Cetin Dam – stabilising troubled abutment slopes

Abstract

The 420 MW Cetin Dam Project in Turkey was subject to severe setbacks, including substantial geotechnical problems. Since 2011, several concessionaires, contractors and designers were involved. In June 2016, a major failure occurred at a high cut slope of the right bank (RB) valley flank. In 2017, contractor Limak took over the project with a US$ 600 mio concession contract. To secure the contractual agreement for state-guaranteed energy remuneration, Cetin Dam and hydro hydroelectric power plant (HEPP) had to be operative in 2020. Missing the time target would have implied high economic losses for the concessionaire, and this set-in-stone deadline imposed extraordinary pressure for developing fast and reliable solutions. Worryingly, progressing failure became evident at the failed RB cut slope, while rehabilitation works were ongoing. In late December 2017, shortly after a review of geotechnical conditions and slope design for the troubled RB slope had started, also parts of the left bank (LB) cut slope failed below crest level and threatened to grow into a global slope failure. With only 26 months’ time left for starting energy production, the slope instabilities jeopardised the economic success of the entire project. Within a 3-month emergency mission for both RB and LB slopes, a dedicated team succeeded in understanding the geotechnical problems, planning and implementing immediate mitigation measures, and developing design solutions. Operation of Cetin Dam and HEPP commenced in 2020.