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Sediment density structure derived from textural analysis of crosssectional Xradiographs


The fluxes of the elements in each section of the core were calculated using the mass sedimentation rates derivedfrom 210Pb dating technique and the sediment density at each location.


Classical treatment of mass conservation of solids in growing sediments states an advectiondiffusion equation for the bulk sediment density.


Complete burial, with a typical sediment density of 2300?kg?m3, results in a 120?mGal difference from a sedimentfree seamount model.


Increasing sediment density results in an exponential decay of the seamount anomaly.

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 Sediment density is one of main physical characteristics of river sediment. Sum of 526 sediment samples from 23 hydrology station, which is basically covered all the main sediment production areas of the upper, middle and lower reaches and branches and therefore is of wide representativeness, in the stem and tributaries of the Yellow River were collected and studied in this experimental study. Analysis results show that there is no relation among sediment density with sediment gradation at different vertical... Sediment density is one of main physical characteristics of river sediment. Sum of 526 sediment samples from 23 hydrology station, which is basically covered all the main sediment production areas of the upper, middle and lower reaches and branches and therefore is of wide representativeness, in the stem and tributaries of the Yellow River were collected and studied in this experimental study. Analysis results show that there is no relation among sediment density with sediment gradation at different vertical location, nor evident relation with sediment concentration; there is a little change of sediment density from upper to lower reaches but is stable year after year. Finally, it is suggested that the sediment density can be 2.74 g/cm 3 for upper reach, 2.73 g/cm 3 for middle reach and 2.71 g/cm 3 for lower Yellow River.  泥沙密度是河流泥沙的主要物理特性之一。本项试验研究采集了黄河干支流２３个水文站５２６个泥沙样品，基本覆盖了黄河上、中、下游各河段及主要支流泥沙来源区，泥沙样品具有广泛的代表性。分析结果表明：泥沙密度与垂线上不同位置处的泥沙颗粒级配无关，与含沙量之间也没有明显的关系；自上游至下游，泥沙密度沿程略有变化，年际间比较稳定。最后建议泥沙密度值上游区选用２７４ｇ／ｃｍ３，中游区选用２７３ｇ／ｃｍ３，下游区选用２７１ｇ／ｃｍ３。  The theoretical relationship between suspended concentration and settling velocity of sediment group during the settling procedure is established.The result is verified by experimental data.It is found that the established concentration\settling velocity relationship is reasonable;the settling procedure of sediment group consists of accelerate,uniform and decelerate stages,if the variation of concentration is taken into account;the effects of grain size,density and original concentration on settling velocity... The theoretical relationship between suspended concentration and settling velocity of sediment group during the settling procedure is established.The result is verified by experimental data.It is found that the established concentration\settling velocity relationship is reasonable;the settling procedure of sediment group consists of accelerate,uniform and decelerate stages,if the variation of concentration is taken into account;the effects of grain size,density and original concentration on settling velocity are remarkable.  本文通过数模对蓄泥库泥沙群体静水沉降速率进行了研究 ,并得到实验验证结果 .这一分析结果最后表明 :建立的浓度 沉速时程关系是合理的 ;考虑浓度变化的泥沙群体沉降过程可分为加速、匀速、减速三个阶段 ;泥沙粒径、泥沙密度、悬液初始浓度对沉速影响较大 ,而悬液初始深度影响较小 .本文建立的沉速与浓度关系对生产实践具有一定的参考价值 .  Equations of mass, momentum and second moments for particulate phase are derived from a particle PDF (probability distribution function) equation in dilute turbulent sedimentladen flows. The equation of momentum in the vertical direction for twodimensional steady and uniform openchannel flows is used to develop a modified sediment diffusion equation, which shows that the vertical gradient of particle velocity fluctuation and lift force contribute to the movement of suspended sediment as well as the effective... Equations of mass, momentum and second moments for particulate phase are derived from a particle PDF (probability distribution function) equation in dilute turbulent sedimentladen flows. The equation of momentum in the vertical direction for twodimensional steady and uniform openchannel flows is used to develop a modified sediment diffusion equation, which shows that the vertical gradient of particle velocity fluctuation and lift force contribute to the movement of suspended sediment as well as the effective gravity and turbulent diffusion. The influences of the density, diameter and average concentration of fine sediment, and those of the water depth and friction velocity on sediment diffusion coefficient and the concentration distribution patterns are analyzed theoretically and numerically. Experiment data of fine sediment is also analyzed quantitatively. It shows that the traditional diffusion equation brings remarkable error under flow conditions where friction velocity, particle diameter and sedimentwater density ratio are relatively large and the water depth is small.  从颗粒运动的PDF(概率密度分布函数)输运方程出发建立颗粒相的质量、动量和脉动速度二阶矩方程。对明渠二维恒定均匀流,利用垂向动量方程导出了修正的泥沙扩散方程,表明颗粒脉动强度梯度、升力、有效重力和紊动扩散都影响悬沙运动。理论和数值分析了细颗粒泥沙的密度、粒径、浓度,挟沙水流的水深和剪切流速等因素对泥沙扩散系数和浓度分布形状的影响,并定量分析了细颗粒试验资料,表明传统扩散方程在粒径、剪切流速相对较大、水深和水沙密度比较小的流动中存在较大误差,需要修正。  
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