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Geotechnical News • June 2019
THE GROUT LINE
Contingencies were taken into
account in case the installation of the
H beam was not possible due to the
presence of boulders and the small
boreholes inside the boulders. Figure
#4.
In this specific case, where it was
not possible to install the designed H
beam, smaller diameter steel pipe-
piles were installed every single
column, instead of every third jet
grouted column.
Jet grouting execution
The main problem was definitely the
drilling in this heterogeneous, cobbly/
bouldery material. Usually with jet
grouting in soft soil the drilling is
done with simple tricone or drug-bit,
but in these difficult soil conditions
a special solution with dedicated
jet grouting tooling was adopted;
a conventional DTH with a special
monitor/tooling to allow drilling and
jetting without the need of pre-drill-
ing. Figure 5.
More than 500 columns were
installed from August to September,
2016, with a double
fluid system up to
15 meters deep. In
50 locations (out of
250) it was not pos-
sible to install the
Figure 5: DTH hammer for jet grouting.
Figure 6: H beam installation with vibrator.
Figure 7: Excavated north wall with boulders Figure 7.jpg
