Enhancing the Erodibility of Cohesive Sediments by Applying Mechanical Vibrations

A list of available codes of practice for self-cleansing sewers is presented and a review of appraisals of minimum velocity criterion is summarised. Comparisons of newly developed “minimum velocity” criteria and “minimum shear stress” criterion are presented. Some design charts are also given. These charts are applicable to non-cohesive sediments (typically storm sewers). It appears that sediment size and concentration need to be taken into account, and that a limited depth of sediment bed is recommended for large pipes (diameters > 1000 mm) to maximise their transport capacity.

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Pickup rate of non-cohesive sediments in low-velocity flows

Journal of Hydraulic Research ◽

10.1080/00221686.2020.1871430 ◽

2021 ◽

pp. 1-11

Author(s):

Dake Chen ◽

Bruce Melville ◽

Jinhai Zheng ◽

Yigang Wang ◽

Chi Zhang ◽

...

Keyword(s):

Cohesive Sediments ◽

Low Velocity

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A Computationally Efficient Shallow Water Model for Mixed Cohesive and Non-Cohesive Sediment Transport in the Yangtze Estuary

Water ◽

10.3390/w13101435 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1435

Author(s):

Peng Hu ◽

Junyu Tao ◽

Aofei Ji ◽

Wei Li ◽

Zhiguo He

Keyword(s):

Sediment Transport ◽

Yangtze Estuary ◽

Water Model ◽

Cohesive Sediments ◽

Shallow Water Model ◽

Computationally Efficient ◽

Time Step ◽

The Yangtze Estuary ◽

Erosion Coefficient ◽

Cohesive Sediment Transport

In this paper, a computationally efficient shallow water model is developed for sediment transport in the Yangtze estuary by considering mixed cohesive and non-cohesive sediment transport. It is firstly shown that the model is capable of reproducing tidal-hydrodynamics in the estuarine region. Secondly, it is demonstrated that the observed temporal variation of suspended sediment concentration (SSC) for mixed cohesive and non-cohesive sediments can be well-captured by the model with calibrated parameters (i.e., critical shear stresses for erosion/deposition, erosion coefficient). Numerical comparative studies indicate that: (1) consideration of multiple sediment fraction (both cohesive and non-cohesive sediments) is important for accurate modeling of SSC in the Yangtze Estuary; (2) the critical shear stress and the erosion coefficient is shown to be site-dependent, for which intensive calibration may be required; and (3) the Deepwater Navigation Channel (DNC) project may lead to enhanced current velocity and thus reduced sediment deposition in the North Passage of the Yangtze Estuary. Finally, the implementation of the hybrid local time step/global maximum time step (LTS/GMaTS) (using LTS to update the hydro-sediment module but using GMaTS to update the morphodynamic module) can lead to a reduction of as high as 90% in the computational cost for the Yangtze Estuary. This advantage, along with its well-demonstrated quantitative accuracy, indicates that the present model should find wide applications in estuarine regions.

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Deposition and erosion behaviour of cohesive sediments in the upper River Taw observatory, southwest UK: Implications for management and modelling

Journal of Hydrology ◽

10.1016/j.jhydrol.2021.126145 ◽

2021 ◽

Vol 598 ◽

pp. 126145

Author(s):

M. Stone ◽

B.G. Krishnappan ◽

S. Granger ◽

H.R. Upadhayay ◽

Y. Zhang ◽

...

Keyword(s):

Cohesive Sediments ◽

Erosion Behaviour

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Lacustrine Slope-Related Soft-Sediment Deformation Structures in the Cretaceous Gyeokpori Formation, Buan Area, SW Korea, and Volcanism-Induced Seismic Shocks as Their Possible Trigger

Minerals ◽

10.3390/min11070721 ◽

2021 ◽

Vol 11 (7) ◽

pp. 721

Author(s):

Ukhwan Byun ◽

A.J. (Tom) van Loon ◽

Kyoungtae Ko

Keyword(s):

Facies Analysis ◽

Deformation Mechanisms ◽

Volcanic Area ◽

Cohesive Sediments ◽

Soft Sediment ◽

Deformation Structures ◽

Sediment Deformation ◽

Soft Sediment Deformation ◽

Siliciclastic Rocks ◽

Sediment Layers

The Gyeokpori Formation in the Buan volcanic area primarily contains siliciclastic rocks interbedded with volcanoclastics. These sediments are characterized by a variety of soft-sediment deformation structures (SSDS). The SSDS in the Gyeokpori Formation are embedded in poorly sorted conglomerates; slump folds are also present in the formation. The deformation mechanisms and triggers causing the deformation are not yet clear. In the present study, the trigger of the SSDS in the Gyeokpori Formation was investigated using facies analysis. This included evaluation of the reworking process of both cohesive and non-cohesive sediments. The analysis indicates that the SSDS are directly or indirectly associated with the alternation of conglomerates and mud layers with clasts. These layers underwent non-cohesive and cohesive deformation, respectively, which promoted SSDS formation. The slump folds were controlled by the extent of cohesive and non-cohesive deformation experienced by the sediment layers in the slope environment. The SSDS deformation style and morphology differ, particularly in the case of reworking by slump activity. This study contributes to the understanding of lacustrine slope-related soft-sediment deformation structures.

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Model approach for electromagnetically excited mechanical vibrations in direct-drive wind turbines

Journal of Physics Conference Series ◽

10.1088/1742-6596/1618/2/022060 ◽

2020 ◽

Vol 1618 ◽

pp. 022060

Author(s):

Christoph Mülder ◽

Tobias Duda ◽

Georg Jacobs ◽

Kay Hameyer

Keyword(s):

Wind Turbines ◽

Direct Drive ◽

Mechanical Vibrations ◽

Model Approach

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Numerical Characterization of Cohesive and Non-Cohesive ‘Sediments’ under Different Consolidation States Using 3D DEM Triaxial Experiments

Processes ◽

10.3390/pr8101252 ◽

2020 ◽

Vol 8 (10) ◽

pp. 1252

Author(s):

Hadar Elyashiv ◽

Revital Bookman ◽

Lennart Siemann ◽

Uri ten Brink ◽

Katrin Huhn

Keyword(s):

Mechanical Response ◽

Burial Depth ◽

Cohesive Sediments ◽

Third Order ◽

First Order ◽

Numerical Characterization ◽

Response To Stress ◽

Bond Strengths ◽

Individual Bond

The Discrete Element Method has been widely used to simulate geo-materials due to time and scale limitations met in the field and laboratories. While cohesionless geo-materials were the focus of many previous studies, the deformation of cohesive geo-materials in 3D remained poorly characterized. Here, we aimed to generate a range of numerical ‘sediments’, assess their mechanical response to stress and compare their response with laboratory tests, focusing on differences between the micro- and macro-material properties. We simulated two endmembers—clay (cohesive) and sand (cohesionless). The materials were tested in a 3D triaxial numerical setup, under different simulated burial stresses and consolidation states. Variations in particle contact or individual bond strengths generate first order influence on the stress–strain response, i.e., a different deformation style of the numerical sand or clay. Increased burial depth generates a second order influence, elevating peak shear strength. Loose and dense consolidation states generate a third order influence of the endmember level. The results replicate a range of sediment compositions, empirical behaviors and conditions. We propose a procedure to characterize sediments numerically. The numerical ‘sediments’ can be applied to simulate processes in sediments exhibiting variations in strength due to post-seismic consolidation, bioturbation or variations in sedimentation rates.

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The effect of vibratory conditioning on tensile strength and microstructure of 1018 mild steel

World Journal of Engineering ◽

10.1108/wje-07-2020-0296 ◽

2020 ◽

Vol 17 (6) ◽

pp. 837-844 ◽

Cited By ~ 1

Author(s):

Venkata Suresh Bade ◽

Srinivasa Rao P. ◽

Govinda Rao P.

Keyword(s):

Tensile Strength ◽

Mild Steel ◽

Fusion Zone ◽

Dc Motor ◽

Grain Structure ◽

Internal Stresses ◽

Skilled Workers ◽

Mechanical Vibrations ◽

Content Type ◽

Weld Defects

Purpose The purpose of this paper is to investigate the prominence of mechanical excitations at the time of welding. In the past years, the process of welding technology has expanded its influence in manufacturing. The crucial drawback of conventional welding is prompted by internal stresses and distortions, which is the focal reason for weld defects. These weld defects can be diminished by the process called post-weld heat treatment (PWHT), which consumes more working hours and needs skilled workers. To replace these PWHT processes, mechanical vibrations are introduced during the process of welding to diminish these weld defects. Design/methodology/approach In the current research, the mechanical vibrations are transferred to weld-pool through vibro-motor and DC motor connected to the electrode. As per standards, the tensile test specimens were prepared for welding with different voltages of vibro-motor and DC motor respectively. The weld joints were tested for tensile strength and analyzed the microstructure at the fusion zone. Findings Melt-ability at fusion zone of 1018 mild steel was investigated by the single-stroke intense heat process of fusion welding. It is observed that the mechanical vibrations technique has a profound influence on the enhancement of the fusion zone characteristics and grain structure. The peak value of the tensile strength is observed at 100 s of vibration, 190 V of vibro-motor voltage and 18 V of electrode voltage. The tensile strength of the welded joints with vibrations is increased up to 22.64% when it is compared with conventional welding. The enhancement of the tensile strength of the weld bead was obtained because of the formation of fine grain structure. So, mechanical vibrations are identified as the most convenient method for improving the mild steel alloys weld quality. Originality/value A novel approach called mechanical vibrations during the process of welding is implemented for fusion zone refinement.

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