论文取得的主要新成果有：1．进行了堆石料单级和分级加载的三轴流变试验，探讨了堆石料应力瞬时加载变形和流变变形的耦合效应。发现流变变形会引起堆石料的塑性硬化，可使得堆石料在后续加载的一定范围内处于弹性再加载状态；另一方面，当堆石料发生瞬时加载塑性变形后，会清除之前所有流变变形的影响。2．基于弹塑性理论的框架，提出了可考虑堆石料应力瞬时加载变形和流变变形耦合效应的计算模型。以沈珠江双曲服面模型为例，给出了考虑上述耦合效应的具体计算方法，应用本文取得的三轴流变试验成果对提出的计算模型和方法进行了验证。3．基于接触力学的方法构建了一套适用于面板堆石坝的接触数值算法，可用于模拟面板-堆石以及面板-面板间的实际接触关系。该算法采用基于局部坐标系下相对位移自由度的直接迭代算法求解接触非线性方程，采用双向链接边表(DCEL)建立接触面拓扑的数据结构，采用带预处理过程的基于径向基点插值法的曲面重建算法重建接触面。该算法能够对包含脱空和大规模滑移等复杂接触状态的接触问题做出合理的模拟。4．构建了一套可进行混凝土面板破损现象模拟的数值计算方法。在该方法中，嵌入了可硬化的弹塑性模型用于模拟面板的压损破坏，发展了弥散固定脆性裂缝模型用于模拟面板的结构性张拉裂缝，引入了组合式模型用于反映钢筋与混凝土间的相互作用。5．在上述工作的基础上，编制了混凝土面板堆石坝应力变形有限元计算程序系统FEMCONT。应用该软件对一个理想高面板堆石坝进行了数值模拟计算，分析了面板脱空和结构性裂缝等问题。
Along with the acceleration of the Western Development Program in China, a large number of high concrete-faced rockfill dams are either under design or being planned. The engineering experiences of existing projects have shown that the key safety problems of high concrete-faced rockfill dams are the overlarge long-term deformation of the dam due to the creep of the rockfill and the structural damage of the concrete face. At present, the mechanisms of these problems are still unclear and there is a lack of effective calculation and analysis methods. Based on previous research works, this dissertation focuses on the creep characteristics of the rockfill and the numerical simulation method for the contact behavior between the concrete face and the rockfill as well as the structural damage of the concrete face. The main achievements of this study are as follows:1. Both single-stage loading and multi-stage loading triaxial creep tests of rockfill are performed to study the coupling of instantaneous loading deformation and creep deformation. It is observed that the creep deformation of rockfill will result in plastic hardening and thus the rockfill will remain in the elastic reloading state in a certain range of the following loading stage. And as soon as instantaneous loading plastic deformation appears again, it will eliminate the effect of all previous creep deformation.2. Within the framework of elasto-plasticity theory, a calculation model, considering the coupling of instantaneous loading deformation and creep deformation, is proposed. Taking Shen's double-yielding-surface model as an example, specific methods are given to consider the coupling effect mentioned above. The developed models and calculation methods are verified by the laboratory test results.3. Based on contact mechanics, a system of numerical algorithms, suitable for concrete-faced rockfill dams, is developed to simulate the contact behavior between concrete face and rockfill as well as between concrete face slabs. In this system, a direct iterative algorithm based on the relative displacement in a local coordinate system is accepted to solve the non-linear system of equations of contact problems, the data structure, named doubly connected edge list, is applied to describe the topology of contact faces, and a surface smoothing method with preconditioning process, based on radius point interpolation method, is used to reconstruct the contact surface. With such treatments, this system can produce reasonable simulation results for complex contact problems such as large area of void or sliding.4. A numerical calculation method is proposed to simulate the structural damage of concrete face slabs. In this method, a hardening elasto-plastic model is embedded to simulate the extruding rupture of concrete face slabs, a smeared fixed-brittle-crack model is used to simulate the tensile cracks, and a combined model is introduced to describe the interaction between the steel bars and the concrete.5. On the basis of above works, a finite element program, named FEMCONT, is developed for the stress-deformation analysis of concrete-faced rockfill dams. The program is applied to simulate the deformation of an ideal high concrete-faced rockfill dam and the problems such as voids under the concrete face and structural cracks are analyzed.
