Study On Dynamic Temperature Control Method Of High Concrete Dams With The Whole Process Of Construction And Operation

As a high concrete dam is bulky with complex constraints and high stress levels, the temperature control and crack prevention is one of the key technologies, which is also the focus issue commonly concerned in the field of engineering and academic. China has made abundant accomplishments in concrete dams, however,"no dam without crack" is still an unavoidable fact, and shows the new features:①Crack distribution is wider and with greater dangers, such as the Xiaowan Arch Dam;②Cracks appear much easier in one region or a grouting blocks densely;③Cracking risk is no longer confined to construction period, there are also a lot of cracks in the storage and operation period.④Cracks which are not effectively remediated in the construction period extended in the second time in the operation period, and so on. When using current conventional methods to control the temperature, it is difficult to adapt to the needs of the continuous and rapid construction technology, which cannot bring RCC’s superiority of crack performance into full play. Therefore, it is necessary to study the dynamic temperature control method, temperature load evolution characteristics, anti-cracking safety evaluation system and other issues of the high concrete dam, from the overall process of the construction and the operation.The monitoring and management of temperature control information is one of the important contents of the anti-cracking safety control of high concrete dams. In order to monitor the construction process of the dam more scientifically, reasonably, and efficiently, an object oriented-programming approach is used to develop the temperature control decision support system (TCDSS for short). A new construction structure framework is defined in this TCDSS. The management methods and operating mechanism of the temperature control are established based on TCDSS. Research results show that the TCDSS has obvious progress in the human-computer interaction and user experience. Through the systematic management of temperature data, the multi-level display of temperature control information, the intelligent analysis and feedback of real-time monitoring data, and the powerful function of experts analysis, the intelligent management and decision support of the temperature control and crack prevention of high concrete dams could be better achieved.The spatial-temporal dynamic control method is presented for the temperature control and crack prevention during the construction of high concrete dams. Some key scientific issues are focused on such as pipe cooling control method, temperature gradient control method for arch dams, real-time acquisition and evaluation method of construction monitoring data, rapid simulation technology of the temperature control analysis, and the early warning mechanism of construction measures. Research results show that the tensile stress of the dam concrete could be reduced through optimizing the change of concrete temperature along with time and space, so as to lower the cracking risk. Through strengthening the real-time collection, analysis and inversion of construction data, and by the rapid simulation of the temperature field and stress field, the efficiency of temperature monitoring and the effects of crack prevention can be improved significantly. Through strengthening the early warning mechanism, all the periods and all parts of the dam can be fully covered to further realize the spatial-temporal dynamic control.A lower temperature rise of hydration heat, and a longer heating time are the important characteristics of roller compacted concrete. In order to research the anti-cracking characteristics, the temperature control analysis method based on life-cycle is presented, and the construction-operation status of Longtan Dam is studied. Research results show:①The evolution of temperature field and stress field of high roller compacted concrete dams is a long and slow course.②The residual temperature load in construction will change the stress state of the dam during the operation period. In addition, aiming at the existing inadaptability of the current design standards, the value of several temperature differences is demonstrated again, and the choice of pipe cooling, the value of design ages are also discussed.Based on the life-cycle theory, the anti-cracking risk analysis method of the high concrete dams is discussed. For the spatial-temporal evolution characteristics of the temperature and stress of roller compacted concrete, an anti-cracking risk assessment system is presented, whose benchmark is the structural stability with the whole process of construction and operation. The assessment system framework includes five parts:the spatial-temporal evolution of concrete material parameters, the whole evolution process of the temperature and stress of roller compacted concrete, the mesoscopic evolution process of concrete cracks, the bad working conditions, and the early warning indicators.