UFC 3-220-01N
15 AUGUST 2005
should be established. The engineer who plans the detailed field exploration program must
have knowledge of the structure, e.g., its configuration and foundation requirements for design
loads and settlement tolerances. The planning engineer should also know the type and
quantity of backfill required. The importance of employing qualified field exploration personnel
cannot be overemphasized. The exploration crews should be supervised in the field by a soils
engineer or geologist familiar with the foundation and backfill requirements so that changes
can be made in the exploration program where necessary to provide adequate information on
subsurface conditions. The field engineer should also know the location of significant features
of the structure so that sampling can be concentrated at these locations. In addition, he should
have an understanding of the engineering characteristics of subsurface soil and rock deposits
that are important to the design of the structure and a general knowledge of the testing
program so that the proper type and quantity of samples will be obtained for testing.
From the samples, the subsurface deposits can be classified and boring logs
prepared. The more continuous the sampling operation, the more accurate will
be the boring logs. All borings should be logged with the description of the
various strata encountered as discussed in ASTM D 1586 and ASTM D 2487.
Accurate logging and correct evaluation of all pertinent information are essential
for a true concept of subsurface conditions.
When the exploratory borings at the construction site have been completed, the
samples and logs of borings should be examined to determine if the material to
be excavated will be satisfactory and in sufficient quantity to meet backfill
requirements. Every effort should be made to use the excavated materials; how-
ever, if the excavated materials are not satisfactory or are of insufficient quantity,
additional exploration should be initiated to locate suitable borrow areas. If
borrow areas are not available, convenient commercial sources of suitable
material should be found. Backfill sources, whether excavation, borrow, or
commercial, should contain several times the required volume of compacted
backfill.
Groundwater studies prior to construction of subsurface structures are of the
utmost importance, since groundwater control is necessary to provide a dry
excavation in which construction and backfilling operations can be properly
conducted. Data on groundwater conditions are also essential for forecasting
construction dewatering requirements and stability problems. Groundwater
studies must consist of investigations to determine: groundwater levels to include
any seasonal variations and artesian conditions; the location of any
water-bearing strata; and the permeability and flow characteristics of
water-bearing strata. Methods for investigating groundwater conditions are
described in Chapter 9.
8-3.3.2.2
Laboratory Testing. The design of any foundation is dependent on the
engineering characteristics of the supporting media, which may be soil or rock in either its
natural state or as compacted backfill. The laboratory-testing program will furnish the engineer
information for planning, designing, and constructing subsurface structures. Laboratory testing
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