Geotechnical News • March 2016
45
THE GROUT LINE
The remedial
cut off works
were executed
throughout with a
rigorous attention
to detail, utilising
continuous real
time control and
monitoring of the
accuracy of the
slurry wall excavation during progress
of each panel. The effectiveness of the
grouting works was verified during the
course of each injection by continuous
monitoring of the injection parameters,
in particular, the Equivalent Lugeon
value. The latest technology available
was employed for all elements of the
works, consistent with the need for
cost effectiveness.
Performance Criteria
Assessment Method
Results Achieved
5 Water absorption tests.
Av. water tightness < 3 Lugeons,
no individual result >10.
Multi-stage water absorption tests in inde-
pendent holes in between the rows of grout
holes.
Hole spacing in grout curtain to be not
greater than 10m but actual spacing to be
proposed by Sub Contractor. At least 3 depth
stages to be tested in each hole.
12 no. water test hole locations agreed with
the Engineer
Single step Lugeon tests executed in 2 no.
stages of all holes
5-step Lugeon tests executed over full length
of all holes
Average test hole spacing 11 m but tests
targeted in areas of increased grout take
Maximum value 1.6 Lugeons
Average value < 1 Lugeons
6 Ensure all of area to be treated is
covered.
Monitoring grout hole locations and plotting
diagrams to overlay results on treated area
and graphical plots of injections
All elements of the works con-
trolled by systematic surveying
and testing, and plotted in 3-D
CAD format for spatial verification
Table 2: Performance criteria, assessment, & results for curtain - extract from Black & Veitch
compliance report.
Figure 8. Plug grouting – general arrangement.
Figure 7. Link hole geometry around culvert, slurry wall,
and rock-head.
