6 Ground improvement by deep vibratory methods
2. The same box is filled with gravelly sand that is compacted in the same
way while water is introduced from below; the sand surface sinks
from its original thickness of 85 cm to a height of 65 cm; comparison trials show that no other compaction method achieves an equally
strong compression of the sand; even with very intensive vibration,
without the rising water the sand thickness is only 72 cm.
This novel method of concrete densification was, for the first and only time,
tried in 1934 for the foundation of an I.G. Farbenindustrie building near
Frankfurt. The system, which proved so successful even in large scale trials, failed in practice when it was applied to densifying the concrete of a
bored pile foundation. The idea of concrete densification was eventually
abandoned, and the focus of development of this method was aimed at its
possibilities of sand compaction.
The method, shown in Figure 2.1, encompasses all the necessary features that today remain important for effective sand compaction: extensive
annulment of internal friction, full saturation of the sand to be compacted,
and complete rearrangement of the sand grains with a minimum void ratio
Figure 2.1 Effect of the vibro flotation method. (a) Abb. 1: Rüttler—vibrator, Zuschlagstoff—
aggregate, Oberfläche des fertigen Betons—concrete surface after densification,
Düse zur Einführung von Zementleim—nozzle to insert cement suspension;
(b) Abb. 2: Rüttler—vibrator, Oberfläche nach Verdichtung—surface after
densification, Rheinsand—Rhine-sand, Düse zur Einführung von Wasser—
nozzle to insert water. (Courtesy of Keller Group plc, London, UK.)
(a)
A b b . Z
(b)
l i w r " 1 » +85
% i
üi
' f T T f
m
R ü t tle r
Z u s c h l a g s t o f f
O b e rflä ch e d e s
f e r t i g e n B e t o n s
D ö s e z u r E in f ü h r u n g
von Z e m e n t le im
'D ü s e z u r E in f ü h r u n g
v o n W a s s e r
R ü ttle r
O b e rflä c h e n a ch
V e r d ic h t u n g
R h ein sa n d
A b b . 1
2. The same box is filled with gravelly sand that is compacted in the same
way while water is introduced from below; the sand surface sinks
from its original thickness of 85 cm to a height of 65 cm; comparison trials show that no other compaction method achieves an equally
strong compression of the sand; even with very intensive vibration,
without the rising water the sand thickness is only 72 cm.
This novel method of concrete densification was, for the first and only time,
tried in 1934 for the foundation of an I.G. Farbenindustrie building near
Frankfurt. The system, which proved so successful even in large scale trials, failed in practice when it was applied to densifying the concrete of a
bored pile foundation. The idea of concrete densification was eventually
abandoned, and the focus of development of this method was aimed at its
possibilities of sand compaction.
The method, shown in Figure 2.1, encompasses all the necessary features that today remain important for effective sand compaction: extensive
annulment of internal friction, full saturation of the sand to be compacted,
and complete rearrangement of the sand grains with a minimum void ratio
Figure 2.1 Effect of the vibro flotation method. (a) Abb. 1: Rüttler—vibrator, Zuschlagstoff—
aggregate, Oberfläche des fertigen Betons—concrete surface after densification,
Düse zur Einführung von Zementleim—nozzle to insert cement suspension;
(b) Abb. 2: Rüttler—vibrator, Oberfläche nach Verdichtung—surface after
densification, Rheinsand—Rhine-sand, Düse zur Einführung von Wasser—
nozzle to insert water. (Courtesy of Keller Group plc, London, UK.)
(a)
A b b . Z
(b)
l i w r " 1 » +85
% i
üi
' f T T f
m
R ü t tle r
Z u s c h l a g s t o f f
O b e rflä ch e d e s
f e r t i g e n B e t o n s
D ö s e z u r E in f ü h r u n g
von Z e m e n t le im
'D ü s e z u r E in f ü h r u n g
v o n W a s s e r
R ü ttle r
O b e rflä c h e n a ch
V e r d ic h t u n g
R h ein sa n d
A b b . 1