Summary
Deformation is the most intuitive reflection of comprehensive behavior of concrete dams; it is of great significance to predict and interpret the deformation observation data for dam health monitoring. The world's highest concrete dam, Jinping I arch dam in China, was discussed in this paper. Aiming at its annually measured continuous growth phenomenon of dam body deformation towards the downstream direction when reservoir keeps stable at the normal water level of 1,880.0 m, influences of cement hydration heat‐induced temperature rise effect, valley contraction, and dam material creep on deformation behavior of this dam were estimated by finite element method (FEM) and the measured data. Combined with the results of the hydraulic, seasonal, and time (HST) model, the abnormal deformation behavior was detected to be jointly caused by the hysteretic hydraulic deformation and the ambient temperature drop effect. Subsequently, to solve the deficiency that the traditional HST model cannot reasonably explain this measured deformation behavior, a hysteretic hydraulic component was introduced into the HST model, and a special hydraulic, hysteretic, seasonal, and time (HHST) model was proposed. Based on the numerical simulation of viscoelastic FEM and the constrained least square method, the newly added component was represented by a continuous piecewise fitting function, with model factors of previous relative water depth and cumulative days of the current water level stage. HHST model results of Jinping I arch dam show that the measured abnormal displacement increment of dam body is 70% caused by the ambient temperature drop effect and 30% caused by the viscoelastic hysteretic hydraulic deformation.
The safety of a high concrete arch dam should be rapidly diagnosed from different angles. Displacement is an actual comprehensive reflection of the arch dam, and it is very important to diagnose the overall deformation behaviour by displacement-based mathematical monitoring models. In this article, based on the spatial association validation of the measured displacement of two high arch dams by the empirical orthogonal function decomposition and the Pearson correlation analysis, two spatial association–considered mathematical models were proposed for the dam displacement of multimonitoring points: one model for the long-term balanced relationship and one model for the short-term fluctuation. To diagnose the abnormality of the dam long-term spatial association, each displacement time series of the multimonitoring points on the dam body with strong spatial associations was decomposed by wavelet multiresolution analysis, and the decomposed high-frequency components, which had the same periodicity as the causal factors of the reservoir water level or air temperature, were determined to establish the cointegration monitoring model. The second model was a combination prediction model, with two sub-models established from the modelling angles of the hydraulic, seasonal and time causal factors and the adjacent point displacement factors, and this second model was mainly used for identifying dam short-term local abnormal deformation behaviour. Engineering examples show that the deformation behaviour of an arch dam under normal conditions has strong spatial associations. The two proposed models have high accuracy and interpreting ability and can effectively reduce the number of needed monitoring models.
Deformation is the most intuitive reflection of comprehensive behavior of concrete dams, and it is of great significance to determine the deformation monitoring indexes for dam abnormality identifying. In this paper, deformation monitoring indexes of arch dam were determined in the form of causal components, and the time-varying effect caused by the degradation of dam material properties was considered. The hydraulic component in monitoring index was determined into three grades by water density overloading method, and the appearances of dam heel yield depth coming up to the curtain axis, the catastrophes of dam body yield volume ratio and dam radial displacement, were respectively taken as the abnormal symbols. The temperature component was determined for two operation conditions, with respect to the measured high and low temperature periods. As for the time effect component, it was initially calculated by FEM with the environmental damage-considered rheological constitutive models, and fitted by the combination of exponential function and periodic function. A case study was performed to give more detailed introductions for determining the proposed deformation monitoring indexes. Research results show that the components of temperature and time-effect occupy a large proportion in monitoring index of arch dams.
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