Refined Numerical Simulation Of Structural Behaviors For High Earth-Rockfill Dam With Considering Real Construction Quality

Plenty of super high earth-rockfill dams are and will be under construction in our country.The construction scale and difficulty all become larger and the safety problems of project will be consequently exposed.High earth-rockfill dam structural behaviors(stress and deformation,uneven settlement,arch effects,hydraulic fracturing,etc.)are directly related to the safe operation of dams.Meanwhile,actual construction quality,construction progress,dam material properties are important factors influencing the structural behaviors of earth-rockfill dams.However,due to lack of necessary techniques available,actual detailed quality information is difficult to be acquired adequately under dam construction.Thus,for the present study we assume that dam materials in the same zone have the same properties,and therefore consistent material property parameters are applied for in the same zone.This assumption disregards spatial differences and randomness in actual construction quality,which affect strength and deformation parameters.The existing research,to a great extent,fails to fully reflect actual conditions,resulting in less precise data for making accurate valuation to the dam structural behaviors.Therefore,the research about impact laws of the actual construction quality on dam structural behaviors and accurately evaluating dam structural behaviors based on advanced construction technology are necessary to guarantee the safe operation of high earth-rockfill dams.This dissertation focuses on high earth-rockfill dam structural behaviors research based on laboratory triaxial tests and numerical analysis.The effects of the dam material compression quality on the values of constitutive model parameters were given a detailed analysis.And the sensitivity analysis of constitutive model parameters for earth-rockfill dams was studied deeply.Meanwhile,the stochastic finite element method which can not only take into full account the correlation between the dam material compression quality and the constitutive model parameters but also consider the binding effect of experimental data on test pits were studied systematically.Further more,the refined numerical method which can consider actual construction quality condition for the simulation of high earth-rockfill dam structural behaviors were researched thoroughly,which would serve as a more accurate approach to the analysis of earth-rockfill dam structural behaviors.The main research work and contributions are as follows:(1)The quantitative relationship between the compaction quality of the dam materials of earth-rockfill dam and the Duncan-Chang constitutive model parameters was built.Multigroup large-scale triaxial tests were carried out to obtain the stress–strain curves and volumetric strain–axial strain curves of rockfill materials with different dam material compression qualities,thus deep research on the relationship between the compaction quality and the model parameters could be conducted in mechanical mechanism.Then the regression models between the dam material compression quality and the constitutive model parameters can be achieved by the method of regression analysis.So it could be effective to achieve the constitutive model parameters through the real dam material compression quality.These useful results would provide a precondition for refined numerical simulation research of structural behaviors for high earth-rockfill dams.(2)A modified method for parameter sensitivity analysis of constitutive model parameters for earth-rockfill dams was proposed.The method is the single factor analysis method based on finite element calculation nodes in the whole zone of the computational dam together with the orthogonal experimental method based on the double discriminant method.The methods proposed in this paper overcome the disadvantages of traditional single factor method,in which the samples are lack of representatives.With these methods,the significance level of parameters sensitivity can be determined in a quantitative way.And the problem of inconsistent conclusions of the parameter sensitivity analysis can be solved,thus improving the comprehensiveness and precision of the sensitivity analysis.The proposed method can provide theoretical foundation of finely assigned model parameters selection for numerical simulation of structural behaviors for earth-rockfill dams.(3)A stochastic FEM,which can not only consider the correlation between the dam material compression quality and the constitutive model parameters but also take into full account the binding effect of experimental data on test pits to simulate the structural behaviors of earth-rockfill dams during construction,was proposed in order to solve the problem of how the spatial differences of actual construction quality affect the structural behavior of earth-rockfill dams.The constraint random field of the dam compaction quality was established by using the Choleski decomposition method based on the experimental data on test pits.Then,the constraint random field of the constitutive model parameters was generated based on the regression models between the compaction quality of the rockfill materials and the constitutive model parameters.The software interface was designed for finite element software Abaqus to generate model parameters constraint random field quickly and complete the batch assignment mission of parameters.Then the variation law of the structural behavior of rockfill dams brought by the spatial difference conditions of actual construction quality was studied based on the stochastic FEM.Therefore the proposed method could consider the spatial difference and the randomness of the constitutive model parameters.And the research can provide theoretical guidance for the design of dam zones and the setting of model calculation parameters for the dam zones during dam design phase.(4)The method of refined finite element analysis under the construction digitization technologies was put forward.With the support of construction digitization technologies,the compaction quality level at any location of a rockfill dam can be estimated in real time.Then the spatial estimation method of mechanical model parameters which could reflect actual compaction quality of the dam materials was proposed based on the quantitative relationship between the compaction quality of the dam materials and the constitutive model parameters.The parameters of each finite element,which can reflect the actual conditions of dam compaction quality information,were assigned accurately.The proposed method considers the spatial difference of the constitutive model parameters caused by the spatial difference of actual dam construction quality,thus avoiding the low accuracy of the conventional method which usually assigns the same value of each constitutive model parameter to all the elements in each dam zone.The method in this paper can be considered as a more-refined approach to the analysis of earth-rockfill dam structural behaviors.(5)The refined extended –finite-element method analysis for hydraulic fracturing of high earth-rockfill dams under the construction digitization technologies was proposed.In order to achieve the constitutive model parameters effectively,the establishment method of the quantitative relationship between the compaction quality of the rockfill materials and the hydraulic fracturing model parameters was proposed.The fracturing model parameters of each finite element,which can reflect the actual conditions of dam compaction quality information,were assigned based on the spatial estimation method of fracture constitutive model parameters under the construction digitization technologies.And then the refined extended-finite-element simulation was achieved for predicting potential hydraulic fractures of the core wall of high earth-rockfill dam.The extended finite element model for hydraulic fracturing could calculate the possibility of occurrence and margin of safety of hydraulic fracturing of the core wall considering the actual conditions of dam compaction quality.The proposed method can solve the problem of large simulation errors for the structure behaviors(hydraulic fracturing)of rockfill dams brought by the continuum hypothesis assumption of traditional finite element method and spatial compaction quality difference and improve the accuracy of the calculation and is a new prediction and simulation method for the hydraulic fracturing of the high earth-rockfill dam.