Allen et al. (2003) proposed a new working stress method, called
the K-stiffness method, for the prediction of reinforcement loads in
walls with granular backfill, considering that the limit equilibrium
concepts used are conservative based on the performance of GRS
walls. They showed that this method gives more accurate estimates
of reinforcement loads. This largely empirical method takes into
account the height of the wall and surcharge loads, global and local
stiffness of the soil reinforcement, resistance to lateral movement
caused by the stiffness of the facing and restraint at the wall toe, face
batter, shear strength and stress-strain behavior of the soil, unit
weight of the soil, and the reinforcement spacing. These key factors
are included in the calculation of the maximum reinforcement load.
Facing stiffness factors are constant and are given as 0.35 for
modular block and concrete panel faced walls, 0.5 for incremental
precast concrete facings, and 1 for flexible facings for preliminary
design purposes, that is, the maximum reinforcement load calculated
for a wall with flexible facing is twice the load for a wall with incremental
precast concrete facing. Using this method, the wall can be
designed to prevent failure of the soil in the reinforced zone, in
addition to preventing reinforcement rupture considered in current
practice.