Abstract
This study was carried by analysis for purposes of finding out a mutual relation between each parameter and shapes of cross section of shield tunnel for which it is possible to reduce a section force, especially bending moment, with respect to elliptical and rectangular shapes.
In case of elliptical shapes, there are elliptical rations which reduce bending moment to minimums.
In case of rectangular shapes, there is a deference tendency between the case width-height ratio is under 0.8 and the one it is over 0.8.
