Practice and Research of Geosynthetic Reinforced Soil Walls in Australia - Reinforced Soil Engineering: Advances in Research and Practice - page 264

Some reinforcement levels had two peaks in the reinforcement tension, with
de-tensioning between the two peaks. Such a pattern was also reflected in the load
bolt readings.
However, field measurements indicated significant settlement and
significant horizontal displacements. Some of the field measurements taken
mid-December 1996 are presented as Fig. 11 (for settlement profiles) and as
Fig. 12 (for horizontal displacements at I-2).
The settlement profiles presented in Fig. 11 were relative to their respective
set of initial readings, which were taken about a month after filling began.
Comparison with readings from settlement plates indicated that the settlement at
HPG-1 could be about 10mm higher than that presented. The I-2 inclinometer
was installed a few days after the job began, and initial readings were taken two
weeks after the job began. However, the inclinometer tube was extended with
wall construction. As such, some of the horizontal displacement that occurred
during wall construction was not fully registered. The magnitude of this error was
considered to be low (10 to 20mm). Although the initial FLAC analysis can
predict the high settlement by assuming low, but tenable, values for Young's
modulus for soils, the significant horizontal movements were not predicted.
Furthermore, the as-measured settlement profile showed a peak near the rear end
of the reinforced zone, and the initial analysis did not predict this feature. A series
of additional analyses was conducted to investigate the status of this GRS wall.
The final assumptions in the analysis were

1. The construction sequence was modeled closely in a layer-by-layer
manner.
2. The soil was modeled as an elastic-plastic material with the elastic
behavior given by the Duncan-Chang nonlinear elastic equation.
3. The modular block facing was modeled as 2D elements with horizontal
no-tension joint planes.

To improve the Duncan-Chang model (which only gives a variation of
tangential Young's modulus with stress), Poisson's ratio was taken as dependent
on stress with the following equation:

2 S

p

v ¼ 0 : 3 þ 0 : $ 0 : 495 ð 3 Þ

r f ð 1 2 sin f Þð s 1 2 s 3 Þ

S ¼ ð 3a Þ

2c cos f þ 2f 3 sin f

The parameters adopted in the analysis are given in Table 1 .
Equations (3) and (3a) ensure that unrealistically large volumetric strain
will not occur (by giving n

! 0.5 as Young's modulus approaches zero).