CHAPTER 9
REMEDIAL PROCEDURES
be allowed to adjust, following completion of remedial
9-1. Basic considerations
measures, for at least a year before cosmetic work is
Remedial work for damaged structures is usually diffi-
done. The structure is seldom rebuilt to its original
cult to determine because the cause of the problem
condition, and in some instances, remedial measures
(e.g., location of source or loss of soil moisture, and
have not been successful.
swelling or settling/shrinking soil) may not be readily
apparent, A plan to fix the problem is often difficult to
execute, and the work may have to be repeated because
9-2. Evaluation of information
of failure to isolate the cause of the moisture changes
in the foundation soil, An effective remedial procedure
All existing information on the foundation soils and
may not be found until several attempts have been
design of the foundation and superstructure should be
made to eliminate the differential movement. Require-
studied before proceeding with new soil investiga-
tions.
ments for minimizing moisture changes (chap. 7) are
therefore essential. The foundation should have suffi-
a. Foundation conditions. The initial soil moisture
cient capacity to maintain all distortion within tolera-
at time of construction, types of soil, soil swell poten-
ble limits acceptable to the superstructure. This distor-
tials, depth to groundwater, type of foundation and
tion occurs from differential heave for the most severe
superstructure, and drainage system should be deter-
climates and changes in the field environment.
mined. The current soil moisture profile should also be
a. Specialized effort. Investigation and repair are
determined. Details of the foundation, such as actual
bearing pressures, size and length of footings, and slab
therefore specialized procedures that usually require
and shaft reinforcing, should also be collected. Drilling
much expertise and experience. Cost of repair work
logs made during construction of shaft foundations
can easily exceed the original cost of the foundation.
The amount of damage that requires repair also de-
may be used to establish soil and groundwater condi-
pends on the attitudes of the owner and occupants to
tions and details of shaft foundations. Actual construc-
tion should be checked against the plans to identify
tolerate distortion as well as damage that actually im-
pairs the usefulness and safety of the structure.
any variances.
fects of swelling soil tends to be cosmetic rather than
well as the time movements first became noticeable,
should be determined, Most cracks caused by differen-
structural, and repairs are usually more economical
tial heave are wider at the top than at the bottom.
than rebuilding as long as the structure remains
Nearly all lateral separation results from differential
sound. At-early signs of distress, remedial action to
heave. Diagonal cracks can indicate footing or drilled
minimize future distortion should be undertaken and
shaft movement, or lateral thrust from the doming
should be given a greater priority than the cosmetic re-
pattern of heaving concrete slabs. Fractures in slabs-
pairs as this action will minimize maintenance work
on-grade a few feet from and parallel with the perime-
over the long term. Maintenance expenses and fre-
ter walls also indicate heaving of underlying soils. Lev-
quency of repairs tend to be greatest in lightly loaded
structures and residences about 3 to 4 years following
el surveys can be used to determine the trend of move-
ment when prior survey records and reliable bench-
the original construction. Overall maintenance can be
marks are available. Excavations may be necessary to
minimized by taking remedial action to minimize fu-
study damage to deep foundations, such as cracks in
ture distortion before extensive repairs are required
(e.g., breaking out and replacing sections of walls).
shafts from uplift forces.
c. Sources of moisture. The source of soil moisture
c. Examples of remedial procedures. The choice of
remedial measures is influenced by the results of site
that led to the differential heave should be determined
and soil investigations as well as by the type of origi-
to evaluate the cause of damage. Location of deeproot-
nal construction. Table 9-1 illustrates common reme-
ed vegetation, such as shrubs and trees, location and
dial measures that can be taken. Only one remedial
frequency of watering, inadequate slopes and pending,
procedure should be attempted at a time so as to deter-
seepage into foundation soil from surface or perched
mine its effect on the structure. The structure should
water, and defects in drain, water, and sewer lines can
9-1
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