Page 257 - Analysis and Design of Energy Geostructures

232 Analysis and Design of Energy Geostructures

Bourne-Webb et al. (2016), the behaviour of NC fine-grained soils upon heating
involves an action on the deformation of energy geostructures that is similar to the
one applied by ground movements such as downdrag or negative skin friction and
should be considered in analysis and design. Time-dependent effects such as creep may
be accelerated by temperature increases (Leroueil and Soares Marques, 1996; Mitchell
and Soga, 2005; Laloui et al., 2008) and result in additional long-term settlement.
Limiting the settlement of energy geostructures under the influence of mechanical
loads may limit time-dependent effects potentially accelerated by temperature.

5.5 Strength of soils under nonisothermal conditions
5.5.1 Yield surface at different temperatures

Along with the decrease of the preconsolidation pressure of fine-grained soils at con-
stant void ratio with increasing temperature, a global shrinkage of the yield surface can
be observed. Experimental results that corroborate the previous consideration have
been reported, for example by Cekerevac and Laloui (2004) and are shown in
Fig. 5.17. The yield surface is represented in two-dimensional space relating the mean
0
effective stress, p , with the deviatoric stress, q. Both stresses are normalised by a scaling
factor that represents the equivalent pressure on the NCL at the specific volume for
0
which yielding is observed, p .
e

Figure 5.17 Normalised yield surfaces for kaolin at different temperatures. Redrawn after Cekerevac,
C., Laloui, L., 2004. Experimental study of thermal effects on the mechanical behaviour of a clay. Int. J.
Numer. Anal. Methods Geomech. 28 (3), 209 228.