A laboratory assessment of the relative importance of turbulence, particle composition, and concentration in limiting maximal floc size and settling behaviour   总被引：1，自引：0，他引：1  

T. G. Milligan  P. S. Hill 《Journal of Sea Research》1998,39(3-4)

The fate of fine particulate material in aquatic environments is closely linked to aggregation and disaggregation processes. Understanding the mechanisms controlling these processes is fundamental to the development of predictive models of fate and effects for particulate discharges in the coastal zone from such sources as offshore hydrocarbon exploration and development. One of the variables required for the development of these models is maximal floc size. Using a non-invasive imaging technique, the significance of turbulence, composition, and concentration on maximal floc size in an inverting column flocculator was determined for materials commonly discharged during offshore hydrocarbon development. The settling velocity of the suspension was determined from volume concentrations of samples obtained by pipette during still water settling in a manner similar to that of Owen tubes. After 20 h, both maximal floc size and settling velocity showed a highly significant dependence on turbulence and type of material in suspension, but showed no effect from concentration.  相似文献   

细粒沉积物(岩)中重矿物提取方法的改进     

刘善品  何况  吴小斌  李吉均  宋春晖 《地质科技情报》2012,31(1):131-136

随着近百年的重矿物研究,从沉积物中提取重矿物的实验方法已经形成了固定模式,然而这些传统方法都是对砂岩粗颗粒矿物研究经验的积累,并不适用于泥质含量高的细粒沉积物.根据溶胶稳定(DLVO)理论,悬浮于溶液中的微细颗粒会因分子间作用力的相互吸引絮凝成团,从而影响细粒沉积物中重矿物提取的效果.实验研究证明,影响重矿物提取的主要因素是微细矿物颗粒间的絮凝作用,而并非有机重液的黏度.如何克服微粒间的絮凝作用是提取泥岩和粉砂岩中重矿物的关键.实验对比分析表明,添加分散剂的超声波振动和自然沉降法可以在克服絮凝作用的前提下有效去除泥质成分,同时对粉砂级矿物进行精确的粒径分选;离心分离同样也可以克服微粒间的絮凝作用,在重液分离过程中使重矿物顺利从轻矿物中分离.以上3种方法的联合使用可以弥补传统的重矿物提取方法的不足,并显著提高泥岩、粉砂岩中重矿物的提取率.  相似文献   

An analysis of the factors contributing to the settling potential of fine fluvial sediment     

N. D. Williams  D. E. Walling  G. J. L. Leeks 《水文研究》2008,22(20):4153-4162

The settling potential of fine sediment is known to be influenced by particle size, shape, density and porosity, and is commonly predicted using Stokes's law, despite its known limitations for modelling the behaviour of natural particles. In order to develop an improved understanding of the potential for fine sediment to settle out of suspension or undergo transport by hydraulic processes, it is important to examine the role of particle structure in detail. In this study, stepwise regression was used to identify which structural properties of particles exert an important control on fine sediment behaviour in river systems. The presence of composite particles and their associated particle size, porosity and fractal dimension were shown to be the most important controls on settling potential. Composite particles that form in the aquatic environment (flocs) were shown to have significantly different form and behaviour from composite particles of terrestrial origin (aggregates). Importantly, it was demonstrated that particle structure and behaviour exhibited consistencies between contrasting river catchments in different locations. An understanding of the mechanisms responsible for the formation of composite particles is viewed as providing a valuable input to efforts to model the mobilisation, transport and fate of fine sediment. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Fenton氧化-混凝法处理含活性染料废水的研究   总被引：8，自引：0，他引：8  

杜桂荣  孙占学  黄克玲  王灶生 《华东地质学院学报》2002,25(4):305-307

运用Fenton试剂对含活性污染废水进行混凝前的预处理。通过预处理前后废水吸光度曲线的变化，探讨其作用机理。试验表明，直接混凝法处理含活性染料废水时，脱色率仅为10％－30％，吸光度曲线几乎不变。当Fenton试剂对其预处理后，吸光度曲线中的吸收峰消失，继续混凝处理，脱色率可达96.77％。  相似文献   

PAA─水泥─泥浆快速絮凝堵漏浆液的研制          下载免费PDF全文

何世呜  任德兵 《探矿工程》1994,(2):52-54

通过正文试验方法及体积比试验选出了ＰＡＡ－水泥－泥浆浆液最优配方，在平顶山岩金矿区２个钻孔３次堵漏成功。这种浆液是因地制宜研制成功的一种快速堵漏浆液。  相似文献   

细颗粒泥沙动水絮凝的机理分析   总被引：20，自引：0，他引：20  

阮文杰 《海洋科学》1991,15(5):46-49

本文首先阐述由环形水槽试验所得出的细颗粒泥沙动水絮凝的若干规律。然后进行絮凝体形成和破碎的机理分析。从而得出产生动水絮凝的充分、必要条件:一是泥沙和电介质的物理、化学性质;二是絮凝体的抗剪能力大于所受到的剪切力,由此引出动水絮凝临界流速的概念。  相似文献   

Water and fine sediment dynamics in transient river plumes in a small, reef-fringed bay, Guam     

Eric Wolanski  Robert H. Richmond  Gerald Davis  Victor Bonito 《Estuarine, Coastal and Shelf Science》2003,56(5-6):1029-1040

Fouha Bay is a 400-m-long funnel-shaped, 10-m-deep, coral-fringed embayment on the southwest coast of Guam. It drains a small catchment area (5 km²) of steeply sloping, highly erodible lateritic soils. River floods are short-lived and the sediment load is very large, with suspended sediment concentration (SSC) exceeding 1000 mg l⁻¹. The resulting river plume is about 1 m thick and is pulsing in a series of 1–2 h-long events, with outflow velocity peaking at 0.05 m s⁻¹. Turbulent entrainment results in an oceanic inflow at depth into the bay. As soon as river flow stops, the plume floats passively and takes 5 days to be flushed out of Fouha Bay. The suspended fine sediment flocculates in 5 min and aggregates on ambient transparent exopolymer particles to form muddy marine snow flocs. In calm weather, about 75% of the riverine mud settles out of the river plume into the underlying oceanic water where it forms a transient nepheloid layer. This mud ultimately settles and is trapped in Fouha Bay. Under typhoon-driven, swell waves, the surface plume is at least 7 m thick and bottom entrainment of mud results in SSC exceeding 1000 mg l⁻¹ for several days. It is suggested that successful management of fringing coral reefs adjacent to volcanic islands may not be possible without proper land use management in the surrounding catchment.  相似文献   

Entropy analysis of in situ particle size spectra     

Ole A. Mikkelsen  Kristian J. Curran  Paul S. Hill  Timothy G. Milligan 《Estuarine, Coastal and Shelf Science》2007,72(4):615-625

Entropy analysis has been used to classify in situ particle (floc) size spectra of suspended particles into groups based on similar distribution characteristics. Results revealed that the in situ spectra sorted into groups that reflected different forcing conditions (e.g. variations in turbulence). The different forcing conditions were not necessarily reflected in other commonly used distribution measures such as median floc diameter. This suggests that entropy analysis may be an effective approach for investigating the effect of changes in forcing conditions on floc size. It is hypothesized that it may be possible to derive the average shape of floc size spectra from measurement of the forcing conditions alone and subsequently derive parameters such as floc fraction, floc density, floc settling velocity and the optical properties of the water column from the average spectra.  相似文献   

含离子浓度参数的粘性泥沙沉速公式研究   总被引：2，自引：4，他引：2       下载免费PDF全文

王家生  陈立  王志国  黄荣敏 《水科学进展》2006,17(1):1-6

以长江为例分析了河流中的水化学特性,得出河流中影响粘性泥沙沉速的主要是Ca2+。阳离子影响泥沙沉速的主要原因是粘性沙的絮凝。对泥沙絮凝沉降过程进行理论分析,推导出絮凝沉速与离子浓度之间的关系式。并且根据试验结果确定以Ca2+浓度为参数时经验关系式中的系数值。用实测的沉速对絮凝沉速公式进行了初步的验证。验证结果表明,用张瑞瑾沉速公式计算结果与实测结果相差很大,而絮凝沉速公式计算结果与实测结果相符合。  相似文献   

Swell-compressibility characteristics of lime-blended and cement-blended expansive clays – A comparative study     

B.R. Phanikumar  Rishi Sreedharan  C. Aniruddh 《Geomechanics and Geoengineering》2015,10(2):153-162

Chemical stabilisation of expansive soils has been quite efficacious in reducing swelling characteristics, namely, swell potential (S%) and swelling pressure (p_s). When chemicals such as lime and cement are added to an expansive clay, flocculation and cementation take place. Flocculation, which is an immediate reaction, is instrumental in reducing plasticity and swell potential significantly. It also reduces the time required for equilibrium heave. This paper presents experimental data on lime-blended and cement-blended expansive clay specimens. Free swell index (FSI), heave, rate of heave and swelling pressure were studied. FSI, heave and rate of heave decreased with increasing lime content and cement content in the blends. But, during a 3-day inundation (a period, generally allowed for the sample to attain to equilibrium heave), cementitious products developed and resisted the applied compressive loads stiffly, resulting in high swelling pressures in the case of lime-blended specimens. Swelling pressure could not be determined in the case of cement-blended specimens. Hence, short inundation tests (inundating the specimens only for 15 minutes) were performed. But, even from these tests, swelling pressure could not be determined for cement-blended specimens. This indicated the development of strong cementitious products in them. It was interesting to find that, in both long and short duration, the lime- and cement-blended specimens attained to equilibrium heave in the same time period. FSI decreased from 185% to 63.63% when lime content was increased from 0% to 4%, and from 185% to 110% when cement content was increased from 0% to 20%. Swell potential reduced by 42.5% at 4% lime and by 46.4% at 20% cement. Swelling pressure increased from 210 kPa to 320 kPa when lime content was increased from 0% to 4%. Linear shrinkage of the specimens also decreased with increasing additive content.  相似文献