Large-Scale Reinforced Clay Walls Backfilled with Clay at Cheng Kung University - Reinforced Soil Engineering: Advances in Research and Practice - page 185

in Fig. 2 . Compaction under other conditions, for example, using the plate
compactor, or increasing the thickness of the soil lift, or increasing the clod size,
all failed to obtain a relative compaction of 90% for the clay. Consequently,
the specification of compaction as summarized in Table 2 was used for the
construction of the test walls.
Triaxial compression tests under the confining pressure ranging between
49 kN/m 2 and 147 kN/m 2 were performed on the compacted soil specimens under
R.C. 90% conditions; the dry unit weight (g d ) and the water content (v) were

16.8 kN/m 3 and 15.7% for the in-lab, and 15.9 kN/m 3 and 14.4% for the in-situ
specimens, respectively. Strength parameters based on Mohr-Coulomb's failure
criterion for the in-lab and in-situ soil specimens are c 0 ¼

<

43 kN/m 2 , f 0 ¼ 30 8 ,

26 kN/m 2 , f 0 ¼ and c 0 ¼ , respectively. The walls at each sides of the

embankment were reinforced using different types of reinforcements. For the
right-side wall (R-wall), a geosynthetic composite formed by a knitted geotextile
layer needle-punched with two layers of nonwoven geotextile was used. For the
left-side wall (L-wall), a geogrid with apertures of 20 mm

32.6 8

20mm formed by
polyester fibers coated with PVC was used. The stress-strain relationships for
these two types of reinforcement are shown in Fig. 3 . A detailed description on
the tensile test and the calibration on the strain gauges attached to the woven-
nonwoven composite is reported elsewhere (Huang, 1998).
The side walls of the plane-strain soil container consisted of 3000-mm-long
and 100-mm

£

150-mm wood studs and 0.5-mm-deep, 0.3-mm-wide, and 3-m-
long strip concrete footings. The frames of the side walls were reinforced with
wood wales and were further supported externally by struts at two levels as
shown in Plate 1. Ten-mm-thick fortified glass was installed on the inner face of
the front side wall to form transparent 0.3-mm

£

0.3-m windows for measuring
the movement of the targets printed on the 0.3-mm-thick rubber membrane sheet.
The interface between the membrane sheet and the glass was lubricated with
silicone grease to reduce the side wall friction.

£

Table 2 Compaction Method Used in the Present
Study (for a 700 N Tamping Rammer 50-700mm
Stroke, < 650 vpm)
Maximum clod size of clay

< 10mm

Water content (%) 16-17

Lift height for water content adjustment

< 20mm

Thickness before compaction

< 120mm

Thickness after compaction

< 80mm

Number of passes 5