Grouting Methods ~ these techniques are used to form a curtain or
cut off wall in high permeability soils where pumping methods could
be uneconomic. The curtain walls formed by grouting methods are
non-structural therefore adequate earth support will be required
and in some cases this will be a distance of at least 4„000 from
the face of the proposed excavation. Grout mixtures are injected
into the soil by pumping the grout at high pressure through special
injection pipes inserted in the ground. The pattern and spacing of
the injection pipes will depend on the grout type and soil
conditions.
Grout Types ~
Cement Grouts † mixture of neat cement and water cement
sand up to 1 : 4 or PFA (pulverized fuel ash) cement to a 1 : 1
ratio. Suitable for coarse grained soils and fissured and
jointed rock strata.
Chemical Grouts † one shot (premixed) of two shot (first
chemical is injected followed immediately by second chemical
resulting in an immediate reaction) methods can be employed
to form a permanent gel in the soil to reduce its permeability
and at the same time increase the soil's strength. Suitable
for medium to coarse sands and gravels.
Resin Grouts † these are similar in application to chemical
grouts but have a low viscosity and can therefore penetrate
into silty fine sands.
Ground Water Control---Permanent Exclusion