Bong-Hyun Cho, manager of the immersed tunnel site for the $1.8-billion Busan-Geoje fixed- link project, finally can get some sleep. Six of 18 concrete tunnel elements, 180-m long and 45,000 tonnes, have been towed successfully from a dry dock 35 km away, sunk into the turbulent depths of the Pacific and placed atop specially designed gravel beds with tight tolerances. "If the gravel beds fail, the project fails," he says. "I was so anxious." Slide Show Photo: Halcrow Korea’s 8.2-km-long sea link will connect the mainland to Geoje Island through three islets. After a rocky start with glitches in the
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.