Research On Generalized Safety Index Of Core Wall Dam Deformation Evaluation

At present, more and more high rockfill dams are under construction or operating. It is very important to guarantee the safe operation of rockfill dam. In order to judge the safety of dams, the safety indicators and corresponding threshold is necessary, however the indicators system of rockfill dam has not been established. Now the profile of high rockfill dam has become very standardized, and we have learnt more about the characteristics of rockfill materials. It is necessary and proper to make generalized models and extract effective safety indicators for rockfill dams. For these purpose, this paper established standardized model for core wall rockfill dams and found the main factors which control the safety of the anti-seepage system through numerical and theoretical analysis, and proposed a method to quantitatively assess the safety of core wall rockfill dams.First, the paper built a series standard finite element models of core wall rockfill dam with different height, slope and valley width. The settlement and the horizontal displacement of these models is analyzed, to study the influence factor and laws of the deformation of core wall rockfill dams.Then, the paper put forward generalized indicators to assess settlement and horizontal displacement of core wall dam respectively.Using Duncan-Chang model to describe the stress-strain relationship, and forming the analytical formula according to layer-wise summation method, the generalized model for the settlement of core wall is established. The parameter K of Duncan-Chang’s model can be considered as afety indicator to evaluate the settlement of the dam, because it reflects the dam’s average vertical compression modulus with simplification of other parameters. If the settlement of the core wall is obtained by monitoring, the safety indicators Kcan be obtained by regression analysis. Taking Nuozhadu project as an example, the value of K is obtained by finite element inverse analysis and the generalized model respectively. By comparison of the two values, the generalized model is effective.This paper also built a generalized model of up-downstream horizontal displacement. The earth pressure acting on the core wall can be obtained with the unit weight of rockfill and water level. Considering the core wall as a cantilever beam, the horizontal displacement of the core wall can be determined. In comparison with the monitored and the predicted horizontal displacement by finite element method, the method is effective and sufficiently accurate as a generalized method.Finally, this paper summarized the basic information and settlement monitoring dataof 55core wall rockfill damsin literatures. The safety indicators K were also obtained with the generalized model proposed in this paper. Assuming that the distribution of K follows a lognormal distribution, the quartile of a given K was identified as the safety degree.In conclusion, this paper proposed safety indicators for settlement and horizontal deformation of core wall dams. The indicator shave extinct physical meaning and can be easily obtained by analytical methods if the monitored displacement value is obtained. An approach to determine the safety degree corresponding to the settlement of core wall dam is also proposed through statistical analysis.