2,617 articles
Tunnelling companies of the Royal Engineers
Tunnelling companies of the Royal Engineers: British Army mine-warfare units raised from February 1915 (33 by June 1916, including Canadian, Australian and New Zealand companies) for Western Front mining such as Messines 1917, and re-formed in 1939-45 for fortress excavation in Gibraltar and Malta.
Tunnels by completion era
Tunnels by completion era is an overview of tunnel history organized into Ancient, Industrial, and Modern eras, from gunpowder blasting at Malpas in 1681 to modern tunnel boring machines.
Tunnels completed in the 15th century
Tunnels completed in the 15th century are transport, water-supply, and mining tunnels finished between 1401 and 1500, when large-scale tunnelling in Europe was re-emerging after the fall of Rome.
Tunnels completed in the 16th century
Tunnels completed in the 16th century are documented underground works built between 1501 and 1600 for mine drainage, water supply, and siege warfare, dug without explosives.
Tunnels completed in the 17th century
Tunnels completed in the 17th century include the Malpas tunnel on France's Canal du Midi, the first navigable canal tunnel, alongside mining, drainage, and irrigation works in Japan, Mexico, and Peru.
Tunnels completed in the 18th century
Tunnels completed in the 18th century were chiefly canal tunnels: between 1760 and 1820, Georgian engineers built 47 in the UK, with Sapperton the longest at 3,490 m.
Tunnels completed in the 21st century
Tunnels completed in the 21st century include the Gotthard Base Tunnel, opened in 2016 as the world's longest railway tunnel, and Norway's deep subsea road tunnels.
Turbidity
Turbidity is a measure of the relative clarity of water, reported in nephelometric turbidity units (NTU) and caused by suspended particles like clay, silt, and algae that scatter light.
Turin–Lyon high-speed railway
The Turin–Lyon high-speed railway, also called the Lyon–Turin railway, is a 270-kilometer passenger and freight line under construction between Lyon, France, and Turin, Italy, whose centerpiece is the 57.5-kilometer Mont Cenis base tunnel.
Turlough Hill Power Station
Turlough Hill Power Station is a pumped-storage hydroelectric plant in the Wicklow Mountains, County Wicklow, Ireland, generating up to 292 MW and the Republic's only pumped storage station.
Turner Construction
Turner Construction Company is a New York City-based general contractor, the largest in the United States by revenue, founded in 1902 and owned by Germany's HOCHTIEF.
Turnkey
Turnkey, also known as a turnkey project or turnkey contract, is a delivery arrangement in which one contractor designs, builds, and commissions a facility for a lump sum, handing it over fully operational.
Turpan water system
The Turpan water system is a network of karez, underground gravity-fed channels carrying mountain groundwater to oasis fields in the Turpan Basin of Xinjiang, China, some at least 600 years old.
Tuttle Creek Dam
Tuttle Creek Dam is an embankment dam on the Big Blue River north of Manhattan, Kansas, built by the U.S. Army Corps of Engineers for flood control.
Tyne Bridge
The Tyne Bridge is a steel through-arch road bridge across the River Tyne between Newcastle upon Tyne and Gateshead, opened by King George V in 1928.
Tyne cyclist and pedestrian tunnels
The Tyne cyclist and pedestrian tunnels are two parallel tunnels beneath the River Tyne, linking Howdon with Jarrow, opened in 1951 as Britain's first built for both cyclists and pedestrians.
U Bein Bridge
U Bein Bridge, also called U Pain Bridge or Taungthaman Bridge, is a 1.2-kilometer wooden footbridge of teak crossing Taungthaman Lake near Amarapura, Myanmar, believed the world's oldest and longest teakwood bridge.
Ujjani Dam (उज्जनी धरण)
Ujjani Dam (उज्जनी धरण), also known as Bhima Dam, is a dam on the Bhima River in Solapur district, Maharashtra, India, completed in 1980 to irrigate drought-prone districts.
Ukai Dam
Ukai Dam, forming the Vallabh Sagar reservoir, is a multipurpose dam on the Tapi River in Gujarat, India, completed in 1972 for flood control, irrigation, and power.
Ultra-high-performance concrete
Ultra-high-performance concrete (UHPC) is a fiber-reinforced cementitious composite with compressive strength above 120 MPa and very low permeability. Developed as reactive powder concrete at Bouygues in 1993, it is used mostly in bridges.
Ultrapure water
Ultrapure water (UPW), known in labs as Milli-Q water, is water purified to remove ions, organics, particles, gases, and bacteria, defined by resistivity of 18.2 MΩ·cm and used mainly in semiconductor fabrication.
Un-Dam the Klamath campaign
The Un-Dam the Klamath campaign was the effort by tribes, fishermen, conservationists, and irrigators to remove four Klamath River dams, culminating in the 2010 settlement and the largest dam removal completed to date in 2024.
Uncompahgre Project
The Uncompahgre Project, originally called the Gunnison Project, is a Bureau of Reclamation irrigation project in western Colorado authorized in 1903, one of the Reclamation Service's first five.
Underground city
An underground city is a network of pedestrian walkways, shops, and transit connections built below street level downtown, letting people move without going outdoors; Montreal's RÉSO and Toronto's PATH are the best-known examples.
Underground City, Montreal
The Underground City of Montreal, officially known as RÉSO, is an indoor pedestrian network of about 32 km of tunnels linking shops, offices, hotels, and metro stations downtown.
Underground irrigation canal
Underground irrigation canal, chiefly the Persian kārēz (کاریز) or qanat: a gravity-fed shaft-and-gallery aqueduct from Iran and Afghanistan irrigating about 1.5 million hectares, with regional names falaj, foggara, and karez.
Underground passages
Underground passages, Exeter: medieval stone-lined access tunnels and conduits in the city's water supply, dating from a 1226 conduit, scheduled monument NHLE 1003851 since 1935, partly open for guided tours.
Underpinning
Underpinning is a construction method that deepens a building's foundations by excavating soil beneath them and replacing it with concrete, done in phases to strengthen or deepen inadequate foundations.
Unfinished obelisk
The Unfinished Obelisk is a colossal granite obelisk still attached to bedrock in the ancient quarries at Aswan, Egypt, probably commissioned by Queen Hatshepsut for the temple of Amun at Karnak.
Unified Soil Classification System
The Unified Soil Classification System (USCS) is an engineering soil classification, standardized as ASTM D2487, that assigns soils two-letter group symbols based on particle size and plasticity.