Page 166 - Analysis and Design of Energy Geostructures

Deformation in the context of energy geostructures 139

framework, the modelled subject is characterised by an elastic behaviour. In the latter
framework, the modelled subject is characterised by a thermoelastic behaviour. A revers-
ible mechanical behaviour is associated with the property of elasticity, which is com-
mon to many materials (and general structural systems) whose deformation is caused
by loads that combined do not exceed a certain limit. Under these conditions, the
loading of any subject (e.g. through a mechanical load, P) produces strains that are
entirely recovered once the loading is removed (cf. Fig. 4.1B), and the combined
effect of several loads (e.g. a mechanical load, P, and a thermal load resulting in a tem-
perature variation, ΔT) acting simultaneously is equal to the algebraic sum of the
effect of each load acting individually based on the superposition principle (cf.
Fig. 4.1C). Situations in which the behaviour of materials or general systems is revers-
ible (under both isothermal and nonisothermal conditions) are typically associated with
small deformations caused by loading (e.g. of the order of 0.001). These situations
characterise energy geostructures in most applications.

Figure 4.1 (A) Application of the continuum idealisation of the materials to an energy pile; (B) con-
cept of reversible mechanical behaviour applied to an energy pile and (C) principle of superposi-
tion applied to the thermomechanical problem of an energy pile.