A critical analysis of the effect of earth pressure balance (EPB) on displacements of tunnel face by numerical modeling (Case study of Abuzar water transitional tunnel)

Overburden has different thickness along the Abuzar water transitional tunnel. For this reason, tunnel face support pressure has been estimated for four different sections having ratio of overburden thickness to diameter of 1.1, 1.33, 1.56 and 1.7 respectively by different empirical and analytical methods. Estimated tunnel face support pressure using each of empirical and analytical methods does not have a considerable variation with an increase of the overburden thickness. Effect of face support pressure using different empirical and analytical methods and the practical measured pressure on the values of face displacements of the tunnel have been investigated in four different sections of tunnel by numerical modeling using FLAC3d software. The results show that values of displacements from the tunnel face modeling using FLAC3d software have a considerably greater value for overburden having a thickness of greater than 6.8 m in comparison with the overburden thickness of smaller than 5.8 m. The empirical and analytical methods cannot estimate acceptable value of face support pressure of tunnel with an increase of the overburden thickness for a tunnel excavated by earth pressure balance (EPB).