Evaluation of safety performance of extremely high slab-faced gravel dams

The structural safety performance of Dashixia concrete face gravel dam (CFGD), an extremely high CFGD in Xinjiang, is studied based on the large-scale triaxial experiments on dam materials and the detailed finite element method-based numerical analyses. Compacted gravel materials are found to exhibit high deformation modulus, small magnitude of creep and small magnitude of shaking-induced residual deformation. The maximum settlement of Dashixia CFGD during operation is evaluated to be about 0.64% of the dam height, while the earthquake-induced permanent settlement at the crest is about 0.40% of the dam height. The maximum settlement and tension of the peripheral joints do not exceed the maximum measured ones in the investigated existing cases. The shear displacement, on the other hand, is larger than all the measured ones in these cases. However, the advancement in sealing structures and materials achieved in China can already satisfy the need of CFGDs as high as 250 m. Therefore, it can be concluded that the difficulty in deformation control is relatively less compared with that of rockfill dams with similar height. What deserves special attention, on the other hand, is the high static and dynamic stresses in concrete slabs, both along the axial and slope directions. The reinforcements near some peripheral joints and the compressive vertical joints are necessary.