Riprap

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Riprap (also known as rip rap, rubble, revetment, shot rock or rock armour) is rock or other material used to armor shorelines against water erosion. Riprap reduces water erosion by resisting the hydraulic attack and dissipating the energy of flowing water or waves. The shape of rock is important. Coarse, angular rock, usually made by crushing or blasting, or from scree, is more effective at ground reinforcement than round river rock. A correct mixture of aggregate size can also aid riprap's ability to create an interlocking structure.

Riprap is graded by size. A specified diameter will have fifty percent of the rock (by weight) larger and fifty percent smaller. The velocity of water flow is generally the determining factor for size of stone. Riprap varies in size from the multi-centimeter range to cast concrete shapes several meters across. Jetty stone is larger than riprap and can have individual pieces that are also several meters in diameter. The size and material will be specified by a civil engineer or local building code.

Riprap is often used in conjunction with a geotextile or in gabion baskets.

Riprap or jetty stone are a byproduct of crushed stone quarries or dimension stone quarries (rubble). Boulders are produced during the drilling and blasting of the rock for other products and are too big to be crushed in the plant. So they are stockpiled at the quarry until they can be sold.

According to the United States Geological Survey, total U.S. riprap and jetty stone production in 2005 was 16.5 million tons (15 million tonnes) valued at $152 million, of which limestone was 8.8 million tons (8 million tonnes) valued at $62.7 million, and granite was 3.8 million tons (3.5 million tonnes) valued at $43.5 million.[1]

References

• Ciria-CUR (2007) - Rock Manual - The use of rock in hydraulic engineering.
• N.W.H. Allsop (2002) - Breakwaters, coastal structures and coastlines.

See also

• Erosion control
• Riparian zone
• Revetment
• Accropode
• Baer's law
• Construction aggregate
• Dimension stone
• Limestone