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(a) uniform seeping
(b) improvement only
along cracks
Fig. 15.18. Configuration of ground improvement by injection of liquid grout
Long-term behavior of silicate grouting
SilicaGroutQu.fig
10
1
Super fine hybrid silica (<6
ยต
m)
0.1
Active silica
0.01
1
10
100
1000
Elapsed curing days
Fig. 15.19. Unconfined compression strengthof sand improved by colloidal silica
(data byMiwaet al., 2001; Yonekura et al., 2001)
Liquid of colloidal silica is injected into ground through tubes or piles under relatively
low pressure. Figure15.20 shows the ongoing injection through multiple tubes, and a
good size of solidified mass of soil is formed. The very small size of colloidal silica
particles (typically 10nm) makes it possible for the silicate grout to seep into fine sand
andsiltysand.Figure15.21manifestsanexcavatedmassofsandwhichisanevidenceof
uniformseepingduetoverylowviscosityandveryfinesizeofsilicagrainsintheliquid.
Oneoftheadvantagesoftheinjectionofcolloidalsilicaliquidisitscapabilitytoimprove
soils under existing structures (Figure15.22). This aim is achieved by drilling a hole in
an oblique direction (Figure15.23) and installingan injection nozzle (Figure15.24).
The extent of uniform seeping was examined by reproducing the process in a labora-
torymodelground(C.ConleeofDrexelUniversityduringherinternshipatUniversityof
Tokyo).Liquidofcolloidalsilicawasinjectedunderlowpressureintosandyground,and
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