State of the Practice: Past, Current, and Future Perspectives of Reinforced Soil Retaining Structures in Turkey - Reinforced Soil Engineering: Advances in Research and Practice - page 155

the geosynthetic layer worked as a lateral drain. Therefore, no pore water
pressure was developed and reduction in the shear strength was not achieved
since no saturation occurred at lower layers. Attempts at bringing the wall to
failure ended at this point, and the project was terminated.
The excellent performance of the wall when overloaded showed that the
use of lime treated clay in this case study allowed the efficient construction of
the wall. This will substantially reduce the cost of similar projects due to the
possibility of using available on-site soils instead of having granular material
transported to the site. Increased permeability and good structural performance
were also observed. Both the instrumentation data, obtained from all sensors, and
observations of the actual wall performance indicated that the wall performed its
intended function with negligible settlement. This case study proved to be cost-
effective and illustrated the importance of drainage.
6 BLOCK FACED GEOSYNTHETIC REINFORCED WALL
The first segmental retaining wall in Turkey, where concrete blocks are used as
the facing and the reinforcement is a geotextile, was constructed during the
summer of 1997. This wall was constructed under the design and supervision of
the second author. Mr. Robert Barrett from the United States was the consultant
during design and construction. The project was constructed as part of the
Altunizade-Umraniye Highway construction. The highway had interrupted
Nurbaba Street, and it had to be elevated to pass over the tunnel portal.
The facing elements were simple building blocks and as the backfill a
greywacke was used, as shown in Fig. 5 . The reinforcement was a woven
geotextile with a tensile strength of 20 kN/m. Though it was the first wall of its
kind in Turkey, it included tremendous amounts of complexities. These can be
summarized as follows:
1. The exiting road had a mixed cross section, and the retaining structures
supporting the fill had deteriorated severely. Therefore, they had to be removed
from the side. Due to this fact and the fact that the original ground is sloped, the
two sides of the road had to be formed on two different elevations, as shown in
Fig. 6 .
2. The foundation of the soil was a heavily weathered rock. Its
consistency was similar to that of overconsolidated clay. The foundations of the
two walls, each on one side of the road, had to be constructed on different
elevations. This fact brought up the concern that there can be a stability problem
on the slope that is created between the two foundation levels. Special concern
and analysis were devoted to the foundation of the wall constructed on the crest of
the slope created by excavation.