ABSTRACT
This article makes a contribution to the data-base that illustrated our experience with displacement, which far exceeded the deformation tolerances anticipated in areas of tunnel excavations conducted in soft ground, and on the changes, it created in the tunnel entrenchment. The subject of this text is an investigation into the deformation effect of soft grounds that cause unavoidable high deformations in the worst ground conditions, with high plasticity, and with a length reaching up to 50 meters in the tunnel alignment and vertically proceeded up to surface level, and additionally did not contain any hard ground, but consisted of faulting layers throughout, and the changes that this type of ground conditions inevitably caused in the tunnel supporting system. One of the biggest challenges during tunnel excavations in “Weak Flyschoid Series”, with a high clay ratio and low geo-mechanical parameters, was the high risk of damage caused by induced deformations to the open tunnel geometry. Therefore, in order to prevent unforeseen and rapidly progressing deformations in the tunnel and any resulting faults, important changes were made and applied to the NATM supporting system.
