RESEARCH PAPER A double hardening thermo-mechanical constitutive model for overconsolidated clays E. L. Liu Æ H. L. Xing Received: 2 July 2007 / Accepted: 3 January 2008 / Published online: 23 April 2008 Ó Springer-Verlag 2008 Abstract On the basis of a double hardening model for clays and available experimental results, a new thermo- elasto-plastic constitutive model for saturated clays is proposed to describe the effects of temperature and over- consolidation ratio on the mechanical properties of saturated clays. Two hardening parameters are introduced: r 0 c and a. The proposed model is then applied to simulate the relevant important features of saturated clays with different overconsolidation ratios under different tempera- ture and loading conditions. The model predictions are compared with available experimental results to demon- strate its accuracy and usefulness. Keywords Constitutive model  Double hardening parameters  Overconsolidated clays  Thermo-mechanical behavior 1 Introduction Recently, more attention has been paid to studying the mechanical response of soils to combined effects of stress and temperature changes. This aspect is important in some engineering applications, such as hydrocarbon extraction from oil-bearing sands, radioactive waste disposal, coal gasification, geothermal energy, and in pavements and buried high-voltage cables. A number of experiments were carried out to investigate the influence of temperature on the behaviors of soils. For example Baldi et al. [2] examined experimentally the effect of temperature on the volumetric deformations of clay skeleton and clay-water system under constant effective stress and isotropic loading conditions at different constant temperatures; Tanaka et al. [16] and Burghignoli et al. [3] investigated the effect of temperature on the mechanical behavior of reconstituted and natural clayey soil specimens using the modified tri- axial cells; Sultan et al. [15] identified experimentally the effect of temperature on the pre-consolidation pressure of the Boom clay and the effect of the overconsolidation ratio on the thermal volume changes by performing temperature- controlled isotropic compression tests; Abuel-Naga et al. [1] carried out tests on the soft Bangkok clay to investigate the effect of temperature on its engineering behavior and concluded that its shear strength and hydraulic conductivity improve with the increase of soil temperature under drained heating conditions. To study the effects of temperature on clays, constitutive models were proposed to describe the thermo-elasto-plastic behavior of the solid skeleton. For example Hueckel et al. [7, 8] extended the elasto-plastic modified Cam-clay model to include the thermal effects following Prager’s thermo- plasticity theory. This model was modified later to include the variability of the carbonate content [9]; Lingnau et al. [12] proposed two models to simulate the behavior of sand–bentonite mixtures at elevated temperatures: the isothermal pseudo-elastic model and the isothermal elasto- plastic model; Modaressi et al. [13] developed a cyclic thermo-visco-plastic model to take thermo-mechanical factors into account. Cui et al. [5] proposed an elasto- plastic model for saturated soils subjected to temperature changes within the framework of the Cam-clay model, but with particular attention to the volume-change behavior and the effects of the overconsolidation ratio; Graham et al. [6] proposed a model which could predict how the E. L. Liu (&)  H. L. Xing Earth Systems Science Computational Centre (ESSCC), The University of Queensland, St Lucia, Brisbane, QLD 4072, Australia e-mail: enlongl@esscc.uq.edu.au; enlong.liu1976@gmail.com 123 Acta Geotechnica (2009) 4:1–6 DOI 10.1007/s11440-008-0053-4