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`Mathematical Problems in EngineeringVolume 2017, Article ID 9387628, 12 pageshttps://doi.org/10.1155/2017/9387628`
Research Article

## Analysis of Pipe-Roof in Tunnel Exiting Portal by the Foundation Elastic Model

1School of Highway, Chang’an University, Middle-Section of Nan’er Huan Road, Xi’an, Shaanxi Province, China
2China Construction Seventh Engineering Division Corp. Ltd., Zhongjian Building, Chengdong Road No. 108, Zhengzhou, Henan, China

Correspondence should be addressed to Jianxun Chen; moc.361@9691xjnehc and Lijun Chen; moc.621@4002nujilnehc

Received 21 April 2017; Revised 1 August 2017; Accepted 17 August 2017; Published 18 October 2017

Academic Editor: Francesco Marotti de Sciarra

Copyright © 2017 Yanbin Luo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

The Pasternak double-parameter elastic foundation model of pipe-roof during the construction of tunnel exits is first established. Based on the portal project of Hanjiashan highway tunnel, an inclinometer is adopted to measure the settlement deformation of a pipe-roof and demonstrates the deformation law in tunnel exiting portals. The formulas for calculating the deflection and internal forces are derived to analyze the deformation of the pipe-roof in each excavation stage, and the results are compared with field monitoring data. Finally, the influences of excavation height, excavation footage, and stiffness of the pipe-roof on the support effect are investigated. Analysis indicates that the longitudinal settlement curve shows a groove distribution, which can be divided into five stages: micro, rapid, continuous, resilience, and stable deformation. Moreover, the subsidence rate reaches its maximum at the tunnel face. The influence of tunnel excavation on the deformation mainly has a range of 1.5 times the excavation height. To control the deflection of the pipe-roof, excavation height should be controlled in the range of 3.5 m, excavation footage should be controlled in the range of 1–1.4 m, and the diameter and thickness of the selected pipe-roof should be in the ranges of 89–159 mm and 5–8 mm, respectively.