堆石料和接触面弹塑性本构模型及其在面板堆石坝中的应用研究

发布时间：2018-08-15 14:52

【摘要】：尽管现代面板堆石坝压实密度和变形模量较早期有很大提高,但坝体变形仍是面板堆石坝安全设计的主要问题。筑坝堆石料的变形特性是影响面板应力量值和分布规律的重要因素。此外,面板应力还与面板与垫层间的接触变形紧密相关。近年来,高面板堆石坝在填筑、蓄水以及地震过程中出现了面板挤压破坏和面板脱空等问题,这些问题与堆石体的变形以及面板与垫层间的接触变形均有着密不可分的关系。筑坝堆石料本构模型以及面板与垫层间接触面本构模型是计算分析面板堆石坝变形和面板应力分布规律的重要理论基础。近年来,面板堆石坝填筑和蓄水过程的弹塑性有限元分析已经有了较大的发展。但由于缺乏强震情况下的震害资料,面板堆石坝动力弹塑性分析方法的发展受到了一定的限制。目前,在面板堆石坝动力分析中广泛采用的等效线性分析方法可以较好的反映中、低强度地震的加速度反应,但不能满足大坝在强震环境中可能出现的强非线性乃至破坏全过程模拟的分析要求。强震下面板堆石坝较大的塑性(残余)变形,是引起面板挤压破坏和面板脱空等现象的主要原因,但等效线性分析方法不能考虑动力条件下塑性变形渐进发展过程,难以合理评价强震下堆石体变形对面板破坏的影响。为此,本文首先采用大型三轴仪对筑坝堆石料的颗粒破碎、临界状态及剪胀特性进行了试验研究,在此基础上提出了一个考虑颗粒破碎的状态相关堆石料广义塑性模型。然后提出了一个三维广义塑性接触面模型。最终建立了一套基于筑坝堆石料和面板与垫层间接触面弹塑性本构模型的面板堆石坝三维静、动弹塑性有限元分析方法,并应用于紫坪铺面板堆石坝填筑、蓄水及地震全过程的静、动弹塑性有限元实例分析。本文的研究内容及主要结论有：(1)采用大型三轴仪对紫坪铺筑坝堆石料进行了颗粒破碎试验研究。试验表明：单调和循环荷载下堆石料的颗粒破碎率与塑性功之间存在良好的双曲线关系,且受孔隙比、围压和应力路径的影响较小(2)采用文献中的砂土试验成果分析了颗粒破碎和临界状态的关系。结果表明,将塑性功引入到临界状态可以较好的反映临界状态随颗粒破碎的变化规律。对紫坪铺筑坝堆石料和米兰河筑坝砂砾料的临界状态进行了研究。试验表明：两种堆石料均存在临界状态,且临界状态受初始孔隙比影响较小。(3)研究了三轴单调压缩荷载下紫坪铺筑坝堆石料和文献中5种堆石料的剪胀规律。结果表明：峰值应力前剪胀比Dp和应力比η呈较好的线性关系,等p和σ3路径的剪胀关系基本一致。剪胀线斜率受孔隙比和围压的影响较小。除1种颗粒破碎较小的堆石料,其他5种堆石料的相位变换应力比均随围压的增加而减小。紫坪铺筑坝堆石料相位变换应力比Mf和状态参数ψ之间呈较好的线性关系,斜率参数k小于0。(4)研究了三轴循环荷载下紫坪铺筑坝堆石料和阿尔塔什砂砾料的剪胀规律。试验表明：三轴拉伸时Dp和η呈近似线性关系,三轴压缩和拉伸相位变换时的摩擦角接近一致。循环加载dη0和dη0路径上的剪胀线都近似地呈线性关系。初始加载(单调)和初始卸载剪胀线是循环加载时剪胀线的边界线(外包线),循环荷载下的剪胀线均位于边界线的内侧,当循环荷载下剪胀线达到初始剪胀线后两者一致。循环荷载下剪胀线位置与卸载反弯点位置有密切关系,反弯点距初始加载剪胀线越远,卸载后剪胀线偏离初始卸载剪胀线的距离越大。离散元数值试验的循环剪胀特性与堆石料的结果是一致的。(5)在试验研究和广义塑性模型框架的基础上,采用边界面和临界状态理论,与刘华北教授合作提出了一个考虑颗粒破碎的状态相关堆石料广义塑性模型。该模型将初始孔隙比作为模型输入参数,模型参数与初始孔隙比无关。模型可以反映堆石料在单调和循环条件下的变形特性。采用该堆石料模型,开展了面板堆石坝静、动弹塑性有限元数值模拟,分析了碾压颗粒破碎引起的级配变化对堆石坝计算变形的影响。计算表明：三轴试验如不考虑碾压过程中颗粒破碎对级配变化的影响,据此计算的结果会明显地低估大坝的变形,对大坝的安全性评价是十分不利的,这可能是目前有限元计算的高坝沉降变形比实测偏小的主要原因之一。(6)在平面应变条件下的接触面模型基础上,采用边界面理论,提出了一个三维广义塑性接触面模型。该模型可以反映不同初始孔隙比和不同法向约束条件下接触面在三维单调和循环条件下的变形特性,能够考虑单调和循环荷载下颗粒破碎的影响及剪切的三维耦合效应。采用该接触面模型,对某在建面板堆石坝进行了三维有限元静、动力弹塑性有限元数值模拟,分析了接触面模型对面板与垫层间接触面变形及面板应力的影响。结果表明：相比双曲线(仅静力计算)和理想弹塑性接触面模型,广义塑性接触面模型能更好地描述三维条件下接触面的剪胀、剪缩和循环残余变形特性。(7)基于本文提出的考虑颗粒破碎的状态相关堆石料广义塑性模型和三维广义塑性接触面模型,对紫坪铺面板堆石坝进行了静、动力弹塑性有限元数值模拟。首先根据大坝填筑沉降和汶川地震后残余变形反馈分析获取了堆石料模型参数。在此基础上,分析了大坝动力反应和残余变形规律,着重研究了汶川地震时紫坪铺面板堆石坝面板脱空现象。结果表明,面板与垫层间的脱空与土体变形和面板刚度有密切的关系。紫坪铺面板堆石坝震后面板脱空区域较大,与震前水位有着密切的关系,水位以上由于面板的法向约束较小,面板更容易发生脱空。面板错台是震后二期面板顶部出现较明显脱空的主要原因。本文发展的筑坝堆石料和面板与垫层间接触面弹塑性模型可以较好的再现汶川地震下紫坪铺面板堆石坝残余变形和面板脱空过程。
[Abstract]:Although the compaction density and deformation modulus of modern CFRD are much higher than those of earlier stage, the deformation of dam body is still the main problem in safety design of CFRD. Guan. In recent years, problems such as compression failure of face slab and void of face slab occurred during filling, impoundment and earthquake of high face rockfill dam. These problems are closely related to deformation of rockfill and contact deformation between face slab and cushion. In recent years, the elastic-plastic finite element analysis of the filling and impoundment process of CFRD has been greatly developed. However, due to the lack of seismic damage data under strong earthquake, the development of dynamic elastic-plastic analysis method for CFRD has been certain. At present, the equivalent linear analysis method widely used in the dynamic analysis of CFRD can better reflect the acceleration response of moderate and low intensity earthquakes, but it can not meet the analysis requirements of the simulation of the whole process of strong nonlinearity and even failure that may occur in the strong earthquake environment of the dam. Deformation is the main cause of extrusion failure and slab void, but the equivalent linear analysis method can not consider the progressive development of plastic deformation under dynamic conditions, and it is difficult to evaluate the effect of rock-fill deformation on slab failure under strong earthquake. In this paper, the effect of large-scale triaxial apparatus on the grain size of dam-building rockfill materials is firstly adopted. A generalized plastic model of state-dependent rockfill material considering particle breakage is proposed. Then a three-dimensional generalized plastic contact surface model is proposed. Finally, an elastoplastic constitutive model based on the interface between rockfill material and face slab and cushion is established. Three-dimensional static and dynamic elastic-plastic finite element analysis method of concrete face rockfill dam is applied to the static and dynamic elastic-plastic finite element analysis of Zipingpu concrete face rockfill dam during filling, impoundment and earthquake. The results show that there is a good hyperbolic relationship between the particle breakage rate and the plastic work under monotonic and cyclic loads, and the effect of void ratio, confining pressure and stress path is less. (2) The relationship between the particle breakage and the critical state is analyzed by using the sand test results in the literature. The critical state of the rockfill materials for Ziping Pavement Dam and the sand and gravel materials for Milan River Dam are studied in order to better reflect the variation of the critical state with particle breakage. The results show that there is a good linear relationship between dilatancy ratio Dp and stress ratio_before peak stress, and the relationship between dilatancy of equal P and_3 paths is basically the same. The stress ratio decreases with the increase of confining pressure. There is a good linear relationship between the phase transformation stress ratio Mf and the state parameter_, and the slope parameter k is less than 0. (4) The dilatancy law of the rockfill and the Altash gravel under Triaxial Cyclic loading is studied. The dilatancy curves on the d 0 and d 0 paths under cyclic loading are approximately linear. The initial loading (monotonic) and initial unloading dilatancy curves are the boundary lines (outer lines) of the dilatancy curves under cyclic loading. The dilatancy curves under cyclic loading are both located inside the boundary lines. The position of dilatancy line under cyclic loading is closely related to the position of unloading reverse bending point. The farther the reverse bending point is from the initial loading dilatancy line, the greater the distance the dilatancy line deviates from the initial unloading dilatancy line after unloading. Consistent. (5) Based on experimental study and generalized plastic model framework, a generalized state-dependent plasticity model for rockfill considering particle breakage is proposed by using boundary surface and critical state theory in collaboration with Professor Liu Huabei. Initial void ratio is taken as the model input parameter, and the model parameters are independent of the initial void ratio. The static and dynamic elastic-plastic finite element numerical simulation of CFRD is carried out by using the model. The influence of gradation change caused by crushing particles on the deformation of CFRD is analyzed. The influence of fragmentation on the gradation change will obviously underestimate the deformation of the dam, which is very unfavorable to the safety evaluation of the dam. This may be one of the main reasons why the settlement deformation of the high dam calculated by the finite element method is smaller than that measured. (6) Based on the contact surface model under plane strain condition, the boundary surface theory is adopted. A three-dimensional generalized plastic contact surface model is proposed. The model can reflect the deformation characteristics of the contact surface under three-dimensional monotonic and cyclic conditions with different initial void ratios and different normal constraints. The influence of particle breakage under monotonic and cyclic loads and the three-dimensional coupling effect of shear can be considered. Three-dimensional finite element static and dynamic elastic-plastic finite element numerical simulation was carried out for the CFRD under construction. The influence of contact surface model on the deformation and stress of the contact surface between the face slab and the cushion was analyzed. The results show that the generalized plastic contact surface model can better describe the deformation of the contact surface between the face slab and the cushion than the hyperbolic (only static calculation) and the ideal elastic-plastic contact surface model. (7) Based on the generalized plastic model of state-dependent rockfill materials and the three-dimensional generalized plastic contact surface model, the static and dynamic elastic-plastic finite element simulation of Ziping Paved Rockfill Dam is carried out. Based on the feedback analysis of the residual deformation after Wenchuan earthquake, the parameters of the rockfill model are obtained, and the dynamic response and residual deformation law of the dam are analyzed. The slab of Zipingpu CFRD has a large void area after the earthquake, which is closely related to the water level before the earthquake. It is easier for the slab to void above the water level because the normal restraint of the slab is small. Surface elastic-plastic model can reproduce the residual deformation and slab void process of Ziping Paved Rockfill Dam under Wenchuan earthquake.
【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TV641.43

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