【作者】 陈辉；

【导师】 戚蓝； 刘东海；

【作者基本信息】 天津大学 ， 水工结构工程， 2018， 博士

【摘要】 我国正在或准备建设一批超高土石坝,其建设规模和难度也越来越大,由此带来的工程安全问题也越发突出。土石坝坝体结构性态(应力变形、不均匀沉降、拱效应及水力劈裂等)直接关系到大坝的服役安全,而实际施工质量、施工进度、坝料特性等是影响高土石坝结构性态的重要因素。然而,由于缺乏相应的技术手段,难以充分地获取实际大坝施工过程中的详细质量信息。故现有相关研究中,大多假设大坝同分区坝料特性同质,即在空间上采用一致的材料属性参数,从而忽略了实际施工质量及坝料特性在空间分布上的差异性与随机性。施工质量的空间差异性会对坝料强度和变形参数带来重要影响,这就导致现有研究在一定程度上不能客观反映实际情况,故不易对大坝结构性态做出准确的评价。因此,如何充分考虑大坝实际施工质量对坝体结构性态的影响,如何利用先进的施工技术实现大坝结构性态的精细模拟,是保证高土石坝又快又好建设和安全服役所需解决的重要科学问题。本文以高土石坝坝体结构性态为研究对象,基于室内三轴试验和数值分析手段,详细分析了坝料压实质量对本构模型参数的影响,系统研究了考虑压实质量与本构模型参数相关性,以及实际试坑压实质量约束作用下的随机模拟方法,并深入探究了能客观反映实际施工质量情况的高土石坝结构性态精细数值模拟方法,为高土石坝结构性态分析提供了一条新的途径。本文主要研究成果如下:(1)构建了土石坝坝料压实质量与邓肯-张本构模型参数之间的定量关系。通过大型三轴试验,获得了不同压实质量下的坝料应力-应变、体积-应变试验曲线,从力学机理上深入分析坝料压实质量与模型参数之间的关系,建立了坝料压实质量与模型参数之间的回归关系;从而可利用实际坝料压实质量,快速估计本构模型参数,为高土石坝结构性态精细数值模拟提供了前提条件。(2)提出了改进的土石坝本构模型参数敏感性分析方法,即基于全域有限元计算节点的单因素敏感性分析方法和基于双判别方式的正交试验参数敏感性分析方法。该方法可以解决传统单因素分析方法样本缺乏代表性的弊端,同时可以定量给出参数敏感性的显著性水平,并解决常用敏感性分析结论不统一的问题,可提高敏感性分析的全面性和准确性,从而也为土石坝结构性态数值模拟中精细赋值的模型参数选取提供了理论依据。(3)提出了考虑压实质量与本构模型参数相关性以及实际试坑压实质量约束作用下的土石坝施工期应力变形预测的随机有限元法,用以分析施工质量空间差异对土石坝结构性态响应的影响规律。利用实测试坑数据,采用乔列斯基分解法,构建坝料压实质量的空间约束随机场,进而利用建立的压实质量与本构模型参数的回归关系,构建了本构模型参数的随机场。开发了Abaqus软件的接口程序,用于模型参数约束随机场的快速生成和参数批量赋值。进而采用随机有限元法,分析了由于不同的施工质量分布情况带来的坝料参数的空间差异性对坝体结构性态(应力变形等)的影响。本文方法可考虑坝料本构模型参数的空间差异性与随机性,可为待建的高土石坝设计中坝体分区设置及分区模型参数设定等提供理论指导。(4)提出了数字化施工下高土石坝应力应变精细有限元分析方法。在数字化施工技术的支撑下,可以实时获取大坝空间任意位置处实际压实质量;利用建立的坝料压实质量与本构模型参数之间的定量关系,可给出反映实际压实质量的模型参数空间估计,并实现了反映空间实际压实质量的任意有限元单元模型参数的精细赋值。本文方法考虑了土石坝实际施工质量的空间差异性而带来的坝料模型参数在空间上的差异性,可避免通常同一分区采用相同坝料力学参数导致的计算精度不足的弊端,为土石坝结构性态分析提供了更精细的方法。(5)提出了数字化施工下高土石坝水力劈裂精细扩展有限元数值模拟方法。为了快速获取水力劈裂断裂模型参数,建立了坝料压实质量与水力劈裂断裂模型参数之间关系;利用数字化施工下高土石坝断裂本构模型参数空间估计方法,实现了能反映实际压实质量的每个计算单元断裂本构模型参数的精细赋值,进而实现了心墙水力劈裂的扩展有限元数值模拟,可以计算分析实际施工质量影响下的水力劈裂发生的可能性与安全裕度。该方法可解决以连续介质假定为基础的传统有限元法在处理非连续变形问题(水力劈裂)时的精度不足,以及大坝施工中压实质量空间差异性带来的计算误差过大的问题,为高土石坝水力劈裂分析提供了一种新的方法。更多还原

【Abstract】 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.更多还原