28 Ground improvement by deep vibratory methods
2.5 METHOD IMPROVEMENTS
During the first years after the war, the vibro flotation method continued to use
the rather ponderous wooden gantries that traveled on rails and from which the
vibrators were suspended and operated by standard rope winches (Figure 2.7).
Soon, however, this slow setup was replaced by standard crawler cranes and,
for moderate compaction depths, by purpose-built lifting gear, the so-called
vibrocats (Figure 2.18), which resulted in a considerably better output. With
Figure 2.17 Preparation of a horizontal load test on vibro stone columns. (Courtesy of
Keller Group plc, London, UK.)
Figure 2.18 First generation vibrocats, 1956. (Courtesy of Keller Group plc, London, UK.)