Rheological behavior of dredged slurries at high water contents     

Gui-Zhong Xu  Ying Zhang  Ruo-Bing Sun 《Marine Georesources & Geotechnology》2017,35(3):357-364

Each year in the world, there is significant amount of dredged slurries generated during geotechnical jobs. In the slurry storage process, the rheological behavior is a key factor affecting the motion of dredged slurries. To gain better understanding on this behavior, experiments on dredged slurries with different liquid limits are conducted using rotary viscometer. It has been found that, as water content increases, slurry property can change from Bingham plastic fluids to Newtonian fluids. In log–log coordinates, their corresponding yield stress and plastic viscosity are in linear relationship with their water contents and the intersection of these two lines can be treated as the turning point which is 4.7 times the liquid limit. The yield stress and plastic viscosity of different dredged slurries can be normalized efficiently using normalized water content. So, in this paper, a new quantitative prediction method for yield stress and plastic viscosity is proposed, which is effective for use in alkined modes of motion, is proposed.  相似文献   

基于旁压试验土体弹塑性本构模型初探     

苏辉  杨石飞  顾国荣 《岩土力学》2015,36(Z1):131-136

在大量旁压试验数据分析的基础上,通过曲线拟合,建立了旁压试验弹塑性阶段曲线的椭圆方程,利用土体SMP屈服准则和Rowe流动法则,推导出土体塑性阶段应力增量与应变增量间关系矩阵。在弹性阶段,假设土体应力-应变服从广义虎克定律,建立了基于旁压试验的土体弹塑性本构模型。编制了相应的计算程序,将文中模型计算结果与实际旁压试验曲线进行对比,初步验证了模型的正确性。将本构模型编译为ABAQUS自定义材料子程序UMAT,通过有限元对比分析,文中模型计算变形较弹性模型小,较摩尔-库仑模型大,与模型建立的假设一致。基于旁压试验的土体弹塑性本构模型参数少,且易于获取,便于在实际工程中应用。  相似文献   

Modelling the runoff-sediment yield relationship using a proportional function in hilly areas of the Loess Plateau, North China   总被引：7，自引：0，他引：7  

Zheng Mingguo  Cai Qiangguo  Cheng Qinjuan   《Geomorphology》2008,93(3-4):288-301

Based on data observed at the 12 small watersheds in hilly areas of the Loess Plateau, North China, the relationship between event runoff volume and sediment yield is examined. The results reveal that the runoff-sediment yield relationship at the inter-event timescale is mainly determined by the runoff-sediment concentration relationship at the intra-event timescale. In the study area, the sediment concentration tends to be stable when the flow discharge exceeds a certain critical value. Many factors that are important for determining the characteristics of low-magnitude events, such as flow discharge, particle size of fluvial sediment, and accumulation of loose material on land surfaces prior to a rainstorm, appear to have little importance for high-magnitude events. Consequently, mean sediment concentration tends to be stable for large flood events, suggesting a strong similarity between the two flow-sediment relationships at inter-and intra-event temporal scales. Furthermore, a proportional function is proposed to predict event sediment yield, and the correspondence between the predicted and observed sediment yields is examined. The performance of the model is good for high-magnitude events, especially extreme events. The applicability of the proposed model at the annual timescale is also discussed.  相似文献   

A new approach for linking event‐based upland sediment sources to downstream suspended sediment transport     

Peng Gao  James Puckett 《地球表面变化过程与地形》2012,37(2):169-179

In this study, we proposed a new approach for linking event sediment sources to downstream sediment transport in a watershed in central New York. This approach is based on a new concept of spatial scale, sub‐watershed area (SWA), defined as a sub‐watershed within which all eroded soils are transported out without deposition during a hydrological event. Using (rainfall) event data collected between July and November, 2007 from several SWAs of the studied watershed, we developed an empirical equation that has one independent variable, mean SWA slope. This equation was then used to determine event‐averaged unit soil erosion rate, Q_S/A, (in kg/km²/hr) for all SWAs in the studied watershed and calculate event‐averaged gross erosion E_ea (in kg/hr). The event gross erosion E_t (in kilograms) was subsequently computed as the product of E_ea and the mean event duration, T (in hours) determined using event hydrographs at the outlet of the studied watershed. Next, we developed two linear sediment rating curves (SRCs) for small and big events based on the event data obtained at the watershed outlet. These SRCs, together with T, allowed us to determine event sediment yield SY_e (in kilograms) for all events during the study period. By comparing E_t with SY_e, developing empirical equations (i) between E_t and SY_e and (ii) for event sediment delivery ratio, respectively, we revealed the event dynamic processes connecting sediment sources and downstream sediment transport. During small events, sediment transport in streams was at capacity and dominated by the deposition process, whereas during big events, it was below capacity and controlled by the erosion process. The key of applying this approach to other watersheds is establishing their empirical equations for Q_S/A and appropriately determining their numbers of SWAs. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

钢结构高温响应影响因素的研究     

江雪玲  魏德敏 《地震学刊》2012,(1):111-116

根据考虑几何和材料非线性及温度沿杆件截面高度线性分布等因素对钢结构常温和高温响应影响的基本方程,用自行编制的计算程序对单层双跨钢框架进行结构非线性温度响应研究,分析了弯曲应变、屈强比、梁柱刚度比、初始弹性模量等因素对结构响应的影响,并研究了温度步长、保护层厚度对结构耐火时间的影响。由计算结果发现,弯曲应变、初始弹性模量、梁柱线刚度比对梁跨中挠度及边柱柱顶水平位移影响较大,而对柱顶竖向位移影响不明显;当结构有防火保护层时,时间步长对结构耐火时间的影响不大,而保护层厚度对结构耐火时间的影响较明显。  相似文献   

两种不同的恒载升温方式下的钢材破坏机理分析     

李焕群  屈立军 《地震学刊》2012,(Z1):50-54

通过对我国建筑结构用钢在拉伸和压缩两种方式下的恒载升温试验,进行了5次受拉试件和2次受压试件的对比研究,根据试验中材料的各自变形规律,对其破坏机理进行了理论分析;从材料屈服的定义出发,给出了恒载升温拉伸试验中的参数(对应温度下的临界荷载水平),并与恒载升温压缩试验中的参数项进行了对比,指出受压构件和受拉构件的高温屈服强度是不同的,因此在钢结构建筑的耐火设计中应分别取不同的安全系数。  相似文献   

地貌特征对约旦南部阿尔阿加河(WadiAl-Arja)流域产沙影响分析(英文)   总被引：1，自引：0，他引：1  

Ali Hamdi ABU SALIM 《地理学报(英文版)》2014,24(3):457-474

This study addresses the morphometric variables that determine the sediment yield in Wadi Al-Arja through the analysis of the impact of different morphometric characteristics along the course of the valley on its sediment yield, as well as the analysis of spatial and formal dimensions and morphologies of the basin and its relationship to the sediment yield. The study also addresses the size of variation in the volume of sediment yield of the river tributaries that make up the water network of the valley under the differences of its morphometric and hydrological characteristics. The study found several results, most notably: The classification of Wadi Al-Arja basin according to the hypsometric integral value(72.1%) within an uneven topography, which increases the force of the erosive activity and the size of the sediment yield if the basin was exposed to moist climatic periods. The study also showed the presence of convergence in the intra-spaces between the river tributaries in the water network. This increases the volume of water flows when these tributaries meet with each other and thus increasing their erosive ability and sediment yield. The study also showed the presence of marked variation in the sediment yield of the river tributaries depending on the differences in its morphometric characteristics. The results of the step-wise regression analysis confirmed the importance of the morphometric and hydrological variables, and plant coverage in interpreting the variation in the size of the sediment yield of the river tributaries of different stream order in Wadi Al-Arja basin, where these variables interpreted 43% of the total variation, with statistical significance less than 0.05.  相似文献   

基于遥感的黄土高原林草植被变化对河川径流的影响分析   总被引：11，自引：1，他引：10  

刘晓燕  刘昌明  杨胜天  金双彦  高亚军  高云飞 《地理学报》2014,69(11):1595-1603

从黄土高原不同地貌区降雨产流机制入手,分析了林草植被影响流域水循环的可能环节;利用20世纪70年代以来不同时期的土地利用和植被盖度解译成果,以及同期实测的降雨和径流数据、供用水数据等,引入林草植被覆盖率、径流系数、产洪系数和基流系数等概念,从流域尺度上构建了林草植被覆盖率与河川径流的定量响应关系,结果发现,在半湿润或半干旱的黄土区,径流系数和产洪系数都将随林草植被的改善而减少,气候越干旱、径流或洪量减少越多;与同气候带的黄土区相比,盖沙黄土区林草植被改善所导致的减水量更大。不过,当林草植被覆盖率大于60%后,产洪系数变化减缓;最终河川径流将稳定在大于基流的某阈值附近。  相似文献   

灾害学定义之下的土壤盐碱化风险评价   总被引：1，自引：0，他引：1  

谷洪彪  迟宝明  姜纪沂 《吉林大学学报(地球科学版)》2013,43(5):1623-1629

为改善灌区中低产地的产量、提高其田间管理及粮食综合生产能力、防止土壤盐碱化灾害的扩展,在土壤盐碱化灾害学研究的基础上,建立了土壤盐碱化灾害风险评价指标体系。选用基于熵权的灰色关联评价方法来构建土壤盐碱化灾害风险评价模型,根据标准自然灾害风险原理,建立土壤盐碱化灾害风险指数计算模型。在松原灌区土壤盐碱化灾害风险评价中的应用表明,灌区各灌片盐碱灾害风险值为0.10～0.36,属于中度风险和重度风险区,风险值由小到大排序为：前郭片、安字片、有字片、龙海片、水字片、大布苏片、潜字片、套浩太片、戎字片、红星片、洪字片。该模型与灌区实情符合较好,客观性较强,表明所建模型可用于土壤盐碱化灾害风险评价。  相似文献   

1995-2010年山东省粮食单产变化空间分异及均衡增产潜力   总被引：4，自引：0，他引：4  

柏林川  武兰芳  宋小青 《地理科学进展》2013,32(8):1257-1265

以县域为基本空间单元,采用GIS 空间分析和ESDA方法,对山东省1995-2010 年间县域粮食单产空间格局变化进行了分析,在此基础上,结合全国农业生态区划,分析山东省粮食均衡增产潜力。结果表明:① 山东省县域粮食单产水平之间的差异整体上呈现出先增大后减小的趋势。鲁北和鲁西北平原农业生产基础差,单产增长速度最快;鲁西南平原农业生产基础差,单产增长速度较慢;鲁中南丘陵和山东半岛农业生产基础好,单产增长速度较慢;② 县域粮食单产变化的Global Moran's I 值为0.5708,表明单产变化的区域分布并非完全随机,而是表现出明显的空间集聚特征,4 种集聚类型中,“H-H”类型区和“L-L”类型区占主导,“H-H”类型区主要分布在鲁北和鲁西北平原,“L-L”类型区主要分布在鲁西南平原、鲁中南丘陵和山东半岛;③ 全省可划分为4 个一级、9 个二级均衡增产类型区,粮食单产增产潜力鲁北和鲁西北平原>鲁中南丘陵>山东半岛>鲁西南平原;总产量增产潜力约为9.50×10⁶ t,其中鲁中南丘陵>鲁北和鲁西北平原>鲁西南平原>山东半岛。  相似文献