Umbrella arch method performance, structural behavior and design elements utilizing in collapsing zones
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ORIGINAL ARTICLE
Umbrella arch method performance, structural behavior and design elements utilizing in collapsing zones Parisa Bagherzadeh1 · Kamran Goshtasbi1 · Mojtaba Kashef2 Received: 10 May 2020 / Accepted: 30 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The umbrella arch method is a pre-reinforcement technique that ensures tunnel stability in poor ground conditions or shallow overburden. Quantitative assessment of this method is still challenging due to its complexity, there is no accurate method to model the behavior of reinforced arch forming with steel pipes and grout. This paper uses finite difference numerical simulation to model and analyze the effectiveness of the umbrella arch method in Qazvin–Rasht railway tunnel as well as in-situ measurement. Umbrella arch has modeled considering pipe, grout and soilcrete as pipe umbrella components; each pipe simulated individually. The structural behaviour of pipes in the excavation sequence is analyzed as well as the importance of geometrical and physical design elements, on tunnel stability using FLAC 3D software. Results indicate that the umbrella arch method has reduced tunnel convergence by 49%. By continuing the excavation step, residual pipe length ahead of the face and tunnel arch, the location of maximum pipe displacement, force, and moment are changed. Furthermore, by considering executive limitation, an increase in pipe angle, diameter and thickness, length and overlapping length, as well as pipes distance decrease, center to center grout penetration radius, and water-cement ratio 0.5 have had a positive effect in providing more strength arch and tunnel stability. Keywords Umbrella arch · Numerical modeling · Instrumentation · Design element · Structural behavior
Introduction Tunnel construction in the weak ground would arise several problems including tunnel instability, damage to existing structures, and ground settlement. To overcome these problems, some auxiliary techniques have been adopted in tunneling. Grouting with pipes is one of the most popular prereinforcement methods of tunnel heading that is called the umbrella arch method or UAM. In this technique, by creating a longitudinal arching parallel to the tunnel axis, safe excavation would be allowed even in poor ground conditions. * Parisa Bagherzadeh [email protected] Kamran Goshtasbi [email protected] Mojtaba Kashef [email protected] 1
Department of Mining Engineering, Faculty of Engineering, Tarbiat Modares University, Tehran, Iran
Department of Mining Engineering, Faculty of Engineering, University of Zanjan, Zanjan, Iran
2
This method is well described in the literature by, Pelizza and Peila (1993),Yoo and Shin (2003), Carrieri et al. (1991), Carrieri et al. (2002), Lunardi (2000), Kim et al. (2005), Aksoy (2010), Ocak (2008), Song et al. (2013), Bagherzadeh et al. (2013), Bagherzadeh and Goshtasbi (2014),Schumacher et al. (2016), Gao et al. (2015), Yahya (2016), Salmi et al. (2017), Taromi and Eftekhari (2018) a
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