Geotextile Reinforced Abutments on Soft Foundation - Reinforced Soil Engineering: Advances in Research and Practice - page 215

1 INTRODUCTION
Geosynthetic reinforced retaining walls and steep slopes have been extensively
used in the last two decades. The main reasons for that are its cost-effectiveness,
improvements in geosynthetic material properties, design procedures, and better
controlled construction techniques. Because they are flexible structures,
geosynthetic retaining walls are likely to accept differential settlements rather
well. Therefore, its use should be considered when dealing with compressive
foundation soil layers, where other solutions might not be appropriate. In these
cases geosynthetic reinforced walls may provide a suitable structure in terms of
flexibility and savings in maintenance costs due to repairs required by any
damage caused by differential settlements (facing damages, for instance). As will
be seen later in this chapter, in some cases the settlements may be significant but
the structure can still be operational.
This chapter describes the design, construction, and performance of five
geotextile reinforced retaining walls used in bridge abutments on soft
foundations. These walls were designed and constructed by the geotechnical
engineering companies Tecnosolo and Odebrecht, respectively, and were built on
soft clay layers with different philosophies to deal with consolidation settlements.
The following sections present and discuss the details and performance of
these works.
2 SITE AND PROJECT CHARACTERISTICS
2.1 Site Characteristics
The reinforced bridge abutments described in the present work were built in the
Linha Verde highway, which is located in the north region of the state of Bahia,
Brazil (Fig. 1). This highway is very important for tourism purposes because it
runs close to the sea line crossing several cities and sites of natural beauty. The
subsoil of the region consists of sedimentary layers with thicknesses reaching up
to 25m. The thickness of the soft layer deposits varies from 1 to 12m and is
particularly thicker close to the rivers crossing the region, where the
sedimentation process was more intense. A typical subsoil profile in the region
of construction of the reinforced retaining walls shows a layer of very clayey
sand, loose to fairly dense, with thicknesses varying between 2 to 5m,
overlaying compressible organic silty clay deposits with thicknesses varying
from 2 to 14 m. Values of N from Standard Penetration Tests in the soft soil
deposits varied between 0 and 4, and the average undrained strength from vane
tests carried out in some sites varied between 10 and 60 kPa, depending on the
site. Fig. 2a and b shows the results of field vane tests performed at the sites of