipticity magnitude and disease distribution of the shield tunnel and the two soil stacking heights, distribution ranges and loading time above the tunnel. (2) The three-dimensional detailed simulation results of the shield tunnel with the maximum stacking height of 6 m regarding to covering soil height of 3.7 m show that circumferential joint bolt is in the elastic stage, the longitudinal joint opening magnitude can be restrained within 1 mm, and concrete tensile cracks of several segments below the arch and the track bed are induced. The simulation results are basically consistent with that of on-site observation. (3) The research results can provide reference for the similar project to judge the safety of shield tunnel structure and to control the upside surcharge. It may also provide important basic data for the upcoming adjacent pit design and construction control.
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