【作者】 张锐；

【导师】 林皋； 迟世春；

【作者基本信息】 大连理工大学 ， 结构工程， 2008， 博士

【摘要】 我国西部即将兴建的众多高土石坝大多位于强震区,确保其安全运行对国民经济的发展和人民生命财产安全具有重大意义。本文就高土石坝的地震作用效应以及坝坡抗震稳定分析开展了系列研究工作。文中分别采用二维与三维解析法和有限单元法分析了高土石坝沿坝高和坝顶河谷方向的地震加速度分布特征,最终提出了300m级高土石坝地震动态分布系数建议图。然后利用改进的极限平衡法和强度折减法分析了地震动态分布系数对高土石坝坝坡抗震安全系数和临界滑动面的影响。利用强度折减法进行坝坡稳定分析时,根据郑颖人院士总结得出的边坡失稳时,滑动面内单元应变的突变特征,提出了塑性贯通区内最大单元等效塑性应变陡增判断准则。考虑到在坝体失稳变形过程中会产生较大的位移和变形,最后将基于更新拉格朗日方法的大变形理论引入到坝坡抗震稳定分析中,并与利用传统小变形理论求得的结果相比较。论文的主要内容包括以下几个方面:1.分别利用:1)基于剪切梁理论的解析法,包括反应谱法、考虑动剪切模量G与动剪应变γ非线性关系的迭代法、考虑三维效应的简化分析法。2)有限单元法,包括基于E-B非线性弹性模型的静力有限元分析程序和基于等效线性黏-弹性模型的动力有限元分析程序,对六座不同高度模型大坝以及拟建的糯扎渡、双江口高土石坝进行了沿坝高和坝顶河谷方向地震加速度分布特征研究。同时讨论了河谷斜率、地震设计烈度、坝坡率、坝型、地震动输入和坝料参数对高土石坝地震加速度分布的影响,最终提出了300m级高土石坝地震动态分布系数建议图。2.利用强度折减法数值模拟一300m土石坝在失稳过程中,通过观测发现塑性贯通区内各单元等效塑性应变具有突变且发展程度不一的变化规律,提出了塑性贯通区内最大单元等效塑性应变陡增判断准则。3.分别利用:1)考虑堆石材料非线性强度准则和土料动强度准则的极限平衡法,2)对判断准则和折减过程加以改进的强度折减法,分析了地震动态分布系数和坝料强度准则对高土石坝坝坡安全系数和临界滑动面的影响。结果表明,在使用地震动态分布系数建议图计算地震力时,坝体所受的地震荷载有所减小,导致土体滑动力矩相应减小,安全系数有所增加。临界滑动面的位置主要取决于坝料强度准则,地震动态分布系数的影响不大。4.高土石坝在失稳过程中,坝坡会产生较大的位移和变形。因此,引入基于更新拉格朗日方法的大变形理论,采用反映岩土材料拉压不等性的修正Drucker-Prager本构模型,对高土石坝的抗震稳定问题进行了大变形有限元分析,并与采用传统小变形理论求得的结果相比较。得出的结论是,采用基于连续介质力学的大变形理论分析高土石坝坝坡稳定问题时,计算所得的坝坡安全系数略有提高,小变形理论求得的坝坡安全系数亦可满足工程应用的要求。最后讨论了修正Drucker-Prager本构模型中材料参数K、剪胀角ψ、黏聚力系数C和内摩擦角φ,以及弹性模量E和泊松比v对坝坡安全系数的影响。更多还原

【Abstract】 Many high earth and rockfill dams to be constructed in the west of China are mostly located at strong earthquake zone. The assurance of their secure operation is very important to the development of national economy and the safety of People’s life and properties. Series of research about the seismic effects and slope seismic stability of high earth and rockfill dams are discussed in the paper. The distribution characteristic of the seismic acceleration along dam bodies and dam top in the direction of canyon of high earth and rockfill dams are analyzed with analytical method and finite element method in two and three dimensional space. Suggested dynamic seismic coefficient figure of high earth and rockfill dams 300m level in height is put forward. Furthermore, with improved limit equilibrium method and strength reduction technique, the influence of dynamic seismic coefficient upon slope safety factor and critical slide surface of high earth and rockfill dams is analyzed. When shear strength reduction technique is applied to analyze the slope stability problem, according to sudden increase characteristic of element strain inside the slide surface zone put forward by Academician Zhen Ying-ren, slope stability criterion by the sudden increase of the maximum element equivalent plastic strain inside the plastic coalescence zone is put forward. Considering large displacement and deformation will occur when dam loses stability status, large deformation theory based on the updated Lagrangian method is introduced to analyze dam slope seismic stability, and the results calculated by large deformation theory are compared with those by small deformation theory. The main research and results involved in the paper includes the following parts:1. With 1) analytical method based on shear beam theory including response spectrum method, iterative method considering nonlinear relationship between dynamic shear modulus G and dynamic shear strainγ, and simplified analysis method considering 3-dimensional effect. 2) finite element method including static computation program based on E-B nonlinear elastic constitutive model, and dynamic computation program based on equivalent linear viscoelastic model, seismic acceleration distribution characteristic analysis along dam bodies and dam top in the direction of canyon of six model dams with different height and engineering example of NuoZhaDu and ShuangJiangKou high earth and rockfill dams to be constructed is made. Influence of grade of canyon, seismic design intensity, slope grade, dam style, seismic wave input, and dam material parameters upon the seismic acceleration distribution of high earth and rockfill dams are also considered. Suggested dynamic seismic coefficient figure of high earth and rockfill dams 300m level in height is put forward ultimately.2. When simulating the loss of stability of a 300-meter-high earth and rockfill dam with strength reduction technique, the characteristic of sudden increase and unbalanced development of the element equivalent plastic strain in the plastic coalescence zone, the criterion of sudden increase of the maximum element equivalent plastic strain inside the plastic coalescence zone is put forward.3. With 1) limit equilibrium method considering nonlinear strength criterion of rock and dynamic strength criterion of soil, 2) strength reduction technique with some improvement about instability criterion and reduction step, influence of dynamic seismic coefficient and dam material strength criterion on the safety factor and slide surface of high earth and rockfill dams is analyzed. The results indicate that when earthquake load is calculated with the use of suggested dynamic seismic coefficient figure, seismic force in the dam body decreases, which result in the reduction of slide moment of soil trips and the increase of dam slope safety factor. The position of the critical slide surface is mostly determined by strength criterion of dam material, and the influence of dynamic seismic coefficient can be neglected.4. When high earth and rockfill dams lose stability, large dam slope displacement and deformation will occur. Therefore, with large deformation theory based on the updated Lagrangian method applied, using Modified Drucker-Prager constitutive model which reflects nonequivalence of tension and compression characteristic of geomaterials, discussion about seismic stability of high earth and rockfill dams with large deformation finite element method is made. The conclusion is when large deformation theory based on Continuous Medium Mechanics is considered to analyze slope stability problem, the value of safety factor will arise slightly. Results based on small deformation theory are sufficient for engineering practice. Finally, for modified Drucker-Prager constitutive model, influence of parameter K、dilation angleψ、cohesion C and internal frictional angleφ, and elastic modulus E and Poisson’s ratioυupon dam slope safety factor is discussed.更多还原