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Sliding stability analysis
Sliding stability analysis checks whether a concrete gravity dam has enough shear resistance along a potential failure plane to resist horizontal forces from water pressure and uplift.
Slope deflection method
The slope deflection method is a classical structural analysis method for finding member end moments in indeterminate beams and frames, introduced by George A. Maney in 1915.
Slope stability analysis
Slope stability analysis is the geotechnical engineering method for assessing whether a soil or rock slope will remain stable, by computing a factor of safety against sliding.
Slow sand filter
A slow sand filter is a drinking-water treatment device in which water passes slowly through fine sand, whose biologically active surface layer removes pathogens; first used at Paisley, Scotland, in 1804.
Sludge thickening
Sludge thickening is a sludge treatment step that removes water from wastewater sludge to reduce volume and lower downstream costs, using gravity, dissolved air flotation, centrifuges, or gravity belts.
Sluice
A sluice, also called a knife gate or stopgate, is a channel or gated opening that controls water flow in canals, dams, locks, and flood defenses.
Slurry shield
A slurry shield is a tunnel boring machine that supports the tunnel face with pressurized bentonite slurry, best suited to coarse sand and gravel with high groundwater pressure.
Slurry trench cut-off wall
A slurry trench cut-off wall is a vertical underground barrier built by excavating a bentonite-stabilized trench and filling it with low-permeability material to block groundwater flow and contain contaminants.
Slurry tunnel boring machine
A slurry tunnel boring machine, commonly called a mixshield, is a TBM that supports the tunnel face with pressurized bentonite slurry, chosen where groundwater must be held under tight pressure control.
SMART Tunnel
The SMART Tunnel (Stormwater Management and Road Tunnel) is a 9.7 km tunnel beneath Kuala Lumpur whose central 3 km section doubles as a double-deck motorway, the first tunnel to combine the two functions.
Smith Mountain Lake
Smith Mountain Lake is a 20,600-acre reservoir in south-central Virginia near Roanoke, created in 1963 by damming the Roanoke River as part of Appalachian Power's pumped storage project.
Smithfield Street Bridge
The Smithfield Street Bridge is a steel lenticular through-truss highway bridge over the Monongahela River in Pittsburgh, designed by Gustav Lindenthal and opened in 1883, the oldest river bridge still standing in Allegheny County.
Smolen–Gulf Bridge
The Smolen–Gulf Bridge is a covered road bridge in Ashtabula County, Ohio, opened in 2008 as the longest covered bridge in the United States at 613 feet.
Snail darter controversy
The snail darter controversy was a 1970s legal conflict in which the endangered snail darter fish halted the nearly completed Tellico Dam in Tennessee until Congress exempted it in 1979.
Snow Hill tunnel (London)
Snow Hill tunnel is a short railway tunnel beneath Smithfield Market in central London, opened in 1866 and reopened in 1988 to carry the Thameslink route between Blackfriars and Farringdon.
Snow load
Snow load is the vertical load that accumulated snow and ice impose on a roof or other structure, treated in structural design as a live environmental load.
Snowy Mountains Scheme
The Snowy Mountains Scheme, also known as the Snowy Mountains Hydro-Electric Scheme, is a hydro-electricity and irrigation complex in southern New South Wales, Australia, built between 1949 and 1974.
Snyder's synthetic unit hydrograph
Snyder's synthetic unit hydrograph is an empirical method published by Franklin F. Snyder in 1938 that constructs a unit hydrograph for ungauged watersheds from measurable basin characteristics.
Sobha Singh (ਸੋਭਾ ਸਿੰਘ) (builder)
Sir Sobha Singh (ਸੋਭਾ ਸਿੰਘ; 1890–1978) was an Indian building contractor and real estate developer who built much of New Delhi after 1911 and was the father of writer Khushwant Singh.
Soft story
A soft story is a building story, often an open ground floor, whose lateral stiffness is much lower than the stories above it, making it vulnerable in earthquakes.
Sogamoso Dam
The Sogamoso Dam, commercially Hidrosogamoso, is a 190-meter-high hydroelectric dam on the Sogamoso River in Santander, Colombia, built by Isagen between 2009 and 2014 with an installed capacity of 820 MW.
Soil mechanics
Soil mechanics is the branch of applied mechanics that predicts the performance of earth structures and foundations from soil properties, founded by Karl Terzaghi in 1925.
Soil nailing
Soil nailing is a geotechnical construction method that reinforces in-place soil with steel bars drilled and grouted into a slope or excavation face, stabilizing cuts built from the top down.
Soil stabilization
Soil stabilization is a geotechnical method that improves the strength and durability of weak soils by blending soil gradations or mixing in additives like lime, cement, fly ash, or bitumen.
Solar still
A solar still, a form of solar distillation, is a device that purifies saline or contaminated water using only sunlight, collecting condensed vapor as fresh water.
Solar water disinfection
Solar water disinfection (SODIS) is a household water treatment method in which contaminated water in transparent PET bottles is exposed to sunlight for at least 6 hours, inactivating pathogens.
Solar water disinfection system
A solar water disinfection system uses sunlight to inactivate drinking water pathogens through ultraviolet radiation, heat, or both, in regions without reliable treated water supplies.
Solar-powered desalination unit
A solar-powered desalination unit is a water-treatment system that uses heat or photovoltaic electricity from sunlight to remove salt from seawater or brackish water, producing fresh water off-grid.
Solomon's Pools
Solomon's Pools (Birak al-Marji', Burak Suliman): three stepped ancient reservoirs southwest of Bethlehem, Palestine, heart of an aqueduct system supplying Jerusalem for about 2,000 years; oldest parts late 1st century BC, Lower Pool Mamluk or Roman.
Sone Canal System
The Sone Canal System is a gravity-fed irrigation network in southern Bihar, India, diverting the Sone river at Dehri; conceived in 1853 and completed in 1874, it made Shahabad the rice bowl of Bihar.