基于Rackwitz-Fiessler方法的土石坝漫顶风险数学模型

为更加准确预估土石坝漫顶风险率,在全面考虑洪峰流量、风浪壅高和波浪爬高各不确定性因素的基础上,提出了基于Rackwitz-Fiessler方法的漫顶风险模型算法.通过对土石坝漫顶风险基本定义的转化,引入调洪系数ρ和基于水位流量过程关系提出基于流量关系式的漫顶风险数学模型;在已知不确定性因素的函数分布基础上,采用Rackwitz-Fiessler方法迭代求解土石坝漫顶风险率.实例结果分析表明,该漫顶风险计算模型能较好地反映土石坝漫顶特性,模型方程相比单一考虑洪峰流量不确定性或风浪壅高及波浪爬高不确定性的方法更贴近实际且验证性好.     

有限元法在土石坝渗流稳定及抗滑稳定分析中的应用

基于渗流有限元分析的基本原理,以某土石坝工程为例,对土石坝的典型断面进行二元渗流分析,应用有限元法对典型坝坡进行渗流稳定及抗滑稳定计算与分析,为土石坝的安全评价提供依据.     

子模型方法研究瀑布沟土石坝防渗结构

根据瀑布沟土石坝防渗体系的结构特点及土石坝施工填筑过程,利用有限元方法对瀑布沟土石坝整体进行了渗流分析和应力变形计算;考虑防渗墙与廊道接头局部构造,采用子模型技术,对接头部位进行了深入的计算分析,得到更加合理的数值解,为大坝防渗结构设计的优化提供了参考依据.     

基于故障树的土石坝漫顶溃坝分析

借助安全评价中的故障树模式,构建土石坝漫顶溃坝的事故树模型,对造成土石坝漫顶溃坝的多种主要因素进行识别和分析。根据故障树的最小割集、最小径集计算基本事件结构重要度,得出土石坝及其配套工程的合理设计是控制其溃坝的关键因素。     

土石坝加固前后应力变形特性分析

以某水库土石坝除险加固工程为实例,综合考虑了大坝渗流场和应力场的耦合效应以及混凝土防渗心墙与土体之间的接触效应,建立了土石坝防渗心墙除险加固前、后的弹塑性有限元模型,对土石坝加固前以及心墙加固后的应力、变形进行了计算,并进行了加固前后土石坝的应力变形对比分析以及加固后防渗心墙的应力变形特征分析,计算结果可为工程除险加固后的大坝安全监测与管理提供重要参考。     

浅析土石坝的快速施工

土石坝又称当地材料坝,具有对地形地质条件要求低,可以就地取材,筑坝经验比较丰富,运用安全等优点,在国内外得到了广泛的应用。近几十年来,随着新型土石方机械的大量投入和填筑施工工艺水平不断提高,同时筑坝材料试验研究的深入,极大的拓宽了土石坝的用料范围和用料模式,为土石坝更广泛的应用提供了有利条件,也改变了土石坝长期存在着建设工期长、填筑强度低等问题。在确保填筑施工质量及安全运行的前提下,本文就土石坝快速施工作以简要分析。     

土石坝稳定分析设计软件开发

论述了土石坝稳定分析设计软件开发的基本思路、土石坝稳定分析的关键技术及设计软件的基本组成。     

邓肯-张E-B模型的ANSYS二次开发及应用

随着土石坝坝体高度的增加,土石坝的应力和变形分析已成为大型土石坝设计中不可缺少的一部分,有限元法是进行应力和变形分析的一种有效方法.在土石坝有限元计算中,难点主要是ANSYS中并不包含土石坝材料的本构关系.利用ANSYS提供的APDL语言二次开发平台,开发出了在土石坝工程中应用广泛的邓肯-张E-B模型,并应用于安宁水电站沥青混凝土心墙堆石坝的应力与变形计算,结果较好地反映了土石坝的实际应力变形规律.     

土石坝渗流的流固耦合方法计算分析

采用有限元流固耦合方法对土石坝的非饱和渗流问题进行计算和分析,设定有限元模型的合理边界条件,计算了均质土石坝和非均质黏土心墙坝的渗流参数,得到了土石坝的渗透流量,绘制了孔隙水压力等值线图和浸润线。从计算结果可知,该方法对于黏土心墙坝适用性良好,计算结果准确。     

江口土坝坝体渗透系数测定的几种方法

土石坝安全评价及加固设计中，坝体土料的渗透系数Ｋ值是一个重要指标。本文介绍了江口土坝测定Ｋ值的几种方法：（１）原位渗透测试；（２）室内渗透试验；（３）原型观测资料反演等；可为土石坝除险加固提供较为可靠的设计依据。     

人工神经网络在堤坝安全评价中的应用

为了综合考虑安全评价中各因素的影响,采用人工神经网络BP网络模型,建立基于人工神经网络的堤坝安全评价方法.以黄河下游堤防工程为例,依据堤坝的设计和检测规范,建立了相应的安全评价指标,利用地质资料和观测资料对堤坝安全进行了分析与评价,验证了模型的可靠性.     

Study on real working performance and overload safety factor of high arch dam

Considering the fact that high arch dams have problems such as complicated stress, high cost, and hazards after being damaged, this paper intends to study the effects of load, material strength, and safety analysis method on dam safety and working performance of arch dams. In this article, the effects of temperature, self weight exaction way and water loading on structure response are first discussed, and a more reasonable way of considering is then put forward. By taking into consideration the mechanical property of materials and comparing the effects of different yield criteria on overloading safety of high arch dams, this paper concludes that brittle characteristics of concrete should be fully considered when conducting safety assessment for high arch dams to avoid overestimating the bearing capacity of the dams. By comparing several typical projects, this paper works out a safety assessment system of multiple safety and relevant engineering analogical analysis methods, which is closer to the actual situation, and thus is able to assess the response of high arch dam structure in a more comprehensive way, elicit the safety coefficients in different situations, and provide a new way of considering the safety assessment of high arch dams.

     

Study on real working performance and overload safety factor of high arch dam

Considering the fact that high arch dams have problems such as complicated stress, high cost, and hazards after being damaged, this paper intends to study the effects of load, material strength, and safety analysis method on dam safety and working performance of arch dams. In this article, the effects of temperature, self weight exaction way and water loading on structure response are first discussed, and a more reasonable way of considering is then put forward. By taking into consideration the mechanical property of materials and comparing the effects of different yield criteria on overloading safety of high arch dams, this paper concludes that brittle characteristics of concrete should be fully considered when conducting safety assessment for high arch dams to avoid overestimating the bearing capacity of the dams. By comparing several typical projects, this paper works out a safety assessment system of multiple safety and relevant engineering analogical analysis methods, which is closer to the actual situation, and thus is able to assess the response of high arch dam structure in a more comprehensive way, elicit the safety coefficients in different situations, and provide a new way of considering the safety assessment of high arch dams.     

上游溃坝洪水在某水库水文计算中的影响分析

当上游有水库,其防洪标准低于下游水库时,下游水库必须考虑上游水库溃坝洪水的影响.否则,会造成计算结果的差异.一旦出现溃坝,必将威胁下游水库的安全.综合国内外研究成果,以某中型水库大坝安全鉴定的水文计算为例,探讨上游溃坝洪水对下游水库调洪演算的影响,并给出上游存在多个这样的水库(防洪标准可不相同)时的处理方法,为类似工程提供参考.     

Numerical investigation of piled raft foundation in mitigating embankment vibrations induced by high-speed trains

A three-dimensional dynamic finite element model of track-ballast-embankment and piled raft foundation system is established. Dynamic response of a railway embankment to a high-speed train is simulated for two cases: soft ground improved by piled raft foundation, and untreated soft ground. The obtained results are compared both in time domain and frequency domain to evaluate the effectiveness of the ground improvement in mitigating the embankment vibrations induced by high-speed trains. The results show that ground improving methods can significantly reduce the embankment vibrations at all considered train speeds(36-432 km/h). The ground response to a moving load is dictated largely by the relationship between load speed and characteristic value of wave velocities of the ground medium. At low speeds, the ground response from a moving load is essentially quasi-static. That is, the displacements fields are essential the static fields under the load simply moving with it. For the soft ground, the displacement on the ballast surface is large at all observed train speeds. For the model case where the ground is improved by piled raft foundation, the peak displacement is reduced at all considered train speeds compared with the case without ground improvement. Based on the effect of energy-dissipating of ballast-embankment-ground system with damping, the train-induced vibration waves moving in ballast and embankment are trapped and dissipated, and thus the vibration amplitudes of dynamic displacement outside the embankment are significantly reduced. But for the vibration amplitude of dynamic velocity, the vibration waves in embankment are absorbed or reflected back, and the velocity amplitudes at the ballast and embankment surface are enhanced. For the change of the vibration character of embankment and ballast, the bearing capacity and dynamic character are improved. Therefore, both of the static and dynamic displacements are reduced by ground improvement; the dynamic velocity of ballast and embankment increases with the increase of train speed and its vibration noise is another issue of concern that should be carefully evaluated because it is associated with the running safety and comfort of high-speed trains.     

Settlement modeling in central core rockfill dams by new approaches

One of the most important reasons for the serious damage of embankment dams is their impermissible settlement.Therefore,it can be stated that the prediction of settlement of a dam is of paramount importance.This study aims to apply intelligent methods to predict settlement after constructing central core rockfill dams.Attempts were made in this research to prepare models for predicting settlement of these dams using the information of 35 different central core rockfill dams all over the world and Adaptive Neuro-Fuzzy Interface System(ANFIS) and Gene Expression Programming(GEP) methods.Parameters such as height of dam(H) and compressibility index(Ci) were considered as the input parameters.Finally,a form was designed using visual basic software for predicting dam settlement.With respect to the accuracy of the results obtained from the intelligent methods,they can be recommended for predicting settlement after constructing central core rockfill dams for the future plans.     

吹填土地基上加筋路堤稳定性的数值模拟

基于强度折减法,通过数值模拟对吹填土地基上加筋路堤的稳定性进行了分析,比较了不同设计方案路堤的位移及稳定安全系数,对路堤填土的黏聚力、内摩擦角、边坡坡比及土工格栅的拉伸刚度等影响路堤稳定性安全系数的因素进行了分析。结果表明：将边坡通过2次放坡可以减小路堤水平位移,路堤稳定安全系数略有增加,在路堤底部铺设土工格栅可以有效减小路堤水平位移,较大幅度提高路堤稳定安全系数。路堤填土的黏聚力不宜小于10 kPa,内摩擦角不宜小于25°,以保障路堤具有较高的稳定安全系数。土工格栅的刚度较小时对路堤稳定性有较大影响,当格栅刚度大于100 kN/m以后,通过提高格栅刚度并不能进一步提高路堤稳定性安全系数。     

Observed displacement data-based identification method of deformation time-varying effect of high concrete dams

The long-term safety of high concrete dams has become the focus and central issues of public attention. Deformation is an actual comprehensive reflection of concrete dams. Especially the deformation time-varying effect, is a key index for evaluating the structural behavior, health status, and their evolution of a concrete dam in long-term service. In this paper, causing factors of the deformation time-varying effect of concrete dams were analyzed, and the time-varying effect was divided into two parts, which are the inherent time-varying effect and the time-varying effect caused by the change of dam structural performance. Then, based on the observed dam displacement and the wavelet multi-resolution analysis, causal models for identifying the later deformation time-varying effect and the identification process were proposed. Finally, the efficiency and rationality of the proposed method were verified by two actual concrete dams with runoff reservoir and regulatory reservoir.     

碾压混凝土重力坝断面优化的探讨

采用非线性优化方法中的序列二次规划法 (SQP)优化碾压混凝土重力坝坝体体型 .此方法能考虑碾压混凝土重力坝材料分区问题 ,采用更多变量的组合 ,进行断面优化设计 .计算实例表明 ,在满足设计安全的前提下 ,能降低断面单宽造价 ,获得经济、实用的坝体体型     

一种气垫船远场波形理论计算方法

将Noblesse新细长船理论应用于气垫船，通过Lagrang多项式和第一类球Bessel函数展开波幅函数中的指数函数，改进了计算方法，通过引入基元波陡限制来综合考虑非线性等因素，目的在于探讨一种简便，快速而有效的气垫船兴波阻力和远场波形理论计算方法，以模型为例，针对不同的气垫压力面边缘压力分布形式计算了远场波形，采用Pentium/PC计算一条波一条波形仅需十几秒钟，理论结果与实验波形吻合较好，结果表明，本文提供的理论计算方法是正确可行的。