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

(USAEWES 1949f).

(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

(a) Modulus of elasticity (Young's Modulus).

model the air trapped within culverts, galleries, or

The modulus of elasticity of foundation materials

other enclosed voids for the heat transfer analysis.

varies greatly with the grain size, moisture content,

These properties should be assigned by the structural

and degree of consolidation. Adequate values for

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-3*b*. 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

properties are the thermal conductivity and specific

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

D 4535 (ASTM 1992b); typical values are

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

A-14

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