Performance and Analysis of Arifiye Overpass Reinforced Earth Walls During the 1999 Kocaeli (Turkey) Earthquake - Reinforced Soil Engineering: Advances in Research and Practice - page 441

Table 1 Model Parameters of the Backfill
Unit weight (kN/m 3 ) 19.6

Young's modulus number, K 500

Young's modulus exponent, n 0.5

Bulk modulus number, K b 300

Bulk modulus exponent, m 0.4

Unload modulus number, K u 800

Failure ratio, R f 0.80

Steel strips were defined using cable elements in FLAC. Cable elements
have a built-in feature that allows the user to define the element connectivity to
the soil media without using interface elements. For this project, the shear
strength of the reinforcement soil interface is defined to have f

. The elastic
modulus of the steel reinforcements, the cross-sectional area, and the perimeter of
the strips were scaled per the actual reinforcement spacing, as recommended by
Donovan et al. (1984). This scaling was performed to average out the discrete
effect of the reinforcement and convert the system into an equivalent
homogenous force system throughout the unit wall width.

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5 STATIC ANALYSIS AND RESULTS

A static analysis was used to model the pre-earthquake conditions by simulating
wall construction. This phase was important because static equilibrium stresses
within the backfill and the reinforcing strips play a major role in the dynamic
behavior of mechanically stabilized earth wall systems. Because the wall is built
in compacted soil lifts, compaction-induced stresses were modeled in the
analyses. It is likely that reinforcement forces especially in the upper layers will
be affected by the compaction effort. This is generally true for earth retention
systems with inextensible reinforcements (comparably stiffer reinforcements and
facing panels) where the structure does not have as much flexibility to deform
laterally.
The static analysis was performed by modeling the sequential construction
stages used for the walls (as indicated by the actual wall construction plans
obtained). Lifts of 37.5 cm thickness (corresponding to two zone levels in the
finite difference grid) were placed in stages. The following sequence was
followed for each lift placement stage:

1. The lift was placed (by switching the model properties of the
corresponding soil zones from null to Mohr -Coulomb), and the system
was brought to equilibrium under this additional load,