FLH PDDM Chapter 9 - Eastern Federal Lands Highway Division

9.4.A. Geometric Design. (continued)and will enhance aesthetics, safety, and maintenance. Slopes 1:3 are generally traversable by a vehicle thathas run off the road but do not provide for vehicle recovery. Slopes 1:3 and flatter are also traversable byself-propelled mowers, and should be used at locations where the grass will be regularly cut. High cutsand fills normally have steeper slopes.Cuts have a high visual impact, therefore, the design of cut slopes requires careful consideration. In somecases, it is desirable to use the same slope throughout the cut, while in other situations a constant distanceto the catch point stake and a continuously varying slope may be appropriate.In steep terrain, the slopes may be varied slightly from standard slopes in order to better fit the topographyor eliminate high "sliver" cuts or fills. Transition slopes between common material and rock requirespecial consideration. Blend the ends of cut slopes into the natural terrain by rounding, flattening, orotherwise shaping the ground line.Transition fill slopes from the main portion of the fill into the cut section. Transitions between flat andsteep slopes should be sufficiently long to provide a pleasing appearance. A transition from a 1:4 slope toa 1:1.5 slope may require a distance of 50 meters or more to appear natural.Table 9-8 lists commonly used slopes for cuts and fills in earth materials. Use this table as a guide, alongwith the recommended slopes in the geotechnical report, to design the slopes on the project. All fill slopessteeper than 1:4 should be evaluated for safety. (See Chapter 8.)Geotechnical reports may not be available for the project when beginning a design. If this is the case,design cut and fill slopes based on available survey or field review data. When a geotechnical reportbecomes available, the designer must review the slopes initially used and make any necessary adjustmentsin the earthwork design.9 - 43