TM
5-818-6/AFM
88-32
SECTION
1.
INTRODUCTION
1.
PURPOSE AND SCOPE. This manual was prepared to provide guidance
in the use of pressure grouting as a means to correct existing or anticipated
s u b s u r f a c e problems. Information on procedures, materials, and equipment
for use in planning and executing a grouting project i's included, and types of
problems that might be solved by pressure grouting are discussed. Methods
of pressure grouting that have proven to be effective are described, and
various types of grouts and their properties are listed.
2.
GENERAL
CONSIDERATIONS.
a. Purposes of Pressure Grouting. Pressure grouting involves the injec-
tion under pressure of a liquid or suspension into the voids of a soil or rock
mass or into voids between these materials and an existing structure. The
injected grout must eventually form either a gel or a solid-within the treated
voids, or the grouting process must result in the deposition of suspended
solids in these voids. The primary purposes of pressure grouting a soil or
rock mass are to improve the strength and durability of the mass and/or to
reduce the permeability of the mass.
b. Problems Related to Strength. Typical problems involving strength
properties of a soil or rock mass include: (a) insufficient bearing capacity
for structural elements such as footings, slabs, or mats; (b) insufficient
strength to preclude sliding failures of embankments or cut slopes; (c) in-
herent mass instability of fractured rock formations; (d) sloughing or com-
plete closure of vertical or horizontal tunnels; and (e) general structural
weaknesses due to underground caverns or solution channels or due to voids
that develop during or following construction.
c. Problems Related to Permeability. Problems related to permeability
of a--soil or rock mass include: (a) reduction in strength of foundation mate-
rials due to high seepage forces; (b) loss of impounded water from a reser-
voir or storage area; (c) high uplift forces at the base of a water- retaining
structure; (d) piping erosion through or under an earth dam; and (e) inability
to complete excavations, shafts, or tunnels extending below the groundwater
table due to caving and sloughing.
d. Selection of Methods of Treatment. Problems of the nature described
above can often be treated by pressure grouting. However, other methods of
treatment may be equally satisfactory and adaptable to the project. The se-
lection of pressure grouting as the method of treatment should be based on
an evaluation of all pertinent aspects of the problem, i.e., engineering needs,
subsurface conditions, economic considerations, and availability of qualified
s u p e r v i s o r y personnel. In some respects, pressure grouting is an art based
on natural and scientific laws but it requires experience and engineering
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