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222 Analysis and Design of Energy Geostructures

Figure 5.8 Volumetric behaviour of fine-grained soils subjected to thermal cycles. Redrawn after Di
Donna, A., Laloui, L., 2015. Response of soil subjected to thermal cyclic loading: experimental and con-
stitutive study. Eng. Geol. 190 (1), 65 76.

accumulated plastic deformation) and the available space for inducing additional col-
lapse reduces, so that accommodation takes place. The thermal cycles result in a
transition from a NC to an OC condition. The oedometric curve expressing a rela-
0
tionship between the void ratio, e, and the vertical effective stress, σ z ,reportedin
Fig. 5.10 with reference to the results of Di Donna and Laloui (2015) highlights the
aforementioned phenomenon. The material was first consolidated to 125 kPa (from
point 1 to point 2 in Fig. 5.10), then subjected to four thermal cycles (from point 2
to point 3) and finally loaded up to 2000 kPa (from point 3 to point 5 in Fig. 5.10,
with an unloading phase). During the final mechanical loading phase after thermal
cyclic loading, the material shows a first phase of reversible behaviour (from point 3