Three-dimensional finite difference analysis of shallow sprayed concrete tunnels crossing a reverse fault or a normal fa
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RESEARCH ARTICLE
Three-dimensional finite difference analysis of shallow sprayed concrete tunnels crossing a reverse fault or a normal fault: A parametric study Masoud RANJBARNIAa* , Milad ZAHERIa, Daniel DIASb,c a
Department of Geotechnical Engineering, Faculty of Civil Engineering, University of Tabriz, Tabriz, Iran School of Automotive and Transportation Engineering, Hefei University of Technology, Hefei 230009, China c Université Grenoble Alpes, Grenoble F-38000, France b
*
Corresponding author. E-mail: [email protected]
© Higher Education Press 2020
ABSTRACT Urban tunnels crossing faults are always at the risk of severe damages. In this paper, the effects of a reverse and a normal fault movement on a transversely crossing shallow shotcreted tunnel are investigated by 3D finite difference analysis. After verifying the accuracy of the numerical simulation predictions with the centrifuge physical model results, a parametric study is then conducted. That is, the effects of various parameters such as the sprayed concrete thickness, the geo-mechanical properties of soil, the tunnel depth, and the fault plane dip angle are studied on the displacements of the ground surface and the tunnel structure, and on the plastic strains of the soil mass around tunnel. The results of each case of reverse and normal faulting are independently discussed and then compared with each other. It is obtained that deeper tunnels show greater displacements for both types of faulting. KEYWORDS
1
urban tunnel, sprayed concrete, reverse fault, normal fault, finite difference analysis
Introduction
The safe construction of urban tunnels against earthquake vibrations is an important issue. The problem is more highlighted when these tunnels are constructed in seismic areas. It is better to avoid constructing tunnels near active faults, but sometimes passing through a fault is even inevitable. In such cases, the moving of faults and subsequently deformation of tunnels are great concerns and can have remarkable effects on the stability of tunnels. In the Kobe earthquake in 1995 and the Chi-Chi earthquake in 1999, some tunnels experienced significant damages due to fault movements. Most of studies in the earthquake engineering focused on the dynamic reaction of the soils and of the structures, and few studies are devoted to evaluate the effects of a moving fault on tunnels [1–5]. In some cases, the effects of faulting on the free field have been investigated [6–9]. In other attempts, the interaction between the faults and Article history: Received Apr 27, 2019; Accepted Jun 17, 2019
shallow or deep foundations has been studied by numerical methods as well as by centrifuge physical tests [10–15]. However, the problem of a fault rupture in constructed tunnels have been rarely studied. Wang et al. [5] numerically investigated the effects of various faults movements on the flexible lining of tunnels. It was found the tunnel lining is seriously damaged for the case of strike-slip faulting. The aim of their study was the recognition of the p
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