The objective of this paper is to present a non-linear elastic model, considering temperature effects, that engineers can readily use to predict the mechanical behaviours of soils in geotechnical applications. Instead of using hyperbolic and exponential models, a non-linear equation is first formatted to describe the tangent moduli for saturated clays by introducing only one additional parameter (i.e. p ). By extending the non-linear equation, a new simplified nonlinear elastic model is obtained that is capable of capturing well the stress-strain relationship of saturated clays at room temperature. Thereafter, based on experimental results, the relationships between cohesion, internal friction angle, index, tangent bulk modulus and temperature are developed and incorporated in the non-linear elastic model. A revised semi-regression method is also developed to determine the relationship between the additional model parameter p and temperature. In this model, all of the eight parameters for the model have clear physical meanings and could be readily obtained by performing temperature-controlled triaxial tests. The accuracy and general applicability of the proposed method was checked by comparing its predictions with experimental results on saturated clay under various stress-path and temperature conditions as well as existing solutions proposed elsewhere. et al., 1989;Rao et al., 2017;Sun et al., 2011), energy piles (Abdelaziz and Ozudogru, 2016;Knellwolf et al., 2011;Saggu and Chakraborty, 2016) and geothermal structures (Brandl, 2006), highway pavements (Bianchini et al., 2011;Kertesz and Sansalone, 2014), thermally active embankments (Coccia and McCartney, 2013) and thermally active retaining walls (Stewart et al., 2014).The volume change for saturated soils performs a transition from contractive to expansive behaviour during drained heating or the temperature cycle with increasing overconsolidation ratio (O CR ) (Abuel-Naga et al., 2006;Baldi et al., 1988;Cekerevac and Laloui, 2004;Romero et al., 2005) or relative density (Ng et al., 2016). Some experimental test results showed that the shear strength of saturated clays under both drained and undrained conditions would increase with increase in temperature (Abuel- However, most of these temperature-dependent constitutive models mentioned previously are based on the elasto-plastic Camclay or modified Cam-clay model in the critical state framework. These models often include a number of parameters which may not have physical meanings or that have values difficult to determine due to the complicated soil properties, particularly considering the effects of temperature. Compared with these elastic-plastic models, it is easier to understand the theory of nonlinear elastic models, and the parameters could also be easily determined by performing triaxial compression tests Chang, 2006, 2008). In addition, the non-linear elastic models (e.g. Duncan-Chang model) could be readily implemented in finite-element analysis software without a singular matrix (Chen and Liu, ...

Multilayered low-stiffness geogrids have been used in constructing embankments, but without full understanding of their true behaviour -for example, the construction of apartments in Northern Ireland failed due to the excessive and continuing deformation of the load transfer platform. This paper presents a numerical simulation of multilayered geogrid-reinforced piled embankments. It shows that the inclusion of geogrids can effectively help transferring stress from subsoil to the pile cap, particularly for stiffer geogrids. Although the maximum settlement is approximately identical, an embankment with a three-layer geogrid provides more uniform stress distribution on the surface of subsoil and results in less differential settlement through the embankment. The maximum settlement and the total tension in the geogrid are found to be dependent only on the total stiffness provided and not on the number of geogrid layers. The parametric study shows that the combination of very soft subsoil and a geogrid with low stiffness results in relatively large settlement and may cause intolerable geogrid strain. The pile spacing is also found to be the most sensitive factor influencing the maximum settlement of the subsoil. Finally, an analytical method is assessed and shows reasonable agreement with the numerical results.

The mechanical properties of soil could be affected by its temperature change and these effects may lead to additional issues in the thermo-mechanical behaviour of energy piles. Laboratory experiments were conducted to assess the thermo-mechanical behaviour of a small-scale instrumented energy pile installed in a saturated clay at different stress histories. The energy pile was subjected to five heating/cooling cycles. The experimental programme involved monitoring the changes in the surrounding soil temperature, pile-head displacement, pile axial load and pile-tip resistance as the temperature of the pile changed. The results show that the thermo-mechanical behaviour of the energy pile depended on the stress history of the surrounding saturated clay. The normally consolidated clay showed a higher irreversible pile-head settlement and pile-tip resistance compared with the overconsolidated clay. This behaviour could be explained in light of the expected contraction thermally induced volume change of the normally consolidated clay that could induce an additional negative skin friction on the pile. Moreover, the observed mechanical engineering behaviour of the energy pile under thermal heating/cooling cycles could be explained in terms of the expected degradation of shaft friction due to the cyclic thermally induced interface shear stress.

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