碾压混凝土拱坝分缝防裂设计关键问题研究

Study on several key problems about anti-cracking design of induced joints in RCC archdams

在实际工程中,很多碾压混凝土(RCC)拱坝并未张开甚至在未设缝位置出现裂缝,诱导缝实际诱导开裂作用并未达到设计预期,甚至还带来一些附加效应。归结未张开原因,以诱导缝布置不当影响最大。由于RCC拱坝温度应力具有复杂性、多变性、动态性等特点,拱坝防裂设计特别是诱导缝布置方面必须真实反映坝体从施工期到运行期全过程的工作性态。实际工程应用成果表明:RCC拱坝诱导缝及横缝采用带开-闭迭代功能的接触单元模拟,破坏准则采用等效强度理论,基于整坝全过程仿真分析技术开展诱导缝防裂设计,是行之有效的方法;根据仿真结果进行坝体分缝布置、缝面结构型式等研究,可使诱导缝按设计要求张开,起到释放温降引起的拉应力的作用,保证坝体混凝土的施工质量。

After decades of practice, it has been proved that setting joints in the dam is an effective mea- sure to prevent cracks in a dam. As for RCC arch dams, transverse joints and induced joints are usually discussed together, and they have played a synergistic effect of preventing cracks because of their different structural features. However, in practical engineering, cracks haven＇t appeared in a lot of RCC arch dams or some cracks appeared in the positions where joints are not set, which means that the induced joints ha- ven＇t met the expectations to induce cracks, instead, they bring some additional effects. In many reasons, improperly arrangement of induced joints affected the most. Since the Thermal Stress of RCC arch dam is complicated, changeable and dynamical, the anti-crack design must truly reflect the whole process of dam behavior from construction to operation. Practical application shows that the research of anti-cracking design based on the overall process simulation technology of the whole dam is an effective method, in which the induced joints and transverse joints of the RCC arch dam are simulated with open-closed iterative func- tion, and the Equivalent Strength Theory is adopted for the failure criterion. Study on joints design and structural types of interface according to the simulation results can make the cracks appear as expected, re- leasing the tension stress caused by the temperature drop, which makes the construction quality of concrete of dam be ensured.