Displacement Monitoring at Verrand High Reinforced Soil Structure - Reinforced Soil Engineering: Advances in Research and Practice - page 123

slightly larger than the specified CA 25 class (5 static tons on drum), and
geotextiles survivability had to be checked by full-scale tests.
The tests suggested that the damage is generally not uniformly spread over
the reinforcement and that the actual strength retained by the whole
reinforcement is 70 to 75% of that of the undamaged material. The corresponding
survivability factor of safety to be applied in the Verrand case was selected as
Fd ¼ 1 : 35 to 1.45.

5 DESIGN OF THE REINFORCEMENT DISTRIBUTION AND
LENGTH

The selection of the reinforcement requirements (force and length) was based on
limit equilibrium, 3

(Christopher et al., 1989; Jewell, 1990). The assumed geotechnical character-
istics of the fill material were total unit weight g

reference minimum factor of safety being Fs ¼ 1 :

m 3

¼ 21 kN = ; cohesion c ¼

0kPa The strength data were obtained from

Triaxial CD tests, on 100-mm-diameter, compacted specimens. Only the fraction
finer than 25mm could be tested, and the measured strength parameters were
conservatively reduced when used in stability computations.
The geotextiles tensile strength values were reduced to account for
installation damage, long-term durability, and creep. The design strength of the
geotextiles was finally assumed to be 27% of the wide-width (200-mm) strength
determined according with CNR-UNI (Italian) standards (Cazzuffi et al., 1986).
The length of the reinforcements was selected so that the computed
minimum factor of safety for surfaces passing just beyond the reinforcements
would be Fs ¼

; and angle of friction f ¼ 35 8:

:
The heaviest reinforcements were located within the lower blocks, not only
to fulfill strength requirements but also to provide greater stiffness to the
structure. Grade 350 reinforcements were used only locally in the very upper
portion of the upper block. Additional reinforcements were introduced at the base
of conventional fill to reduce the earth pressure on the reinforced blocks.

1 : 3

6 BEHAVIOR

Since early construction, vertical and horizontal displacements of reference
points at cross sections 6 and 12 were monitored by topographic surveying. Long-
base extensometers installed on the same cross sections to measure horizontal
average strains of the reinforced mass suffered a wrong installation and could not
provide reliable and usable readings.