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because the engineering properties of the compacted clay could be
susceptible to various factors. Therefore, a systematic employment of clays
as the backfill of reinforced walls requires more studies on the relationship
between the performance of reinforced clay walls and the factors that control
the quality of the compacted clay. This report covers the design and
construction of the reinforced walls, the long-term monitoring, and the results
of seepage analyses.
2 CONSTRUCTION OF NCKU WALLS
A 2.77-m-high, 6-m-wide, and 3-m-long reinforced embankment was con-
structed on a competent ground at the campus of National Cheng Kung
University in Tainan City, Taiwan. Two vertical reinforced walls (called NCKU
walls hereafter) were constructed as side faces of this test embankment as shown
in
Fig. 1
.
Preliminary studies on the soil properties, the reinforcement strength,
and the field compaction methods were conducted. The soil employed was an
Alluvial deposit containing 98% fine particles. The soil classification
according to the Unified Soil Classification System was CL. Index properties
of the clay are summarized in Table 1. Air-dried clay was crushed to produce
adequate clod sizes. A vibration plate compactor weighted 780 N and a
tamping rammer weighted 700 N were used in the preliminary study on the
compaction method.
It was found that using the tamping rammer under an average clod size for
about 10 mm, a small life height of 20mm for water spreading, and a total lift
height of 120mm with 5 passes of compaction under optimum water contents
(v
opt
<
16%, lift 17%) resulted in a homogeneous soil mass with 90% relative
compaction (R.C.). A smaller lift height of 80mm with otherwise the same
condition resulted in a similar degree of compaction. The results are summarized
Table 1
Index Properties of the Clay Used in the
Present Study
Percentage of sand (
.
0.06mm) by weight
2.5%
Percentage of silt (0.06-0.002mm) by weight
79.1%
Percentage of clay (
,
0.002mm) by weight
18.4%
USCS
CL
G
s
2.72
LL
31
PL
17
PI
13
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