Safety
The building of a dam and the filling of the reservoir behind it places a new weight on the floor and sides of a valley. The stress of the water increases linearly with its depth. Water also pushes against the upstream face of the dam, a nonrigid structure that under stress behaves semiplastically, and causes greater need for adjustment (flexibility) near the base of the dam than at shallower water levels. Thus the stress level of the dam must be calculated in advance of building to ensure that its break level threshold is not exceeded. [4]
Overtopping or overflow of an embankment dam beyond its spillway capacity will cause its eventual failure. The erosion of the dam's material by overtopping runoff will remove masses of material whose weight holds the dam in place and against the hydraulic forces acting to move the dam. Even a small sustained overtopping flow can remove thousands of tons of overburden soil from the mass of the dam within hours. The removal of this mass unbalances the forces that stabilize the dam against its reservoir as the mass of water still impounded behind the dam presses against the lightened mass of the embankment, made lighter by surface erosion. As the mass of the dam erodes, the force exerted by the reservoir begins to move the entire structure. The embankment, having almost no elastic strength, would begin to break into separate pieces, allowing the impounded reservoir water to flow between them, eroding and removing even more material as it passes through. In the final stages of failure the remaining pieces of the embankment would offer almost no resistance to the flow of the water and continue to fracture into smaller and smaller sections of earth or rock until they disintegrate into a thick suspension of earth, rocks and water.
Therefore, safety requirements for the spillway are high, and require it to be capable of containing a maximum flood stage. It is common for its specifications to be written such that it can contain at least a one-hundred-year flood. [5] A number of embankment dam overtopping protection systems were developed in the early 21st century. [6] These techniques include concrete overtopping protection systems, timber cribs, sheet-piles, riprap and gabions, reinforced earth, minimum energy loss weirs, embankment overflow stepped spillways, and precast concrete block protection systems.
All dams are prone to seepage underneath the dam, but embankment dams are prone to seepage through the dam as well; for example, the Usoi landslide dam leaks 35-80 cubic meters per second. Sufficiently fast seepage can dislodge a dam's component particles, which results in faster seepage, which turns into a runaway feedback loop that can destroy the dam in a piping-type failure. Seepage monitoring is therefore an essential safety consideration. [7]
Geotechnical engineering is the branch of civil engineering concerned with the engineering behavior of earth materials. It uses the principles of soil mechanics and rock mechanics for the solution of its respective engineering problems. It also relies on knowledge of geology, hydrology, geophysics, and other related sciences. Geotechnical (rock) engineering is a subdiscipline of geological engineering.
A levee, dike, dyke, embankment, floodbank, or stop bank is a structure that is usually earthen and that often runs parallel to the course of a river in its floodplain or along low-lying coastlines.
Dartmouth Dam is a large rock-fill embankment dam with an uncontrolled chute spillway across the Mitta Mitta, Gibbo, and Dart rivers, the Morass Creek and a number of small tributaries. The dam is located near Mount Bogong in the north-east of the Australian state of Victoria. The dam's purpose includes irrigation, the generation of hydro-electric power, water supply and conservation. The impounded reservoir is called Dartmouth Reservoir, sometimes called Lake Dartmouth. The Dartmouth Power Station, a hydro-electric power station that generates power to the national grid, is located near the dam wall.
A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aquaculture, and navigability. Hydropower is often used in conjunction with dams to generate electricity. A dam can also be used to collect or store water which can be evenly distributed between locations. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. The earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC.
A diversion dam is a dam that diverts all or a portion of the flow of a river from its natural course. Diversion dams do not generally impound water in a reservoir; instead, the water is diverted into an artificial water course or canal, which may be used for irrigation or return to the river after passing through hydroelectric generators, flow into a different river or be itself dammed forming an onground or groundwater reservoir or a storm drain.
A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure that water does not damage parts of the structure not designed to convey water.
Soil mechanics is a branch of soil physics and applied mechanics that describes the behavior of soils. It differs from fluid mechanics and solid mechanics in the sense that soils consist of a heterogeneous mixture of fluids and particles but soil may also contain organic solids and other matter. Along with rock mechanics, soil mechanics provides the theoretical basis for analysis in geotechnical engineering, a subdiscipline of civil engineering, and engineering geology, a subdiscipline of geology. Soil mechanics is used to analyze the deformations of and flow of fluids within natural and man-made structures that are supported on or made of soil, or structures that are buried in soils. Example applications are building and bridge foundations, retaining walls, dams, and buried pipeline systems. Principles of soil mechanics are also used in related disciplines such as geophysical engineering, coastal engineering, agricultural engineering, hydrology and soil physics.
Table Rock Lake is an artificial lake or reservoir in the Ozarks of southwestern Missouri and northwestern Arkansas in the United States. Designed, built and operated by the U.S. Army Corps of Engineers, the lake is impounded by Table Rock Dam, which was constructed from 1954 to 1958 on the White River.
The Wolf Creek Dam is a multi-purpose dam on the Cumberland River in the western part of Russell County, Kentucky, United States. The dam serves at once four distinct purposes: it generates hydroelectricity; it regulates and limits flooding; it releases stored water to permit year-round navigation on the lower Cumberland River; and it creates Lake Cumberland for recreation, which has become a popular tourist attraction. Because of seepage problems in the dam's foundation, it has become the U.S. Army Corps of Engineers's top dam priority. U.S. Route 127 is built on top of the dam.
Copeton Dam is a major clay core and rock fill embankment dam with nine radial gates and a gated concrete chute spillway across the Gwydir River upstream of Bingara in the New England region of New South Wales, Australia. The dam's purpose includes environmental flows, hydro-electric power generation, irrigation, and water supply. The impounded reservoir is called Lake Copeton.
Googong Dam is a minor ungated earth and rock fill with clay core embankment dam with concrete chute spillway plus a nearby 13 metres (43 ft) high earthfill saddle embankment across the Queanbeyan River upstream of Queanbeyan in the Capital Country region of New South Wales, Australia. The dam's purpose includes water supply for Canberra and Queanbeyan. The impounded reservoir is called Googong Reservoir.
Lake Needwood is a 75-acre (300,000 m2) reservoir in Derwood, Maryland, United States. Located east of Rockville, in the eastern part of Montgomery County, it is situated on Rock Creek. The lake was created by damming Rock Creek in 1965 with the goal of providing flood control and reducing soil erosion. Lake Needwood also protects the water quality of the creek by functioning as a retention basin to trap sediment from storm-water runoff.
Internal erosion is the formation of voids within a soil caused by the removal of material by seepage. It is the second most common cause of failure in levees and one of the leading causes of failures in earth dams, responsible for about half of embankment dam failures.
The Nillahcootie Dam, a rock and earth-fill embankment dam with a unique Gothic arch-shaped crest spillway across the Broken River that is located near Mansfield, in the Alpine region of Victoria, Australia. The dam's purpose is for the supply of potable water and for irrigation. The impounded reservoir is called Lake Nillahcootie.
A dam failure or dam burst is a catastrophic type of structural failure characterized by the sudden, rapid, and uncontrolled release of impounded water or the likelihood of such an uncontrolled release. Between the years 2000 and 2009 more than 200 notable dam failures happened worldwide.
The Jamestown Dam is a rolled-earth dam spanning the James River in Stutsman County in the U.S. state of North Dakota, serving the primary purpose of flood control. It is north of the city of Jamestown, North Dakota. Built from April 1952 to September 1953, the dam measures 1,418 feet (432 m) long at the crest and 85 feet (26 m) high. It impounds the James River to form the Jamestown Reservoir. A small islet lies shortly upstream of the dam, where the James River previously split into two channels.
Fontenelle Dam was built between 1961 and 1964 on the Green River in southwestern Wyoming. The 139-foot (42 m) high zoned earthfill dam impounds the 345,360-acre-foot (0.42600 km3) Fontenelle Reservoir. The dam and reservoir are the central features of the Seedskadee Project of the U.S. Bureau of Reclamation, which manages the Fontenelle impoundment primarily as a storage reservoir for the Colorado River Storage Project. The dam suffered a significant failure in 1965, when the dam's right abutment developed a leak. Emergency releases from the dam flooded downstream properties, but repairs to the dam were successful. However, in 1983 the dam was rated "poor" under Safety Evaluation of Existing Dams (SEED) criteria, due to continuing seepage, leading to an emergency drawdown. A concrete diaphragm wall was built through the core of the dam to stop leakage.
The Fürstenteich is a reservoir near Silberhütte in the German state of Saxony-Anhalt. It has an earth-filled dam with an impervious core. It impounds the Teufelsgrundbach stream.
San Antonio Dam is an embankment flood control and debris dam on San Antonio Creek in San Bernardino County, California, about 5 miles (8.0 km) north of Ontario. The dam was authorized by the Flood Control Acts of 1936 and 1938 as part of a major program to provide flood protection in the Santa Ana River system. Construction began in April 1952 and finished in May 1956. The dam controls runoff from a rugged catchment area of 27 square miles (70 km2) in the San Gabriel Mountains.
Eightmile Lake is a reservoir lake located on the eastern slope of Eightmile Mountain, in Chelan County in Washington. It is a reservoir lake formed along the beginning route of Eightmile Creek as it exits Jack Ridge.
