1771
Technical Committee 204 /
Comité technique 204
Table 2. Test conditions with Repetition of water penetration
4 MODEL TEST WITH REPETITION OF WATER
PENETRATION
4.1
Test apparatus and conditions
Test apparatus was composed only of the center soil chamber.
This soil chamber size is 30cm long, 20cm high, 5cm wide. It
has the 5mm width opening at the center of the bottom plate and
soil was drained from there. Two patterns of water supply point:
“Opening” and “Side wall”, were set as presented in Figure 8.
Overburden weight was equivalent to the weight at 100cm deep
of the ground. A wooden block (2.1cm length, 10cm height,
5cm width) was set into the ground with 4 kinds of the
position.(as shown in Figure 4) Toyoura sand was used and
particle size distribution was shown in Figure . In Lfar test case,
colored sand layer was made in every 3cm thickness. Table 2
was shown the test conditions.
4.2
Test procedure
Model ground was compacted on around 10% water content.
Approximately 100cc water was supplied with head difference
of 100cm. Water supply cycle was repeated until the cavity
reach ground surface.
4.3
Test Result
Cavity formations of TSwne and TSwa are shown in Figure 9.
Arrow signified the direction of water supply. If water was
supplied from horizontal direction, cavity was generated around
the block. In TSwf test case, water content was measured at
several points as shown in Figure 10. Figure 10 suggested water
content was not uniform in the model ground. It was supposed
that water flew from water supply to the opening and passed
through the right side of the block.
Dry weight of drained soil was measured in each cycle, and
ratio of cumulative soil loss to total weight of soil in the model
ground was calculated. Rapid soil loss was observed in the test
case which the block didn’t disturb water flow (such as TOps
and TOpa cases). Although the cavity expansion was stopped
after a certain cycle in the test case without the block because
amount of water is not enough for reaching to the top of the
cavity and breaking the arching of the ground, it didn’t stop in
that with the block. Ground arching around a cavity was
disturbed by the block and water pathway was generated. Total
Code
Material Position of the
block
Initial Water
content (%) Dr (%)
TOpn Toyoura
None
10 Dr 80
TOpf
Toyoura
L far
10 Dr 80
TOpne Toyoura
Lnear
10 Dr 80
TOpa
Toyoura
above
10 Dr 80
TOps
Toyoura
side
10
Dr80
SiOps
Silica no.5
sude
10
Dr80
SiOpn Silica no.5
None
10
Dr80
TSwf
Toyoura
Lfar
10
Dr80
TSwne
Toyoura
Lnear
10
Dr80
TSwa
Toyoura
above
10
Dr80
TSws
Toyoura
side
10
Dr80
7.5CM
A) Sn, w
initial
=10%
Figure 9. Cavity formation with repetition of water penetration
b) TSwa, 7
th
water supply
a) TSwne, 7
th
water supply
Figure 6. Cavity formation of the model test
with horizontal water level
10 CM
B) Ts, w
initial
=10%,
12 CM
7 CM
TOYOURA SAND, DR=80%, W
i
=10%, Lfar,
Water level L:7cm R:12cm
Figure 7. Water penetration around the block with inclined
water level
