Istanbul is a growing city characterized by large infrastructural projects under planning and construction to develop the city transportation system. The Gayrettepe – Istanbul 3rd Airport Rail Metro Line (or “Gayrettepe – Istanbul Yeni 3rd Havalimani”) is part of this development: the new line will allow integration of city’s major rebroadcasting centers of mass transportation with the urban rail system lines, in order to provide quick access to the new Istanbul Airport, foreseen to be the largest and busiest airport in the World. Unfortunately, a collapse occurred along the alignment during an excavation carried out by an EPB shield machine in a critical area, where there is a sudden change in the geology from good rock to soil.