Grouting and Injection.

Grouting is a high-cost soil stabilization method that can be used where there is sufficient confinement to permit required injection pressures.  It is usually limited to zones of relatively small volume and to special problems.  Some of the more important applications are control of groundwater during construction; void filling to prevent excessive settlement; strengthening adjacent foundation soils to protect against damage during excavation, pile driving, etc.; soil strengthening to reduce lateral support requirements; stabilization of loose sands against liquefaction; foundation underpinning; reduction of machine foundation vibrations; and filling solution voids in calcareous materials.

a. Grout types and groutability.  Grouts can be classified as particulate or chemical.  Portland cement is
the most widely used particulate grouting material. Grouts composed of cement and clary are also widely used, and lime-slurry injection is finding increasing application.  Because of the silt-size particles in these
materials, they cannot be injected into the pores of soils finer than medium to coarse sand.  For successful grouting of soils, use the following guide

Type I portland cement, Typeportland cement, and  Type III portland cement, Type III portland cement, and processed bentonite cannot be used to penetrate soils finer than 30, 40, and 60 mesh sieve sizes, respectively.

Different types of grouts may be combined to both coarse- and fine-grained soils.

b. Cement and soil-cement grouting.  See TM 5-818-6/AFM 88-32 for discussion of planning and
implementation of foundation grouting with cement and soil-cement.

c. Chemical grouting.  To penetrate the voids of finer soils, chemical grout must be used.  The most
common classes of chemical grouts in current use are silicates, resins, lignins, and acrylamides.  The viscosity of the chemical-water solution is the major factor controlling groutability.  The particle-size ranges over which each of these grout types is effective is shown in figure 16-6.

 Soil particle sizes suitable for different grout types and several concentrations and viscosities shown.
Figure 16-6.  Soil particle sizes suitable for different grout types and several concentrations and viscosities shown.

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