**6.1 Jewell et al. design method**

Jewell et al. [8] proposed a method of design based on Limit Equilibrium analysis and local check on individual reinforcement spacing for geogrid reinforced embankment slope for slope angles, β, ranging from 30° to 80°. Embankment soil is granular and the crest is horizontal. Length of reinforcement is based on (i) no overstressing of lower layers, (ii) no outward sliding along the interface between soil and reinforcement layer and (iii) no tension on the base. Two-part wedge analysis is used and critical wedge surface for failure is located by varying wedge angles θ1 and θ2 (**Figure 7**) and the location of intersection of the two wedge lines, i.e., the wedge point.

**Figure 7.** *Steep slope embankment (after [8]).*

The interslice forces are assumed to be zero. Design charts calculate total reinforcement force and length of reinforcement in terms of slope angle, β, effective critical state friction angle of soil, φ c, and porewater pressure parameter, ru = *u z* / γ . The strength of reinforcement is the strength of geogrid at the end of design life for most severe condition expected during service life. Factor of safety of 1.3 to 1.5 for the slope is achieved by applying the same to the reinforcement strength as well. All reinforcement layers are of equal length. Surcharge and earthquake loads are not included in the analysis.
