FLOOD00950

• County: Statewide
• Title: Rock Riprap Design for Protection of Stream Channels near Highway Structures volume 2
• Date: 1/1/1986
• Prepared By: USGS
• Floodplain - Doc Type: Educational/Technical/Reference Information

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FIGURE 8. Typical riprap failure area in the shape of a horseshoe, caused by particle erosion.

Translational Slide

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A translational slide is a rip rap failure caused by the downslope movement
of a mass of stones that consists of a single or closely related units with the
fault line usually on the horizontal plane (Schuster and Krizek, 1978), as shown
in figure 4. The rip rap is undisturbed except at the fault line and a bulge at
the toe. If the moving mass is not greatly deformed, it may be called a block
slide. The initial phases of a translational slide are indicated by cracks in
the upper part of the rip rap bank that extend parallel to the channeL The
movement of translational slides is controlled by (1) variations in shear
strength along the interface between the riprap and the base material, and
(2) stability of the riprap at the junction point with the channel bed. A
translational slide is initiated if the channel bed scours and undermines the
toe of the rip rap layer, or particle erosion of the toe material occurs, reduc-
ing the support of the upslope material. In either case, the shear resistance
of the interface between the bed material and rip rap may be insufficient to
resist translational movement. The translational slide may progress downslope
indefinitely if erosion of the riprap material at the toe (which constitutes tbe
bulge shown in fig. 4) continues. Continued downslope creep of the riprap ...
also occur if the base material underlying the rip rap is sufficiently satu~atee
with water and the shear resistance along the interface is less than the arav'.
.atlonal force.

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