Seismic Sensitivity Analysis of Rigidity and Thickness of Tunnel Lining by Using Ground_Structure Interaction Method Case Study: Roudbar Lorestan Dam

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 FLAC 3 D 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 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.