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Indexed by:期刊论文

Date of Publication:2016-11-01

Journal:KSCE JOURNAL OF CIVIL ENGINEERING

Included Journals:SCIE、EI、Scopus

Volume:20

Issue:7

Page Number:2965-2980

ISSN No.:1226-7988

Key Words:NATM tunnel; feet-lock pipe; steel frame; mechanism; mechanics of underground structures

Abstract:In the past few decades, an effective support method, i.e., adopting feet-lock pipe combined with steel frame, has been successfully applied to the settlement control in excavation of many weak rock tunnels. However, the mechanism of this combined support has not yet well been understood, and there is a lack of a general approach to explain it. This paper aims to present an analytical approach to explain and evaluate the mechanism of this support. First, an arch model with elastic supports and an elastic foundation beam model are established respectively to model the steel frame and feet-lock pipe. With the force and deformation compatibility conditions between the two members, the formulae for calculating the deflection and internal forces of the feet-lock pipe are derived. The theoretical support effects of the feet-lock pipe are calculated and compared with the existing studies through case studies. Then, with two cases of under symmetrical and unsymmetrical earth pressures being considered, the mechanical behaviors of the feet-lock pipe are analyzed in detail. Finally, a parametric study of an example tunnel is conducted in detail.