Performance and Analysis of Arifiye Overpass Reinforced Earth Walls During the 1999 Kocaeli (Turkey) Earthquake - Reinforced Soil Engineering: Advances in Research and Practice - page 440

within practical limits. The asphalt pavement and other structural elements on the
top of the wall were not incorporated into the analysis.
The foundation soil and the backfill were modeled using the Mohr-
Coulomb model built into the FLAC code. This is an elastoplastic model with a
nonassociated flow rule in which the yield surface is defined by the Mohr-
Coulomb shear strength criteria. The stress-strain relationship is linear elastic
below yielding, and the material attains plastic flow at yielding (Itasca
Consulting, 2000). The foundation soil was defined to have a cohesion of
150 kPa, f

¼ 40 8 , and a shear modulus of 15,000 kPa. The backfill was assigned

a f 40 and a cohesion of zero. The stiffness of the backfill was stress level-

dependent, and these properties were updated during the analyses at each lift
placement. Tangential values of bulk and shear modulus were defined to
incrementally follow a hyperbolic stress strain relationship (i.e., Duncan and
Chang, 1970; Duncan et al., 1980). In this model, tangential Young's modulus, E,
and Bulk modulus, B, are defined as

¼

" # K

s 1 2

n

R f 1 2 sinf ð s 3 Þ s 3

p a

E ¼ 1 2 p a

2 ccosf þ s 3 sinf

m

s 3
p a

B ¼ K b p a

where

K, n: Young's modulus number and exponent.
B, m: Bulk modulus number and exponent.
c, f: Shear strength parameters.
s 1, s 3: minor and major principal stresses.
p a: atmospheric pressure.
Parameters typical of those used in previous numerical studies were
selected to define the stress-level dependency of the backfill (Adib, 1988;
Schmertmann et al., 1989), as summarized in Table 1 .
Interface elements were used to model the connectivity between the
backfill soil and the facing panels. In FLAC a contact logic is defined between
each side of the interface by the use of normal and shear springs. The interface
can be defined between adjacent soil surfaces along discontinuities, or between
soil media and structural elements. The shear strength of the interface is defined
by Mohr-Coulomb strength parameters. The shear strength of the soil/facing
panel interfaces were assigned f

¼ 30 8 . Normal and shear spring stiffnesses of

10 6 kN/m 2 /m and 5.0 10 3 kN/m 2 /m, these interfaces were defined to be 1.0 £ £

respectively.