Effect of the impounding process on the overall stability of a high arch dam: a case study of the Xiluodu dam, China

摘要

Effects of the first filling process of the Xiluodu super-high arch dam are studied by both field monitoring and numerical modelling methods. The numerical modelling is conducted by the three-dimensional nonlinear finite element method, which takes into account the nonlinear contact of the transverse joints between dam monoliths and adopts both the design and feedback parameters of the dam. The results obtained from the various numerical analysis cases for different impounded water levels are comprehensively compared with those obtained from the field monitoring. Throughout this study, it is concluded that: (1) changes of the hydrostatic load resulting from the filling process have a significant effect on the deformation and stress states of the dam and foundation. The foundation settles as a consequence of consolidation of the reservoir bed under the effect of the water mass. During the filling process, the compressive stress of the dam in the sealed region increases in the arch direction while that in the cantilever direction decreases, which reveals an enhancement of dam thrust into the two banks. (2) The transverse joints between the dam monoliths are compressed almost over the entire height of the poured dam, and their aperture gradually decreases as the impounded water level increases. (3) The overall deformation of the Xiluodu dam is obviously affected by the uneven foundation settlement due to the complex reservoir basin. The tensile stress concentration appears at the crossing zone of the top of the dam's sealed region and the dam-foundation interface. Thus, reasonable layout of steel bars and suitable jointing design are essential in these tensile stress concentration regions. (4) The dam behaviour predicted using the three-dimensional numerical modelling is in good agreements with that from the field measuring in terms of the stress and strain distribution characteristics in the dam and foundation, especially when the feedback parameters are adopted for the numerical analysis. The results from both the field monitoring and numerical modelling reveal that overall stability of the dam during the first filling process meets the dam operational requirements.