| Summary: | Having different characteristics, when rigid pavement structure is
constructed above clay and sand soil, they will indicate behavior of slab
deflection and subgrade reaction modulus. The nailed slab system is one of the
solutions to increase the modulus of subgrade reaction (k). Piles set in monolite
on the slab are used to muffle the slab deflection when loading is in progress. This
study observed the increment value of modulus subgrade reaction (�k) due to the
pile support to the nailed slab system, which was carried out in two methods:
observed plate bearing test in the laboratory and calculation under the formula
proposed by Hardiyatmo (2011).
This research was taken in two specimens modeling within 1:10 scale. The
soil used was clay and sand. The soil density during the test was 95 % MDD and
95 % OMC (standard Proctor). The plate load test was supported by single pile in
9
�
9 cm
2
dimension and pile in 1,5 cm diameter and 15 cm length. The plate
bearing test was supported by piles with plate sizes based on the variations of
plate numbers (2, 3 and 4 piles) and variations of distance between the piles, s (s
= 5d, 6d and 7d). The pile was buried in the ground by using the test media box in
1, 2 � 1, 2 � 0, 5 m
3
dimension. The loading was applied in sequences up to reach
0,8 kN that the slab was still elastic and has not experience damage and crack.
The tension test on pile was carried out to pile in 1,5 cm diameter and pile of 15
cm length.
Results of the test indicated that the pile contributed significantly to reduce
the slab deflection and to increase the modulus of subgrade reaction (k value).
More numbers of pile supporting the slab (4 piles) were capable to reduce the
slab deflection more than the less numbers if piles (2 piles). The reduction of the
slab deflection supported by 4 piles was 52 % for clay and 53 % for sand. The
determination of modulus subgrade reaction was calculated by using the formula
proposed by Hardiyatmo (2011). It was indicated that the calculation result (�khit)
difference was relatively smaller than the observed results (�kuji). On clay, the
average increase for �khit and �kuji were 22 % and 23 %, respetively. On sand,
the average increase for �khit and �kuji were 62 % and 64 %, respectively. The
slab deflection resulted from BoEF program calculation indicated that it was
effective for long slab (slab supported by 3 and 4 piles on clay and 4 piles on
sand). For shorter slab (slab supported by 2 piles), the BoEF program was not
effective. The difference of the slab deflection(δuji and δhit) for the distance (s) =
6d indicated that slab supported by 2 , 3 and 4 piles on clay were 42 %, 7 %, and
14 % , respectively. Where as for slab supported by 2, 3 and 4 piles on sand were
204 %, 107 % and 23 %.
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