a deep learning model for concrete dam deformation prediction...

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Research Article A Deep Learning Model for Concrete Dam Deformation Prediction Based on RS-LSTM Xudong Qu , 1 Jie Yang , 1 and Meng Chang 2 1 Institute of Water Resources and Hydro-Electric Engineering, Xian University of Technology, Xian 710048, China 2 Department of Development, Sino Hydro Engineering Bureau 15 Co., Ltd, Xian 710016, China Correspondence should be addressed to Xudong Qu; [email protected] Received 23 June 2019; Accepted 14 September 2019; Published 31 October 2019 Guest Editor: Samir Mustapha Copyright © 2019 Xudong Qu et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Deformation is a comprehensive reection of the structural state of a concrete dam, and research on prediction models for concrete dam deformation provides the basis for safety monitoring and early warning strategies. This paper focuses on practical problems such as multicollinearity among factors; the subjectivity of factor selection; robustness, externality, generalization, and integrity deciencies; and the unsoundness of evaluation systems for prediction models. Based on rough set (RS) theory and a long short- term memory (LSTM) network, single-point and multipoint concrete dam deformation prediction models for health monitoring based on RS-LSTM are studied. Moreover, a new prediction model evaluation system is proposed, and the model accuracy, robustness, externality, and generalization are dened as quantitative evaluation indexes. An engineering project shows that the concrete dam deformation prediction models based on RS-LSTM can quantitatively obtain the representative factors that aect dam deformation and the importance of each factor relative to the eect. The accuracy evaluation index (AVI), robustness evaluation index (RVI), externality evaluation index (EVI), and generalization evaluation index (GVI) of the model are superior to the evaluation indexes of existing shallow neural network models and statistical models according to the new evaluation system, which can estimate the comprehensive performance of prediction models. The prediction model for concrete dam deformation based on RS-LSTM optimizes the factors that inuence the model, quantitatively determines the importance of each factor, and provides high-performance, synchronous, and dynamic predictions for concrete dam behaviours; therefore, the model has strong engineering practicality. 1. Introduction Due to unique advantages in design, construction, and opera- tional management, concrete dams account for a large propor- tion of all dams and have become the preferred dam type for the construction of high dams. However, most of the concrete dam projects are located in harsh alpine valleys. Thus, the dams are subjected to various dynamic, static, and special cyclic loads during service, and the design, construction, and operational management must be tailored to these conditions. Therefore, service safety behaviour involves a nonlinear dynamic process that includes material and structure interac- tions and multiple factors [1]. As a comprehensive variable that reects the safety state of concrete dams, deformation can be used as an important index of structural behaviours and trends. Therefore, strengthening the prediction models for deformation, conducting safety monitoring, and estab- lishing early warning systems are important ways to ensure long-term service safety of concrete dams [2]. In recent years, the successful application of dam engineering theory, nite element theory, and articial intel- ligence (AI) technology has greatly promoted the develop- ment of concrete dam deformation prediction models. The most commonly used methods [3] for inuential factor selec- tion in concrete dam deformation prediction models include prior knowledge, linear correlation coecient, stepwise regression, principal component analysis (PCA), and grey correlation analysis methods. However, in actual applications, the prior knowledge method relies too much on experience and has large errors. Notably, the water pressure, temperature, and dam age are generally selected as inuential factors in hydrostatic seasonal temporal (HST) models considering Hindawi Journal of Sensors Volume 2019, Article ID 4581672, 14 pages https://doi.org/10.1155/2019/4581672

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  • Research ArticleA Deep Learning Model for Concrete Dam DeformationPrediction Based on RS-LSTM

    Xudong Qu ,1 Jie Yang ,1 and Meng Chang2

    1Institute of Water Resources and Hydro-Electric Engineering, Xi’an University of Technology, Xi’an 710048, China2Department of Development, Sino Hydro Engineering Bureau 15 Co., Ltd, Xi’an 710016, China

    Correspondence should be addressed to Xudong Qu; [email protected]

    Received 23 June 2019; Accepted 14 September 2019; Published 31 October 2019

    Guest Editor: Samir Mustapha

    Copyright © 2019 Xudong Qu et al. This is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

    Deformation is a comprehensive reflection of the structural state of a concrete dam, and research on prediction models for concretedam deformation provides the basis for safety monitoring and early warning strategies. This paper focuses on practical problemssuch as multicollinearity among factors; the subjectivity of factor selection; robustness, externality, generalization, and integritydeficiencies; and the unsoundness of evaluation systems for prediction models. Based on rough set (RS) theory and a long short-term memory (LSTM) network, single-point and multipoint concrete dam deformation prediction models for health monitoringbased on RS-LSTM are studied. Moreover, a new prediction model evaluation system is proposed, and the model accuracy,robustness, externality, and generalization are defined as quantitative evaluation indexes. An engineering project shows that theconcrete dam deformation prediction models based on RS-LSTM can quantitatively obtain the representative factors that affectdam deformation and the importance of each factor relative to the effect. The accuracy evaluation index (AVI), robustnessevaluation index (RVI), externality evaluation index (EVI), and generalization evaluation index (GVI) of the model are superiorto the evaluation indexes of existing shallow neural network models and statistical models according to the new evaluationsystem, which can estimate the comprehensive performance of prediction models. The prediction model for concrete damdeformation based on RS-LSTM optimizes the factors that influence the model, quantitatively determines the importance ofeach factor, and provides high-performance, synchronous, and dynamic predictions for concrete dam behaviours; therefore, themodel has strong engineering practicality.

    1. Introduction

    Due to unique advantages in design, construction, and opera-tional management, concrete dams account for a large propor-tion of all dams and have become the preferred dam type forthe construction of high dams. However, most of the concretedam projects are located in harsh alpine valleys. Thus, thedams are subjected to various dynamic, static, and specialcyclic loads during service, and the design, construction, andoperational management must be tailored to these conditions.Therefore, service safety behaviour involves a nonlineardynamic process that includes material and structure interac-tions and multiple factors [1]. As a comprehensive variablethat reflects the safety state of concrete dams, deformationcan be used as an important index of structural behavioursand trends. Therefore, strengthening the prediction models

    for deformation, conducting safety monitoring, and estab-lishing early warning systems are important ways to ensurelong-term service safety of concrete dams [2].

    In recent years, the successful application of damengineering theory, finite element theory, and artificial intel-ligence (AI) technology has greatly promoted the develop-ment of concrete dam deformation prediction models. Themost commonly used methods [3] for influential factor selec-tion in concrete dam deformation prediction models includeprior knowledge, linear correlation coefficient, stepwiseregression, principal component analysis (PCA), and greycorrelation analysismethods. However, in actual applications,the prior knowledge method relies too much on experienceand has large errors. Notably, thewater pressure, temperature,and dam age are generally selected as influential factors inhydrostatic seasonal temporal (HST) models considering

    HindawiJournal of SensorsVolume 2019, Article ID 4581672, 14 pageshttps://doi.org/10.1155/2019/4581672

    https://orcid.org/0000-0002-3630-3666https://orcid.org/0000-0002-3706-2462https://creativecommons.org/licenses/by/4.0/https://doi.org/10.1155/2019/4581672

  • simplified physical models of dams and dam foundations, theburial conditions of monitoring equipment, prototype moni-toring data, engineering mechanical analysis, and deductiveinvestigation. The limitation of the PCA method is that onlylinear relations between variables are considered. If the depen-dence is nonlinear, themisinterpretation of resultsmay occur.The grey correlation analysis method can only sort factorsaccording to their relevance, and there is no clear criterionfor selecting influential factors. Moreover, multiple collinear-ity can exist among the factors selected by conventionalmethods, which may reduce the accuracy of the model andadversely affect the prediction results [4]. Meanwhile, predic-tion models do not consider the influence of nonquantitativefactors such as the seepage flow, crack opening degree, andlifting pressure; the dam constructionmaterials; the construc-tion quality; and the geological conditions. Additionally,model interpretation is important for evaluating the perfor-mance of prediction models, especially the model accuracy.The HST model has been traditionally used to identify theresponse of a dam to a considered action, such as a hydrostaticload, or to variations in factors such as temperature and time[5]. However, such analyses are only valid if the predictorvariables are independent, which is not generally true [6]. Incontrast, intelligent models (such as neural network, multi-layer perceptron, and support vector machine models) havenot been applied to interpret dam behaviour. Traditionalmodels are frequently termed “black box”models, in referenceto their lack of interpretability. Therefore, in the selection pro-cess of the factors that influence concrete dam deformationprediction models, imperfect selection criteria and neglectingimportant factors can seriously affect the prediction perfor-mance of the model. Single-point statistical models, deter-ministic models, and hybrid models [7–10] have evolvedinto multipoint intelligent models [11–16]. Based on thetraditional statistical model, Gu et al. treated deformation atmultiple measurement points and the spatial coordinates ofthese points as variables and established a spatiotemporaldistributed prediction model of the deformation field of aconcrete dam. Li et al. investigated the spatial and temporalexpression of the factors that affected the deformation of anRCC dam and established a spatiotemporal deformationprediction model for RCC dams based on measured data.The prediction results agreed to the actual dam deformationdata. Li et al. used the strong functional nonlinear mappingability of a back propagation (BP) neural network to replacethe complex factor subset in the traditional spatial deforma-tion field model with water level, temperature, time, andmea-surement point variables as the input of the neural network. ABP network prediction model was established for dam defor-mation at multiple points. Chen et al. proposed a spectraldecomposition method to decompose the monitoring datacollected at multiple measurement points into several mutu-ally independent latent variables for noise reduction andmonitoring data processing. A least square support vectormachine prediction model was established between the envi-ronmental data and latent variables, and the horizontaldisplacement ofMianhuatan Damwas successfully predicted.Many scholars have addressed these issues. The successfulapplication of new methods has expanded the theoretical

    knowledge of dam deformation prediction and model estab-lishment and provided important guiding significance forengineering practice. However, due to the complexity ofconcrete dam engineering, the structural volatility of dams,and the uncertainty of working conditions, there are still someshortcomings in existing prediction models. It is difficult forsome models to process massive amounts of monitoring datain real time with extensive mining data mechanisms for high-performance prediction targets, such as those in practicalapplications. It is important to appropriately evaluate theprediction performance of a model from all angles becausethe practical value of the models can be guaranteed, differentmodels can be compared, and different warning thresholdscan be defined. There are various indexes [17] that can be usedto assess how well a model matches the observed data, amongwhich the most commonly used are the mean squared error(MSE), root mean squared error (RMSE), coefficient of deter-mination (R2), mean absolute error (MAE), mean absolutepercentage error (MAPE), and average relative variance(ARV). The result of any of these indexes is frequentlyequivalent to a given prediction task. Specifically, an accu-rate model will have small MSE, RMSE, MAE, and MAPEvalues and high R2 and ARV values. However, these accuracyindexes have differences that can be relevant but are often notconsidered [18]. Commonly, robustness and generalizationability are neglected in themodel assessment, and quantitativeevaluation indexes are not always used in practical applica-tions. Therefore, it is necessary to explore methods for factorselection, establish high-performance, dynamic, synchronousprediction models, and design a scientific and comprehensiveevaluation system which are urgent for concrete dam defor-mation prediction.

    Attribute reduction is one of the core concepts of RStheory, which addresses incompleteness, redundancy, andambiguity in data in the field of machine learning. Thisapproach avoids the use of complex discernibility matricesand uses attribute importance as heuristic information toobtain inductive sets and importance analysis results; excel-lent results can be obtained in factor selection for predictionmodels based on RS theory [19–21]. Moreover, long short-term memory (LSTM) based on the memory architecture indeep learning (DL) can overcome the memory shortage andvanishing gradient issues of recurrent neural networks(RNNs). Besides, this method is characterized by controllablememory and rapid convergence. LSTM has achieved goodpractical application results in the dynamic and deepprocessing of massive, long-term, dependent data series[22–25]. To overcome the shortcomings of existing concretedam deformation prediction models, RS theory and an LSTMnetwork are applied to a concrete dam deformation predic-tion model in virtue of Tensor Flow. Finally, a concretedam deformation prediction model based on RS-LSTM isestablished, and a new predictive model evaluation systemis proposed.

    2. Materials and Methods

    2.1. Rough Set Theory. RS theory was proposed by Polishscholar Pawlak in the 1980s. The core objectives are the

    2 Journal of Sensors

  • mining and refining of essential information under thepremise of maintaining equivalence relations. The maintasks in this approach are attribute reduction, correlationanalysis, and importance evaluation for uncertain infor-mation systems.

    2.1.1. Information System. To describe the samples thatencompass the necessary information in RS theory, a quater-nary information system S is established, and it can beexpressed as follows:

    S = U , R, V , ff g, ð1Þ

    where U is a nonempty finite set of all samples; R is a setof attributes, including a set of conditional attributes Cand a set of decision attributes D; V is the attribute valueset; and f is the information function, also known as thedecision table.

    2.1.2. Attribute Reduction. For arbitrary P ⊆ R and P ≠Ø, theindistinguishable relationship between P and U is defined asfollows.

    IND Pð Þ = x, yð Þ ∈U2 ∀α ∈ P, α xð Þ = α yð Þj� �: ð2ÞFor an arbitrary set of objects X ⊆U and attributes B ⊆ C

    in a given information system S, the approximation of X isdefined as BX = fxj½x�B ⊆ Xg; the approximate definition ofX is defined as �BX = fxj½x�B ∪ X ≠Øg; and the boundary areaof x is defined as BNBðXÞ = �BX − BX. In this case, ½x�B repre-sents the set of indistinguishable relations for the division ofU by B.

    If BNBðXÞ is not empty, then X is called a rough set of B.The positive region of B relative to D is as follows.

    POSB Dð Þ =BXjX ∈UIND Dð Þ

    � �: ð3Þ

    When SIM = POSCðDÞ − POSC−fagðDÞ = 0, where a ∈ C,a can be omitted. Additionally, when each element in C isnot omissible from D, it can be concluded that C is indepen-dent of D. When C′ = C − C∗, where C′ is independent of Dand all the elements in C∗ can be omitted, then C′ is calledthe relative reduction of D.

    2.1.3. Importance Evaluation. In attribute reduction, theimportance of the attribute can be defined by the degree ofinterdependence between the attribute sets B and D. Thedegree of interdependence between P and R is defined asfollows:

    γB Dð Þ =POSB Dð Þj j

    Uj j , ð4Þ

    where j·j represents the cardinality value of a set.The importance of the conditional attribute a to the

    decision attribute D based on the attribute dependency

    degree is defined as follows.

    Sig α, B,Dð Þ = γB Dð Þ − γB− αf g Dð Þ: ð5Þ

    2.2. LSTM Network Based on a Memory Architecture. LSTMis obtained by improving the hidden layer of the RNN struc-ture. LSTM based on a memory architecture can overcomememory shortage and vanishing gradient problems. TheLSTM model structure is shown in Figure 1. The key advan-tages of LSTM are twofold. Notably, the hidden layer includesa hidden state and a cell state, and a threshold mechanism isestablished in the RNN. These factors strengthen the abilityof the model to learn current information, extract the infor-mation and rules associated with the data, and simultaneouslytransmit information to reduce memory use. The thresholdmechanism uses input gates, forget gates, and output gatesto selectively memorize the feedback parameters of the feed-back error function as the gradient decreases, achieving rapidgradient convergence [26].

    2.2.1. Input Gate Updates. The input gate controls the infor-mation xðtÞ transmitted from the input of the network atmoment t and hidden state at the final moment hðt−1Þ tothe cell state CðtÞ. The function of the input gate is to filternew information. The structure of an input gate is shown inFigure 2.

    Figure 2 shows that the input gate consists of two parts.The first part selects the sigmoid activation function, forwhich the output is iðtÞ, and the second part selects the tanhactivation function, for which the output is aðtÞ. The twopartial outputs are multiplied to update the cell state. Therenewal process can be mathematically expressed as follows:

    i tð Þ = σ Wih t−1ð Þ +Uix tð Þ + bi� �

    ,

    a tð Þ = tanh Wah t−1ð Þ +Uax tð Þ + ba� �

    ,ð6Þ

    whereWi,Ui, bi,Wa,Ua, and ba are the weights and biases ofthe input gate and σ is the sigmoid activation function.

    2.2.2. Forget Gate Updates. The forget gate controls the infor-mation transmitted from the cell state Cðt−1Þ at moment t − 1to the cell state CðtÞ at moment t, and the information thatshould be discarded is identified. The structure of the forgetgate is shown in Figure 3.

    Figure 3 shows that the hidden state hðt−1Þ at momentt − 1 and the input xðtÞ at moment t activate the sigmoidfunction, and the output f ðtÞ is in the range of [0, 1].This value represents the probability of forgetting theinformation associated with the cell state at a previousmoment. The renewal process can be mathematicallyexpressed as follows:

    f tð Þ = σ Wf h t−1ð Þ +Uf x tð Þ + bf� �

    , ð7Þ

    3Journal of Sensors

  • where Wf , Uf , and bf are the weights and biases of theforget gate.

    2.2.3. Cell State Updates. The cell state controls the informa-tion aðtÞ transmitted from the result of the input gate f ðtÞ andthe result of the forget gate iðtÞ to the cell state CðtÞ. The struc-ture of a cell state is shown in Figure 4.

    Figure 4 shows that the cell state updating result CðtÞ ismainly determined by the cell state Cðt−1Þ at moment t − 1and the results of the input and forget gates (f ðtÞ, iðtÞ, andaðtÞ) at moment t. The renewal process can be mathemati-cally expressed as follows:

    C tð Þ = C t−1ð Þ ⊙ f tð Þ + i tð Þ ⊙ a tð Þ, ð8Þ

    where ⊙ is the Hadamard product.

    2.2.4. Output Gate Updates. The output gate controls theinformation transmitted from the hidden state hðt−1Þ atmoment t − 1, the cell state CðtÞ at moment t, and the inputxðtÞ at moment t. The function of the output gate is to deter-mine the final retained information. The structure of anoutput gate is shown in Figure 5.

    Figure 5 shows that the hidden state hðtÞ at moment tcontains two parts. The first part oðtÞ is determined by thehidden state hðt−1Þ at moment t − 1, the input xðtÞ at momentt, and the sigmoid activation function. The other part isdetermined by the cell state CðtÞ at moment t and the tanhactivation function. The renewal process can be mathemati-cally expressed as follows:

    o tð Þ = σ Woh t−1ð Þ +Uox tð Þ + bo� �

    ,

    h tð Þ = o tð Þ ⊙ tanh C tð Þ� �

    ,ð9Þ

    where Wf , U f , and bf are the weights and biases of theoutput gate.

    2.2.5. Output Layer Updates. The output of the model isdetermined by the hidden state hðtÞ at moment t and thesigmoid activation function. The renewal process can bemathematically expressed as follows:

    y∧ tð Þ = σ Vh tð Þ + c� �

    , ð10Þ

    Output layer

    Input layer

    Hidden layerσ

    +

    σσat otitft ...

    ...

    ...

    tanh

    tanh

    At t-1 moment At t moment At t+1 moment At t+n moment

    ht+n

    ht+n

    ht+1

    ht+1

    ht–1

    ht–1

    yt–1

    xt–1

    ht

    ht

    Ct+1Ct–1 CtCt+n

    yt+n

    xt+n

    yt+1

    xt+1

    yt

    xt

    Figure 1: Long short-term memory network model structure.

    σ

    +

    σσ

    yt

    ht

    ht

    CtCt–1

    tanh

    tanh

    ht–1

    at otitft

    xt

    Figure 2: Input gate structure.

    σ

    +

    σσ

    yt

    ht

    ht

    CtCt–1

    tanh

    tanh

    ht–1

    at otitft

    xt

    Figure 3: Forget gate structure.

    σ σσ

    yt

    ht

    ht

    CtCt–1

    tanhtanh

    ht–1

    at otitft

    xt

    +

    Figure 4: Cell state structure.

    4 Journal of Sensors

  • where V and c are the weight and bias of the output layer,respectively.

    2.2.6. Model Parameter Updating. To obtain the optimalsolution, this paper iteratively updates all the parameters inthe LSTM model based on the gradient descent algorithmand error BP algorithm.

    The objective loss function LðtÞ is defined to minimizethe sum of squared residuals between the predictions y∧ðtÞ

    of the output layer and the target outputs yðtÞ. LðtÞ is dividedinto two parts: the loss lðtÞ at moment t and the subsequentloss lðt + 1Þ moments later.

    L tð Þ =l tð Þ + l t + 1ð Þ, t < τ,l tð Þ, t = τ:

    (ð11Þ

    The gradients of the hidden state hðtÞ and cell state CðtÞ

    are defined as δðtÞh and δðtÞC , respectively, and the gradient at

    position τ can be expressed as follows.

    δτð Þh =

    ∂L τð Þ∂h τð Þ

    = ∂L τð Þ∂O τð Þ

    ∂O τð Þ∂h τð Þ

    =VT y∧ τð Þ − y τð Þ� �

    , ð12Þ

    δτð ÞC =

    ∂L τð Þ∂C τð Þ

    = ∂L τð Þ∂h τð Þ

    ∂h τð Þ∂C τð Þ = ∂h τð Þ ⊙ o

    τð Þ ⊙

    � 1 − tanh2 C τð Þ� �� �

    :

    ð13Þ

    The output gradient error at a given moment is deter-

    mined in two parts, respectively, because δðtÞh and δðtÞC are

    obtained for lðtÞ and lðt + 1Þ. Thus, according to equations(12) and (13), the gradients of the hidden state hðtÞ and cellstate CðtÞ can be expressed as follows.

    δtð Þh =

    ∂L∂h tð Þ

    =VT y∧ tð Þ − y tð Þ� �

    + δ t+1ð Þh ∂h t+1ð Þ/∂h tð Þ, ð14Þ

    δtð ÞC =

    ∂L∂C tð Þ

    = δ t+1ð ÞC f t+1ð Þ + δtð Þh ⊙ o

    tð Þ ⊙ 1 − tanh2 C tð Þ� �� �

    :

    ð15ÞAccording to equations (14) and (15), the following

    formula can be obtained.

    ∂L∂Wf

    = 〠τ

    t=1

    ∂L∂C tð Þ

    ∂C tð Þ

    ∂f tð Þ∂f tð Þ

    ∂Wf

    = 〠τ

    t=1δ

    tð ÞC ⊙ C

    t−1ð Þ ⊙ f tð Þ ⊙ 1 − f tð Þ� �h i

    h t−1ð Þ� �T

    :

    ð16Þ

    The other parameters in the model are derived similarly.The updating step size and learning rate of the model aredefined as λ and α, respectively. The parameters in the LSTMmodel are iteratively updated using the gradient BPalgorithm. The corresponding formula can be expressed asfollows:

    βt+1 = βt − α∂L∂β

    , ð17Þ

    where β represents the parameters in the LSTM model and∂L/∂β represents the gradients of the parameters.

    In summary, the updating process of the parameters inthe LSTM network model based on a memory architecturecan be expressed as follows. First, a parameter initializationprocess is implemented. Second, the iterative process isrepeated by the gradient descent algorithm and the errorBP algorithm until the target loss function converges. Finally,the parametric optimal solution of the LSTM model isobtained. Moreover, the Dropout algorithm is adopted inthe training process of the LSTM model to avoid the overfit-ting phenomenon [27] and improve network performance bypreventing feature detectors from working together.

    2.3. Concrete Dam Deformation Prediction Model Based onRS-LSTM. With the advantages of RS, the mapping rela-tionship between the factors that influence dam operatingbehaviour and the corresponding effects is establishedunder the premise of retaining the key information. Addi-tionally, the redundant information is eliminated, theexpression space of the influential factors is simplified,and the importance of each factor is evaluated. Moreover,because the LSTM model overcomes the memory shortageand gradient dissipation issues of traditional RNNs and ischaracterized by controllable memory and fast gradientconvergence, the model yields high-performance dynamicpredictions based on long-term data series. Therefore, bycombining the advantages of RS theory and the LSTMnetwork, this paper establishes a concrete dam deformationprediction model based on RS-LSTM, and the predictionmodel is optimized considering the relevant influentialfactors and interactive mechanisms between these factorsand concrete dam deformation in a quantitative manner.The process of establishing a concrete dam deformationprediction model based on RS-LSTM is shown in Figure 6.The specific modeling steps are as follows.

    2.3.1. Data Acquisition. Statistical methods are used toperform gross error processing for concrete dam monitoringdata. Such methods provide a reliable data foundation for theestablishment of prediction models. Attribute reduction in

    σ

    +

    σσ

    yt

    ht

    ht

    Ct

    CtCt–1

    tanh

    tanh

    ht–1

    at otitft

    xt

    Figure 5: Output gate structure.

    5Journal of Sensors

  • RS theory is conducted based on a complex multivariatedataset composed of water depth, temperature, seepage flow,fracture aperture, and uplift pressure information toaccurately obtain the representative factors that affect thedeformation behaviours of concrete dams. Deformationmonitoring data and the representative influential factorscorresponding to certain measurement points are selectedas the model dataset. The representative factor dataset isstandardized using an independent standardization formula,and the model dataset is divided into a training set andtesting set by a cross-validation method.

    2.3.2. Model Training. The preprocessed and standardizedtraining set samples are used as model inputs. Error backpropagation based on the gradient descent algorithm drivesthe model loss function to converge, and the optimal modelparameters are obtained. The Dropout algorithm is used toovercome the problem of overfitting in training, and finally,a prediction model with optimal parameters is obtained.

    2.3.3. Model Prediction. The testing set samples are input intothe trained prediction model to obtain the correspondingdeformation prediction results.

    2.3.4. Model Performance Evaluation. According to theestablished evaluation system, the results of the concretedam deformation prediction model based on LSTM, a classi-cal least squares (OLS) model, a support vector machine(SVM) model, and a multilayer perceptron (MLP) modelwith 2 hidden layers are compared based on accuracy,robustness, externality, and generalization.

    2.4. Evaluation System for the Concrete Dam DeformationPrediction Model. A concrete dam deformation predictionmodel plays an important role in operational behaviourmonitoring, real-time abnormality detection, and decision-making, and its performance directly affects conditionassessments and early warning strategies. In actual applica-tion processes, a single accuracy evaluation index may havecertain limitations, and it is often impossible to evaluate therobustness, externality, and generalization of a model. There-fore, a complete evaluation system for concrete dam deforma-tion prediction models must be established for practicalapplications. Therefore, this paper evaluates model perfor-mance from the aspects of accuracy, robustness, externality,and generalization, and quantitative evaluation indexes areused to comprehensively evaluate the performance of the

    Accuracy Robustness Externality

    Testing dataset

    Start

    Model database

    Stop

    Datasetdivision

    Training dataset Testing dataset

    Training results

    Model parameters training

    Prediction results

    Trained model

    Model performance evaluation

    Generalization

    Concrete dam monitoring data

    Deformation Influence factors

    Preprocessing

    Trained modelData acquisition

    Training dataset

    Prediction results

    Conventionalmodels

    Modeltraining

    Model evaluation

    system

    Model evaluation

    system

    Model prediction

    Attribute reduction

    OLS, SVMMLP models

    Figure 6: Process of establishing the concrete dam deformation prediction model based on RS-LSTM.

    6 Journal of Sensors

  • concrete dam deformation prediction model based onstatistical theory.

    2.4.1. Accuracy. The accuracy of the concrete dam deforma-tion prediction model refers to the degree of agreementbetween the predicted and true values. This evaluation indexis the most widely used in model assessment. In actualengineering, the MAPE, MSE, and RMSE are usually selectedto evaluate the accuracy of a model. Considering the nonsta-tionarity of deformation monitoring data and the overlapamong evaluation indexes, the RMSEP and MAPEP areselected to establish the accuracy evaluation index (AEI) ofthe concrete dam deformation prediction model. The corre-sponding formulas are defined as follows.

    RMSEP =ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi1n〠n

    t=1yt − y∧tð Þ2

    s,

    MAPEP =100n

    〠n

    t=1

    yt − ŷtyt

    :

    ð18Þ

    2.4.2. Robustness. The robustness of a concrete dam deforma-tion prediction model refers to its resistance to the inherenterrors in training data. Model training and prediction areperformed by establishing normal training samples andtraining samples with a certain degree of random error. Theability of a model to learn the true nonlinear mapping rela-tionships when there is a small gross error in the trainingset is tested. The absolute difference between the RMSEO ofthe training model prediction results with no gross errorand the RMSEE of the training model prediction results withgross error is selected as the robustness evaluation index(REI) for the concrete dam deformation prediction model.The corresponding formula is defined as follows.

    REI = RMSEO − RMSEEj j: ð19Þ

    2.4.3. Externality. The externality of the concrete dam defor-mation prediction model refers to its adaptability to accu-rately process samples outside the training set with thesame mapping relationship. A high-performance modelbased on its externality ability can learn the mapping rela-tionships hidden in data through training set. Even if somesamples are outside the training set, a model with a satisfac-tory externality can achieve accurate predictions. The sam-ples outside the training set are fused with the testingsamples, and the prediction performance of the model basedon a training set with the same mapping relationship istested. The accuracy index of the model under this condition,the RMSEP , is selected as the externality evaluation index(EEI). The corresponding formula is defined as follows.

    EEI = RMSEP =ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi1n〠n

    t=1yt − y∧tð Þ2

    s: ð20Þ

    2.4.4. Generalization. The generalization of a concrete damdeformation prediction model refers to its adaptability toprocess samples with the same mapping relationship. A poor

    generalization ability can lead to overfitting. In such cases,the model error for the training set is very low, but the erroris very large for the testing set. The model is optimized byadding training samples, performing regularization process-ing, and applying the Dropout algorithm to improve itsgeneralization performance. Selecting the ratio of RMSETin the training process to RMSEP in the prediction processis selected as the generalization evaluation index (GEI). Thecorresponding formula is defined as follows.

    GEI = RMSEPRMSET: ð21Þ

    In each evaluation index formula above, yðtÞ representsa measured value; ŷðtÞ represents a predicted value; nrepresents the number of predicted samples; the subscriptT represents the training process; the subscript P representsthe prediction process; the subscript O represents sampleswith no gross error; and the subscript E represents sampleswith gross error.

    2.5. Simulation Environment and Engineering Project.Concrete dam deformation prediction models based onOLS, SVM, MLP, and LSTM are established in accordancewith the horizontal displacement of concrete gravity dams,and the evaluation system is used to evaluate the accuracy,robustness, externality, and generalization of each model.Additionally, a comparative analysis is performed. The simu-lation environment includes the Windows 10 operatingsystem, an Intel Core i5 CPU, 8GB of memory, the Pythonprogramming language version 3.7.2rcl, and the TensorFlowdeep learning framework version 1.12.0.

    2.5.1. Engineering Situation. Zhouning Hydropower Stationis a diversion-type power station on the Muyang River inFujian Province that performs step exploitation. The totalinstalled capacity is 250MW, the total storage capacity ofthe reservoir is 47 million m3, and the designed flood level is633.00m. The power station consists of a barrage, a sluicebuilding, a water conveyance system, an underground power-house, and a ground switch station. The barrage is an RCCgravity dam with a foundation plane elevation of 562.00m, amaximum dam height of 72.40m, and a dam crest length of206.00m. The body of Zhouning Dam is divided into ninedam sections, of whichNos. 1-4 andNos. 7-9 are nonoverflowsections and Nos. 5-6 are overflow sections.

    The deformation monitoring data collected by ZhouningHydropower Station include horizontal and vertical dam dis-placement data. The horizontal displacement monitoring ofthe dam crest is performed by the extension wire alignmentmethod. The fixed end of the extension wire with a totallength of 200.75m is arranged at Sta. R01+107.025 and theguide end is placed at Sta. L0+93.50. In total, 11 monitoringpoints are arranged along the dam, of which nine datumpoints are located at the top of each dam section and twocheckpoints are set at the left and right ends of the extensionwire to check the displacement of each end. The extensionwire system was automated in April 2005 with an observationfrequency of 1 time per day. The layout of the extension wire

    7Journal of Sensors

  • measurement points for horizontal displacement is shown inFigure 7.

    2.5.2. Selection and Optimization of Influential Factors in thePrediction Model. According to theoretical knowledge, mon-itoring data, expert experience, etc., the initial selection ofempirical influence factors was as follows:

    H −H0ð Þ1, H −H0ð Þ2, H −H0ð Þ3, T5 − Tð Þ, T20 − Tð Þ,�

    T60 − Tð Þ, T90 − Tð Þ, θ, ln 1 + θð Þ, J ,Q,U�,

    ð22Þ

    where H is the water depth on a day when observations arecollected, H0 is the water depth on the base day; Ti is themean reservoir region temperature i days ago, and T is theannual mean temperature. Additionally, θ = ðt − t0Þ/100,where t is the observation date and t0 is the date of the baseday. J is the average fracture aperture at measurement points,Q is the seepage flow, and U is the average uplift pressure atmeasurement points.

    The initial empirical influential factors are selected as theconditional attributes X, and the horizontal displacementsobtained by the dam crest extension wire (to the left bank ispositive and to the right bank is negative) at point EX1 areset as the decision attributes Y in the single-point predictionmodel. Additionally, the horizontal displacements of EX1,EX2, EX4, EX5, EX6, and EX7 are selected as the decisionattributes YM in the multipoint prediction model (becausethe extension wire at EX3 contacted a stainless-steel rod, themonitoring data at the point are not reliable). Overall, 864monitoring samples of horizontal displacement and influen-tial factors were selected as the sample set U . The attributerange V was determined based on the K-means clusteringalgorithm with adaptive discretization, and the number ofclusters was experimentally determined to be 7. To eliminateirrelevant orweakly informative input variables and keep onlythe representative factors that affect concrete dam deforma-tion, the RS theory is used to conduct an attribute reductionand importance evaluation and obtain an initial informationtable S = fU , X ∪ Y , V , f g. The attribute reduction and

    importance evaluation results for the single-point and multi-point prediction models are shown in Table 1.

    According to attribute reduction and importance evaluationresults, the influential factors of the single-point predictionmodel are {H‐H0, ðH‐H0Þ2, ðH‐H0Þ3, ðT5‐TÞ, ðT20‐TÞ, θ, lnð1 + θÞ}, and the importance evaluation values for each compo-nent of horizontal displacement at EX1 are 0.12, 0.08, 0.13, 0.42,0.20, 0.02, and 0.03, respectively. The influential factors of themultipoint prediction model are {H‐H0, ðH‐H0Þ2, ðH‐H0Þ3,ðT5‐TÞ, ðT20‐TÞ, θ, ln ð1 + θÞ, J ,Q,U}, and the importanceevaluation values of each component of the horizontaldisplacement at EX1, EX2, EX4, EX5, EX6, and EX7 are0.10, 0.07, 0.06, 0.33, 0.19, 0.00, 0.00, 0.02, 0.04, 0.06, 0.08,and 0.05. Therefore, it can be concluded that the horizontaldisplacement of the extension wire is greatly affected bytemperature changes and water level fluctuations. Specifically,the temperature component accounts for 60% of the horizontaldisplacement, and the lag period of the water level is approxi-mately 20 days.

    2.5.3. Sample Selection for Prediction Models. According toattribute reduction and importance evaluation results, theinfluential factor monitoring data of the single-point andmultipoint prediction models are selected to obtain samplesas independent variables, and the horizontal displacementat points EX1-EX7 (except EX3) is selected to obtain samplesas dependent variables. The dataset is established betweenJune 2, 2016, and October 22, 2018, and has a total of 864samples of data. The dataset of 700 samples selected fromJune 2, 2016, to May 10, 2018, is used as the training set,and the dataset of 164 samples selected from May 11, 2018,to October 22, 2018, is adopted as the testing set. Investiga-tions of the concrete dam deformation prediction modelbased on the OLS, SVM, MLP, and LSTM methods areperformed using the dataset with 864 samples of data. Varia-tions in the water depth and horizontal displacement areshown in Figures 8 and 9.

    2.5.4. Model Parameter Setting. The performance of SVM,MLP, and LSTM models depends greatly on the setting ofsome parameters. According to experience and experiment

    Checkpoint

    J1 EX1 EX2 EX3 EX4

    Sta.D. 0+0222.78

    Sta.D. 0+040.06

    Sta.D. 0+048.36

    Original roadSJ2

    EX5 EX6 EX7 EX8 EX9 J2Extension wire

    Working basic point

    Sta.L

    . 0+0

    88.5

    0

    Sta.L

    . 0+0

    63.0

    0

    Sta.L

    . 0+0

    42.4

    0

    Sta.L

    . 0+0

    23.0

    0

    Sta.L

    . 0+0

    00.0

    0

    Sta.R

    . 0+0

    23.0

    0

    Sta.R

    . 0+0

    46.0

    0

    Sta.R

    . 0+0

    70.0

    0

    Sta.R

    . 0+0

    99.0

    0

    Sta.R

    . 0+1

    07.2

    5

    Benhmark

    B4

    Figure 7: Layout of the extension wire measuring points for horizontal displacement.

    8 Journal of Sensors

  • results, parameters of the adapted algorithms, namely, regu-larization parameters, kernel function parameters, networkparameters, learning rates, and so on, are given before thesimulation.

    Parameters in the SVM model: the kernel function isdetermined as a radial basis function (RBF) according toexperience. Parameter range of the SVM model is deter-mined based on experience, penalty parameter C ∈ ½−256,

    Table 1: Attribute reduction results of the single-point and multipoint prediction models.

    Experienceimpact factors

    Componentname

    Single-pointmodel SIM

    ReductionImportance evaluation

    Sig a, X, Yð ÞMultipointmodel SIM

    ReductionImportance evaluation

    Sig a, X, Yð ÞH‐H0

    Waterpressure

    -5 No 0.12 -4 No 0.10

    H‐H0ð Þ2 -2 No 0.08 -2 No 0.07H‐H0ð Þ3 -2 No 0.13 -4 No 0.06(T5‐T)

    Temperature

    -5 No 0.42 -7 No 0.33

    (T20‐T) -4 No 0.20 -2 No 0.19(T60‐T) 0 Yes 0.00 0 Yes 0.00(T90‐T) 0 Yes 0.00 0 Yes 0.00θ

    Aging-2 No 0.02 -2 No 0.02

    ln 1 + θð Þ -1 No 0.03 -3 No 0.04J Fracture -1 Yes 0.00 -2 No 0.06

    Q Seepage -2 Yes 0.00 -4 No 0.08

    U Upliftpressure

    -3 Yes 0.00 -3 No 0.05

    50

    55

    60

    65

    70

    75

    2016/4 2016/9 2017/3 2017/8 2018/1 2018/6 2018/12

    Wat

    er d

    epth

    (m)

    Date

    Figure 8: Variations in the water depth.

    –5

    –2

    1

    4

    7

    10

    2016/4 2016/9 2017/3 2017/8 2018/1 2018/6 2018/12

    Disp

    lace

    men

    t (m

    m)

    DateEX1

    EX2EX4EX5EX6

    EX7

    Figure 9: Variations in horizontal displacement.

    9Journal of Sensors

  • 256�, kernel parameter γ ∈ ½−256, 256�. Parametric tuning isimplemented with Grid Search, C is set to 8, and γ is set to0.72 according to the experimental relationship between theobjective functions and parameters.

    Parameters in the MLP model: according to experimentresults, the network is composed of input layer, hiddenlayers, and output layer with the three-layer topology of 7-15-15-1 for single-point prediction model and 10-15-15-1for multipoint prediction model, and the learning rate is alsoset to 0.08. The network variable parameter weights andbiases are initialized randomly and calculated by gradientdescent algorithms, and the activation function is the ReLUfunction.

    Parameters in the LSTMmodel: hyperparameter range ofthe LSTM model is determined based on experience, batchsize ∈ ½0, 1000�, timestep ∈ ½20, 300�, hidden layers ∈ ½20,200�,and the initial value of learning rate is set to 0.1. Taking theminimum RMSE value as the objective function, andaccording to the experimental relationship between theobjective function and parameters, parametric tuning isimplemented with Grid Search. Finally, batch size, time-step, hidden layers, and learning rate are set to 12, 46,42, and 0.12, respectively. The network variable parametersincluding weights and biases are generated using theglorot_uniform initializer and calculated by gradientdescent algorithms.

    3. Results

    To verify the superiority of the concrete dam deformationprediction model based on LSTM compared to other modelsin terms of accuracy, robustness, externality, and generaliza-tion, a comparative analysis of the OLS, SVM, MLP, andLSTM models is conducted based on the prediction resultswith preprocessed training and testing samples.

    3.1. Single-Point Prediction Model. Single-point predictionmodels for concrete dam deformation based on the OLS,SVM,MLP, and LSTM algorithms are established to facilitatecomparative analysis.

    3.1.1. Model Prediction Analysis. Concrete dam deformationprediction models based on the OLS, SVM, MLP, and LSTMalgorithms were established based on the preprocessed stan-dardized environmental dataset and the unnormalized defor-mation dataset. Based on the objective functions, the trainingsamples are used to train the models, and the optimal modelparameters are obtained. Finally, a concrete dam deforma-tion prediction and performance analysis are performed.The measured and predicted values of concrete dam defor-mation based on the OLS, SVM, MLP, and LSTM modelsare shown in Figure 10.

    Figure 10 shows that the predicted values of the OLSmodel largely deviate from the measured values, but the over-all trend is similar to that for the measured values. The devi-ation between the predicted values of the SVM, MLP, andLSTM models and the measured values is small, but thelate-stage prediction trend of the SVMmodel deviates signif-icantly from the measured values. The LSTMmodel not onlyexhibits the highest degree of agreement between the pre-dicted and measured values but also yields the same trendas that for the measured values. Therefore, the predictionperformance of the concrete dam deformation predictionmodel based on LSTM is significantly better than that basedon the OLS, SVM, and MLP models.

    3.1.2. Model Performance Evaluation. A prediction model forconcrete dam deformation is an important tool for quantita-tively evaluating the safety status of dams, revealing abnor-malities in the service status and ensuring engineeringsafety. A high-performance deformation prediction modelshould meet the relevant accuracy, robustness, externality,and generalization requirements to implement effective earlywarning strategies and feedback control for engineeringsafety. To verify the reliability of the concrete dam deforma-tion prediction model based on LSTM, concrete dam defor-mation prediction models based on OLS, SVM, MLP, andLSTM were compared and analyzed according to the evalua-tion system established in this paper. The horizontal dis-placement residuals of each prediction model are shown inFigure 11. Evaluation index values of all prediction modelsare shown in Table 2.

    0

    0.4

    0.8

    1.2

    1.6

    2

    2018/4 2018/5 2018/6 2018/7 2018/8 2018/9 2018/10

    Disp

    lace

    men

    t (m

    m)

    Date

    EX1 measured values OLS predicted valuesSVM predicted values MLP predicted valuesLSTM predicted values

    Figure 10: Measured and model-predicted values.

    10 Journal of Sensors

  • (1) Accuracy. Figure 11 and AVI value of each model inTable 2 show that the horizontal displacement residuals ofthe concrete dam deformation prediction model based onLSTM are the smallest, RMSEP is lower than 0.1, MAPEP islower than 10, and all these are in the low range comparedwith those of the models based on OLS, SVM, and MLP.Therefore, the concrete dam deformation prediction modelbased on LSTM displays better accuracy than the othermodels, and the prediction results better agree with the realdata.

    (2) Robustness. The REI value of each model in Table 2 showsthat the concrete dam prediction models based on OLS,SVM, MLP, and LSTM are all affected by the gross error,resulting in different degrees of prediction accuracy. TheREI value of the concrete dam deformation prediction modelbased on LSTM is the smallest among the REI values of all themodels; thus, the gross error associated with the data samplehas little impact on the prediction results of the proposedmodel, which displays the strongest robustness.

    (3) Externality. The EEI value of each model in Table 2 showsthat the accuracy of the models decreases after addingsamples outside the training set to the model testing samples.Nevertheless, the concrete dam deformation predictionmodel based on LSTM exhibits the smallest EEI, representingthe strongest externality and the most powerful learningability.

    (4) Generalization. The GEI value of each model inTable 2 shows that the generalization of the concretedam deformation prediction models based on OLS andSVM is poor. These models likely experience overfittingduring training, resulting in an increase in the error forthe testing set and poor performance. The concrete damdeformation prediction models based on MLP and LSTMdisplay good generalization performance, and the LSTMmodel yields the best performance.

    In summary, the successful application of machinelearning technology has greatly promoted the developmentof concrete dam deformation prediction model comparedwith using traditional statistical methods. The concretedam deformation prediction models based on SVM,MLP, and LSTM all displayed high accuracy, but theperformance of each model in terms of robustness, exter-nality, and generalization varies. The concrete deformationprediction model based on LSTM displays the highestaccuracy, robustness, externality, and generalization bycomparison with the performance of the other models.Therefore, the application of LSTM to concrete deforma-tion prediction models further promotes the developmentof concrete dam prediction model.

    3.2. Multipoint Synchronized Prediction Model for ConcreteDam Deformation. According to the theoretical, mathemat-ical, and mechanical principles of concrete dams, theconcrete dam deformation is affected not only by loadssuch as water pressure and temperature loads but also byadjacent local factors. The sudden displacement of somedam parts will influence the surrounding areas, and asingle-point prediction model for concrete dam deforma-tion does not consider the relationships among points;therefore, it is difficult to grasp the displacement fieldunder a given load. It is necessary to establish a multipointsynchronized prediction model for concrete dam deforma-tion that can effectively improve the prediction perfor-mance compared to that of traditional models and theaccuracy of mechanical parameter inversion and feedbackanalysis. Additionally, such a method could improve the

    –1

    –0.6

    –0.2

    0.2

    0.6

    1

    2018/4 2018/5 2018/6 2018/7 2018/8 2018/9 2018/10

    Disp

    lace

    men

    t (m

    m)

    Date

    OLS residuals SVM residualsMLP residuals LSTM residuals

    Figure 11: The horizontal displacement residuals of each prediction model.

    Table 2: Evaluation index values of all prediction models.

    Prediction modelOLS SVM MLP LSTM

    AVI

    RMSEP 0.32833 0.2466 0.1604 0.0690MAPEP 29.7077 24.7789 16.3695 6.3213

    REI 0.3253 0.3672 0.2865 0.1760

    EEI 0.4032 0.2739 0.1892 0.1023

    GEI 0.8266 0.8788 0.9336 0.9610

    11Journal of Sensors

  • safety monitoring level of concrete dams. This paperestablishes a multipoint synchronized prediction modelfor concrete dam deformation based on the datacollected at multiple points and the advantages of LSTMfor multiple inputs and outputs.

    3.2.1. Model Prediction Analysis. The factors that influencethe multipoint synchronized prediction model for concretedam deformation are determined by attribute reduction. Allthe data are normalized and used as samples of the indepen-dent variables in the LSTM model, and the deformationmonitoring data from points EX1-EX7 (except EX3) areselected as samples of the dependent variable (no normaliza-tion processing). The training data and testing set are dividedin the same way as in the single-point model. The outputlayer is a multidimensional fully connected layer, the modellearning rate is 0.18, and other parameters are the same asthose in the single-point model. The six-point synchronizedprediction model for concrete dam deformation with optimalparameters is obtained by training, and the deformationvalues are predicted based on the testing samples. The actualmeasured values and the predicted values of the single-pointand multipoint models are shown in Figure 12 (taking the

    measured values at EX1 as an example). The measured valuesand values predicted with the multipoint synchronizeddeformation model are shown in Figure 13 (taking the mea-sured values at EX4-EX6 as examples).

    3.2.2. Model Performance Evaluation. Since the predictionmodel is based on the deformation values at multiple points,the error of the multipoint model includes the error at allpoints. According to error theory, RMSE of the multipointmodel is the weighted average of RMSE at each point, andit can be expressed as follows:

    S =ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffins21 + ns22+⋯+ns2k

    kn

    r=

    ffiffiffiffiffiffiffiffiffiffi〠k

    i=1

    s2ik

    vuut , ð23Þ

    where S represents the RMSE of the multipoint model, sirepresents each point, and k represents the number of testingsamples.

    The RMSE values of the multipoint synchronized predic-tion model and single-point prediction model are comparedand analyzed, as shown in Table 3.

    0

    0.6

    1.2

    1.8

    2.4

    3

    2018/4 2018/5 2018/6 2018/7 2018/8 2018/9 2018/10

    Disp

    lace

    men

    t (m

    m)

    DateEX1 measured valuesSingle-point valuesMulti-points values

    Figure 12: Actual values and predicted values with the single-point and multipoint models.

    –4.5

    –3.3

    –2.1

    –0.9

    0.3

    1.5

    2018/4 2018/5 2018/6 2018/7 2018/8 2018/9 2018/10

    Disp

    lace

    men

    t (m

    m)

    Date

    EX4 measured values EX4 predicted valuesEX5 measured values EX5 predicted valuesEX6 measured values EX6 predicted values

    Figure 13: Measured values and values predicted with the multipoint deformation prediction model.

    12 Journal of Sensors

  • Figures 12 and 13 and Table 3 show that the performanceof both models is good, and the error is within the acceptableprecision range. The RMSE value of the multipoint predic-tion model is smaller than that of the single-point predictionmodel, and the predicted values of the multipoint model arecloser to the measured values. Additionally, the weightedaverage RMSE of the single-point prediction model is largerthan the RMSE of the multipoint model, which indicates thatthe prediction accuracy at each point in the multipoint modelis high. Therefore, the multipoint synchronized predictionmodel for concrete dam deformation based on LSTMexhibits good performance, and the analysis results arelocally meaningful and spatially representative at large scales.

    4. Conclusions and Discussion

    RS theory and an LSTM network are introduced for concretedam safety monitoring in the TensorFlow framework, andsingle-point and multipoint concrete dam deformationprediction models based on LSTM are established. Moreover,a new evaluation system and quantitative evaluation indexesfor the concrete dam deformation prediction model areproposed. The following conclusions were obtained fromapplication examples.

    (1) RS theory is applied to optimize the selection andevaluate the importance of the factors that influenceconcrete dam deformation based on the internal rela-tionships among the monitoring dataset. Thisapproach overcomes the deficiencies of intelligentprediction models related to the quantitative inter-pretation and ensures the objectivity of predictionmodel analysis

    (2) According to statistical theory, an evaluation systemis proposed, and accuracy, robustness, externality,and generalization evaluation indexes are given asperformance inspection criteria to comprehensivelyevaluate the performance of concrete dam deforma-tion prediction models in practical engineering

    (3) The single-point prediction model for concrete damdeformation based on LSTM displays high predictionaccuracy and strong robustness, externality, and gen-eralization. Moreover, the multipoint synchronizedprediction model for concrete dam deformationbased on LSTM is locally pertinent and spatiallyrepresentative at large scales. Thus, the multipointapproach can be effectively used in the deformationprediction of concrete dams at large scales

    The continuous improvements in concrete dam tech-nology have resulted in high requirements for predictionmodel performance, and establishing high-performancespatiotemporal prediction models will be important asconcrete dam safety monitoring continues to progress.Therefore, the combination of AI, deep learning theory,online dynamic learning, and space-time deformationprediction models should be promoted to establish an idealconcrete dam monitoring system and achieve the goal of“intelligent monitoring.”

    Data Availability

    “Dataset of Zhouning dam.xlsx” used to support the findingsof this study is available from the corresponding author uponrequest.

    Conflicts of Interest

    The authors declare that there is no conflict of interest.

    Acknowledgments

    This research was supported by the National Natural ScienceFoundation of China (No. 51809212), the Key Projects ofNatural Science Basic Research Program of Shaanxi Province(No. 2018JZ5010), and the Water Science Plan Project ofShaanxi Province (No. 2018SLKJ-5).

    Supplementary Materials

    The supplementary material submitted is the dataset used tobuild the prediction model based on RS-LSTM in the article.The dataset named “Dataset of Zhouning dam.xlsx” includesvalues of Zhouning dam’s horizontal displacement at pointsEX1-EX7 (except EX3) and its impact factors from June 2,2016, to October 22, 2018, which are selected to obtainsamples. The dataset of 700 samples selected from June 2,2016, to May 10, 2018, is used as the training set, and thedataset of 164 samples selected from May 11, 2018, toOctober 22, 2018, is adopted as the testing set.(Supplementary Materials)

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    Table 3: RMSE values of the multipoint prediction model andsingle-point prediction model.

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