13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- Down stream: 2.5 times of the height of dam (700 m); Left and right banks: 3 times of the height of dam (800 m each); Height above the dam: 50 m; Height beneath the dam: 324 m. Fig. 2(b) is photo of the arch dam model and distribution of devices. The geo-mechanical model is built in a steel frame whose size is 4.6 m×4.6m×2.8 m. The model scale is 1:250. (a) Numerical mesh (b) geo-mechanical model Figure 2. Numerical mesh and geo-mechanical model of Baihetan arch dam Fig. 3 shows that unbalanced forces of upstream surface concentrate near the foundation plane, especially the dam heel near river bed area. Unbalanced forces distribution contour of dam heel in different work conditions are shown in Fig. 4. The unbalanced forces concentrated in the upstream river bed area near the dam heel instead of the dam itself, where there is a fault crossing. Unbalanced forces form a significant banding in this area, which is termed as the indication of cracks initiation. Cracking status of the dam heel near river bed area during the geo-mechanical test are illustrated in Fig. 5. When work load reaches 1.5 times water pressure, micro-cracks initiate in the upstream river bed about 14.5 m away from dam heel, which agrees with the FE analysis results. Cracks propagate as work load increases to 2.0 times water pressure, and begin to penetrate through the river bed. Figure 3. Unbalanced forces distribution of upstream surface (a) 1.5 times water pressure (b) 2.0 times water pressure Figure 4. Unbalanced forces distribution of dam heel crack Dam crack Dam
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