Research Of Crack Arrest Mechanism Of Artificial Joints In Arch Dams

Arch dams have been widely applied in the hydraulic engineering due to their many advantages. The problem that cracks occur in the concrete dam body becomes common and should be handled with care. One of the structural measures in the arch dam design is to assign artificial guiding joints to free the complex stress and to reduce cracks caused by water load and temperature stress, or the structural design with some mistakes. Measures should be also taken to prevent the jointsfrom propagatingin depth under complex load combinations. So the research on the crack arresting mechanisms at the tip of the artificial guide joint is of theoretical and practical interest. Based on the nonlinear fracture mechanics and model tests, the dissertation makes a fundamental study on the crack mechanisms of arch dam. The main contents and results of the research can be stated as follows.1. Aanalytical method of mechanics of materials and a finite element model of nonlinear damage fracture mechanics which is built on the ABAQUS platform are used to study the failure characteristics in a notched concrete beam. The effects with or without channel steel plate at the tip of the artificial guiding joints are compared and the channel steel plate reinforcing mechanisms in a pure bending component are analyzed. The bond-slip interface between concrete and channel steel plate, after verification through the model tests, is modeled to simulate the effect of the crack arresting mechanisms by the channel steel plate.2. A large-scale notched arch beam model test is established for studying the failure characteristics, in particular the strengthening mechanism of channel steel plate for notched arch concrete beam. Two cases are comparatively analyzed, of which one artificial guiding joint in the middle of arch beam and two artificial guiding joints in the three dividing point of arch beam, to explore the process of crack initiation, evolution and propagation and the distribution of cracks at the tip of the artificial guiding joint. The different joint locations and the channel steel plate styles are studied for the bearing capacity contribution in the arch concrete beam.3. The arch beam model tests and numerical study are comparatively analyzed for the crack arresting mechanism by the channel steel plate at the tip of artificial guiding joint. It can be found the strengthening mechanism of channel steel plate for the notched arch concrete beam on the crack initiation, crack evolution and the beam failure. The comparative analysis results show that the strengthening mechanism by the channel steel plate is different between the straight beam and arch beam including the artificial guide joint in the position, number and channel style.4. The data of more than ten years observation in the Shimenzi RCC dam is filed and used to analyze the artificial guiling joint for the crack arresting mechanism and the adaptability to soft base. The influences of the artificial guiding joint structure to the dam stiffness and to rock deformation compatibility are studied by, respectively, the improved finite element model of temperature and stress coupling and nonlinear fracture mechanics model. The research shows that the introduce of artificial guiding joint structure can effectively reduce the local tensile stresses in crown cantilever and form an effective secondary stress arch structure, as a result can reduce the risk of dam fracture.