scholarly journals Laboratory and field tests and distinct element analysis of dry granular flows and segregation processes

2019 ◽  
Vol 19 (1) ◽  
pp. 181-199 ◽  
Author(s):  
Yung Ming Cheng ◽  
Wing Hong Ivan Fung ◽  
Liang Li ◽  
Na Li
Keyword(s):  
Debris Flow ◽  
Numerical Simulations ◽  
Granular Flow ◽  
Laboratory Tests ◽  
Large Scale ◽  
Distinct Element ◽  
Field Tests ◽  
Flow Process ◽  
Flume Tests ◽  
Dry Granular Flow

Abstract. Natural as well as fill slopes are commonly found in Hong Kong, China, and many other countries, and slope failures with the subsequent debris flows have caused a serious loss of life and property in the past until now. There are various processes and features associated with debris flow which engineers need to know so as to design for the precautionary measures. In this study, experiments on flume tests, friction tests, deposition tests, and rebound tests were carried out for different sizes of balls to determine the parameters required for the modelling of dry granular flow. Different materials and sizes of balls are used in the flume tests, and various flow pattern and segregation phenomena are noticed in the tests. Distinct element modelling (DEM) of dry granular flow is also carried out for the flow process. It is found that for simple cases, the flow process can be modelled reasonably well by DEM, which is crucial for engineers to determine the pattern and impact of granular flow, which will lead to further study in more complicated debris flow. From laboratory tests, large-scale field tests, and numerical simulations of single- and multiple-material tests, it is also found that the particle size will be the most critical factor in the segregation process during granular flow. It is also found from the laboratory tests and numerical simulations that a jump in the flume can help to reduce the final velocity of the granular flow, which is useful for practical purposes.

scholarly journals Laboratory and Field Test and Distinct Element Analysis of Debris Flow

2018 ◽  
Author(s):  
Yung Ming Cheng ◽  
Na Li ◽  
Ivan Wing Hong Fung
Keyword(s):  
Debris Flow ◽  
Numerical Simulations ◽  
Field Test ◽  
Laboratory Tests ◽  
Large Scale ◽  
Distinct Element ◽  
Critical Factor ◽  
Flow Process ◽  
Element Analysis ◽  
Flume Tests

Abstract. Natural as well as fill slopes are commonly found in Hong Kong, China and many other countries, and slope failures with the subsequent debris flows have caused serious loss of lives and properties in the past till now. There are various processes and features associated with debris flow for which the engineers need to know so as to design for the precautionary measures. In this study, experiments on flume tests, friction tests, deposition tests, rebound tests have been carried out for different sizes of balls to determine the parameters required for modelling of debris flow tests. Different materials and sizes of balls are used in the flume tests, and various flow pattern and segregation phenomenon are noticed in the tests. Distinct element (DEM) debris flow modeling are also carried out to model the flow process. It is found that for simple cases, the flow process can be modelled reasonably well by DEM which is crucial for engineers to determine the pattern and impact of the debris flow. The single material and multiple material laboratory tests and numerical simulations can provide further insight into the debris flow process for which only limited field test data can be obtained in general. From the laboratory tests, large scale field tests and numerical simulations, it is also found that the particle size will be the most critical factor in the segregation process during debris flow. It is also found from the laboratory tests and numerical simulations that a jump in the flume can help to reduce the final velocity of the debris flow which is useful for practical purposes.

scholarly journals EDDA: integrated simulation of debris flow erosion, deposition and property changes

2014 ◽  
Vol 7 (6) ◽  
pp. 7267-7316
Author(s):  
H. X. Chen ◽  
L. M. Zhang
Keyword(s):  
Debris Flow ◽  
Yield Stress ◽  
Water Flow ◽  
Large Scale ◽  
Limit Equilibrium ◽  
Flow Density ◽  
Catchment Scale ◽  
Flow Process ◽  
One Dimensional ◽  
Property Changes

Abstract. Debris flow material properties change during the initiation, transportation and deposition processes, which influences the runout characteristics of the debris flow. A quasi-three-dimensional depth-integrated numerical model, EDDA, is presented in this paper to simulate debris flow erosion, deposition and induced material property changes. The model considers changes in debris flow density, yield stress and dynamic viscosity during the flow process. The yield stress of debris flow mixture is determined at limit equilibrium using the Mohr–Coulomb equation, which is applicable to clear water flow, hyper-concentrated flow and fully developed debris flow. To assure numerical stability and computational efficiency at the same time, a variable time stepping algorithm is developed to solve the governing differential equations. Four numerical tests are conducted to validate the model. The first two tests involve a one-dimensional dam-break water flow and a one-dimensional debris flow with constant properties. The last two tests involve erosion and deposition, and the movement of multi-directional debris flows. The changes in debris flow mass and properties due to either erosion or deposition are shown to affect the runout characteristics significantly. The model is also applied to simulate a large-scale debris flow in Xiaojiagou Ravine to test the performance of the model in catchment-scale simulations. The results suggest that the model estimates well the volume, inundated area, and runout distance of the debris flow. The model is intended for use as a module in a real-time debris flow warning system.

scholarly journals EDDA 1.0: integrated simulation of debris flow erosion, deposition and property changes

2015 ◽  
Vol 8 (3) ◽  
pp. 829-844 ◽  
Author(s):  
H. X. Chen ◽  
L. M. Zhang
Keyword(s):  
Debris Flow ◽  
Yield Stress ◽  
Water Flow ◽  
Large Scale ◽  
Limit Equilibrium ◽  
Flow Density ◽  
Catchment Scale ◽  
Flow Process ◽  
Runout Distance ◽  
Property Changes

Abstract. Debris flow material properties change during the initiation, transportation and deposition processes, which influences the runout characteristics of the debris flow. A quasi-three-dimensional depth-integrated numerical model, EDDA (Erosion–Deposition Debris flow Analysis), is presented in this paper to simulate debris flow erosion, deposition and induced material property changes. The model considers changes in debris flow density, yield stress and dynamic viscosity during the flow process. The yield stress of the debris flow mixture determined at limit equilibrium using the Mohr–Coulomb equation is applicable to clear water flow, hyper-concentrated flow and fully developed debris flow. To assure numerical stability and computational efficiency at the same time, an adaptive time stepping algorithm is developed to solve the governing differential equations. Four numerical tests are conducted to validate the model. The first two tests involve a one-dimensional debris flow with constant properties and a two-dimensional dam-break water flow. The last two tests involve erosion and deposition, and the movement of multi-directional debris flows. The changes in debris flow mass and properties due to either erosion or deposition are shown to affect the runout characteristics significantly. The model is also applied to simulate a large-scale debris flow in Xiaojiagou Ravine to test the performance of the model in catchment-scale simulations. The results suggest that the model estimates well the volume, inundated area, and runout distance of the debris flow. The model is intended for use as a module in a real-time debris flow warning system.

scholarly journals On mechanical behaviour of clastic soils: numerical simulations and constitutive modelling

2021 ◽  
Author(s):  
shun wang ◽  
Wei Wu ◽  
Deshan Cui
Keyword(s):  
Numerical Simulations ◽  
Mechanical Behaviour ◽  
Large Scale ◽  
Field Tests ◽  
Stress Path ◽  
Constitutive Modelling ◽  
Failure Pattern ◽  
Soil Matrix ◽  
Deformation And Failure ◽  
Large Scale Tests

Clastic soil is ubiquitous in practice but still poses challenges for testing and modelling. Conventional laboratory tests with small sizes are not suitable for the large grain size, while large-scale tests and field tests are often too costly and time-consuming. In this paper, the mechanical behaviour of clastic soil is described by a hypoplastic constitutive model based on numerical simulations considering both the soil matrix and breccia. The numerical simulations indicate that the breccia content, gradation, and overconsolidation ratio have a significant influence on the strength, deformation, and failure pattern of the clastic soil. The coarse particles are found to change the stress path developed in the soil matrix and consequently influence the critical state of the soil matrix. Moreover, the coarse particle distribution based on computed tomography scan seems to have a larger impact than the breccia content for the failure pattern of the clastic soils.

scholarly journals Mitigation Method of Rockfall Hazard on Rock Slope Using Large-Scale Field Tests and Numerical Simulations

2020 ◽  
Vol 2020 ◽  
pp. 1-6
Author(s):  
Jinam Yoon ◽  
Hoki Ban ◽  
Youngcheol Hwang ◽  
Duhee Park
Keyword(s):  
Numerical Simulation ◽  
Numerical Simulations ◽  
Large Scale ◽  
Rock Slope ◽  
Field Tests ◽  
New Method ◽  
Rockfall Hazard ◽  
Pendulum Test ◽  
Scale Field ◽  
Large Scale Field

This paper presents the mitigation of rockfall hazard on the large-scale rock slope using the field tests with numerical simulation. To this end, field tests including the pendulum test and real rock falling tests were performed to investigate the rock movements such as rotation, repulsion, and speed. In the simulation, the validation of the developed model followed by calibration processes was made on the field tests. In this study, a simple and new method was proposed to mitigate the rockfall hazard using the so-called sand pool made by ditching and then filling sand where the rock should be stopped or arrested. The results showed that the sand pool method was very effective and economical.

Unsteady Simulations of Recess Casing Treatment in Axial Flow Fans

2006 ◽  
Author(s):  
Abdurazag M. Ghila ◽  
Antonios Tourlidakis
Keyword(s):  
Steady State ◽  
Numerical Simulations ◽  
Large Scale ◽  
Axial Flow ◽  
Rotor Blades ◽  
Flow Process ◽  
Important Conclusion ◽  
Casing Treatment ◽  
Steady State Simulation ◽  
Casing Treatments

This paper deals with unsteady numerical simulations of a low-speed axial-flow fan with recess casing treatment in order to investigate the interaction between the rotor blades and the vanes inside the recess. The numerical simulations were carried out for a single blade passage using a 3-D Navier-Stokes solver. The examination of the unsteady simulation of the recess treatment cavities demonstrated that there is no large scale unsteady activity at the flow condition investigated, this is on itself quite significant and enables the drawing of an important conclusion namely that large casing treatments rely primarily on a steady-state flow process. The corollary of this conclusion is that a steady-state simulation should be sufficient to capture the essential features of the effects of recess casing treatments.

New simple method for measuring impact force on a flexible barrier from rockfall and debris flow based on large-scale flume tests

2020 ◽  
Vol 279 ◽  
pp. 105881
Author(s):  
Dao-Yuan Tan ◽  
Jian-Hua Yin ◽  
Wei-Qiang Feng ◽  
Jie-Qiong Qin ◽  
Zhuo-Hui Zhu
Keyword(s):  
Debris Flow ◽  
Large Scale ◽  
Impact Force ◽  
Simple Method ◽  
Flexible Barrier ◽  
Flume Tests
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