Basic HTML Version
www.geotechnicalnews.com
Geotechnical News • September 2014
37
THE GROUT LINE
was further increased to 17 m, with a
5.5 m overlap of the second campaign.
This time both drilling and grout-
ing were performed in two different
stages; up to 9 m for the first, and up
to 17 m for the second. The campaign
was completed in 2 months.
3rd Campaign - Technical data:
• Number of holes drilled: 101
(Including re-drilled + different
stages)
• Total length drilled: 1,246 m
• Total quantity injected: 294 m3
• Volume injected: 236 l/m
A summary of the three grouting cam-
paigns is shown in Table 1.
After completion of the third cam-
paign, on February 19, 2013 a perme-
ameter test was performed to reach 0
bar of pressure. This is the first time
we were able to lower the face pres-
sure to atmospheric conditions. The
overall water inflow was reduced from
1,100 m3/h (290 gal/h) to 220 m3/h
(587 gal/h), and a face inspection was
accomplished. Even if the total water
inflow was reduced however, the over-
all stability of the tunnel face was not
completely safe.
Under such hydro-geological condi-
tions we were able to perform the
following maintenance and repairs:
• Full cutter head inspection
• Changed 4 cutters
• Cleaning of the cutter head open-
ings
• Replaced level sensors in the work-
ing chamber
• Maintenance on the compressed air
line (SAMSON)
• Free the stone crusher and the
working chamber from the grout-
ing injected during the three
campaigns
The most important activities were
the replacement of worn pipelines,
valves, pumps and the installation of
a new hydraulic valve on the slurry
return line just behind the suction pipe
in the drilling chamber, which became
an additional safety device in case the
pipe would burst.
When maintenance was completed,
the TBM was able to advance forward
through the fault area and reach a zone
with better hydro-geological condi-
Figure 7: Grouting campaigns.