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Abstract
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Urban development and rapid extension of cities have been accompanied by a considerable growth in
mechanized shield tunnelling. Commonly precast concrete segments are used as tunnel lining which
comprises relatively considerable part of tunnelling cost. The optimum design of lining needs to an accurate
evaluation of loads acting on the lining.
In this paper, the effects of ground stratification, surface buildings specifications and tunnel depth on
lining loads were studied. For this purpose a 3D finite element model was used employing the ABAQUS
software (Ver. 6.11). The geometry of tunnel, lining segments, injection grout and the surrounding soil
properties were adopted from the under construction Tabriz urban railway line 2 project.
The results show that the studied parameters have considerable effects on lining loads. For mentioned
case study, surface buildings with 5 and more story have a considerable effect on lining loads, especially
for shallow tunnels. The geometry of surface buildings influences the internal forces of the tunnel lining
and increase of buildings width and length increases the lining loads. The building width is the most
important parameter and with increase of that the influence of other parameters increases. Also by comparison
of obtained results in this study with results of 2D analysis, reliability of 2D models was investigated.
The comparisons show that 3D analysis is superior to 2D analysis, particularly in the cases of
surface buildings presence. The difference between results increases with decrease of building length
and increase of tunnel depth and building weight.
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