Seismic Assessment and Strengthening of a Slender Arch Dam

Abstract eng:
With the ageing of existing dams, introducing of new safety regulations and evolution of Earthquake and dam Engineering and computation; the safety reassessment of existing dams is inevitable. In the legal framework of dam surveillance in Switzerland, dam owners have to conduct seismic assessment studies of their dams based on the recently implemented federal Guidelines. Les Toules 86-m high double-curvature arch dam has been built in the early sixties and enjoys a particular design. The Dam has been constructed in a wide and U-shape valley with very high ratio of the crest length to the height. The dam was built in two separate phases, leaving a special joint grouted later on. Recent static and dynamic verifications based on the reassessed seismic hazard studies showed that the dam does not meet the seismic safety requirements. Therefore, the reservoir maximum operation level was lowered by 10 m as an immediate safety measure before conducting more sophisticated studies and developing of a strengthening concept. More detailed analyses allowed understanding the behavior and weak points of the dam. Dynamic analysis revealed the necessity of cantilevers and arch strengthening as well as shear keys in the middle part of the dam. On this basis, some strengthening alternatives were studied and compared. The final solution comprises several reinforcing measures. Firstly, a downstream strengthening in form of abutment thickening transfers the load from over-loaded cantilevers to the thickened arches. Secondly, adding shear keys in the vertical joints guaranties the stability of the blocks in case of seismic events. Moreover, local foundation treatment and some other rehabilitation works have been planned. The construction has started in 2008 and will be completed by 2011.

• Export as: BibTeX | MARC | MARCXML | DC | EndNote | NLM | RefWorks
• Add to your basket