Page 196 - Analysis and Design of Energy Geostructures

Deformation in the context of energy geostructures 169

Figure 4.15 Thermally induced strain caused by (A) heating and (B) cooling of an energy pile
under free expansion conditions.

Figure 4.16 Thermally induced stress caused by (A) heating and (B) cooling of an energy pile
under completely restrained conditions.

the observed strain is

ε 5 0 ð4:77Þ
th
o
Therefore a thermally induced stress

th th
ð4:78Þ
σ 5 Eε 5 EαΔT
b b
arises in the energy pile (cf. Fig. 4.16).
In reality, energy piles do not deform freely because of the presence of the sur-
rounding ground and superstructure. Therefore the observed thermally induced strain
is generally
ε # ε th ð4:79Þ
th
o f