拱坝坝肩稳定地质力学模型试验及孔口概化影响分析

在拱坝坝肩稳定地质力学模型试验中,坝身的泄洪孔口经缩尺后尺寸偏小,模拟困难,通常需概化模拟,以方便模型的加工制作和加载,但孔口概化对试验结果的影响需深入研究。为此,以立洲拱坝工程为例,分别开展了孔口概化后的坝肩稳定地质力学模型试验、坝身开孔与不开孔的两个三维有限元模型模拟分析,并对比分析三种方案所获得的应力分布特征、位移分布规律、塑性区分布范围和稳定安全度,探讨了孔口概化对地质力学模型试验结果的影响。结果表明,有限元开孔方案与不开孔方案坝体应力相差不超过10%,坝体位移相差不超过12%,塑性区发展过程基本一致,开孔方案的起裂、塑性区贯通和失稳略早于不开孔方案;有限元不开孔方案极限超载安全系数较地质力学模型试验方案大0.65%,有限元不开孔方案极限超载安全系数较开孔方案小15.48%。原因系拱坝坝身开孔导致拱效应降低,梁效应增强,但对坝体的位移、应力、塑性区分布影响较小。因此在研究拱坝坝肩稳定性的地质力学模型试验中,其采取的坝身孔口概化模拟方法对试验结果影响不大。     

复杂地质条件下拱坝坝肩滑动块体稳定性地质力学模型试验

拱坝坝肩岩体在断层、裂隙、层间剪切带等地质缺陷的作用下形成了不同规模的滑动块体,从而削弱了坝肩岩体的完整性,降低了坝肩岩体的承载能力,影响坝肩的稳定安全。为了分析坝肩滑动块体稳定性,以立洲拱坝工程为例,采用地质力学模型试验,分析两坝肩的地质构造及主要软弱结构面的产状发现,两坝肩存在四种潜在的滑动块体。在此基础上,通过地质力学模型超载法对坝肩岩体进行破坏试验,得到了滑动块体的失稳破坏机理、破坏形态及影响滑动块体稳定的控制因素,为解决类似工程问题提供了参考。     

高拱坝坝肩稳定综合法破坏试验加载方式研究

地质力学模型综合法试验为工程的整体稳定安全问题提供了研究方法,但其加载方式能否反映工程实际及不同加载方式对综合法试验结果所产生的影响仍需开展深入研究。采用ANSYS有限元分析软件,选取典型高拱坝工程沙牌拱坝建立三维有限元模型,计算分析四种不同的加载组合方案,并结合沙牌高拱坝工程的综合法破坏试验加以验证。结果表明,四种加载组合方案中,岩体降强前的超载荷载倍数KP1取1.0或1.2时,坝体变位符合一般工程规律,且得出的综合稳定安全度均较其他方案小,从工程安全角度考虑,这两种加载方式均较合理。鉴于大部分高拱坝工程在蓄水运行后,由于水文预报、水库调度和工程措施等较为完善,出现超标洪水的概率不大,因此目前所采用的综合法破坏试验加载方式是合理的。     

坝肩混凝土置换洞塞的传力规律及加固效果分析

为真实地模拟拱坝拱端、置换洞、断层和蚀变带之间的相互作用,通过建立地质力学平面模型模拟某高拱坝工程的典型高程断面,采用超载法研究坝肩经混凝土置换洞塞加固处理后的破坏规律和破坏形态,同时建立了未加固方案和加固方案的有限元模型,对模型试验进行补充和对比分析。结果表明,左、右坝肩经加固处理后,坝肩拱推力向山体深部坚硬岩体传递,大坝的超载能力明显提高,坝肩的抗滑稳定性和变形稳定性增强,说明左、右坝肩采用混凝土置换洞塞的加固措施切实可行,研究成果可供类似工程参考。     

基于矢量和安全系数法的乌东德拱坝坝肩稳定性分析与评价

针对影响拱坝坝肩稳定性因素诸多问题，以乌东德高拱坝为例，采用非线性有限元数值分析法与矢量和安全系数法，分析了影响拱坝坝肩稳定的因素。计算结果表明，不同工况和影响因素下，坝肩岩体具有较高的矢量和安全系数；相对于比较方案，可研方案建基面的选择更合理；当裂隙连通率达到30%以上时，坝肩岩体不满足稳定性要求，需进行加固处理；拱端与上、下游基岩采用摩擦连接对拱端的受力更有利。     

某水电站顺层岩质高边坡稳定性地质力学模型试验研究

针对顺层岩质高边坡稳定性问题,提出了基于变温相似材料的降强法与倾斜抬升超载法相结合的综合法模型试验方法,推导了边坡稳定的地质力学模型综合法安全系数表达式,并将其应用到某典型顺层岩质边坡工程实例中,对其地质缺陷较集中的I5剖面开展综合法模型试验,获得了边坡的变形特征和破坏过程,揭示了边坡破坏模式为滑移-拉裂破坏,确定了边坡整体稳定综合法安全系数为KSC=1.526~1.575。     

新疆大山口拱坝坝肩预应力锚固技术应用研究

以新疆大山口电站拱坝为实例，在分析拱坝坝肩边界条件、荷载的基础上提出了坝肩综合加固处理方案，指出锚固设计、参数确定方法、施工工艺对锚固效果的影响，并通过坝肩加固后大坝监测系统的资料分析对坝肩工作状态及加固效果进行了评价。     

水下爆炸冲击下重力拱坝的破坏特性

为了了解重力拱坝在水下爆炸冲击荷载下的破坏模式,通过建立混凝土重力拱坝水下爆炸全耦合模型,考虑混凝土高应变率效应,对水下爆炸冲击下重力拱坝动态破坏过程进行了全性能数值仿真,针对重力拱坝的结构特性及受力特点,探讨了大坝在水下爆炸冲击荷载作用下的可能破坏模式及破坏机理。结果表明,重力拱坝抗爆薄弱部位主要位于坝体中上部,坝身下部抗爆性能较强;当炸药在拱冠梁处起爆时,表孔中墩及边墩发生冲切和震塌滑移破坏;当炸药在距右岸1/4拱圈处爆炸时,坝肩发生震塌破坏,影响坝肩抗滑稳定及坝体整体安全性。     

基于ABAQUS的拱坝坝肩稳定分析

基于有限元分析软件ABAQUS,结合梅峰双曲拱坝建立三维有限元拱坝模型,研究了拱坝的失稳模式、渐进破坏发展过程及坝肩稳定安全系数,验证了由刚体极限平衡法得到的安全系数与强度折减法得到的折减系数在物理意义上具有一致性,且在允许误差内,数值具有近似性.     

高拱坝坝肩开挖集中堆渣对河道截流的影响分析

分析了高拱坝坝肩开挖施工过程中产生的集中堆渣对河道截流的有利影响,提出了坝肩附近集中堆渣能降低截流戗堤龙口水力参数需具备的水力控制条件.以锦屏一级水电站为例,从截流模型试验和水力控制条件计算两方面给予验证,提出对截流难度较大的工程可利用坝肩集中堆渣的方法降低截流难度,建议综合考虑坝肩开挖、截流、坝基开挖、上下游围堰填筑、洪水期河道过渣能力等因素对堆渣位置和形状及数量进行合理规划的原则.     

小型锅炉烟尘测试时锅炉出力的计算

锅炉烟尘测试时,必须对锅炉出力进行测试。但监测中,许多小型锅炉往往不具备相关的计量装置和仪表,为解决这一问题,文章提出了用烟气量和空气过剩系数来计算锅炉的出力的公式,在实际使用中,该方法简单易行,其结果和实测值具有很好的一致怀。     

Unerroric of control of mutual compliance of the efficiency of hydrogen engines of unmanned vehicles in the conditions of mass production

The issues related to the reliability of hydrogen engines of unmanned vehicles and increasing the efficiency of using hydrogen as fuel when using the method of its production during the decomposition of hydrogen-containing molecules of liquid-phase organic compounds in a plasma discharge under the action of intense ultrasonic exposure are considered. Experiments have shown that as a result of decomposition in the acoustoplasma discharge of liquid hydrocarbons, solid-phase carbon-containing products are formed, chemical transformations occur in the liquid phase and hydrogen-containing combustible gas is formed. Hydrogen-containing gas can be used as fuel immediately after synthesis, i.e. it does not require separation, since in addition to hydrogen it contains only impurities of CO₂ and water vapor. The purpose of the study is to formalize the basic conditions for tightening the control of mutual compliance with the efficiency of hydrogen engines of the same series in the conditions of their mass production. Methods of mathematical statistics and hardware-software modeling were used in the study. The term “unerroric of quality mutual compliance control” is introduced to describe a set of hardware and software tools for such control. The principle of in-depth testing of the technical condition of such engines of one series is described in a multidimensional formulation of the quality control problem for three of their operating parameters at once. The conditions for increasing the mutual correspondence of the measured values of such parameters in the conditions of serial production of hydrogen engines are formalized.     

中国煤炭地下气化技术的发展

本文综述了煤炭地下汽化技术的国内外发展现状,对我国“长通道、大断面”煤炭地下气化新工艺给予了技术经济评述,并提出了发展煤炭地下汽化技术的政策建议。     

Review of theory of distortion and disintegration of liquid streams

Linear and nonlinear analyses of the instabilities and distortion of liquid streams injected into a gaseous media are discussed. The various fundamental mechanisms and the predictive capabilities for the distortions are emphasized. Round jets, planar sheets, annular sheets, and conical sheets are discussed in detail. The balance between capillary and inertial forces is primarily examined. The method for simplifying the analyses in the case of thin liquid sheets is discussed. The capabilities for representing the droplet size distribution that follows the stream disintegration are outlined.     

MgO膨胀剂细度对MgO水化和水泥浆体膨胀的影响

基于《水工混凝土掺用氧化镁技术规范》中的Ⅰ型氧化镁（MgO）,研究了该型MgO膨胀剂（MEA）细度对掺粉煤灰水泥浆体膨胀性能的影响。即采用X射线衍射分析(XRD)及同步热分析（TG DSC）分析了掺MEA水泥浆体中MgO的水化性。结果表明,养护温度相同时,MEA的细度对水泥浆体内MEA中MgO的水化和水泥浆体的膨胀无显著影响,产生的膨胀均能补偿水泥浆体的收缩;MEA的细度可从试验设计采用的45 μm筛筛余15%左右增加到30%左右,这将有利于MEA生产企业的节能降耗。     

机车车轮多轴疲劳强度安全评定的研究

使用ANSYS8.0软件对高速列车车轮进行了三维有限元分析,计算出车轮在直线、曲线和道岔条件下牵引、制动共6种工况时孔边薄弱部位的应力,分别通过Mises等效平均应力方法、Sines平均主应力方法和应力分量中考虑平均应力方法计算出应力在极值位置时的等效应力幅、等效平均应力,从而进一步算出车轮的安全系数,对其疲劳强度进行评定,并对3种方法进行了比较研究。     

Constructal optimization of the geometry of an array of micro-channels

This paper documents the geometric optimization of an array of circular and non-circular ducts. The optimization was carried out numerically using finite volume method. As optimal dimensions were independent of the array configuration, the numerical simulation was performed on a unit cell. Numerical optimization for circular, square and isosceles right triangle cross-sections of channels was performed. Based on the results of this investigation, some correlations were proposed to predict the optimal hydraulic diameter and dimensionless heat transfer per unit volume. In addition to examining the effect of pressure drop on these parameters, it was showed that among the different geometries of this study, square cross-section has the most efficiency for a given volume. The numerical results of the present study were compared with approximate results reported in the literature which a good agreement was observed.     

固体热辐射Yong性能分析

本文对漫灰均温物体在常物性条件下对外辐射传热的Ｙｏｎｇ值计算建立了数学模型。通过与物体内能Ｙｏｎｇ公式的数值计算比较,得出了辐射能量的Ｙｏｎｇ值不大于内能Ｙｏｎｇ值的结论。从初步的热射Ｙｏｎｇ值计算公式发现。Ｙｏｎｇ与物体表面辐射率有关。     

Measurements of concentration distribution of hydrogen jet using deflection of center of the laser spot

The main purpose of this work is to propose a new method to evaluate the concentration distribution of the hydrogen jet by using a He–Ne laser through the jet. This research attempts to apply the expression of concentration Gaussian distribution, the refraction formula of inhomogeneous refractive index medium, and the concentration inversion function to disclose the displacement of the center of the laser spot at different heights in the gas jet. The spot images of the laser beam passing through the gas jet at three vertical heights z = 10d, 20d, 30d, and different radial positions are obtained. The radial spatial asymmetry of the gas jet is also found in the experiment. Finally, the calculated concentration distribution curve and the fluent simulation curve, it is found that the two results are very similar. Our findings show that the error between the concentration distribution of this method and the simulated concentration distribution reaches 2.43%.     

Heat of vaporization of mixtures

General expressions for the heat of vaporization of mixtures at constant pressure; at constant temperature; and at constant pressure, temperature, and composition are proposed. The last one is related to the liquid-vapor interface where steady vaporization or condensation is taking place. Numerical examples by the proposed expressions are shown for binary mixtures of HCFC22(R22) and (HCFC123(R123) © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(1): 12–24, 1996