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Buttress Dam
Buttress dams have multiple names such as hollow dams, hollow gravity dams, and multiple arch dams. John S. Eastwood an engineer, was a designer and proponent of multiple-arch dams. The benefits of multiple-arch dams can be most readily seen when looking into small agricultural towns. These people lack the necessary capital to build massive and expensive gravity dams but they could finance lighter, cheaper, multiple-arch designs. An example of the benefits that come from Multiple-arch dams was Littlerock dam, completed in 1924 it helped gather water from the Littlerock and Palmdale district in California. Throughout their history prominent engineers have denounced multiple-arch dams do to having financial and professional stakes in gravity dams.

The Buttress dam does however, run into certain problems that are not as prevalent in other dams. Even though they tend to be more economical they run the risk of not reaching the proper height required to become effective. An example would be as follows with a slope of 50 degrees the crown of each arch will have to be 0.84 feet farther forward at the crest than at the base for each foot of height. This defect will demand that the dam is either much taller than calculated or a lot wider to accommodate for it problem. Another issue is that the dam has to have a proper foundation of bedrock or other suitable material. If the buttresses for the dam are not properly seated the dam runs the chances of a possible collapse. Some problems that might occur during the construction of a buttress dam is cracks along the convex side near the cresting of the dam due to thermal stresses and the dam not being ‘loaded’. Once the dam has been reinforced if cracks continue to occur the cracks will close once the force of the water is against it.

Buttressing applications
Existing dams can also be modified to possess qualities of the buttress dams. An example of this modification would be the Butt Valley dam in Plumas county, California. The dam is located within 0.5 km of the Butt Valley Fault zone and within 7 km of the Lake Almanor Fault. The location of the dam makes its highly susceptible to seismic failure leading engineers to reinforce it with rock fill buttresses. Other alternatives were considered however, due to multiple factors such as reliability, environmental impact, materials available, cost, expedience, and construction practicality they were rejected. The evaluation led to the selection of the upstream and downstream rock fill buttresses. The application of buttresses would protect intake towers and assure upstream and downstream stability under difficult conditions. The Butt Valley dam is able to return to normal operations due to the fact that applying buttresses takes the least amount of time when compared to other practical options. Through multiple experiments the conclusion was reached that the reinforcements would be sufficient enough to pass MCE regulations allowing for the appropriate amount of deformation.

Another example of applying buttresses would be East River from Astoria to the Bronx, where it was necessary to construct a concrete blanket to resist the upward thrust of water under considerable pressure. There was insufficient room for a blanket that would provide the required resistance due to its weight, so the concrete was laid in the form of an inverted arch.

Multiple Dome Buttress dam
Within the Buttress dam family there exists a dam called a multiple dome buttress dam. Most of its characteristics are the same as a multiple arch dam, however instead of having arches it has domes instead. Applying multiple domes help reduce the number of buttresses required to make sure the dam is stable.

Deck Slab Buttress dam
The deck slab buttress dam tends to be smaller ranging from 20 to 50 meters. The slab is inclined to between 40- 55 degrees, to help provide for necessary stability when under load. The deck slab buttress dam can also be categorized into three types fixed deck slab, free deck slab, or cantilever slab each providing its own benefits and drawbacks. A benefit of the deck slab dam is that if the deck slabs work together like a multiple arch dam for proper support. However, unlike the multiple arch dam if if one of the slabs gets damaged the damage will not affect the other slabs. If a dam is trying to be constructed in an area with loose soil they might elected to build a free deck slab dam. Unlike the fixed deck slab dam it will provide necessary support downstream of the face of the dam.