循环往复水流对反滤系统的作用机理研究   总被引：1，自引：1，他引：0  

庄艳峰  陈轮  许齐  王钊 《岩土力学》2008,29(7):1773-1777

通过自行研制的循环往复水流试验装置,研究了不同频率的正弦循环水流对反滤系统的作用机制,建立了与试验模型相一致的定解条件,并求得孔压微分方程的解析解。理论分析表明,土的固结系数与循环往复水流的频率的比值越小,靠近边界处土体的水力梯度就越大,土体内部的水力梯度就越小。试验中,当周期为0.5 min时,边界处水力梯度振幅接近系统平均水力梯度振幅的2倍;当周期为62.5 min时,则基本没有边界水力梯度集中现象。实测结果与理论分析结果较为一致。这种水力梯度边界集中现象,容易加剧渗透边界层的冲刷,降低反滤系统的渗透稳定性,应当在试验研究和工程实践中引起注意。  相似文献   

Removal of Elongated Particle Aggregates on Fibrous Filters     

Lucija Boskovic  Igor S. Altman  Roger D. Braddock  Igor E. Agranovski 《洁净——土壤、空气、水》2009,37(11):843-849

Elongated aerosol particle removal on fibrous filters has been investigated. It was shown that particle agglomerates are removed much more efficiently compared to the regularly shaped single particles with identical electrical mobility diameter at two filtration velocities tested. The experimental results were compared with the classical filtration theory and it was shown that the theoretical predictions, which are based on the assumption that the particles are spherical, are significantly different compared to an agglomerate filtration efficiency value. In order to account for a particle shape non-regularity, dominating nanoparticle removal mechanisms were firstly evaluated for a regular particle of certain size and then adjusted by fitting coefficients k₁ (for diffusion component) and k₂ (for interception). These coefficients were determined by fitting the theoretical values that gives the best coincidence with the measured data points. As was further demonstrated theoretically, the coefficient k₁ is identical to the ratio of the actual particle surface area to the surface area of the spherical particle of the equivalent diameter. On the other hand, the coefficient k₂ was found to be equal to the ratio of the projection of a given particle on a plane perpendicular to a streamline, to that of the spherical particle of the equivalent diameter. The reported findings would allow undertaking more accurate evaluation of the removal efficiency of non-regular aerosol particle, which is especially important for industrial applications where non-regular aerosols are frequently met.  相似文献   

筑堤土防渗性状试验研究   总被引：2，自引：1，他引：1  

钱玉林 《岩土力学》2004,25(5):824-826

结合淮河入海水道河道工程,通过渗透变形试验确定了筑堤土料的渗透变形型式、临界水力坡降和允许坡降,同时指出了采用泓道开挖土筑堤的施工控制措施、质量要求和防渗措施。  相似文献   

多尺度分割在中低分辨率遥感影像解译中的灵活应用     

崔会娟  马旭燕  张富玲 《测绘与空间地理信息》2016,(9)

介绍了一种将像素级的分类与对象级分类相结合的遥感影像分类方法。该方法将面向对象的概念引入影像分类中。但与纯粹的基于对象的分类有所不同,这种分类方法仍然是以像素级分类为基础。这种分类方法既继承了像素级分类精细、准确的优势,又通过分割对象,增加了分类图斑的同质性,极大地改善了信噪比,使分类结果更清楚。  相似文献   

Nitrate transport in the unsaturated zone: a case study of the riverbank filtration system Karany,Czech Republic     

Frantisek Buzek  Renata Kadlecova  Ivana Jackova  Zdena Lnenickova 《水文研究》2012,26(5):640-651

Nitrate transport in the unsaturated zone of a riverbank filtration (RBF) system in Karany, Czech Republic, was studied. Previous study of the system estimated RBF recharge as 60% riverbank filtrate and 40% local groundwater contaminated by nitrates. Nitrate concentrations observed in RBF recently cannot be explained by simple groundwater contamination and a new conception of groundwater recharge is suggested. A two‐component model based on water ¹⁸O data modelled recharge of local groundwater. One component of groundwater recharge is rainfall and irrigation water moving through the unsaturated zone of the Quaternary sediments in piston flow. The second component is groundwater from the Cretaceous deposits with a free water table. Both the components of groundwater recharge have different nitrate concentrations, and resulting contamination of groundwater depends on the participation of water from Quaternary and Cretaceous deposits. Nitrates' origins and their mixing in the subsurface were traced by ¹⁵N data. Nitrate transport from the unsaturated zone is important and time variable source of groundwater contamination. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Evaluation of high-flow rate continuous-flow centrifugation and filtration devices for sampling and concentrating fine-grained suspended sediment     

Masoud Goharrokhi  David A. Lobb  Philip N. Owens 《水文研究》2020,34(19):3882-3893

  相似文献   

Research and application of mud proportioning optimization of slurry balance shield in mudstone and gravel composite stratum     

SONG Yang  LI Ang  WANG Wei-yi  DU Chun-sheng  ZHANG Duo  FU Xing-xing 《岩土力学》2021,41(12):4054-4062

Slurry performance is one of the key factors to maintain the stability of excavation face when slurry balance shield is tunneling in complex strata. Based on the engineering background of slurry shield tunneling in mudstone and gravel composite stratum of Nanning Metro Line 5, the control variable method and the self-made slurry shield tunneling system are adopted to compare and select the mud admixture and to analyze the influence of the admixture amount and the formation composite ratio on the slurry relative density. Then, the mud permeability law and the dynamic and static mud film forming law under different formation composite ratios, swelling water ratios and slag dosages are analyzed comprehensively by factorial design. The results show that different admixtures have significant influence on the properties of bentonite slurry. Specifically, potassium methyl silicate and potassium chloride can effectively reduce the relative density of slurry, while sodium chloride and sodium silicate can promote the disintegration of mudstone in water. In addition, the slag admixture can effectively reduce the water filtration, improving the film quality and reducing the consumption of bentonite. When the cutter head speed is less than or equal to 2.5 r/min, the formation rate of mud film is greater than or equal to the failure rate so as to ensure the stability of driving face. The mud swelling water ratio suitable for mudstone and gravel composite stratum (composite ratio: 0?1) is 0.1?0.20, the residue content is 100?200 g/kg, and the potassium methyl silicate is 3.75%?7.50%.  相似文献   

水温、盐度和饵料密度对橄榄蚶滤水率的影响   总被引：1，自引：0，他引：1  

张媛  方建光  毛玉泽  梁峻  赵学伟 《海洋科学》2015,39(9):39-43

用实验生态学的方法研究了不同水温(15、20、25、30℃)、盐度(16、21、26、31、36)和饵料密度(0.5×104、1.5×104、2.5×104、3.5×104、5×104个/m L)对橄榄蚶(Estellarca olivacea)滤水率的影响。实验结果表明,以金藻作为饵料,水温、盐度、饵料密度对橄榄蚶的滤水率有显著影响(P0.05)。水温15~30℃、盐度16~36、饵料密度为0.5~5×104个/m L时,橄榄蚶的滤水率都呈峰值变化。水温25℃、盐度26、饵料密度3.5×104个/m L时,其滤水率分别达到最大值。在所研究的范围内,水温、盐度、饵料密度与滤水率之间分别满足函数关系:FRT=–0.3396T2+1.8937T+0.2728(R2=0.9857,P0.05);FRS=–0.3424S2+1.9626S+0.7112(R2=0.9683,P0.05);FRC=1.7395 C 0.4607,(R2=0.9062,P0.05)。  相似文献   

The progression of flow rates in variable declining rate filter systems     

Wojciech Dabrowski 《洁净——土壤、空气、水》2006,34(5):442-452

It has been demonstrated that the mathematical model of variable declining rate filters developed by Di Bernardo may be described by (z + 1) non‐linear equations, where z is the number of filters in a bank. Three approximate solutions to this system of equations have been developed and then verified by comparison with numerical solution and published experimental data. Two of these solutions appeared to be very accurate, while the third showed higher, but still acceptable errors of calculation. According to this approximation, flow rates through filters are elements of a geometric progression.  相似文献   

基于离散点绘制等高线算法的研究     

吕建升  须鼎兴 《现代测绘》2006,29(5):5-7

等高线图在实际工作中应用非常广泛，在离散点数据的基础上自动生成等高线图有许多算法。本文着重讨论了如何在采集离散点时加入编码的基础上，尽量减少或不进行人工干预，基于有约束的TIN构建方法一次性生成等高线图。实践表明该方法能够明显加快成图速度与提高等高线成图的精度。  相似文献