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Thermohydromechanical behaviour of soils and soil structure interfaces 219

Figure 5.5 Temperature-stress paths in the mean effective stress temperature plane. Redrawn
after Di Donna, A., Laloui, L., 2015. Response of soil subjected to thermal cyclic loading: experimental
and constitutive study. Eng. Geol. 190 (1), 65 76.

considerations, the volumetric behaviour of fine-grained soils under NC conditions
upon a heating cooling cycle is partly irreversible, that is thermoelastic,
thermoplastic.
Soils under highly OC conditions are characterised by a stress temperature state
that lies within the yield surface (state B in Fig. 5.5). In other words, the current
mechanical pressure, p , applied to the material at a temperature T 0 is lower than the
0
B
0
preconsolidation pressure, p . Because of the considered stress temperature state,
c
drained heating up to a temperature T 1 . T 0 from the initial state under a constant
0
mean effective stress induces thermoelastic strain (i.e. path B B ). The reason for this
phenomenon is because the stress temperature state remains within the yield surface.
Upon thermal unloading under a constant mean effective stress, the material still
remains OC. Based on the previous considerations, the volumetric behaviour of fine-
grained soils under highly OC conditions upon a heating cooling cycle is reversible,
that is thermoelastic.
Soils under slightly OC conditions are characterised by a stress temperature state
that lies within the yield surface (state C in Fig. 5.5). In other words, the current
0
mechanical pressure, p , applied to the material at a temperature T 0 is lower than the
C
0
preconsolidation pressure, p . Because of the considered stress temperature state,
c
drained heating from the initial state under a constant mean effective stress induces ini-
tial thermoelastic strain (i.e. path C C ) and subsequent thermoplastic strain when
0
loading from a stress temperature state lying on the yield surface occurs (i.e. path
0
C Cv). Based on the previous considerations, the volumetric behaviour of fine-
grained soils under slightly OC conditions upon a heating cooling cycle can be
reversible or partly irreversible.