Geotechnical aspects and seismic damage of the 156-m-high Zipingpu concrete-faced rockfill dam following the Ms 8.0 Wenchuan earthquake

Abstract Damage to the Zipingpu concrete-faced rockfill dam (CFRD) with the maximum height of 156 m was induced by the great May 12, 2008 Wenchuan earthquake with a magnitude of Ms 8.0. The dam is the first CFRD over 150 m high experiencing the strong shallow earthquake of IX degree in the world. The seismic damage to the dam raised a number of questions concerning the safety of the dam as well as the adequacy of design criteria. Extensive investigation has been carried out accordingly and is summarized in this paper. The purpose of this paper is to document geotechnical aspects of the design and seismic damage during earthquake, and in particular to highlight key experiences and lessons learned. Analysis of the instrumental records during the earthquake and results of the subsequent surveys following the quake yield three key conclusions as follows. (1) The earthquake motion mainly caused significant seismic non-uniform deformation of the embankment and damage to the face slabs, structures on the crest and downstream stone masonry. The predominantly longitudinal seismic motion intensified the interaction between the embankment and the abutments. The seismic deformation of the embankment and the strong interaction between the abutments and embankment were believed to have been responsible for damage to face slabs. Seepage through the dam increased, but was not significant, due to water-seal damage in the concrete face and peripheral joints. In general, the damage to the dam, although serious in some parts, was minor as a whole and was reparable. (2) Several design considerations contributed to the safety of the Zipingpu dam. Shallow-angle slopes on the downstream dam face were used to enhance the stability of the dam. Most significantly, the adequate zoning and well-compacted rockfill enabled effective deformation control of the embankment, thus greatly reducing the seismic deformation during ground shaking and ensuring the safety of the seepage control system. The performance of the Zipingpu dam during the earthquake evidenced the success of the design. (3) Overall, the Zipingpu CFRD was structurally stable and safe even though it was subjected to seismic shaking at a greater magnitude than the design seismicity. High CFRDs are feasible in seismic regions of western China if adequate design considerations are implemented to alleviate as much damage as possible during major earthquakes.