Internal Forces Generated in the Circular and Rectangular Tunnels Lining Due to Seismic Loading

Result of an underground tunnel designation is determining the static and seismic forces generated in the tunnel lining. For calculating of these forces in static and quasi- static mode¡ several relationships have been presented that briefly in this article is cited. Then for two tunnels with circular and square sections¡ numerical- seismic analysis were done and the results are compared with each other. According to the results¡ the axial force created in the circular tunnel lining in static and seismic conditions¡ is greater than those in square tunnels¡ but bending moment and shear force in square tunnel are larger than those for the circular tunnel. The resulting forces of seismic analysis of circular tunnel averagely are 12 times of static analysis and for the square tunnel are 6 times of the static analysis. Ground surface settlement profile in static mode is symmetric¡ and settlements above the square tunnel are greater than those for circular tunnel. Ground surface settlement profile is asymmetric in seismic condition¡ but the settlement values are almost identical for both sections of the tunnel.
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