Visual characterization technique for gravel‐cobble river bed surface sediments; validation and environmental applications Contribution to the programme of CIRSA (Centre Interuniversitaire de Recherche sur le Saumon Atlantique)     

Christian Latulippe  Michel F. Lapointe  Tracey Talbot 《地球表面变化过程与地形》2001,26(3):307-318

This paper presents an evaluation of the feasibility and the reliability of a visual characterization technique for gravel–cobble river bed surface substrate. Based on principal axis regressions, using phi scale (ϕ), comparisons of visual estimation and grid sampling techniques show that useful predictive relations (R² = 0·78–0·88) exist between visual estimates of the surface d₁₆, d₅₀ and d₈₄ and estimates obtained for the same percentiles with the grid sampling technique. Comparisons of visual estimation and the surface‐bulk sampling technique also indicate a predictive relation (R² = 0·70) between the d₅₀ of the two methods. Trained operators can visually estimate gravel–cobble bed surface d₁₆ to uncertainties of 41 per cent, d₅₀ to 15 per cent and d₈₄ to 11 per cent (for example, there is a 5·5 mm error on a d₈₄ size of 50 mm). Furthermore, evidence shows that if operators are properly trained, a calibration relation for each percentile can be applied independently of operators. This visual characterization allows effective detailed mapping of spatial patterns in substrate size distribution along extensive reaches of gravel‐bed rivers. The technique can be very useful in creating terrain models for various geomorphological, hydrological and biological applications such as the determination of entrainment thresholds, hydraulic roughness and substrate suitability for benthic insects or salmonid habitat. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Turbulent structure in uniform inclined open channel flow over different rough porous beds     

Evangelos Keramaris 《国际泥沙研究》2017,32(1)

In this study the effects of the different rough porous beds in an open inclined channel are studied experimentally for impermeable and permeable porous bed.For the simulation of porous bed two different types of permeable bed with the same thickness(s' = 3 cm) and the same porosity ε=0.70 are used:(a) porous filters and(b) gravel bed.Laboratory experiments were used for the calculation of turbulent velocity profiles.Measurements of velocity were taken for inclined channel for three different slopes(S=-0.002,S=-0.004 and S=-0.006) and for five different flow depths(h=5 cm,7 cm,9 cm,11 cm and 13 cm).The total discharge Q varies from 0.78 to 1.31 1/s.The measurements were obtained using a two-dimensional(2D) Particle Image Velocimetry(PIV).The total discharge was estimated using a calibrated venture apparatus.Results showed that the presence of rough porous bed in inclined open channels influence significantly the turbulent characteristics of the flow in comparison with impermeable open channels with the same slopes.  相似文献   

The concept of travelling bedload and its consequences for bedload computation in mountain streams          下载免费PDF全文

Guillaume Piton  Alain Recking 《地球表面变化过程与地形》2017,42(10):1505-1519

In bedload transport modelling, it is usually presumed that transported material is fed by the bed itself. This may not be true in some mountain streams where the bed can be very coarse and immobile for the majority of common floods, whereas a finer material, supplied by bed‐external sources, is efficiently transported during floods, with marginal morphological activities. This transport mode was introduced in an earlier paper as ‘travelling bedload’. It could be considered an extension of the washload concept of suspension, applied to bedload transport in high‐energy, heavily armoured streams. Since this fine material is poorly represented in the bed surface, standard surface‐based approaches are likely to strongly underestimate the true transport in such streams. This paper proposes a simple method to account for travelling bedload in bedload transport estimations. The method is tested on published datasets and on a typical Alpine stream, the Roize (Voreppe, France). The results, particularly on active streams that experience greater transport than expected from the grain sizes of their bed material, reinforce the necessity of accounting for the ‘travelling bedload concept’ in bedload computation. The method relevance is discussed regarding varying flood magnitudes, geomorphic responses and eventual anthropic origin of the ‘travelling bedload’ phenomena. To conclude, this paper considers how to compute bedload transport for a wide range of situations, ranging from sediment‐starved cases to the general mobile bed alluvial case, including the intermediate situation of external source supply on armoured bed. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

A wind tunnel investigation of particle segregation,ripple formation and armouring within sand beds of systematically varied texture          下载免费PDF全文

Cheryl McKenna Neuman  ottO Bédard 《地球表面变化过程与地形》2017,42(5):749-762

This paper reports on a wind tunnel investigation of particle segregation, ripple formation and surface armouring within sand beds of systematically varied particle size distribution, from coarsely skewed to bimodal. By design, the system was closed with no external inputs of mass from an external particle feed. Particles too coarse to travel in saltation for the given range in wind speed were dyed red in order to distinguish them in optical images from finer sand particles, which could be entrained into the unidirectional airflow. A 3D laser scanner measured the changing bed topography at regular time intervals during 18 experiments involving varied combinations of wind speed and bed texture. Image classification techniques were used to investigate the coincident self‐organization of the two populations of particles, as distinguished by their colour. As soon as saltation commenced, some of the red particles segregated into thin discontinuous patches. Particle trapping and sheltering on these rough patches was strongly favoured, causing them to grow preferentially. During the earliest stages of formation, bedform growth coincided with: (i) rapid coarsening of the surface texture; and (ii) the merging of proto‐ripple ‘crests’ to generate larger rhythmic bedforms of lower frequency. Consistent with previous work, ripple size was observed to increase under stronger winds when not exceeding the threshold for entrainment of the coarse‐mode or red particles from the crest. With declining rates of mass transport and particle segregation as the bed surface armoured, and the consequent deceleration of ripple propagation through to the end of each experiment, all surfaces eventually attained a steady‐state morphometry. At saturation, the largest ripples developed on beds having the lowest initial concentration of red particles. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Transport of moderately sorted gravel at low bed shear stresses: The role of fine sediment infiltration          下载免费PDF全文

Emeline Perret  Céline Berni  Benoît Camenen  Albert Herrero  Kamal El Kadi Abderrezzak 《地球表面变化过程与地形》2018,43(7):1416-1430

A reliable estimation of sediment transport in gravel‐bed streams is important for various practical engineering and biological studies (e.g., channel stability design, bed degradation/aggradation, restoration of spawning habitat). In the present work, we report original laboratory experiments investigating the transport of gravel particles at low bed shear stresses. The laboratory tests were conducted under unsteady flow conditions inducing low bed shear stresses, with detailed monitoring of the bed topography using a laser scanner. Effects of bed surface arrangements were documented by testing loose and packed bed configurations. Effects of fine sediments were examined by testing beds with sand, artificial fine sand or cohesive silt infiltrated in the gravel matrix. Analysis of the experimental data revealed that the transport of gravel particles depends upon the bed arrangement, the bed material properties (e.g., size and shape, consolidation index, permeability) and the concentration of fine sediments within the surface layer of moving grains. This concentration is directly related to the distribution of fine particles within the gravel matrix (i.e., bottom‐up infiltration or bridging) and their transport mode (i.e., bedload or suspended load). Compared to loose beds, the mobility of gravel is reduced for packed beds and for beds clogged from the bottom up with cohesive fine sediments; in both cases, the bed shear stress for gravel entrainment increases by about 12%. On the other hand, the mobility of gravel increases significantly (bed shear stress for particle motion decreasing up to 40%) for beds clogged at the surface by non‐cohesive sand particles. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

级配碎石填料大三轴试验及累积塑性应变预测模型     

杨志浩  岳祖润  冯怀平  叶朝良  马德良 《岩土力学》2020,41(9):2993-3002

级配碎石作为重载铁路基床表层的主要填料,其受列车荷载的影响最大。因此,研究级配碎石在循环荷载作用下的动力行为及累积塑性应变演化特征变得尤为重要。首先,通过制备不同细粒含量的级配碎石填料,开展一系列大型动三轴试验,探究细粒含量、围压及动应力幅值对循环荷载作用下试样累积塑性应变的耦合影响机制。其次,基于塑性安定理论,确定不同应力水平下试样的动力行为,得到考虑围压及细粒含量参数的塑性蠕变状态临界动应力计算模型。最后,结合试验数据,建立考虑应力水平及细粒含量参数的塑性蠕变动力行为累积塑性应变预测模型,并明确各参数的物理意义。其研究成果可为既有重载铁路路基健康状态评估及考虑强度、变形综合控制的路基结构设计提供参考。  相似文献   

Bed material transport estimated from the virtual velocity of sediment     

Judith K. Haschenburger  Michael Church 《地球表面变化过程与地形》1998,23(9):791-808

This study evaluates the possibility of determining bed material transport using the virtual rate of travel of individual particles, dimensions of the active layer of the streambed, and porosity and density of streambed material. Magnetically tagged stones and scour indicators were employed in Carnation Creek, British Columbia, to quantify transport rates. Observations cover flows up to 36 m³ s⁻¹ (τ* = 0·081). Transport rates, ranging from 0·090 to 9·7 kg s⁻¹ (0·12–13·2 m³ h⁻¹), display a relatively sensitive trend with maximum stream power, as expected. Error analysis indicates that uncertainty in virtual velocity covers the majority of sample variance. An evaluation of the two measurement techniques used to delineate active layer dimensions, magnetically tagged stones and scour indicators, indicates that they yield comparable depths, widths and transport rates over the range of flows observed. Issues for further study are discussed. © 1998 John Wiley & Sons, Ltd.  相似文献   

大北油田萨尔图油层特低渗储层宏观非均质性研究   总被引：3，自引：0，他引：3  

常波涛  单玄龙  那晓红  刘新月  孙连浦 《世界地质》2005,24(2):168-173

大北油田萨尔图油层属于特低渗透储层。从沉积微相的角度对萨尔图油层宏观非均质性研究表明,储层非均质性较强,而其非均质性主要受控于沉积环境、成岩作用及裂缝发育情况等因素。萨尔图油层在本区发育水下分流河道、席状砂、远砂坝和浊积扇(滑塌沉积)等4种储层微相,油层非均质性在各种沉积微相之间的过渡部位及浊积扇微相中较强;其次为席状砂微相和远砂坝微相,在水下分流河道中相对较弱。  相似文献   

基于BP神经网络的薄互层储层预测   总被引：1，自引：0，他引：1  

张大智  纪友亮  刘洪林 《上海国土资源》2005,(4):47-50,57

根据地震属性来进行储层预测的研究,对于寻找油气具有十分重要的意义。而由于地下地质情况千变万化,不确定的因素太多,对这种多自变量与因变量的复杂关系模拟问题,神经网络技术是目前较成熟、实际应用效果也较好的方法之一。用BP神经网络来预测薄互层储层厚度,它可以建立属性参数与预测目标之间的高度非线性映射,并应用于具体的实例,为薄互层储层预测提供了新的思路。  相似文献   

红螯螯虾鳃细胞与血细胞分子标记的鉴定          下载免费PDF全文

钟苏鸣  朱坤  杨丰  李钫 《应用海洋学学报》2024,43(2):245-254

甲壳动物的鳃中富集了大量血细胞,在循环血细胞稳态调节和免疫防御中发挥重要作用,因此获得区分鳃细胞和血细胞的分子标记将有助于研究鳃血细胞的功能。本研究采用SDS-PAGE电泳法比较了红螯螯虾(Cherax quadricarinatus)鳃细胞和血细胞的蛋白表达谱,获得3条组织特异性蛋白条带,并通过质谱技术鉴定了8个候选蛋白。实时荧光定量PCR(qRT-PCR)分析表明,空泡型-H⁺-ATP合酶C亚基(vacuolar-H⁺-ATPase subunit C, V-H⁺-ATPase)在鳃细胞中的转录水平是在血细胞中的53.3倍;而α-2-巨球蛋白(alpha-2-macroglobulin, α2M)和卵黄膜外层蛋白(vitelline membrane outer layer protein I-like protein, VMO-Ia)在血细胞中的转录水平分别是在鳃细胞中的10.3倍和10.9倍。Western-blot和免疫荧光分析表明,V-H⁺-ATPase和VMO-Ia蛋白分别在鳃细胞和血...  相似文献