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根据前人的理论和研究成果,通过分析水平管道中推移质与悬移质组成的几何关系,对于水平管道中推移质与悬移质的之间比例与平均流速之间的关系进行了深入研究,得出推移质、悬移质与平均流速之间的关系式,确定了管道输送中的重要系数K4,对以后研究管道内流速分布以及确定临界速度奠定了基础。 相似文献
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基于双面弹性地基梁理论、修正纵向等效连续化模型以及浆液环向充填理论,在考虑上浮力时变性的基础上,进一步综合考虑了盾构施工步叠加效应、浆液压力分布和盾构台车的影响,构建了管片上浮预测模型,讨论了现有研究中浆液未凝固区域等效地层抗力系数的两种计算方式对预测结果的影响。结果表明,提出的双面弹性地基梁修正计算方法能够较好体现周围土层对管片的抗浮作用;浆液未凝固区域的等效地层抗力系数采用盾尾区域和浆液凝固区域的等效地层抗力系数取平均值的方法,计算结果和实测结果更为接近。 相似文献
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盾构隧道衬砌内力计算的方法有多种,但各有优缺点。针对潮河输水管道盾构法隧道衬砌结构,分别采用荷载结构法中考虑土体侧向弹性抗力的匀质圆环修正惯用法和连续介质有限元法进行内力计算。通过比较衬砌管片结构内力和变形分布规律,得到了对设计有参考价值的结论。 相似文献
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长空间声学理论及其在地铁车站设计中的应用 总被引:1,自引:0,他引:1
声学问题在长空间中普遍存在,例如地铁车站中广播系统的语言清晰度问题,鉴于经典声学理论在长空间中的不适用性。本文发展了一套长空间声学理论,包括混响时间,声压级分布及语言传输指数的计算方法等。基于理论计算和缩尺模型实验结果,给出了一系列声学设计准则。另外,本文还给出了一个预测长空间声学指标的计算机模型。 相似文献
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超大断面黄土公路隧道围岩压力计算方法分析 总被引:1,自引:0,他引:1
文章基于唐家塬超大断面黄土隧道工程实例,采用常用的五种围岩压力计算方法分别计算了围岩压力,并与实测值进行了对比分析,得出了现场实测垂直压力与太沙基理论计算结果基本吻合的结论。在此基础上提出了太沙基理论侧压力系数修正方法,并推荐采用修正后的太沙基理论作为唐家塬隧道的围岩压力计算方法。针对现有隧道深、浅埋界定标准的问题,提出了以中心线土体侧压力系数变化规律为依据的深、浅埋界定数值模拟方法。由此认为,唐家塬隧道为浅埋隧道,隧道深浅埋界限为90 m。 相似文献
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文章首先对管片上浮作用机理进行了分析,确定了盾构隧道施工阶段上浮计算模型荷载分布规律和计算方法;其次指出了弹性支撑法和修正惯用法直接运用于盾构隧道上浮阶段设计所存在的问题,即弹性支撑法计算得到管片底部向下位移,与实际上浮阶段管片隆起不符,而修正惯用法又不能考虑拱顶上覆土体反向压缩特性;最后,基于弹性支撑法并利用修正惯用法思想提出了能规避上述两个问题的反转抗力力学模型。结果表明:提出的计算模型与施工阶段管片上浮变形特征吻合度高,施工阶段管片上浮状态下弯矩、轴力和剪力最值较弹性支撑法和修正惯用法获得的结果分别增加68%、21%和51%以及34%、69%和22%,说明按本文推荐计算模型进行上浮管片设计可避免实际工程配筋不足造成的管片破损、开裂或渗漏。其结论可为盾构隧道设计提供一定理论支撑和参考。 相似文献
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Runoff and water erosion on road side-slopes: Effects of rainfall characteristics and slope length 总被引:2,自引:0,他引:2
Xian-Li Xu Wen Liu Ya-Ping Kong Ke-Li Zhang Bofu Yu Ji-Ding Chen 《Transportation Research Part D: Transport and Environment》2009,14(7):497-501
To investigate the effects of rainfall and slope length on water erosion on road side-slopes, runoff and soil loss are measured from natural runoff plots along the Qinghai-Tibet highway near Tuotuo River. Rainfall erosivity used in the revised universal soil loss equation is a good predictor for runoff and soil loss from road side-slopes. Runoff depth, sediment concentration and soil loss decreases as slope length increases. 相似文献
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Mohamed F. Yassin Masaake Ohba 《Transportation Research Part D: Transport and Environment》2012,17(2):161-168
Vehicle emissions inside an urban environment are investigated using a wind-tunnel under neutral atmospheric conditions. The urban environment was formed as street canyon model. The diffusion flow field in the boundary layer inside the street canyon was examined at different locations of varying geometry of the street and wind directions in the downwind distance of the leeward side of the street canyon model. The results show that the vertical velocity increases as the aspect ratio increases and with wind direction increases from θ = 90°. The pollutant concentration increases as the aspect ratio decreases. The pollutant concentration decreases as the wind direction increases from θ = 90°. The pollutant concentration distributions indicate that the variability of the structure, geometry and wind direction inside the street canyon are important parameters for estimating air quality in the urban street canyon. 相似文献
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在借鉴已有成果,特别是许振良教授提出的水平管道固体粒子处于滑、跳移时的速度分布模型理论的基础上,结合底层固体颗粒的起动条件,运用数值逼近方法确定堆积速度的计算公式。最后用相关数据对这些公式进行检验,计算结果与实际测量结果较为符合。 相似文献
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在设备运行中发现HFETR二次冷却水超声波流量计测量值比文丘里式流量计偏低。为了满足冗余性、多样性的设计原则,对HFETR二次冷却水设计了两套不同原理的流量测量装置。从超声波流量计的原理分析出由于HFETR二次水含沙量高,造成声波传播速度比理想情况下水中的传播速度高,使超声波流量计测量的流量偏低。通过引入修正因子可以消除偏差。 相似文献
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Edward N. Holland Andrew W. Woods 《Transportation Research Part B: Methodological》1997,31(6):473-485
A continuum model for two-lane traffic flow is developed using the theory of kinematic waves in which the wavespeeds in the two lanes are assumed constant but unequal. The transient behaviour is found exactly using Riemann's method of characteristics and an asymptotic model of the long time flow is described. It is shown, that for large times, the traffic concentration moves with a weighted mean wavespeed of the two lanes and disperses about this mean speed as a result of interlane concentration differences generated by the relative wavespeeds. The dispersion can be described by a virtual coefficient of diffusion proportional to the square of the differences of the two wavespeeds and inversely proportional to the rate of lane changing. The technique is extended to describe three-lane traffic flow and to include the dependence of wavespeed upon concentration. 相似文献
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《Transportation Research Part D: Transport and Environment》1999,4(1):65-70
The applicability of General Finite Line Source Model (GFLSM), based on the Gaussian diffusion equation, was assessed by comparing predicted CO concentrations with the measured values obtained from the experiments conducted by Central Pollution Control Board (CPCB), New Delhi, India at three traffic intersections in the Delhi city. Using the CPCB data, a Delhi Finite Line Source Model (DFLSM) has been developed by modifying the GFLSM, considering the existing traffic and meteorological conditions in the Delhi city. The predicted and observed CO concentration data reveals that the DFLSM model works more accurately for the existing traffic and meteorological conditions in the Delhi city in comparison to the GFLSM. 相似文献
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子午线轮胎有着节能、耐用的优点。使用Abaqus有限元软件建立三维有限元轮胎模型并通过将有限元模拟计算结果和实际实验数据对比,验证了模型的正确性。在此基础上,探究了加强层帘线角对胎圈部位应力影响,结果表明:在充气和垂直载荷下,随着帘线角的增加,胎体与加强层端点最大应力、应变能均出现先增后减的趋势。垂直载荷下胎圈部位的刚度随着帘线角增加而一直减小。拟合出了出垂直载荷最大应力、应变能和加强层端点下沉量随帘线角变化的函数。计算得到40.7°的帘线角能够大幅降低加强层端点处的应力、应变能,同时对该处的刚度影响较小。研究结果可为选用适合的加强层帘线角以保证节能和负载的同时减少早期破坏提供理论依据。 相似文献