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1.
Jie Yin Ming-ming Hu Gui-zhong Xu Wen-xia Han Yong-hong Miao 《Marine Georesources & Geotechnology》2020,38(5):611-620
AbstractThis paper presents an experimental investigation into the effect of salinity on Atterberg limits, flowability, viscosity and strength properties of cement-stabilized clay minerals. Three groups of clay minerals (illite, kaolinite and montmorillonite) were obtained. Specimens with different porewater salinities were prepared by mixing the air-dried clays with sodium chloride (NaCl) at various salt concentrations (i.e., 0%, 2% 4%, 6% and 8%). Atterberg limits test results indicated that liquid limit and plasticity index decreased insignificantly with increasing salinity for Kaolinite and illite but significantly for montmorillonite. Flow test results indicated that of all specimens of three groups of clay minerals with or without adding cement consistently increase with increasing salinity. The flow value of montmorillonite increased more significantly than kaolinite and illite. Viscosity test results indicated that all the specimens tested behave as Bingham plastic. Flow value consistently decreased with increasing dynamic viscosity or yield stress, regardless of clay mineralogy, porewater salinity and cement amount. Strength test results indicated that all cement-stabilized specimens exhibit strain softening behavior. Unconfined compressive strength for three groups of clay minerals stabilized with cement consistently decreased with increasing salinity indicating that the presence of salt had an adverse effect on the development of strength. 相似文献
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Settling characteristics of soils carry great importance for geotechnical engineers since sediments properties are formed during the settling of soil particles in an aqueous environment. In this study, settling characteristics of kaolinite are investigated. Different ionic strengths of NaCl, CaCl2 and AlCl3 were considered as a function of pH in aqueous environment of varying solid concentrations. Factors affecting the settling characteristics and fabric of kaolinitic sediments have been identified. The results of the study reveal that kaolinite settles in either flocculated or dispersed forms depending on pH and ion concentration. Flocculated settling occurs in acidic pH due to formation of flocs in edge-to-face structure with increasing positive charges at the particle edges. Dispersed settling occurs in alkaline pHs when ionic strength is low. When ionic strength is increased in alkaline pHs, kaolinite particles settle in flocculated form. Furthermore, the results show that pH has a significant role on the final sediment thickness or void ratio of kaolinite. Densely packed structures in alkaline and loosely packed structures in acidic aqueous environments are formed depending on pH level. Results also show that as the solid concentration increases, the settling rate decreases due to buoyancy effect. Finally, the zeta potential of kaolinite is correlated with the final sediment thickness or void ratio of kaolinite as a function of pH. This correlation proves that there is a good agreement between zeta potential and the final sediment thickness or void ratio, especially when the soil is settled in a dispersed form. 相似文献
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《Marine Georesources & Geotechnology》2006,24(3):203-218
Settling characteristics of soils carry great importance for geotechnical engineers since sediments properties are formed during the settling of soil particles in an aqueous environment. In this study, settling characteristics of kaolinite are investigated. Different ionic strengths of NaCl, CaCl2 and AlCl3 were considered as a function of pH in aqueous environment of varying solid concentrations. Factors affecting the settling characteristics and fabric of kaolinitic sediments have been identified. The results of the study reveal that kaolinite settles in either flocculated or dispersed forms depending on pH and ion concentration. Flocculated settling occurs in acidic pH due to formation of flocs in edge-to-face structure with increasing positive charges at the particle edges. Dispersed settling occurs in alkaline pHs when ionic strength is low. When ionic strength is increased in alkaline pHs, kaolinite particles settle in flocculated form. Furthermore, the results show that pH has a significant role on the final sediment thickness or void ratio of kaolinite. Densely packed structures in alkaline and loosely packed structures in acidic aqueous environments are formed depending on pH level. Results also show that as the solid concentration increases, the settling rate decreases due to buoyancy effect. Finally, the zeta potential of kaolinite is correlated with the final sediment thickness or void ratio of kaolinite as a function of pH. This correlation proves that there is a good agreement between zeta potential and the final sediment thickness or void ratio, especially when the soil is settled in a dispersed form. 相似文献
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北戴河海滩泥沙捕获实验及其初步结果分析 总被引：2，自引：1，他引：2
介绍了利用泥沙捕获器观测破波带泥沙垂直分布结构的现场实验方法和基本程序，以及利用实验结果计算泥沙通量的方法。研究表明，近岸带泥沙运移通量及其在垂向上的分布受破波带相对位置和海滩地形变化的影响。在破波点附近，波浪的搅动和流场作用强，泥沙运移通量增大，泥沙在波浪的作用下可以大量进入垂直水体以悬移和跃移的方式运移。在本实验中，破波点附近的泥沙在距海底100cm的垂直水体中运移，通量垂向向上逐渐减小。远离破波点，泥沙运移通量和进入垂直水体的高度明显下降。在地形变化复杂的有坝海滩，沙坝顶部的泥沙运移通量最大，泥沙进入垂直水体运移的机率增加，而在沙坝问的沟槽内，波浪和海流作用减弱，泥沙通量和垂向进入水体运移的比例下降。 相似文献
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High-organic-content dredged soils are known to have inferior mechanical characteristics because they are highly compressible and have low shear strength. To recycle dredged soil with a high organic content as a top soil this study describes an investigation of the mechanical properties and germination characteristics of stabilized organic soils using unconfined compression tests, pH tests, and seed germination tests. Several mixtures with organic contents in the range 0–30% by mass and binder contents in the range 5–15% were prepared to evaluate the effects of the organic content on the mechanical and germination characteristics of the stabilized soils. The results show that an increase in the organic content leads to a decrease in the strength and pH of the stabilized organic soil, which are favorable conditions for germination. The germination rate increased significantly with the increasing organic content, and the plant growth rate also increased. The addition of a binder into the mixtures increased the strength of the soil; however, it also increased the pH and decreased the rate of seed germination and plant growth. 相似文献
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风暴过程中潮滩悬沙浓度和悬沙输运的变化及其动力机制——以长江三角洲南汇潮滩为例 总被引：1，自引：1，他引：0
悬沙浓度是淤泥质海岸重要的环境指标。为探讨潮滩悬沙浓度和悬沙输运对风暴事件的响应过程及其动力机制,于2014年9月"凤凰"台风过境前、中、后在长江三角洲南汇潮滩进行了现场观测,获得同步高分辨率的水深、波高、近底流速和浊度剖面时间序列(9个潮周期)。结果表明,风暴中平均和最大波高、波-流联合底床剪切应力、悬沙浓度和悬沙输运率可比平静天气高数倍;风暴期间高潮位低流速阶段悬沙沉降导致近底发育数十厘米厚的浮泥层(悬沙浓度大于10 g/L)。研究认为风暴事件中淤泥质海岸悬沙浓度和悬沙输运的剧烈变化其根本动力机制是风暴把巨大能量传递给近岸水体,进而显著增大波-流联合底床剪切应力,导致细颗粒泥沙再悬浮。 相似文献
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In order to gain insight into the formation dynamics of mudbanks off the Kerala coast of India, extensive surveying of the nearshore bathymetry along with sediment characterization was undertaken. The textural and geotechnical properties of the surficial sediments of a mudbank were determined during pre-monsoon, monsoon, and post-monsoon periods. The mudbank sediments were clayey silts with high water and organic carbon contents, high Atterberg limits, and low bulk density, and therefore very susceptible to entrainment. During the monsoon, the mudbank regime was characterised by enhanced turbidity and a benthic fluff layer, triggered by the increasing swell of the early monsoon period. Re-suspension exposed a more consolidated, previously sub-bottom, layer which exhibited lower water content and greater shear strength than the pre-monsoon seabed. Texturally, the monsoon seabed was similar to the pre-monsoon seabed, with the same modal grain size, but the proportions of sand and coarse silt increased nearshore, while the proportions of fine and very fine silt increased offshore. There was a seaward-fining textural gradient at all times, but this became pronounced during the monsoon period. Paradoxically, the monsoonal seabed displayed greatly reduced wet bulk density. It is hypothesized that this was due to the presence of gas, probably methane, in the sediments (while the pre-monsoon sediments were fully saturated, the monsoon sediments were only 83% saturated). We speculate that the gas was forced into the surficial sediments either by wave pumping (at the onset of the monsoon) or by seaward-flowing subbottom freshwater (derived from monsoonal rains). With the waning of the monsoon, the benthic fluid mud layer rapidly disappeared and the seabed returned to its pre-monsoon state as suspended sediments were redeposited. The mudbank regime is therefore essentially an in situ phenomenon. It is suggested that the mudbanks are palimpsest, marshy, lagoonal deposits, rich in organic matter and derived gas, that were submerged after a marine transgression. The surficial sediment is annually entrained during the monsoon, but erosion is limited by the formation of the benthic fluid mud layer, which attenuates wave generated turbulence. Although some fine sediment disperses alongshore and offshore, most is returned to the seabed as the monsoon declines. 相似文献
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开展枯季河口悬沙输运机理研究对于揭示弱径流条件下的陆海相互作用、河口季节性冲淤和水沙关系等具有重要的科学意义.本文根据2018年12月18-25日长江口南槽3个站位连续13个潮周期的同步流速、流向和悬沙浓度等观测资料,运用通量机制分解法研究了各输沙项的特征、贡献和输运机理.结果 表明,从小潮至大潮流速和悬沙浓度不断增加,由南槽上部至下部流速和悬沙浓度逐渐降低.观测期间平均流速与平均悬沙浓度存在明显的正线性关系,但受底质空间差异影响,悬沙浓度对流速的响应强度存在显著的空间变化.枯季期间南槽存在着中上部向陆净输沙、下部向海净输沙的空间输运格局.平流输沙和潮泵输沙是影响和控制净输沙的关键因素,二者的强度和贡献存在明显的潮周期变化和空间变化,垂向环流输沙的强度很弱,对净输沙贡献很小.南槽涨落潮输沙不对称现象明显,流速、悬沙浓度和历时都具有一定的涨落潮不对称性,这些不对称现象共同调节和控制着潮周期净输沙强度和方向的时空变化. 相似文献
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伶仃洋河口泥沙絮凝特征及影响因素研究 总被引：1，自引：1，他引：0
泥沙絮凝对河口细颗粒泥沙运动过程起着极其重要的作用。本文通过LISST-100激光粒度仪等仪器实测伶仃洋河口2013年洪季悬浮泥沙絮凝体现场粒径及水动力、泥沙条件,结合实验室悬沙粒径分析,研究大小潮期间伶仃洋河口泥沙絮凝特征,探讨紊动剪切强度、含沙量、盐度分层及波浪等因素对伶仃洋河口泥沙絮凝的影响。结果表明:伶仃洋河口水体中现场粒径平均值为148.53 μm,大于实验室悬沙分散粒径36.74 μm,河口絮凝现象明显;沉速与有效密度、粒径呈正相关,絮团平均有效密度为153.49 kg/m3,平均沉速达1.13 mm/s;小潮时絮团平均粒径大于大潮,垂向上表底层絮团粒径小、中层大,中底层絮团沉速大于表层。伶仃洋河口水动力、泥沙条件是影响其泥沙絮凝的重要因素,低剪切强度（小于5 s-1）、低含沙量（小于50 mg/L）及高体积浓度有利于细颗粒泥沙之间的相互碰撞,促进絮凝作用;当剪切强度与颗粒间碰撞强度高于絮团所能承受的强度时,絮团易破碎分解成小絮团或更细的泥沙颗粒;伶仃洋河口盐度层化引起的泥沙捕获现象增大中层泥沙体积浓度,有利于中层絮凝体的发育;观测期相对较大的波浪增强水体紊动,增大了水体细颗粒泥沙的碰撞几率,表层絮团粒径随波高峰值的出现而增大。 相似文献
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根据2006年7月—2007年12月,对长江口及邻近海域春、夏、秋和冬季4个航次的现场调查数据,对硅酸盐(SiO3-Si)在长江口及邻近海域表层海水的混合模式及影响因素进行初步探讨。结果表明:(1)该海域表层海水SiO3-Si浓度四季均与盐度(S)相关性较好,秋、冬季稀释模式与理论稀释线(TDL)相符,春、夏季因生物作用、悬浮颗粒物解析和沉积物再溶作用的影响,稀释模式与TDL线存在差异。(2)长江口及邻近海域S<18海域,表层海水四季SiO3-Si浓度随温度升高略有上升,可能是由于悬浮颗粒物中SiO3-Si的解析量和沉积物的再溶增加;pH值为7.7~7.9时,SiO3-Si浓度基本不变,pH值为7.9~8.2时SiO3-Si浓度随pH升高而降低,主要受物理混合作用影响;SiO3-Si浓度与溶解氧(DO)含量无明显相关关系。(3)长江口及邻近海域S>18海域表层海水,长江口和杭州湾SiO3-Si含量相对较高,除上述2个高硅区域外,四季在5~32 ℃温度范围内,SiO3-Si浓度均低于20 μmol/L,且相差不大;春、夏季受生物作用和物理混合作用共同影响,秋、冬季受物理混合作用影响,pH值为7.9~8.3时SiO3-Si浓度随pH升高逐渐降低,pH大于8.3时SiO3-Si浓度基本不变;春、夏季主要受生物作用影响,SiO3-Si浓度与DO含量呈负相关,秋、冬季因物理混合作用影响呈正相关。 相似文献
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胶州湾近岸沉积物-海水汞的释放研究 总被引：2，自引：0，他引：2
本文通过模拟实验研究了胶州湾海泊河口和李村河口沉积物中的汞在不同环境条件下向海水的释放,并对汞的释放动力学数据进行了拟合。总体上两种沉积物汞的释放浓度分别为1.41~5.99μg/L和1.06~3.62μg/L,最大释放率分别为2.7%和3.4%,对胶州湾潮间带水质产生较大的影响。海水的pH值、温度和沉积物厚度都会影响汞的释放。pH<7时,汞的释放作用随pH值的升高而降低,pH>7时,汞的释放作用随pH值的升高而增大;海水温度越高,汞的释放作用越强;随沉积物厚度的增加,汞的释放量增加,释放率降低,海泊河口和李村河口沉积物的有效厚度分别为3.5cm和2.5cm。汞的释放动力学拟合结果表明多个方程都能较好的描述汞的释放动力学过程,其中以Ho的二级动力学方程拟合结果最好。 相似文献
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各类海洋工程如码头、航道、海上风电、海底管道管线、填海造陆、防波堤等涉及的抛石、爆破、疏浚、打桩、开沟、吹填溢流等作业环节产生的悬浮物,在水动力作用下输移、扩散,会引起周边海域悬浮泥沙浓度增加,对海洋生态环境产生不利影响。文章对国内施工悬浮泥沙浓度扩散规律研究方法和数值模型中悬浮泥沙源强的选取方法进行了综述,为海洋工程施工过程产生的悬浮泥沙扩散研究提供参考和依据。 相似文献
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B. J. Lees 《Geo-Marine Letters》1981,1(3-4):249-254
A method is described to calculate the relationship (β) between the eddy diffusivity of suspended particles and the eddy viscosity
of the fluid. The data were obtained while making suspended sediment concentration measurements near the seabed on the British
continental shelf. β was calculated for 0.50 size fractions and varies inversely with the suspended sediment concentration.
The values were used successfully to calculate suspended sediment transport rates for separate sand fractions through a spring
tidal cycle. Finally, specific values of β are suggested for varying concentrations of sand at a reference height of 100 cm
above the seabed. 相似文献
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Abstract The San Diego Trough Geotechnical Test Area, located about 24 km southwest of San Diego in a water depth of about 1.2 km, lies near the base of the Coronado Escarpment directly north of the Coronado Fan. A new bathymetric map delineates a shallow basin in the soft, highly plastic, clayey silts flooring the Test Area. Measurements of shear strength by vane and static cone pene‐trometer, and bulk density by nuclear densitometer, were made in place from the submersible Deep Quest. Sixteen short (< 1.6 m) gravity cores were collected from ships. The geotechnical properties show little areal variation and generally change uniformly with depth within the 55 km2 Test Area. Silt is the predominant grain size, averaging about 62%. In‐place bulk density shows little change with increasing depth, values range from 1.23 to 1.26 Mg/m3; laboratory density values increase with depth, ranging from 1.30 to 1.52 Mg/m3 between the surface and a depth of about 1.1 m. The difference between the in place and laboratory values may indicate sampling densification of the cored sediment. Water content in the cores decreases uniformly within the range of 249 to 43% dry weight. Shear strength increases linearly with depth. The laboratory shear strength values are lower than the in place values, which range from 4 kPa at the surface to about 29 kPa at a depth of 3.27 m. Predictor equations relate Atterberg limits, bulk density, water content, and laboratory and in place shear strength to depth. Sedimentation‐compression e log p curves have an equivalent compression index of 1.5 to nearly 2. Excluding rurbidite layers and sampling disturbance effects, all cores indicate a uniform depositional environment in the surface to 1.6 m of sediment sampled. The geotechnical properties indicate that the sediments in the west central and southwest parts of the Test Area exhibit vertical heterogeneity due to thin silt‐sand layers, presumably of turbidity current origin, that originated from the Coronado Canyon. 相似文献
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Jintang Ou Haoyan Dong Liangwen Jia Xiangxin Luo Zixiao He Kanglin Chen Jing Liu Yitong Lin Mingdong Yu Mingen Liang 《海洋学报(英文版)》2022,41(5):51-63
Knowledge of sediment variation processes is essential to understand the evolution mechanism of beach morphology changes. Thus, a field measurement was conducted at the Heisha Beach, located on the west coast of the Zhujiang River(Pearl River) Estuary, to investigate the short-term variation in suspended sediment concentrations(SSCs) and the relationship between the SSC and turbulent kinetic energy, bottom shear stress(BSS), and relative wave height. Based on extreme event analysis results, extr... 相似文献
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沙纹微地形普遍存在于海底,沙纹的消长能改变底部应力进而影响泥沙的运移。以往研究较多侧重于波致沙纹,并已应用于波浪模式的底摩擦计算,而较少考虑波流联合效应产生的沙纹,也未将其应用于综合的水动力模式和沉积物输运模式。本文在POM水动力模式中嵌入新南威尔士大学泥沙模式,通过耦合波流共同作用的微地形模型与波流相互作用底边界层模型,发展了波浪-海流-微地形（沙纹）耦合的沉积动力模式。本文将该模式应用于澳大利亚Jervis湾,针对波主导和波流联合主导沙纹两种类型,分别进行了沙纹发展状态、几何形态的分布及悬浮泥沙的模拟。结果表明:波致沙纹比波流联合作用的沙波具有更大的波高和波长,因此当波主导时沙纹对悬浮泥沙起着关键作用。通过考虑随沙纹变化的粗糙度,相比于以往模式设置均一的粗糙度,该模型能对悬浮物浓度的骤升过程进行更精细的预测。 相似文献
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Prediction of the concentration of suspended cohesive sediment in the marine environment is constrained by difficulties in interpreting experimental evidence on bed exchange, i.e. erosion and deposition of particles, which remains sparse in mechanistic details. In this paper, conditions under which bed exchange in turbulent flows collectively determines the concentration of suspended matter have been examined in the heuristic sense based on selective experimental data. It is argued that interpretation of such data can be significantly facilitated when multi-class representation of particle size, collisional interaction between suspended particles and probabilistic representations of the bed shear stress along with variables describing particle behavior (critical shear stress for deposition, bed floc shear strength) are taken into account. Aggregation—floc growth and breakup kinetics—brings about shifts in the suspended particle size distribution; bed exchange is accordingly modulated and this in turn determines concentration dynamics. Probabilistic representation of the governing variables broadens the suspended sediment size spectrum by increasing the possibilities of inter-particle interactions relative to the mean-value representation. Simple models of bed exchange, which essentially rely on single-size assumption and mean-value representation of variables, overlook the mechanistic basis underpinning particle dynamics. 相似文献