土石坝抗震稳定的极限能力分析

发布时间：2018-02-27 19:29

本文关键词： 土石坝极限抗震能力稳定性极限分析　出处：《大连理工大学》2014年博士论文　论文类型：学位论文

【摘要】：汶川大地震之后,国家加强了水电工程的抗震防震工作。《水电工程防震抗震研究设计及专题报告编制暂行规定》指出,对特别重要的挡水建筑物,除满足设计及校核地震工况下大坝抗震安全性要求外,还应研究极限抗震能力。目前,我国对土石坝极限抗震能力的研究尚处于起步阶段,其分析方法尚不成熟,发展一些更有效的土石坝极限抗震能力分析方法,具有较高的理论价值和实际工程意义。分析实际震害资料及现有研究成果发现,坝坡抗震稳定是影响土石坝极限抗震能力的最关键问题之一。因此,土石坝坝坡稳定的极限抗震能力分析是研究的重点问题之一。极限分析是塑性力学的重要内容,它通过直接分析结构的极限状态,并根据上、下限定理计算与之相对应的极限荷载,已经广泛应用于地基承载力、土坡稳定等岩土工程问题中。因此,本文主要采用塑性极限分析方法对土石坝抗震稳定的极限能力进行研究,主要内容如下： (1)基于极限分析上限定理,提出了一种分析土石坝抗震稳定极限能力的新方法。该方法首先将坝坡滑动体划分为若干水平土条,计算各滑动土条的外功率与内能耗散率,然后通过功能平衡方程,利用优化算法确定土石坝抗震稳定的极限能力。采用水平条分可避免以往竖向条分对地震惯性力计算的不精确问题。此外,本文将素土和筋材内能耗散率分开考虑,以评估加筋土石坝的抗震稳定极限能力及不同加筋方式对大坝极限抗震能力的提高。 (2)基于极限分析下限定理,同时考虑了堆石料内摩擦角较大以及抗剪强度具有非线性的特性,发展了一个用于求解土石坝抗震稳定极限能力的有限元计算方法。该方法通过静力平衡条件、应力间断面连续条件、边界条件、屈服条件以及所求极限荷载,形成标准的二次锥规划数学模型,并用内点法进行优化求解,得到土石坝坝坡极限抗震能力的下限值。根据下限值可估计土石坝坝坡抗震稳定极限能力的最低值,以评价土石坝的抗震安全性。计算中没有对屈服函数进行线性化处理,因而消除了由此带来的误差。 (3)采用六节点三角形单元及二次锥规划,本文提出了土石坝抗震稳定极限能力的上限有限元法。上限极限分析由于构建的是运动许可速度场,因而在计算中无法较好地考虑堆石料强度的非线性特性。将二次锥规划数学模型转换为其对偶问题的静力形式,并迭代求解极限状态时土体各点的等效线性剪切强度参数,解决了有限元上限分析考虑非线性强度问题。此外,为了考虑孔隙水压力作用,本文还将渗透孔隙水压力以外力的形式出现在功能平衡方程中。与三节点三角形单元相比,采用六节点单元的上限法具有较高的计算精度,其计算结果不依赖于网格密度。通过土石坝坡抗震稳定极限能力的上限法与下限法分析,可确定大坝坝坡极限抗震能力的上、下限值,进而可判断大坝的抗震安全性。 (4)根据土石坝抗震稳定性问题的特点,运用有限元超载法对土石坝抗震稳定的极限能力进行了分析,研究了失稳判据、屈服准则、流动法则及有限单元类型与尺寸的选取对计算结果的影响。
[Abstract]:After the Wenchuan earthquake , the state has strengthened the anti - seismic and anti - seismic work of the hydropower project . In addition to meeting the seismic safety requirements of the dam under the design and check seismic conditions , it is pointed out that the research on the limit seismic capacity of the earth - rock dam is still in the initial stage , and the analysis method is not mature enough to develop some more effective methods for seismic capacity analysis of earth - rock dams , which have higher theoretical value and practical engineering significance . It is found that the seismic stability of the dam slope is one of the most critical issues affecting the seismic capacity of the earth - rock dam . Therefore , the limit seismic capacity analysis of the slope stability of the earth - rockfill dam is one of the key problems in the study . The ultimate analysis is an important part of plastic mechanics , and the ultimate load corresponding to it is calculated according to the upper and lower limit theorems , which has been widely used in geotechnical engineering problems such as foundation bearing capacity and soil slope stability . Therefore , this paper mainly adopts plastic limit analysis method to study the limit ability of seismic stability of earth - rock dam . The main contents are as follows : ( 1 ) Based on the limit analysis upper limit theorem , a new method for analyzing the seismic stability limit capacity of earth - rock dams is presented . First , the dam slope sliding body is divided into several horizontal soil strips , the outer power and the inner energy dissipation rate of each sliding soil strip are calculated , then the limit capacity of the earth - rock dam is determined by using the optimization algorithm . ( 2 ) Based on the limit analysis lower limit theorem , a finite element method for solving the seismic stability limit capacity of earth - rock dams is developed by considering the characteristics of large internal friction angle and non - linearity of shear strength . ( 3 ) The upper limit finite element method for seismic stability limit of earth - rock dams is proposed by using six - node triangle unit and twice cone programming . The upper and lower limits of the seismic capacity of the dam slope limit can be determined by the upper limit method and the lower limit method of the limit capacity of the anti - seismic stability of the earth - rock dam slope , and then the seismic safety of the dam can be judged . ( 4 ) According to the characteristics of anti - seismic stability of earth - rock dam , the limit capacity of seismic stability of earth - rock dam is analyzed by finite element method , and the influence of instability criterion , yield criterion , flow rule and the selection of finite element type and size on the calculation results are studied .

【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV641;TV312

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