Seismic Sensitivity Analysis of Rigidity and Thickness of Tunnel Lining by Using Ground_Structure Interaction Method Cas
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ORIGINAL PAPER
Seismic Sensitivity Analysis of Rigidity and Thickness of Tunnel Lining by Using Ground_Structure Interaction Method Case Study: Roudbar Lorestan Dam Ali Mazaheri . Masoud Cheraghi Seifabad . Saeed Mahdavi . Bijan Dehghani
Received: 22 May 2020 / Accepted: 18 September 2020 Ó Springer Nature Switzerland AG 2020
Abstract In the present study the design accelerograms were obtained based on MDE, SEE and MCE seismic levels, scaled accelerograms of Bam and Bojnurd earthquakes under the response spectrum of the Roudbar Lorestan Pumped Storage Hydroelectricity (PSH). Then, using the numerical method and FLAC3D software, the effect of concrete lining with thicknesses of 60, 70 and 80 cm on internal loads arising from the interactions between the linings and rocks was investigated. Also, the impact of rigidity on these internal loads was studied through simulations by different elastic moduli of 20–45 GPa. The sensitivity analysis showed that by increasing the thickness of lining, the internal load increases significantly due to the ground structure interaction resulting from seismic conditions. However, as the load carrying capacity increases, the safety factor does not change. At the seismic levels of MDE, SEE and MCE, the minimum safety for thicknesses of 60–80 cm is estimated to be 4.3, 2.9 and 1.5, respectively. In addition, an increase in the rigidity causes a relatively high increase of structural forces and also a significant increase in the moment and forces tangent to the tunnel perimeter. At the MCE levels, doubling the elastic modulus of lining the moment and force along
A. Mazaheri M. Cheraghi Seifabad (&) S. Mahdavi B. Dehghani Department of Mining Engineering, Isfahan University of Technology, 8415683111 Isfahan, Iran e-mail: [email protected]
the tunnel tangent have increased by 1.83 and 1.3 times and along tunnel axis by 1.73 and 1.83, respectively. Along the tunnel axis, the forces increased more strongly than the moment, although the moment values were relatively low. Keywords Response spectrum Scaling of accelerogram Lining thickness and rigidity Interaction effect of axial force_bending moment Numerical method
1 Introduction Nowadays, underground spaces especially tunnels are utilized for welfare and engineering purposes, such as transportation, urban facilities services and access to underground power plants. These structures may not be safe if they are adjacent to seismic areas, which are hence very likely to cause human capital losses or national disasters. Seismic design methods are necessary to encounter the natural disasters. It is clear that the time, location and intensity of earthquake are not predictable and the seismic design is subject to a set of unknown forces for which the designer has to get the best results with minimal possibilities. The first confirmation of the successful performance of a seismic design in underground structures came about between 1989 and 1991. In 1989, BART based on seismic design r
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