The Delhi Metro Rail Corporation (DMRC) is close to completing tunneling for its second phase of construction, with less than 2 kilometers left out of 35 km, following the completion of India’s longest tunnel in an urban area built using the New Austrian Tunneling Method (NATM). The 2.85-km-long tunnel is part of the 22.7-km Airport Express Line, which will connect the Delhi city center to the international airport when completed in the summer of 2010. Photo: Neelam Mathews / ENR Delhi Metro rail cars are delivered by Russian Antonov cargo plane earlier this year. Photo: Delhi Metro Rail Corp. New
Arch dams, classically curved monoliths situated in narrow valleys, are not as common as other types of dams, such as embankment dams and gravity dams. ENR takes a look at some of the biggest arch dams in the world, both completed and under construction.