Terrain assessment, drainage and erosion - Geotechnical Investigation and Design Tables - page 194

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Apply a reverse slope of 10-15%, and a minimum depth of 0.3m.

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The bench width is typically 2-4m. But this should consider rock fall bench width
requirements, and maintenance access requirements.

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Benching also aids in slope stability.

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The bench height is dependent on the run off, type of material and overall risk
associated with the slope.

Table 15.13 Typical benching requirements.

Slope Vertical height between benches

1V : 4H 20 m

1V : 3H 15-20 m

1V : 2H 10-15 m

1V : 1H 5-10 m

Figure 15.2 Erosion protection.

15.14 Subsurface drain designs
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A subsurface drain reduces the effects of saturation of the pavement subgrade.