盾构排浆管道内块石流速分析与沉积临界泥浆流速公式推导

为了明晰排浆管道内各种块石的流速情况,探讨块石沉积形成的管道堵塞和泥浆流速的关系,首先,根据流体力学基本方程推导出泥浆液动力计算式;然后,从运动力学角度对水平、斜向上、斜向下、垂直向上管道内的石块取最难排出的状态进行受力分析;最后,对不同形状、不同粒径石块,在不同倾斜角度的泥浆通道内随泥浆流动,达到受力平衡时和泥浆流速差值计算公式进行推导,进而分析推导出各种块石沉积临界泥浆流速计算公式,并设定工程数据试算。得出以下结论:1)不同尺寸、不同形状、不同密度的块石在不同倾角排浆管道内差速流动、流动速度自动分级、沉积临界泥浆流速不同;2)密度小、体积小的块石运动速度快、沉积临界泥浆流速小;3)相同重量、密度的块石,球形的运动速度最快、沉积临界泥浆流速最小,正方体形的次之,长条形的运动速度最慢、沉积临界泥浆流速最大,长径比越大流速越慢、沉积临界泥浆流速越大;4)同一块石,在向下管道流速最快、沉积临界泥浆流速最小,水平管道次之,在垂直上升管道流速最小、沉积临界泥浆流速最大。重点控制始发井和地面垂直向上管道内的泥浆流速至关重要。通过计算以适用经济的泥浆流速来预防排泥管道堵塞。

矿浆管道输送沉积临界流速公式探讨

本文根据多种金属矿浆管道输送试验数据,分析了适用于高、低浓度浆体输送时沉积临界流速计算新公式的形式。经数据处理后,得出了公式中的系数和指数数值。 用新公式计算的数值与试验数据进行了比较,同时还对公式的误差进行了分析。

瓮福中低品味磷精矿浆管道输送系统工艺设计

瓮福集团针对磷矿石品位较低,大量资源不能利用的现状,为提高资源利用率,投资7亿元进行了中低品位磷矿石的扩建工程,其中新建磷精矿管道输送系统,将磷精矿浆从新龙坝选矿厂输送至马场坪工业场地,输送距离46.9km。文章主要介绍了磷精矿浆管道系统的输送工艺设计,设计时考虑到实际生产中不可避免的产量波动,设计背压可调的消能站实现流量多级调节。通过调节泵速和消能站中消能孔板组合的运行模式,矿浆可控制在最低能耗下输送,生产灵活性较高,吨矿运输成本大幅降低,由原来的0.2元/吨·公里降低到0.1元/吨·公里,经济效益显著。新管道系统于2013年5月成功投产使用,技术装备和经济指标达到世界先进水平。

Using ^(137)Cs Tracing Methods to Estimate Soil Redistribution Rates and to Construct a Sediment Budget for a Small Agricultural Catchment in the Three Gorges Reservoir Region,China

Soil erosion and associated off-site sedimentation are threatening the sustainable use of the Three Gorges Dam. To initiate management intervention to reduce sediment yields, there is an increasing need for reliable information on soil erosion in the Three Gorges Reservoir Region （TGRR）. The purpose of this study is to use 137Cs tracing methods to construct a sediment budget for a small agricultural catchment in the TGRR. Cores were taken from a pond and from paddy fields, for laTCs measurements. The results show that the average sedimentation rate in the pond since 1963 is 1.50 g cm-2 yr-1 and the corresponding amount of sediment deposited is 1,553 t. The surface erosion rate for the sloping cultivated lands and the sedimentation rate in the paddy fields were estimated to be 3,770 t km-2 yr-1 and 2,600 t km-2 yr^1 respectively. Based on the estimated erosion and deposition rates, and the area of each unit, the post 197o sediment budget for the catchment has been constructed. A sediment delivery ratio of 0.5 has been estimated for the past 42 years. The data indicate that the sloping cultivated lands are the primary sediment source areas, and that the paddy fields are deposition zones. The typical land use pattern （with the upper parts characterized by sloping cultivated land and the lower parts by paddy fields） plays an important role in reducing sediment yield from agricultural catchments in the TGRR. A 137Cs profile for the sediment deposited in a pond is shownto provide an effective means of estimating the land surface erosion rate in the upstream catchment.

市政排水管道在清淤方面的规划设计研究

市政排水管道的过水能力受悬浮物颗粒淤积情况的影响,若不及时清淤会导致管道过水能力降低。分析了沉积物流速、沉积作用以及水力清淤作用在市政排水管道清淤方面的应用,为提高市政排水管道规划设计的合理性提供思路。

Model for seawater fouling and effects of temperature,flow velocity and surface free energy on seawater fouling

A kinetic model was proposed to predict the seawater fouling process in the seawater heat exchangers.The new model adopted an expression combining depositional and removal behaviors for seawater fouling based on the Kern–Seaton model.The present model parameters include the integrated kinetic rate of deposition(k d)and the integrated kinetic rate of removal(k r),which have clear physical signi ficance.A seawater-fouling monitoring device was established to validate the model.The experimental data were well fitted to the model,and the parameters were obtained in different conditions.SEM and EDX analyses were performed after the experiments,and the results show that the main components of seawater fouling are magnesium hydroxide and aluminum hydroxide.The effects of surface temperature,flow velocity and surface free energy were assessed by the model and the experimental data.The results indicate that the seawater fouling becomes aggravated as the surface temperature increased in a certain range,and the seawater fouling resistance reduced as the flow velocity of seawater increased.Furthermore,the effect of the surface free energy of metals was analyzed,showing that the lower surface free energy mitigates the seawater fouling accumulation.

Uranium comminution age responds to erosion rate semiquantitatively

Here we present(^(234)U/^(238)U)data from river sediments collected on the Tibetan Plateau.The(^(234)U/^(238)U)ratios of a specific grain size fraction show good correlation with erosion rates,which were determined by in-situ–produced cosmogenic nuclides.This correlation has previously been observed in a wide range of geomorphic settings,suggesting that(^(234)U/^(238)U)ratios of fluvial sediments have great potential to quantify erosion rates.

High-Throughput Multi-Plume Pulsed-Laser Deposition for Materials Exploration and Optimization

A high-throughput multi-plume pulsed-laser deposition （MPPLD） system has been demonstrated and compared to previous techniques. Whereas most combinatorial pulsedlaser deposition （PLD） systems have focused on achieving thickness uniformity using sequential multilayer deposition and masking followed by post-deposition annealing, MPPLD directly deposits a compositionally varied library of compounds using the directionality of PLD plumes and the resulting spatial variations of deposition rate. This system is more suitable for high-throughput compound thin-film fabrication.

Astronomical forcing of sedimentary cycles of Late Eocene Liushagang Formation in the Bailian Sag, Fushan Depression, Beibuwan Basin, South China Sea

Sediments in the Liushagang Formation of Late Eocene form a group of key hydrocarbon play fairways in the Beibuwan Basin,South China Sea.As an important reservoir-forming combination,the Liushagang Formation consists of deltaic siliciclastic and show clear sedimentary cyclicity.According to paleontology research and stratigraphic correlation,the boundary between Liushagang Formation(Els)and Weizhou Formation(Ewz)is regarded as the Eocene-Oligocene boundary.The oxygen isotope dating for well cores from the top of the first Member of Liushagang Formation(Els1)and the bottom of the third Member of Weizhou Formation(Ewz3)give an isochron age of 35.2 Ma.Here,we use GR logging data as a paleoenvironmental proxy to conduct a detailed cyclostratigraphic study of the Els1 in the Bailian Sag,Fushan Depression.Power spectra,evolutionary fast Fourier transformation and wavelet analysis all reveal significant sedimentary cycles in Els1.The ratios of cycle wavelengths in these stratigraphic units are 21?5?2.8?1.2?1,and are interpreted as Milankovitch cycles of 400 ka and 96 ka eccentricity,52 ka obliquity,22ka and 19 ka precession cycles,respectively.An astronomical time scale is established by tuning filtered 96 ka eccentricity cycles to a target curve of Well L2 in the Bailian Sag.Based on regional stratigraphic framework,combined with seismic,cores and logging data,the HST of the first member of the Liushagang Formation(Els1)delta in Well L2 was divided into six parasequence sets named Ps1-Ps6.According to the spectrum analysis by Simple Lomb periodogram from PAST program packages,the sediment accumulation rate of each parasequence sets first increased and then decreased as time went by.The sediment accumulation rate of Ps4 reached the maximum(0.127 m/ka)during the most prosperous period of delta prograding.Finally,the duration of each period of parasequence sets and more accurate geological age were calculated on the basis of sediment accumulation rate.The ages of each depth are precisely estimated and provide new constraints on the Late Eocene.

Three Gorges Dam Controls Sediment Coarsening of the Mud Patch on the Inner East China Sea Shelf

The well-known Three Gorges Dam(TGD) within the Yangtze catchment launched its operation in 2003. The effect of the TGD operation on the sediment size on the East China Sea shelf is rarely known. High resolution(0.5 cm sampling) grain size analysis and 137 Cs and 210 Pb dating of the DH8-1 core were conducted with core collected from the distal part of a main sink for the modern Yangtze sediment entering the sea, the Min-Zhe Coastal Mud Deposits(MZCMD) on the inner East China Sea shelf. The 137 Cs dating results show that the core DH8-1 formed during 1946–2012 with a mean deposition rate of 0.65 cm yr^(-1), indicating that the 0.5 cm sampling for grain size analysis in this local area could reflect environmental changes generally on a one-year time scale. The mean grain size of DH8-1 core sediment that deposited after 2003 is significantly larger than that deposited during 1988–2002. After ruling out other possible factors, we infer that the sediment coarsening of DH8-1 core after 2003 is attributed to the TGD operation which causes the erosion of the Yangtze subaqueous delta. Specifically, the TGD operation significantly intensifies the declining trend of the Yangtze sediment loads to the sea despite no decreased water discharge, which results in extensive erosion of the Yangtze subaqueous delta. The relatively coarse sediment of the subaqueous delta is eroded and resuspended by ocean dynamics and then transported by coastal current, finally depositing on the MZCMD area. In addition, the general sediment fining of core DH8-1 that deposited during 1988–2002, comparing with 1946–1987, is mainly caused by dam construction and soil and water conservation within the Yangtze catchment. Our findings are helpful for better understanding the effects of such a huge dam as the TGD on a sediment sink like the MZCMD of such a large river as the Yangtze River.

Role of debris flow on the change of^10Be concentration in rapidly eroding watersheds:a case study on the Seti River,central Nepal

The concentration of cosmogenic loBe in riverine sediments has been widely used as a proxy for catchment-wide denudation rate （CWDR）. One of the key assumptions of this approach is that sediments originating from sub-basins with different erosional histories are well mixed. A tragic debris flow occurred in the Seti River watershed, central Nepal, on May 5, 2012. This catastrophic debris flow was triggered by slope failure on the peak of Annapurna IV and resulted in many casualties in the lower Seti Khola. However, it provided an opportunity to test the assumption of equal mixing of sediments in an understudied rapidly eroding watershed. This study documents the CWDR of ^10Be to evaluate the extent of the influence of episodic erosional processes such as debris flow on the spatio-temporal redistribution of loBe concentrations. Our data show that the debris flow caused little change in CWDR across the debris flow event. In addition to isotopic measurement, we calculated denudation rates by using the modeled concentrations in pre- and post-landslide sediments based on the local ^10Be production rate. The modeled result showed little change across the event, indicating that the debris flow in May 2012 played a minor role in sediment evacuation, despite the rapid erosion in the catchment. Our study concludes that although the 2012 event caused many casualties and severe damage, it was a low-magnitude, high frequency event.

Effects of Electrolyte Concentration, Temperature, Flow Velocity and Current Density on Zn Deposit Morphology

The most critical disadvantages of the Zn-air flow battery system are corrosion of the zinc, which appears as a high self-discharge current density and a short cycle life due to the non-uniform, dendritic, zinc electrodeposition that can lead to internal short-circuit. In our efforts to find a dendrite-free Zn electrodeposition which can be utilized in the Zn-air flow battery, the surface morphology of the electrolytic Zn deposits on a polished polymer carbon composite anode in alkaline, additive-free solutions was studied. Experiments were carried out with 0.1 M, 0.2 M and 0.5 M zincate concentrations in 8 M KOH. The effects of different working conditions such as： elevated temperatures, different current densities and different flow velocities, on current efficiency and dendrite formation were investigated. Specially designed test flow-cell with a central transparent window was employed. The highest Coulombic efficiencies of 80%-93% were found for 0.5 M ZnO in 8 M KOH, at increased temperatures （50-70 ℃）, current densities of up to 100 mA.cm2 and linear electrolyte flow velocities higher than 6.7 cm.s1.

Mechanisms of suspended sediment restoration and bed level compensation in downstream reaches of the Three Gorges Projects(TGP)

River basin reservoir construction affects water and sediment transport processes in downstream reaches. The downstream impact of the Three Gorges Projects （TGP） has started to become apparent： （1） reduction in flood duration and discharge, and significant reduction in sediment load. Although there was some restoration in downstream sediment load, the total amount did not exceed the pre-impoundment annual average; （2） in 2003-2014 the d 〉 0.125 mm （coarse sand） load was restored to some degree, and to a maximum at Jianli Station, which was mainly at the pre-impoundment average. After restoration, erosion and deposition characteristics of the sediment was identical to that before impoundment. The degree of restoration during 2008-2014 was less than during 2003-2007; （3） after TGP im- poundment, there was some restoration in d 〈 0.125 mm （fine sand） sediment load, however, it was {ower than the pre-impoundment average; （4） due to riverbed compensation, the d 〉 0.125 mm sediment load recovered to a certain degree after impoundment, however, the total did not exceed 4400x104 t/y. This was mainly limited by flood duration and the average flow rate, and was less affected by upstream main stream, tributaries, or lakes. Restoration of d 〈 0.125 mm suspended sediment was largely controlled by upstream main stream, tributaries, and lakes, as well as by riverbed compensation. Due to bed armoring, riverbed fine suspended sediment compensation capability was weakened; （5） during 2003-2007 and 2008-2014, Yichang to Zhicheng and upper Jingjiang experienced coarse and fine erosion,lower Jingjiang experienced coarse deposition and fine erosion, Hankou to Datong had coarse deposition and fine erosion, and Chenglingji and Hankou was characterized by coarse deposition and fine sand erosion in 2003-2007, and coarse and fine erosion in 2008-2014. This difference was controlled by flood duration and number at Luoshan Station.

Deposition rate and interaction of human-riverine from height increase and permanent function of an 1180 years weir in Southeast China

This paper is to present an efficient approach to enriching the quantification model of human-riverine interactions and its anthropogenic impact by a retrospective study on one of the four most famous historical hydraulic projects in China,the Tuoshan Weir.It was constructed in 833 AD and had trajectories of natural resilience and hydraulic engineering maturity more than thousand years.Extensive historical data and maturation procedure of the hydraulic system were used judiciously to examine the spatial patterns of the long-term water conservancy system with agriculture,urbanization and civilization of Ningbo City in Zhejiang Province,Southeast China.Interaction framework is assessed from historical perspective and the deposition rate(DR)is calculated by analyzing the continuous increase of the Tuoshan Weir height.The results show that the declining DR during the 1180 years guaranteed the beneficial role the Tuoshan Weir played in spite of some negative river responses caused by the increase of sediment deposition and decrease of fresh water-retention capacity.The following up revamped workings and well matured hydraulic system around the Tuoshan Weir also contribute a lot to the designed mission of the weir.We conclude that hydraulic system maturation is very important for the proper function and life span of huge hydraulic projects.