Modeling granular soils liquefaction using coupled lattice Boltzmann method and discrete element method     

《Soil Dynamics and Earthquake Engineering》2014

In this paper, a novel coupled pore-scale model of pore-fluid interacting with discrete particles is presented for modeling liquefaction of saturated granular soil. A microscale idealization of the solid phase is achieved using the discrete element method (DEM) while the fluid phase is modeled at a pore-scale using the lattice Boltzmann method (LBM). The fluid forces applied on the particles are calculated based on the momentum exchange between the fluid and particles. The presented model is based on a first principles formulation in which pore-pressure develops due to actual changes in pore space as particles׳ rearrangement occurs during shaking. The proposed approach is used to model the response of a saturated soil deposit subjected to low and large amplitude seismic excitations. Results of conducted simulations show that at low amplitude shaking, the input motion propagates following the theory of wave propagation in elastic solids. The deposit response to the strong input motion indicates that liquefaction took place and it was due to reduction in void space during shaking that led to buildup in pore-fluid pressure. Soil liquefaction was associated with soil stiffness degradation and significant loss of interparticle contacts. Simulation results also indicate that the level of shaking-induced shear strains and associated volumetric strains play a major role in the onset of liquefaction and the rate of pore-pressure buildup.  相似文献   

A micro-mechanical investigation of the dynamic response and liquefaction of saturated granular soils   总被引：4，自引：0，他引：4  

U. El Shamy  M. Zeghal   《Soil Dynamics and Earthquake Engineering》2007,27(8):712-729

A coupled continuum-discrete hydromechanical model was utilized to analyze the meso-scale pore fluid flow and micro-scale solid phase deformation of saturated granular soils. The fluid motion was idealized using averaged Navier–Stokes equations and the discrete element method was employed to model the solid particles. Well established semi-empirical relationships were used to quantify the fluid–particle interactions. Numerical simulations were conducted to investigate the mechanisms of granular deposit liquefaction in the presence of a critical upward pore fluid flow as well as when subjected to a dynamic base excitation. The outcome of these simulations was consistent with experimental observations and revealed valuable information on the micro-mechanical characteristics of soil liquefaction and associated loss of stiffness and strength.  相似文献   

Sediment detachment and transport processes associated with internal erosion of soil pipes          下载免费PDF全文

Glenn V. Wilson  Robert Wells  Roger Kuhnle  Garey Fox  John Nieber 《地球表面变化过程与地形》2018,43(1):45-63

Subsurface flow can be an important process in gully erosion through its impact on decreasing soil cohesion and erosion resistance as soil water content or pressure increases and more directly by the effects of seepage forces on particle detachment and piping. The development of perched water tables fosters lateral flow that can result in seepage at the surface and/or formation of soil pipes by internal erosion of preferential flow paths. Continued internal erosion of soil pipes can lead to gullies, dam and levee failures. However, the processes involved in particle and aggregate detachment from soil pipe walls and transport processes within soil pipes have not been well studied or documented. This paper reviews the limited research on sediment detachment and transport in macropores and soil pipes and applies the knowledge learned from the much more extensive studies conducted on streams and industrial pipes to hydrogeologic conditions of soil pipes. Knowledge gaps are identified and recommendations are made for future research on sediment detachment and transport in soil pipes. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Simulation of submerged granular flows by development of a two-phase incompressible explicit mesh-free method     

Tibing Xu  Shuangke Sun  Peng Wu 《国际泥沙研究》2023,38(4):530-542

The interaction between fluid and sediment particles is widely involved in hydraulic engineering problems. In the current study, an explicit incompressible mesh-free method in the framework of the Moving Particle Semi-implicit(MPS) method is proposed to simulate the interaction between the two phases in submerged conditions. The proposed method solves two sets of the continuity and momentum equations, respectively, for the fluid phase and the sediment phase according to the mixture theory. In th...  相似文献   

Raindrop‐impact‐induced erosion processes and prediction: a review     

P. I. A. Kinnell 《水文研究》2005,19(14):2815-2844

Raindrop‐impact‐induced erosion is initiated when detachment of soil particles from the surface of the soil results from an expenditure of raindrop energy. Once detachment by raindrop impact has taken place, particles are transported away from the site of the impact by one or more of the following transport processes: drop splash, raindrop‐induced flow transport, or transport by flow without stimulation by drop impact. These transport processes exhibit varying efficiencies. Particles that fall back to the surface as a result of gravity produce a layer of pre‐detached particles that provides a degree of protection against the detachment of particles from the underlying soil. This, in turn, influences the erodibility of the eroding surface. Good understanding of rainfall erosion processes is necessary if the results of erosion experiments are to be properly interpreted. Current process‐based erosion prediction models do not deal with the issue of temporal variations in erodibility during a rainfall event or variabilities in erodibility associated with spatial changes in dominance of the transport processes that follow detachment by drop impact. Although more complex erosion models may deal with issues like this, their complexity and high data requirement may make them unsuitable for use as general prediction tools. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Simulations demonstrating interaction between coarse and fine sediment loads in rain‐impacted flow     

P. I. A. Kinnell 《地球表面变化过程与地形》2006,31(3):355-367

Rain‐impacted flows dominate sheet and interrill erosion and are important in eroding soil rich in nutrients and other chemicals which may have deleterious effects on water quality. Erosion in rain‐impacted flow is associated with raindrop detachment followed by transport either by the combination of flow velocity and raindrop impact (raindrop‐induced flow transport, RIFT) or the inherent capacity of the flow to transport detached material. Coarse particles tend to be transported by RIFT, while fine particles tend to be transported without any assistance from raindrop impact. Because the transport process associated with coarse particles is not 100 per cent efficient, it generates a layer of loose particles on the soil surface and this layer protects the underlying soil from detachment. Simulations were performed by modelling the uplift and downstream movement of both fine and coarse particles detached from the soil surface by individual raindrop impacts starting with a surface where no loose material was present. The simulations produced a flush of fine material followed by a decline in the discharge of fine material as the amount of loose material built up on the bed. The decline in the discharge of fine material was accompanied by an increase in the discharge of coarse material. The relative amounts of coarse and fine material discharged in the flow varied with flow velocity and cohesion in the surface of the soil matrix. The results indicate that the discharge of various sized sediments is highly dependent on local soil, rain and flow conditions and that extrapolating the results from one situation to another may not be appropriate. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Experimental investigation of internal erosion behaviours in inclined seepage flow     

Yue Liang  Tian-Chyi J. Yeh  Chen Ma  Qiang Zhang  Dehong Yang  Yonghong Hao 《水文研究》2020,34(26):5315-5326

Internal erosion is one of the most common causes of failure in hydraulic engineering structures, such as embankments and levees. It also plays a vital role in the geohazards (such as landslides and sinkhole developments) and more importantly, the earth landscape evolution, which has a broad environmental and ecosystem impacts. The groundwater seepage is multi-directional, and its multi-dimensional nature could affect the initiation and the progression of internal erosion. With a newly developed apparatus, we carry out nine internal erosion experiments under five different seepage directions. The results reveal that the critical hydraulic gradient increases as the seepage direction varies from the horizontal to the vertical. After a global erosion is triggered, preferential erosion paths distribute randomly from the bottom to the top of the specimen. If the seepage direction is not vertical, small preferential erosion paths merge into a large erosion corridor, in which the loss of fine particles is significant but negligible outside. Results of experiments manifest that the erosion is heterogeneous and three-dimensional, even in the unidirectional seepage flow. The particles are rapidly eroded at the early stage of the erosion, indicating a high erosion rate. With the erosion time increasing, the particle loss slows down and even ceases if the time is long enough. The erosion rate increases if the seepage direction approaches a vertical direction. Overall, the erosion rate approximately decreases with erosion time exponentially. We proposed exponential equations to illustrate the variation of the erosion rate in the erosion process.  相似文献   

Effects of the undecomposed layer and semi-decomposed layer of Quercus variabilis litter on the soil erosion process and the eroded sediment particle size distribution     

Xiaona Liu  Guodong Jia  Xinxiao Yu 《水文研究》2021,35(5):e14195

Simulated rainfall experiments were performed on bare, undecomposed litter layer and semi-decomposed litter layer slopes with litter biomasses of 0, 50, 100 and 150 g m⁻², respectively, to evaluate the effect of the undecomposed layer and semi-decomposed layer of Quercus variabilis litter on the soil erosion process and the particle size distribution of eroded sediment. The undecomposed layer and semi-decomposed layer of litter reduced the runoff rate by 10.91–27.04% and 12.91–36.05%, respectively, and the erosion rate by 13.35–40.98% and 17.16–59.46%, respectively. The percentage of smaller particles (clay and fine silt particles) decreased and the percentage of larger particles (coarse silt and sand particles) increased with an increased rainfall duration on all treated slopes, while the extent of the eroded sediment particle content varied among the treated slopes with the rainfall duration, with bare slopes exhibiting the largest variability, followed by undecomposed litter layer slopes and finally semi-decomposed litter layer slopes. The clay and sand particles were transported as aggregates, and fine silt and coarse silt particles were transported as primary particles. Compared with the original soil, sediment eroded from all treated slopes was mainly enriched in smaller particles. Furthermore, the loss of the smaller particles from the undecomposed litter layer slopes was lower than that from the semi-decomposed litter layer slopes, indicating that the undecomposed litter layer alleviated soil coarsening to some extent. The findings from this study improve our understanding of how litter regulates slope erosion and provide a reference for effectively controlling soil erosion.  相似文献   

Effects of hydrophobicity on splash erosion of model soil particles by a single water drop impact     

Sujung Ahn  Stefan H. Doerr  Peter Douglas  Robert Bryant  Christopher A.E. Hamlett  Glen McHale  Michael I. Newton  Neil J. Shirtcliffe 《地球表面变化过程与地形》2013,38(11):1225-1233

Raindrop impact can be a major contributor to particle mobilization for soils and other granular materials. In previous work, water repellent soils, comprised of hydrophobic particles, have been shown to exhibit greater splash erosion losses under multiple drop impact. However, the underlying principle differences in splash behavior between hydrophobic and hydrophilic granular surfaces have not been studied to date. In this study the effects of particle hydrophobicity on splash behaviour by a single water drop impact were examined using high‐speed videography. Water drops (4 mm in diameter) were dropped on beds of hydrophilic and hydrophobic glass beads (sieved range: 350–400 µm), serving as model soil particles. The drop velocity on impact was 2.67 m s^‐1, which corresponds to ~30% of the terminal velocity of a raindrop of similar size. The resulting impact behaviour was measured in terms of the trajectories of particles ejected from the beds and their final resting positions. The response to the impacting water drop was significantly different between hydrophilic and hydrophobic particles in terms of the distance distribution, the median distance travelled by the particles and number of ejected particles. The greater ejection distances of hydrophobic particles were mainly the result of the higher initial velocities rather than differences in ejecting angles. The higher and longer ejection trajectories for hydrophobic particles, compared with hydrophilic particles, indicate that particle hydrophobicity affects splash erosion from the initial stage of rainfall erosion before a water layer may be formed by accumulating drops. The ~10% increase in average splash distance for hydrophobic particles compared with hydrophilic particles suggests that particle hydrophobicity can result in greater net erosion rate, which would be amplified on sloping surfaces, for example, by ridges in ploughed agricultural soils or hillslopes following vegetation loss by clearing or wildfire. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Scouring of a granular bed by dam break: Experimental study and numerical simulation by a VOF-LPT coupling     

Quyen Thi Le Nguyen  Viet Dung Nguyen  Patrice Coorevits 《国际泥沙研究》2023,38(3):432-445

The first part of the research reported here consists of an experimental campaign to study the scouring of a granular bed(glass beads, sand) induced by a dam break in an open channel. Two configurations are considered: with and without cylinders. In the second part of this study, the volume of fluid method coupled with the shear stress transport turbulent model and the lagrangian particle tracking method is used to simulate the local scour processes. The four-way coupling is realized by consider...  相似文献   

APPLICATION OF GEOPHYSICAL METHODS FOR STUDYING THE TECHNICAL STATUS OF EARTH DAMS*     

V. A. BOGOSLOVSKY  A. A. OGILVY 《Geophysical Prospecting》1970,18(Z1):758-773

Earth dams are constructed on a wide scale for hydrotechnical and reclamative purposes. However, the great water permeability of soils and their bad gradation are frequently responsible for the development of mechanical suffusion and other phenomena resulting in dam destruction. Geophysical observations allow under certain conditions to forecast the development of adverse factors. They thus are, as practice shows, an important tool to observe the technical status of dams. The difference in propagation velocities of elastic waves in the zone of aeration and full saturation determines the applicability of the reflected wave method for determining the depth of seepage flow in the dam supporting mass. This can be also achieved by electrical sounding and induced polarization methods since the resistivity and polarizability of air-dry and water-saturated grounds differ considerably. Maps of equal potentials measured on the dam slope reflect the configuration of the contours of water table of the water flow passing through the dam. This makes it possible to obtain data on the direction and intensity of flow as well as on the presence of heterogeneous grounds filling the dam supporting mass. Besides, regime observations conducted according to the SP method allow to forecast the development of suffusion and observe the redeposition of grounds. If the SP anomalies do not increase with time, the suffusion processes can be regarded as fading out. Enhanced amplitude and increasing areas of anomalies show the intensification of these processes. Combined application of some of the above mentioned methods allowed to obtain many practical results on a number of dams in Transcaucasia and Central Asia. The true position of the depression surface determined in the dam of one of the high-mountain water reservoirs, for instance, considerably differed from the designed one. The configuration of the seepage flow surface and its fluctuation caused by the rise and drop of the water level in the reservoir have been studied in detail on another dam situated on a plain. The sites of the most intensive outwash of fine material have also been located and the processes of soil redeposition in the dam supporting mass characterized. The data of the geophysical investigations were used to plan hydroinsulation and repair work.  相似文献   

Particle velocity and concentration profiles in bedload experiments on a steep slope          下载免费PDF全文

Philippe Frey 《地球表面变化过程与地形》2014,39(5):646-655

Depth profiles of particle streamwise velocity, concentration and bedload sediment transport rate were measured in a turbulent and supercritical water flow. One‐size 6 mm diameter spherical glass beads were transported at equilibrium in a two‐dimensional 10% steep channel with a mobile bed. Flows were filmed from the side by a high‐speed camera. Particle tracking algorithms made it possible to determine the position, velocity and trajectory of a very large number of particles. Approximately half of the sediment transport rate was composed by rolling grains, and the other half by saltation. This revealed a complex structure, with several concentration and flux peaks due to rolling, and one peak due to saltation. With an increase of the sediment transport rate, the depth structure remained the same at the water/granular interface, with peak value increases but with no shift in elevations. The saltation region expanded towards higher elevations with an increase of the particle velocity commensurate to the water velocity. The proportion of the sediment transport rate in saltation did not vary significantly. The particle streamwise velocity profiles exhibited three segments: an exponential decay in the bed, a linear increase where rolling and saltation co‐existed, and above this, a logarithmic‐like shape due to saltating particles. These results are comparable to profiles measured and modelled in dry granular free surface flows and in more intense bedload such as sheet flows. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

A lattice Boltzmann model coupled with a Large Eddy Simulation model for flows around a groyne     

Xin YU  Xuelin TANG  Wuchang WANG  Fujun WANG  Zhicong CHEN  Xiaoyan SHI 《国际泥沙研究》2010,25(3):271-282

This present paper proposes a two-dimensional lattice Boltzmann model coupled with a Large Eddy Simulation (LES) model and applies it to flows around a non-submerged groyne in a channel. The LES of shallow water equations is efficiently performed using the Lattice Boltzmann Method (LBM) and the turbulence can be taken into account in conjunction with the Smagorinsky Sub-Grid Stress (SGS) model. The bounce-back scheme of the non-equilibrium part of the distribution function is used to determine the unknown distribution functions at inflow boundary, the zero gradient of the distribution function is set normal to outflow boundary to obtain the unknown distribution functions here and the bounce-back scheme, which states that an incoming particle towards the boundary is bounced back into fluid, is applied to the solid wall to ensure non-slip boundary conditions. The initial flow field is defined firstly and then is used to calculate the local equilibrium distributions as initial conditions of the distribution functions. These coupled models successfully predict the flow characteristics, such as circulating flow, velocity and water depth distributions. The comparisons between the simulated results and the experimental data show that the model scheme has the capacity to solve the complex flows in shallow water with reasonable accuracy and reliability.  相似文献   

TEMPORAL AND SPATIAL DYNAMICS OF DIFFERENT PARTICLE SIZE OF SUSPENDED SEDIMENT IN THE LIU RIVER CATCHMENTS, CHINA     

Haoming FAN Qiangguo CAI Chengjiu GUO Tieliang WANG 《国际泥沙研究》2006,21(3):209-219

1 INTRODUCTION The particle size of sediment eroded from basins can provide basic information about erosion processes (Meyer et al., 1980), which can be divided into sheet wash sediment processes on hill slopes and fluvial sediment processes in rivers. In…  相似文献   

Availability and performance of sediment detachment and transport functions for overland flow conditions     

Mazhar Ali  Geert Sterk 《水文科学杂志》2013,58(9):1550-1565

Abstract

Soil erosion is a global environmental problem. To quantify water erosion rates at the field, hillslope or catchment scale, several spatially-distributed soil erosion models have been developed. The accuracy of those models depends largely on the sediment detachment and transport functions used, many of which were developed from empirical research. In this paper, the physical basis of the available sediment detachment and transport functions is reviewed, and their application boundaries determined. Well-known and widely-used sediment detachment and transport functions are discussed on the basis of composite force predictors, i.e. shear stress, stream power, unit stream power and effective stream power, and their suitability is elucidated based on information in the literature. It was found that only a few sediment detachment functions are available, and those have been poorly tested. Most erosion models ignore direct calculation of sediment detachment, but use the sediment transport capacity deficit approach to estimate detachment rate. Many more sediment transport functions are available that also tested better for overland flow conditions. However, our tests did not result in a single function that appeared to perform best under a range of experimental conditions. The unit stream power-based functions developed by Govers seem to be the most promising ones for water erosion modelling. It is therefore recommended to evaluate the performance of existing sediment transport functions with more detailed field and laboratory datasets.