Roller-compacted concrete dams have steadily taken their place in the menu of possible dam types over the past four decades, with over 650 of them completed or under construction, according to HydroWorld magazine. China is far and away the leading RCC dam builder, with 165 as of 2012; of those, 40 are higher than 100 meters. Japan, the United States, Brazil and Spain are the other most prolific RCC dambuilders.Roller-compacted concrete dams evolved in the 1970s to satisfy a particular need by dambuilders and owners. The percentage of dams built with concrete dropped steadily between 1950 and the late 1970s,
Related Links: Precast Concrete Network Arch Bridge Is A First Unusually Slender Arch Marks Prague Bridge Arch bridges are one of the oldest types of bridges. The oldest known bridge in the world known to still be in use is the Caravan Bridge, a stone arch bridge across the Meles River in Izmir, Turkey. It was built in 850 B.C.Roman engineers built many arch bridges, quite a few of which are still standing. Probably the most famous is the Pont du Gard, an aqueduct bridge in southern France. Built in the first century A.D., it features three tiers of limestone
The projects we profile in this special section all stretch the limits of what is possible. At first glance, they may seem impossible to build. some of the projects are technically possible to build but may be economically unfeasible.
Metro systems are vital circulatory systems for moving large numbers of residents, commuters and tourists around large cities. Metros are mass-transit systems that are generally heavy rail lines that operate on their own rights-of-way, whether underground, at grade or on elevated viaducts. They are distinct from light-rail and commuter rail networks.According to the International Association of Public Transport (UITP), the world's 148 metro systems carry, every day, more than 150 million passengers on 540 lines over 11,000 kilometers to and from 9,000 stations.Since the earliest metro systems were built more than 100 years ago, there have been many advances in
Map by Jeffrey Cox/ENR Rail Baltica will extend European standard gauge through the Baltic states. Related Links: For Panamax Port Expansions, The Freight Wait is Almost Over Saudi Arabia Upgrading Rail Passenger and Freight Service Lithuania, Latvia and Estonia are aiming to take their railway destinies more firmly in hand through Rail Baltica, a multinational effort to improve freight rail connectivity between Central and Northern Europe. Running from the port of Tallinn, Estonia, south through Latvia and Lithuania, the high-speed, standard-gauge line will connect with Warsaw, Poland, and ultimately, Berlin.Construction of Baltica 1, the first 115-kilometer segment between the Polish-Lithuania
Photo Courtesy U.S. Marine Corps The Tarbela Dam in Pakistan quadrupled in cost by the time it was completed in 1984. Related Links: Should We Build More Large Dams? The Actual Costs of Hydropower Megaproject Development Megaprojects Need More Study Up Front to Avoid Cost Overruns "Multiyear Jobs, Even Small Ones, Are Biggest Risk for Overruns" Large dam projects make bad investments, according to a new global study by a team from Oxford University, England. Three-quarters of the projects analyzed by researchers experienced cost overruns, with the average increase reported as 96% higher in real terms than the figure cited
Hydropower produces 16% of the world’s electricity and plays a strong role in satisfying the national energy needs of certain countries. Paraguay produces all of its electricity from hydropower, while exporting most of its excess supply to neighboring Brazil and Argentina. Albania, Bhutan and Lesotho also depend exclusively on hydroelectricity. Norway produces more than 98% of its electricity from hydropower, Brazil draws upon it for 85%, Iceland for 80%, Venezuela for 69%, Colombia for 65% and Canada for 61%. Austria (60%), Switzerland (56%) and New Zealand (53%) are other countries that generate the majority of their electricity from hydro sources.
