Abstract:Predictive models are essential in dam safety assessment. They have been traditionally based on simple statistical tools such as the hydrostatic-seasontime (HST) model. These tools are well known to have limitations in terms of accuracy and reliability. In the recent years, the examples of application of machine learning and related techniques are becoming more frequent as an alternative to HST. While they proved to feature higher flexibility and prediction accuracy, they are also more difficult to interpret. … Show more
“…In recent years, there is a tendency towards employing advanced tools in the machine learning community to establish prediction models, such as neural network, 12,13 support vector machine, 14,15 random forests, 16 extreme learning machine, 17 and boosted regression tree. 18 Dam effect quantity and its influencing factors are respectively taken as the output and input variables, and according to the observation data, monitoring models can be established by training the learning rules of the used artificial intelligence algorithm. 10 However, the machine learning technique-based monitoring models are without considering the structure characteristics of concrete dams, and there are no direct mathematical expressions, so that they can only be used for prediction, rather than causal interpretation of dam deformation like statistical model.…”
Section: Discussionmentioning
confidence: 99%
“…To conquer such drawbacks, the second category of data‐based model has been developed. In recent years, there is a tendency towards employing advanced tools in the machine learning community to establish prediction models, such as neural network, support vector machine, random forests, extreme learning machine, and boosted regression tree . Dam effect quantity and its influencing factors are respectively taken as the output and input variables, and according to the observation data, monitoring models can be established by training the learning rules of the used artificial intelligence algorithm .…”
Section: Introductionmentioning
confidence: 99%
“…Dam effect quantity and its influencing factors are respectively taken as the output and input variables, and according to the observation data, monitoring models can be established by training the learning rules of the used artificial intelligence algorithm . However, the machine learning technique‐based monitoring models are without considering the structure characteristics of concrete dams, and there are no direct mathematical expressions, so that they can only be used for prediction, rather than causal interpretation of dam deformation like statistical model …”
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.
“…In recent years, there is a tendency towards employing advanced tools in the machine learning community to establish prediction models, such as neural network, 12,13 support vector machine, 14,15 random forests, 16 extreme learning machine, 17 and boosted regression tree. 18 Dam effect quantity and its influencing factors are respectively taken as the output and input variables, and according to the observation data, monitoring models can be established by training the learning rules of the used artificial intelligence algorithm. 10 However, the machine learning technique-based monitoring models are without considering the structure characteristics of concrete dams, and there are no direct mathematical expressions, so that they can only be used for prediction, rather than causal interpretation of dam deformation like statistical model.…”
Section: Discussionmentioning
confidence: 99%
“…To conquer such drawbacks, the second category of data‐based model has been developed. In recent years, there is a tendency towards employing advanced tools in the machine learning community to establish prediction models, such as neural network, support vector machine, random forests, extreme learning machine, and boosted regression tree . Dam effect quantity and its influencing factors are respectively taken as the output and input variables, and according to the observation data, monitoring models can be established by training the learning rules of the used artificial intelligence algorithm .…”
Section: Introductionmentioning
confidence: 99%
“…Dam effect quantity and its influencing factors are respectively taken as the output and input variables, and according to the observation data, monitoring models can be established by training the learning rules of the used artificial intelligence algorithm . However, the machine learning technique‐based monitoring models are without considering the structure characteristics of concrete dams, and there are no direct mathematical expressions, so that they can only be used for prediction, rather than causal interpretation of dam deformation like statistical model …”
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.
“…On the other hand, powerful tools such as neural networks and support vector machines have been developed, which make use of observed data for interpreting complex systems . These more flexible and accurate models are available but are more difficult to implement and analyze …”
Summary
The unique structures and foundations of a dam make its safety monitoring a complex task. As the most intuitive effect of dams, deformation contains important information on dam evolution. Actual response has the purpose of diagnosis and early warning compared with model prediction. Given the poor generalization ability of the conventional statistical model, establishing a dam deformation monitoring model is thus essential. The prediction of concrete dam deformation using statistical model and random forest regression (RFR) model is studied. To build an optimized RFR model, the statistical model is used to establish input variables, select the appropriate parameters Mtry and Ntree according to out‐of‐bag error, and extract strong explanatory variables. The model's advantage is that the influence factors can describe concrete dam deformation, and RF can serve as a sensible new data mining tool. The importance of variables for deformation prediction is measured by RF. The RFR method can extract representative influencing factors based on variable importance. The methods are applied to an actual concrete dam. Results indicate that the RFR model can be applied for analysis and prediction of other structural behavior.
“…Forward analysis models are fundamental approaches that play a major role in dam safety assessment systems . By using these models, it is possible to determine the expected response from the prototype observations.…”
Summary
The displacement at arbitrary point in the dam is composed of two parts: One is the elastic deformation of dam body and the other that is due to the constrained deformation of foundation. The two parts should be separated to obtain reliable information reflecting the different characteristics of dam body and foundation. A simplified simulation method for gravity dam foundations is proposed that reflects the constrained deformation of foundation in a rational manner while taking into account the complex and diverse mechanical properties. Only the effects of the foundation on dam is investigated in the proposed model, and they are considered either centralized constraints or distributed constraints. The solution of the global foundation deformation is based on the monitoring displacements at measuring points in the gravity dam section using the hybrid partition finite element–interface boundary element approach. The reaction of the foundation on dam can be reflected by the global foundation deformation and the constrained force at dam bottom. On the basis, the whole dam response under a given load combination can be estimated using finite element theory. Three analyses have been performed on a typical gravity dam section to verify the feasibility of simplified simulations for different foundations as well as to allow for discussions regarding the differences among the simulations. An example analysis based on the proposed method is performed on a prototype gravity dam, and the results, which compared with actual measurements for discussions, show that the proposed method is reasonable and practical.
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