ABSTRACT
Frequently new Metro lines have to cross their path with existing ones, combined with the frequent need to encounter better geological conditions and preserve archeological heritages; due to this tunnels, stations and technological shafts are often designed to be realized at deeper depth. Another topic is related to the very frequent limited construction space available with space constraint, interferences with existing buildings and infrastructures. In the last 2 decades trench cutter technology evolution has been quite and as a matter of fact the world is looking for something new since a long time. What has been really, technologically speaking, evolving in the last decade is the “marriage” between heavy duty crawler crane and both mechanical and hydraulic grab. The well-known traditional diaphragm wall excavation has experienced new applications also in urban metro projects; deeper depth, higher accuracy, top joint quality, easy and fast mob & demob phases in limited site spaces.
