Recent Experiences of Reinforced Soil Retaining Structures in China - Reinforced Soil Engineering: Advances in Research and Practice - page 168

difficult to determine the parameters of the anisotropy composite in situ by
laboratory tests.
A new approach, the equivalent additional stress method, has been used to
calculate the reinforced earth. The basic principle of the method is that only the
soil skeleton is concerned in the analysis of reinforced soil. The reinforcing
material is considered to be an equivalently additional stress acting on the soil
skeleton in the direction in which reinforcement is bedded. Namely, only soil
elements are used in FEM, and elements of reinforcing material do not appear;
their effect is treated as external stress acting on the soil elements. The existing
constitutive models of soil can be directly used without equationing any new
model. Because the equivalent additional compressive stress acts in the direction
in which reinforcement is placed, the anisotropy of reinforced soil can be
reasonably described.
The additional stress can be expressed as

K1 r Ds r ¼ ð 3 Þ

where 1 r is the strain of reinforced soil element in reinforcement direction, and
parameter K may be determined from Ds rf and 1 rf , which are the additional stress
from reinforcement and strain of sample in the reinforcement direction when the
sample fails in a conventional triaxial test. In the case of the layer-built reinforced
earth with geotextile, 1 r is the strain of reinforcing material that may be equal to
the strain of soil element when the modulus of reinforcing material is not stiff. In
addition, K relates to the spaces of geotextile.
By using the equivalently additional stress concept, an FEM program has
been composed, and a full-scale model retaining wall, the “Denver Wall”, is
analyzed. Figure 9 shows the predicted result of the new method, as well as the test
results and calculated results with the conventional method (Jie Yuxin, 1998).

Figure 9 The predicted result of reinforced sand retained wall.