scholarly journals The effect of debris-flow sediment grain size distribution on fan forming processes

2021 ◽  
Author(s):  
Haruka Tsunetaka ◽  
Norifumi Hotta ◽  
Yuichi Sakai ◽  
Thad Wasklewicz
Keyword(s):  
Grain Size ◽  
Debris Flow ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Flow Characteristics ◽  
Granular Flows ◽  
Spatial Diversity ◽  
Flume Experiments ◽  
Sediment Grain Size ◽  
Average Grain Size

Abstract. Knowledge of the processes driving debris-flow fan evolution are critical in the support of efforts to mitigate related hazards, reduce risk to populations and infrastructure, and reconstruct the history of sediment dynamics in mountainous areas. Research on debris-flow fan development has focused on topographic controls, debris-flow volume and rheology, and the sequence of occurrence of debris flows. While these items have explained a great deal about fan formation and specifically avulsion and runout mechanisms, there is a need to further investigate other properties as they relate to debris-flow fan formative process. Here, we examined the role of debris-flow grain-size distribution on fan formation. Flume experiments were employed to examine the morphology of debris-flow fans that resulted from flows with mono- or multi-granular sediment composition with the same average grain size. All other flow characteristics were held constant. The mono-granular flows formed a symmetric-like fan morphology because there was little avulsion during the formation process. The multi-granular flows produced fans with an asymmetric morphology. Avulsions occurred on both lateral extents of the fan during the early stages of fan development and caused the runout direction to shift produce the fan asymmetry. Grain-size distribution was closely related to spatial diversity in fan morphology and stratigraphy.

scholarly journals Debris flow sediment control using multiple herringbone water-sediment separation structures

2016 ◽  
Author(s):  
Xiangping Xie ◽  
Fangqiang Wei ◽  
Xiaojun Wang ◽  
Hongjuan Yang ◽  
James S. Gardner
Keyword(s):  
Grain Size ◽  
Debris Flow ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Sediment Grain Size ◽  
Sediment Control ◽  
Separation Rate ◽  
Control Effectiveness ◽  
Separation Ratio ◽  
Opening Width

Abstract. Single herringbone water-sediment separation structures (HWSS) have limited sediment control effectiveness in debris flows. A series of such structures in a debris flow channel to form a multiple structure system (M-HWSS system) should be more effective in debris flow mitigation. Hydraulic model tests reveal that a M-HWSS system does perform better in coarse sediment separation and has better stability in differing debris flow situations. The mean particle size of discharged sediment is gradually and significantly decreased down channel by M-HWSS system. The separated sediments are moderately sorted and this can be improved by optimizing the structure design parameters and increasing structure numbers. The fraction separation ratio (λi), coarse separation ratio (λc) and total sediment separation rate (Pt) are suggested parameters to express the sediment control effectiveness. All are closely related to the herringbone opening width and the input sediment grain size distribution. The quantitative relationships among them are proposed. On the basis of the tests, conclusions and guidelines for effective M-HWSS design include: (1) three structures in the M-HWSS located in succession upstream, midstream and downstream, each with substantially different in sediment control functions, (2) a structure's performance is strongly influenced by that of the preceding one so that every structure is designed to fully implement the sediment control function, especially for those in the upstream and midstream, (3)the suggested herringbone opening width in a structure should be set at the percentile of d50 ~ d84 of the input sediment grain size distribution so that 20 ~ 60 % of the effective separation rate can be achieved.

scholarly journals Flow Characteristics and Grain Size Distribution of Granular Gangue Mineral by Compaction Treatment

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Ran Yuan ◽  
Dan Ma ◽  
Hongwei Zhang
Keyword(s):  
Weight Loss ◽  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Water Flow ◽  
Fine Particles ◽  
Flow Characteristics ◽  
Test System ◽  
Chemical Components ◽  
Gangue Mineral

A test system for water flow in granular gangue mineral was designed to study the flow characteristics by compaction treatment. With the increase of the compaction displacement, the porosity decreases and void in granular gangue becomes less. The main reason causing initial porosity decrease is that the void of larger size is filled with small particles. Permeability tends to decrease and non-Darcy flow factor increases under the compaction treatment. The change trend of flow characteristics shows twists and turns, which indicate that flow characteristics of granular gangue mineral are related to compaction level, grain size distribution, crushing, and fracture structure. During compaction, larger particles are crushed, which in turn causes the weight of smaller particles to increase, and water flow induces fine particles to migrate (weight loss); meanwhile, a sample with more weight of size (0–2.5 mm) has a higher amount of weight loss. Water seepage will cause the decrease of some chemical components, where SiO2 decreased the highest in these components; the components decreased are more likely locked at fragments rather than the defect of the minerals. The variation of the chemical components has an opposite trend when compared with permeability.

Recrystallization of Oxygen Contaminated Al Films

1986 ◽  
Vol 71 ◽  
Author(s):  
G.J. Van Der Kolk ◽  
M.J. Verkerk
Keyword(s):  
Grain Size ◽  
Silicon Nitride ◽  
Substrate Temperature ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Relative Increase ◽  
Partial Pressures ◽  
Average Grain Size

AbstractAl was evaporated at oxygen partial pressures, PO2, varying between 10−7 and 10−4 Pa on substrates of silicon nitride. The substrate temperature was varied between 20 °C and 250°C. The films were annealed at temperatures up to 500°C.For Al films deposited at 20°C, it was found that the average grain size decreases with increasing oxygen partial pressure. After annealing recrystallization was observed. The relative increase of grain size was less for higher values of pO2. Annealing gave rise to a broad grain size distribution.For Al films deposited at 250°C, the presence of oxygen caused the growth of rough inhomogeneous films. This inhomogeneous structure remained during annealing.

Calculating debris flow density based on grain-size distribution

Landslides ◽  
2019 ◽  
Vol 16 (3) ◽  
pp. 515-522
Author(s):  
Taiqiang Yang ◽  
Yong Li ◽  
Qishu Zhang ◽  
Yu Jiang
Keyword(s):  
Grain Size ◽  
Debris Flow ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Flow Density

Study on the downcutting rate of a debris flow dam based on grain-size distribution

Geomorphology ◽  
2021 ◽  
pp. 107891
Author(s):  
Hechun Ruan ◽  
Huayong Chen ◽  
Yong Li ◽  
Jiangang Chen ◽  
Huibin Li
Keyword(s):  
Grain Size ◽  
Debris Flow ◽  
Size Distribution ◽  
Grain Size Distribution

The Inverse Hall-Petch Effect—Fact or Artifact?

2000 ◽  
Vol 634 ◽  
Author(s):  
Carl C. Koch ◽  
J. Narayan
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Computer Simulations ◽  
Nanocrystalline Materials ◽  
Grain Sizes ◽  
Average Grain Size

ABSTRACTThis paper critically reviews the data in the literature which gives softening—the inverse Hall-Petch effect—at the finest nanoscale grain sizes. The difficulties with obtaining artifactfree samples of nanocrystalline materials will be discussed along with the problems of measurement of the average grain size distribution. Computer simulations which predict the inverse Hall-Petch effect are also noted as well as the models which have been proposed for the effect. It is concluded that while only a few of the experiments which have reported the inverse Hall-Petch effect are free from obvious or possible artifacts, these few along with the predictions of computer simulations suggest it is real. However, it seems that it should only be observed for grain sizes less than about 10 nm.

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