Geosynthetic Reinforced Containment Dike Constructed over Soft Foundation: Numerical Analysis - Reinforced Soil Engineering: Advances in Research and Practice - page 277

Figure 2 Soil profile and properties.

Duffield Associates (1994). The recent or Holocene Age deposits consisted of
very soft, dark gray, highly plastic clayey silts and silty clays of 25 0 to 100 0 (8.3 to
33m) thick, overlying a relatively thin 5 0 to 20 0 (1.7 to 6.7 m) thick sand layer of
the Pleistocene Age Columbia formation. These sediments were underlain by the
Cretaceous Age Potomac formation that consisted of variegated silt and clays
containing highly variable interbedded sand and gravel layers.
Table 1 summarizes the results of soil testing for the foundations based on
standard classification, consolidation, permeability, triaxial compression, and
unconfined compression tests. The design cross section incorporated the greatest
thickness of compressible clay encountered in the soil boring. These
compressible clays were separated into three strata, Strata 1, 2A, and 2B,
based on the soil properties. The parameters used for each stratum are included in
Fig. 2.

3 CONSTRUCTION AND INSTRUMENTATION

The dike was constructed in two stages. Stage I consisted of hydraulic placement
between March 1987 to December 1988 for the whole embankment. The fill
provided a platform to install the wick drains and geotechnical instrumentation.
The final dike was constructed in Stage II. It started in late December 1988 and
was completed in April 1990. Generally, Stage II was constructed one half to one
year after completion of Stage I construction.