Geotechnical News • June 2019
29
THE GROUT LINE
H beam (25%). In these cases steel
pipe piles 4” diameter were installed
re-drilling in these bouldery zones.
H beams, where possible, were
installed with a dedicated vibrator as
shown in figure #6.
The results
The excavation, done between Sep-
tember 2016 and April 2017, showed
excellent results in terms of both
continuity and impermeability of
the wall. The excavation was com-
pleted safely, without issues and, also
importantly, on schedule.
Some examples of how the jet was
able to “embrace” the boulders are
shown in Figure #7 to #11. No further
descriptions are necessary as these
figures are self-explanatory.
Figure 12 shows ingress of water
once the impervious wall was drilled
for the anchor installation, demon-
strating the impermeability of the
jetted wall.
Conclusion
And again in conclusion, after this
experience, the same question: does it
still make sense to talk about shadow-
ing in jet grouting? It is clear that if
the drilling for a column intercepts
a boulder, the jet in this zone is
not created and does not exist, and
consequently no shadowing effect is
created; the source of the shadow, the
jet, is missing. But in the other situa-
tions, outside of the boulders, keeping
a smaller column diameter and small
spacing, with the right jetting param-
eters, very challenging projects can be
solved with this versatile and flexible
soil improvement technique.
As usual I conclude with the same
request, asking you to send me your
grouting comments or grouting stories
or case histories. My coordinates
remain:
Paolo Gazzarrini,
,
or
Ciao! Cheers!
Figures 8/9/10: “Embraced” boulders by jet grouting.
Figure 11: A bouldery frozen area in during winter
excavation
Figure 12: Water from the drilled soil anchors.
