31 Aug 94
be determined by the geotechnical engineer. The
(1) Thermal properties.
in situ density of a soil foundation can be estimated
(a) Thermal conductivity. The thermal conduc-
from boring data by means of ASTM D 1586
tivity of the foundation material is affected by density
(ASTM 1992c). Undisturbed samples of soil can be
and moisture content. The thermal conductivity of
tested in accordance with EM 1110-2-1906, Labora-
foundation materials ranges from 2.4 for clay to
tory Soils Testing; and undisturbed samples of rock
2.8 for sand to 3.0 for gravel and from 2.4 for lime-
can be tested in accordance with the Rock Testing
stone to 3.1 Btu/ft-hr-F for granite. Thermal con-
Handbook (USACE 1990).
ductivity can be determined according to CRD-C 44
(b) Initial temperature. The initial temperatures
for the foundation should be provided as a distribu-
(b) Specific heat. Specific heat for foundation
tion of temperature with depth. These distributions
materials ranges from 0.22 for clay to 0.19 for sand
should be determined from a heat transfer analysis of
and from 0.22 for limestone to 0.19 Btu/lb F for
the foundation for a period of not less than 1 year
granite. Specific heat can be determined according to
proceeding the start of concrete placement.
CRD-C 124 (USAEWES 1949b).
(2) Mechanical properties.
(1) General. Several parameters are required to
model the air trapped within culverts, galleries, or
other enclosed voids for the heat transfer analysis.
varies greatly with the grain size, moisture content,
These properties should be assigned by the structural
engineer and they are assumed to be constant during
soils can be estimated by the geotechnical engineer.
the analysis. The key parameters are listed below
Values for foundation rock can be determined by
and have similar definitions to those presented in
ASTM D 3148 (ASTM 1992a); typical values range
paragraph A-3b. Film coefficients can be used in lieu
between 4 and 7 106 psi for granite and between
of air elements in the analysis. A film coefficient of
0.01 Btu/day-in.2-F should be used.
(b) Poisson's Ratio. As with the modulus of
(2) Thermal properties. The required thermal
elasticity, adequate values for Poisson's Ratio for
foundation soils can be estimated by the geotechnical
heat. Reasonable values are 0.00126 Btu-in./
engineer. Values for foundation rock can be deter-
mined by ASTM D 3148; typical values range
for specific heat.
between 0.25 and 0.33 for both granite and limestone.
(3) Physical property. The density of air must
(c) Coefficient of thermal expansion. Soil foun-
be input into the analysis. A density of 0.000046 lb/
in.3 should be used for the analyses.
dations will be modeled in the heat transfer analysis
only and, therefore, the coefficient of thermal expan-
sion is not needed. The coefficient of expansion for
rock types can be determined according to ASTM
A-4. Construction Parameters
D 4535 (ASTM 1992b); typical values are
4.4 10-6 in./in./F for both limestone and granite.
Differences in the way a monolith is constructed will
impact the behavior of a structure to varying degrees.
(d) Pile-subgrade reaction modulus. The pile-
The response of the structure to changes of the con-
subgrade reaction modulus should be determined in
struction parameters in the analysis will often dictate
accordance with the guidance given in EM 1110-2-
whether or not cost reducing measures can be taken
2906, Design of Pile Foundations, 15 January 1991.
in the field. Construction parameters can also be
varied in an attempt to improve the performance of a
(3) Physical properties.
structure. The paragraphs below describe the primary
construction parameters that can be considered for
(a) Density and moisture content. The density
changes during the NISA for accomplishing cost
and moisture content of the foundation material must
reductions or improved structural behavior. Values