Within the scope of Eurasia Tunnel Project (İstanbul Strait Road Tube Crossing Project); which was opened on December 21, 2016 that connects Asian and European continents with highway tunnel under seabed for the first time; excavation support systems of temporary structures called as transition boxes and prepared for TBM (Tunnel Boring Machine) entrance and breakout points were executed in both European and Asian sides. Deep excavations of up to 30 m in a region only 25m-30m far away from the Sea of Marmara were successfully completed without damaging surrounding roads and structures, Periodically, displacement were measured at each stage of the project and necessary measures were taken at stages where the design criteria differed.