Analysis Of Base Joint Of High Arch Dam Based On Linear Elastic Fracture Mechanics

During the design of dams, usually there is too lager beam-axial tension stress on the foot of arch dams under the loads of temperature, water, soil, etc., and then it will cause crazing on that zone. As soon as broad river valley and high arch dams of 300 meters high concerned, the situation will be worse. Once the foot of arch dams craze, cracks maybe continue to expand under the high-press water, even destroy the preventing water purdah. For the reason, designers often take all measures avoid the appearance of tension stress in arch dams. All these measures can be specified into 2 classes: no.1 is to optimize the arch dam's bodily form or to control the concrete's temperature before casting into storehouse etc.; no.2 is to take effect structure measures, for revulsive joint, peripheral joint, and base joint etc.There are relatively many disputed problems about the structure measures in current dams design. Some succeeded, and some failed painfully. In this paper, first I expatiate the resource of base joint method in high arch dams then introduce the elementary theory of fracture mechanics and the computational theory of fracture finite element. In succession, I put the 20m depth base joint project of Xiao-Wan arch dam as a research item, and calculated the tension stress on the foot of arch dam before and after setting base joint, analyzed the situation of tension stress releasing and the influence to arch dam of displacement's variety, and also analyzed the stress field on arch dam's shoulder and its stability. Designers, usually, only consider the whole stability of body-foundation of the dam after setting base joint, while ignore the stability of base joint itself. In this paper, the method of fracture finite element was applied, by applying Williams's formula I calculated the stress intensity factor of base joint after knowing the displacement field of tip of base joint then distinguished the stability of base joint by terms of composite crack's K fracture criterion. The result is: the project of 20m depth base joint of Xiao-Wan arch dam has obvious effect to release the too lager tension stress on the foot of arch dam, at the same time the differences of the displacement field of dam body and stress filed of dam shoulder are potty, the base joint itself exists in rough stability, but the middle dam bodies need some partial adjustment.