U.K. Case Study: Bluewater Retail and Leisure Destination Reinforced Soil Slopes to Form Steep-Sided New Lakes - Reinforced Soil Engineering: Advances in Research and Practice - page 138

stability calculations take the form of a two-part wedge analysis through the
reinforced soil block. A series of two-part wedges is examined with the lower part
of the wedge originating at the structure face and passing through the block, and
the upper part of the wedge passing up the back face of the reinforced soil block.
The active pressure, above that point where the lower part of the wedge cuts the
back face of the reinforced soil block, is added to the disturbing forces acting on
the two-part wedge to give the total disturbing force. In the case of internal
stability, the resultant active force is taken to act on angle equal to the friction
angle of the soil block rear face.
Reinforcement must be provided to resist the disturbing force on each two-
part wedge by intercepting the wedge being considered. The two-part wedge
stability calculation should be carried out from the toe of the structure, the bottom
grid layer, at all levels where the grid spacing alters, and at every level where the
grid type alters.
The reinforcement design strength is obtained from the creep-limited
strength appropriate to the design life and in-soil temperature. Specific partial
factors are then applied to take account of such factors as installation damage.
Finally, an overall FoS 75 is applied to the strength.

The reinforcement layout was derived by analysis with lower part wedge
angles (u) set at 3 8 intervals (Fig. 5) using the specialist designer's computer
program, Winwall (Tensar International, 1995).

¼ 1 :

Figure 5 Two-part wedge analysis.