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Last modified
1/26/2010 10:10:55 AM
Creation date
10/5/2006 4:42:54 AM
Metadata
Fields
Template:
Floodplain Documents
County
Statewide
Community
State of Colorado
Basin
Statewide
Title
Use of Riprap for Bank Protection
Date
6/1/1967
Prepared By
USDOT
Floodplain - Doc Type
Project
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<br />:. <br /> <br />, <br /> <br />. <br /> <br />. <br /> <br />ii <br /> <br />~ <br /> <br />. <br /> <br />low tensile strell8th aDd is susceptible to daIlIage from floating ice. It <br />requires firm support from the protected bank and usually requires a <br />filter blanket underneath the riprap. Adequate protection ot the termi- <br />nals and toe is essential. The toe trench must end in firm support and <br />extend below the depth of anticipated scour. Details ot terminal pro- <br />tection and cutott stubs are shown in figure 6. (See also p. 134-135, ~.) <br /> <br />The bags make close contact with each other and some bond is secured <br />between the bags by the cement mortar leaking through the porous bags. <br />Flat slopes reduce the area of contact between the sacks and thus bond is <br />less. Slopes of the protected embankment are generally 1 1/2: 1. It the <br />slopes are as flat as 2:1, all sacks after the bottom row should be laid <br />as headers (long way of sack in line with the slope) rather tban as <br />stretchers (long way at right angles to slope direction). <br /> <br />Concrete riprap in bags is sometimes placed as a dry mix. The rip- <br />rap is thoroughly wetted as the work progresses. Some bond between sacks <br />is probably lost by this method, but it allows the sacks to be filled at <br />a convenient location and brought to the construction site. A well graded <br />filter blanket is essential to drain the water that is added during <br />construction. <br /> <br />2.6 - Design at Concrete-Slab Riprap <br /> <br />Concrete slabs, plain or reinforced, are cast in place on the pre- <br />pared slope (2, p. 266-267). The slab is generally 4 inches thick ot <br />class B concrete (4 1/2 bags cement per yard) except when the slab is <br />exposed to salt water in which case class A concrete is used. Joints <br />between slabs are discussed in section 4.7. Precast concrete slabs can <br />be used in place of cast-in-p1ace slabs. <br /> <br />Concrete slabs 6 1/2 teet by 5 feet and 8 inches thick were used on <br />the Belle Fourche Dam (Bureau of Reclamation) in South Dakota. The slabs <br />were much deteriorated after 40 years of service in spi te of considerable <br />maintenance. Continuous reinforced concrete pavement used on earth dam <br />faces has a much better service record than concrete-slab riprap. <br /> <br />A variation in concrete slab riprap is discussed by Parsons and <br />Apmann (11). The slabs discussed in reference 11 are 4-inch thick, cel- <br />lular coiiCrete blocks, 16 inches by 24 inches. Each block contains 24 <br />2-inch by 2-inch holes that go completely through the 191ock. Gravel or <br />crushed stone can be placed in the holes. The weight of each block is <br />about 80 pounds. The experimental revetment has given 8 years of satis- <br />factory service. <br /> <br />11-15 <br />
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