Sensitivity of interfacial hydraulics to the microtopographic roughness of water‐lain gravels          下载免费PDF全文

Stephen P. Rice  Thomas Buffin‐Bélanger  Ian Reid 《地球表面变化过程与地形》2014,39(2):184-199

Flow within the interfacial layer of gravel‐bed rivers is poorly understood, but this zone is important because the hydraulics here transport sediment, generate flow structures and interact with benthic organisms. We hypothesized that different gravel‐bed microtopographies generate measurable differences in hydraulic characteristics within the interfacial layer. This was tested using a high density of spatially and vertically distributed, velocity time series measured in the interfacial layers above three surfaces of contrasting microtopography. These surfaces had natural water‐worked textures, captured in the field using a casting procedure. Analysis was repeated for three discharges, with Reynolds numbers between 165000 and 287000, to evaluate whether discharge affected the impact of microtopography on interfacial flows. Relative submergence varied over a small range (3.5 to 8.1) characteristic of upland gravel‐bed rivers. Between‐surface differences in the median and variance of several time‐averaged and turbulent flow parameters were tested using non‐parametric statistics. Across all discharges, microtopographic differences did not affect spatially averaged (median) values of streamwise velocity, but were associated with significant differences in its spatial variance, and did affect spatially averaged (median) turbulent kinetic energy. Sweep and ejection events dominated the interfacial region above all surfaces at all flows, but there was a microtopographic effect, with Q2 and Q4 events less dominant and structures less persistent above the surface with the widest relief distribution, especially at the highest Reynolds number flow. Results are broadly consistent with earlier work, although this analysis is unique because of the focus on interfacial hydraulics, spatially averaged ‘patch scale’ metrics and a statistical approach to data analysis. An important implication is that observable differences in microtopography do not necessarily produce differences in interfacial hydraulics. An important observation is that appropriate roughness parameterizations for gravel‐bed rivers remain elusive, partly because the relative contributions to flow resistance of different aspects of bed microtopography are poorly constrained. © 2014 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd.  相似文献   

拉力分散型锚索锚固段荷载传递机制     

丁瑜  王全才  何思明 《岩土力学》2010,31(2):599-603

预应力锚索是岩土锚固最常用的结构形式之一,使用的锚索类型越来越多。锚索锚固段的荷载传递是控制锚索性能和工程设计的关键,应用剪滞理论分析了锚固段的受力和荷载传递机制,并对拉力分散型锚索的锚固机制进行探讨。分析结果表明,拉力分散型锚索锚固段剪应力在软化段逐渐增加至峰值剪应力,随后减小,其分布模式与现场试验结果比较一致。  相似文献   

自由段先注浆对预应力锚索抗拔试验结果影响研究     

杨庆光  柳雄  刘杰  何杰  梁凌川  陈斌 《岩土力学》2020,41(10):3317-3325

为了解决无法采用已注浆锚索进行抗拔试验问题,基于界面脱黏剪切模型,利用荷载传递和弹性变形理论,考虑锚索锚固段与自由段长度比Lb /La的影响,建立了采用自由段已注浆锚索抗拔试验结果评价锚索抗拔性能的方法。结果表明：自由段注浆对锚索抗拔力有较大幅度的提高,尤其是当界面剪切阶段由弹性向脱黏过渡时,提高比例快速增加,并在脱黏后逐渐趋于稳定。其次,锚索自由段与锚固段交界面处剪切位移和轴力最大,并向两端逐渐降低。随着拉拔力的提高,界面剪切位移和轴力都不断增大,同时向锚索两端的衰减速度也加快。此外,弹性阶段时剪应力曲线为山峰型,而脱黏阶段为马鞍型,并随抗拔力的提高,马鞍开口逐渐扩大。最后,锚固段与自由段长度比Lb /La对锚索极限抗拔力的影响较小,其极限抗拔力折减系数?Q取值介于0.81～0.83之间,且Lb /La =2.5时,?Q计算值仅比实测结果小6.02%,验证了本文方法的可行性。  相似文献   

用面角公式标定锆石晶面符号初探     

崔海 《吉林地质》1991,10(4):55-61

锆石晶体测量后,用面角公式计算相邻两晶面面角值来标定晶面符号是一个探索性的方法。锆石晶面符号这一测定方法的论证,也为不同成因的同种矿物对应面夹角的对比,提出了新的研究课题。  相似文献   

STUDY ON THE ISOTHERMS OF THE INTERACTION BETWEEN SUSPENDED PARTICLES AND Cu (Ⅱ) IN THE HUANGHE RIVER   总被引：1，自引：0，他引：1  

李改枝  郭博书  刘颖  红霞  李景峰  李北罡 《中国海洋湖沼学报》2000,18(2)

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｖａｒｉｏｕｓｐｈｙｓｉｃａｌａｎｄｃｈｅｍｉｃａｌｒｅａｃｔｉｏｎｓｔｈａｔｏｃｃｕｒｂｅｔｗｅｅｎｔｈｅｓｕｓｐｅｎｄｅｄｐａｒｔｉｃｌｅｓ,ｓｅｄｉｍｅｎｔｓ,ｅｔｃ.ａｎｄｈｅａｖｙｍｅｔａｌｓｉｎａｎａｔｕｒａｌａｑｕａｔｉｃｓｙｓｔｅｍｐｌａｙｅｘｔｒｅｍｅｌｙｉｍｐｏｒｔａｎｔｐａｒｔｓｉｎｃｏｎｔｒｏｌｌｉｎｇｔｈｅｄｉｓｔｒｉｂｕｔｉｏｎｐａｔｔｅｒｎ,ｍｉｇｒａｔｉｏｎａｎｄｔｒａｎｓｆｏｒｍａｔｉｏｎｏｆｈｅａｖｙｍｅｔａｌｓｔｈｅｒｅ.Ｓｉｎｃｅ…  相似文献   

Revisiting the constitutive equations of unsaturated porous solids using a Lagrangian saturation concept     

O. Coussy 《国际地质力学数值与分析法杂志》2007,31(15):1675-1694

This paper aims at revisiting the constitutive equations of unsaturated porous solids at the light of a Lagrangian saturation concept. By referring the currently wetted porous volume to the reference configuration, the Lagrangian saturation is the state variable associated with the interfacial energy changes only, irrespective of the elastic energy required for deforming the solid matrix. The Lagrangian saturation concept provides the basis of a generic approach to the theory of poroelastoplasticity in unsaturated conditions. We successively examine the case where the saturating fluids occupy disconnected networks and the case where the networks are connected so that the saturating fluids can invade the porous solid or recede from it. The analysis provides the restricted situations where the averaged pore pressure may play the role of an effective pore pressure. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Influence of the earth rotation on the interfacial wave solutions and wave-induced tangential stress in a two-layer fluid system     

SONG Jinbao  LIU Yongjun 《海洋学报(英文版)》2009,28(2):115-120

Interfacial waves and wave-induced tangential stress are studied for geostrophic small amplitude waves of two-layer .uid with a top free surface and a .at bottom. The solutions were deduced from the general form of linear .uid dynamic equations of two-layer .uid under the f -plane approximation, and wave-induced tangential stress were estimated based on the solutions obtained. As expected, the solutions derived from the present work include as special cases those obtained by Sun et al. (2004. Science in China, Ser. D, 47(12): 1147–1154) for geostrophic small amplitude surface wave solutions and wave-induced tangential stress if the density of the upper layer is much smaller than that of the lower layer. The results show that the interface and the surface will oscillate synchronously, and the in.uence of the earth’s rotation both on the surface wave solutions and the interfacial wave solutions should be considered.  相似文献   

埕北油田弱碱三元复合驱可行性实验研究     

刘义刚  ;卢祥国  ;张运来  ;王晓燕 《海洋地质译丛》2009,(3):31-36

埕北油田具有原油黏度高、油层渗透能力强和非均质性严重等特点，水驱开发效果差，剩余油储量大，而生产平台工作时间已达到设计使用寿命，急需高效、快速的提高采收率技术。针对埕北油藏地质、流体性质和开发现状，利用仪器检测和理论分析方法，开展了聚合物溶液、三元复合体系和改性三元复合体系性质和调驱效果实验研究。结果表明，与三元复合体系相比较，添加入Cr^3＋后得到的改性三元复合体系在黏度和界面张力性质方面几乎没有发生变化，但其阻力系数和残余阻力系数有了较大幅度提高。在化学费用相近条件下，“调剖＋三元复合驱”和改性三元复合驱要比三元复合驱增油效果好，采收率增幅可以达到15％以上。推荐埕北油田采用弱碱三元复合驱，三元复合体系配方组成为“大庆超高”聚合物（CP=1600～1800mg／L）＋弱碱Na2CO3（CA=0．6％～1．0％）＋重烷基苯石油磺酸盐（Cs=0．10％～0．15％）＋有机铬（聚：Cr^3＋=120：1～240：1）”，段塞组合方式为“0．025～0．05 PV Cr^3＋聚合物凝胶＋0．12～0．15PV三元复合体系”。  相似文献   

Existence and uniqueness of Stoneley waves     

P. Chadwick  P. Borejko 《Geophysical Journal International》1994,118(2):279-284

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Elastic-wave scattering and Stoneley wave localization by anisotropic imperfect interfaces between solids     

W. Huang  S. I. Rokhlin 《Geophysical Journal International》1994,118(2):285-304

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