能源桩在经济发达的沿海地区有广泛的应用前景，但在当前的设计中主要依靠工程师的经验，采用力传递与热传递分算，理论研究的滞后，限制了能源桩的快速发展。本项目针对沿海地区广泛分布的强结构性的饱和黏土，将通过物理参数实验、模型试验、理论分析及多场耦合有限元模拟等手段来研究能源桩-土体受温度循环下的热力学响应。首先，基于室内试验，确定合适的状态参量，将温度对土性质的影响解耦，定义新的热屈服面并配合荷载屈服面，在临界状态土力学及边界面塑性理论的框架下，建立可以考虑温度对土体应力历史、结构、各向异性影响的边界面热弹塑性本构模型。其次，考虑温度场、应力场及渗流场，建立能源桩热力耦合关系的控制方程，选用合适的桩土界面接触单元并编制有限元程序。通过模型试验结果不断矫正优化计算模型，最终建立能源桩工程热-水-力（Thermo-hydro-mechanical THM）多场耦合的分析方法。

Energy pile, which can not only bearing the load of up-structure but also be used as an energy sink to exchange heat between piles and surrounding soils, has a great potential to be used in the developed coastal area. However, its design were mostly based on the past experience, the research of such technology is still far from complete. Besides, the fully saturated soft clay in coastal area is highly structured, the soil-structure interaction under thermal and mechanical load is even more complicated. Thus, an advanced theoretical designing method is urgently necessary. This research will study the thermo-mechanical response of energy pile during the thermal cycle. Method such as parameter lab tests, physical modelling tests, theoretical analysis and multi-phase coupling finite element simulations will be adopted. Firstly, A new thermal yield surface will be defined through an appropriate state parameter to represent the soil responses of thermal effects. Then a thermo-elastoplastic constitutive model can be developed by the combining thermal and load yield surface based on the critical state soil mechanism and bounding surface plasticity framework. The significant contribution of this model is that it can be used to consider the influence of thermal effects on stress history, soil structure and soil anisotropic characteristic. Secondly, the governing functions for energy pile problem can be built up by fully considering the coupling between thermal field, drainage field and stress field. Such functions can be discretized according to virtual work principle and be used to develop the multi-phase coupling finite element modelling program. A new kind of contact element will be implemented to represent the stress and heat transfer between soil-pile boundary. In order to promote the calculation efficiency, coupling FEM-FDM method will also be used in this numerical modelling. Then, the constitutive model and contact element model will be adjusted and optimized according to the physical modelling results. In the end, the Thermo-hydro-mechanical (THM) coupling finite element methods will be built up to provide a better design guide for energy pile problems.