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Study on the force chain characteristics with coal dust layer and the three-body contact stiffness

Particuology 2024年第9期92卷 288-304页

作者： Xinwei Yang Dongxuan Wu Hongyue Chen Dong Wang School of Mechanical Engineering Liaoning Technical UniversityFuxin123000China Ordos Institute of Liaoning Technical University Ordos017000China School of Mining Liaoning Technical UniversityFuxin123000China China National Coal Association Dynamic Research for High-end Complete Integrated Coal Mining Equipment and Big Data Analysis CentreFuxin123000China

To explore the influence of the meso-mechanical behaviors of the wet coal dust layers on the contact stiffness of mechanical bonding surfaces,a three-body contact model incorporating an interface with wet coal dust was constructed based on breakage *** model considered the mechanical surface morphology and contact characteristics of the wet coal *** force chain evolution laws of the wet coal dust layer were elucidated under the effects of gap filling and the cover layer,and the bearing characteristics of the three-body contact bonding surfaces were revealed by quantitative analyses of the number,length,collimation coefficient,and coordination number of the force chains within the wet coal dust ***,the three-body normal contact stiffness under various preload forces was computed and experimentally *** results demonstrate that the external load transfer path of the three-body contact bonding surfaces was from mechanical surface(macroscopic stress)to wet coal dust layer(mesoscopic force chains)and then to mechanical surface(peaks and valleys).The interactions among these three elements contributed to transforming the distributions of the macroscopic stresses and mesoscopic force chains to the locations at the peaks and valleys of the mechanical *** them,the proportion of short force chains in the wet coal dust layer increased from approximately 0.8%–91%,while the proportion of long force chains exhibited an opposite changing *** force chain collimation coefficient initially increased and subsequently stabilized,reaching a maximum value of 0.93.A large number of broken,small particles in the wet coal dust layer mainly served to fill the gaps among large *** maximum relative error between the experimental and simulated values on the three-body contact stiffness is 7.26%,indicating that the simulation results can be an approximate substitute for the experimental results with a certain degree of accuracy and practic

关键词： Wet coal dust force chain Three-body contact stiffness Gap filling effect Cover layer effect

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Probability analysis of contact forces in quasi-solid-liquid phase transition of granular shear flow

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Science China(Physics,Mechanics & Astronomy) 2013年第2期56卷 395-403页

作者： JI ShunYing State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology

The quasi-solid-liquid phase transition exists widely in different fields,and attracts more attention due to its instinctive *** structure of force chains is an important factor to describe the phase transition *** this study,the discrete element model(DEM) is adopted to simulate a simple granular shear flow with period boundary condition on micro *** quasi-solid-liquid phase transition is obtained under various volume fractions and shear *** on the DEM results,the probability distribution functions of the inter-particle contact force are obtained in different shear flow *** normal,tangential and total contact forces have the same *** distribution can be fitted as the exponential function for the liquid-like phase,and as the Weibull function for the solid-like *** describe the progressive evolution of the force distribution in phase transition,we use the Weibull function and Corwin-Ngan function,*** of them can determine the probability distributions in different phases and the Weibull function shows more reasonable ***,the force distributions are discussed to explain the characteristics of the force chain in the phase transition of granular shear *** distribution of the contact force is an indicator to determine the flow phase of granular *** the discussions on the statistical properties of the force chain,the phase transition of granular matter can be well understood.

关键词： granular materials quasi-solid-liquid phase transition force chain statistical characteristics simple shear flow

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The Material Deformation and Internal Structure Development of Granular Materials under Different Cyclic Loadings

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Computer Modeling in Engineering & Sciences 2022年第2期130卷 653-670页

作者： Jiao Wang Xihua Chu Jinbao Wang School of Mechanics and Engineering Southwest Jiaotong UniversityChengdu610031China Department of Engineering Mechanics Wuhan UniversityWuhan430072China School of Marine Engineering Equipment Zhejiang Ocean UniversityZhoushan326022 China

Common structures in engineering such as slopes,roadbeds,ballasts,etc.,are closely related to granular *** are usually subjected to long-term cyclic *** study mainly focused on the mechanical behaviors of randomly arranged granular materials before they reach a stable state under different cyclic *** variation of the maximum axial strain and the influence of CSR(cyclic stress ratio)were *** energy consumed in each cycle under constant confining stress loading condition is significantly greater than that of the fixed wall loading *** internal deformation evolution of granular materials is studied in *** deformation mode of granular material under cyclic loading at different positions inside the material is different according to the strain *** addition,the strain,force chain structure and contact force magnitude are combined to explore their effects on local deformation of granular materials under cyclic *** the perspective of the deformation form,the material sample can be divided into several regions,and the ability to adjust particle positions determines the deformation mode of different *** changes of local strain with the cyclic loading also reflect the contribution of particle displacements to the evolution *** research will provide insights into the understanding of granular materials behaviors under cyclic loading.

关键词： Granular material DEM cyclic loading mesostructured force chain

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Laboratory Model Tests and DEM Simulations of Unloading-Induced Tunnel Failure Mechanism

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Computers, Materials & Continua 2020年第5期63卷 825-844页

作者： Abierdi Yuzhou Xiang Haiyi Zhong Xin Gu Hanlong Liu Wengang Zhang School of Hehai Chongqing Jiaotong UniversityChongqing400074China School of Civil Engineering Chongqing UniversityChongqing400045China Key Laboratory of New Technology for Construction of Cities in Mountain Area Chongqing UniversityChongqing400045China

Tunnel excavation is a complicated loading-unloading-reloading process characterized by decreased radial stresses and increased axial *** approach that considers only loading,is generally used in tunnel model ***,this approach is incapable of characterizing the unloading effects induced by excavation on surrounding rocks and hence presents radial and tangential stress paths during the failure process that are different from the actual stress state of *** paper carried out a comparative analysis using laboratory model testing and particle flow code(PFC2D)-based numerical simulation,and shed light upon the crack propagation process and,microscopic stress and force chain variations during the loading-unloading *** failure mode observed in the unloading model test is shear *** force chains are strongly correlated with the concrete fracture *** addition,the change patterns of the radial and tangential stresses of surrounding rocks in the broken region,as well as the influence of the initial stress on failure loads are *** surrounding soil of tunnel failure evolution as well as extent and shape of the damage zone during the excavation-induced unloading were also studied.

关键词： Tunnel unloading model testing particle flow model force chain

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Some open problems in granular matter mechanics

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Progress in Natural Science:Materials International 2009年第5期19卷 523-529页

作者： Qicheng Sun a, Guangqian Wanga, Kaiheng Hub a Department of Hydraulic Engineering, State Key Laboratory for Hydroscience and Engineering, Tsinghua University, Beijing 100084, China b Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China [a]Department of Hydraulic Engineering State Key Laboratory for Hydroscience and Engineering Tsinghua University Beijing 100084 China [b]Institute of Mountain Hazards and Environment Chinese Academy of Sciences Chengdu 610041 China

Granular matter is a large assemblage of solid particles, which is fundamentally different from any other type of matters, such as solid and liquid. Most models presented for granular matter are phenomenological and are only suitable for solving engineering problems. Many fundamental mechanical problems remain open. By analyzing characteristics of internal state structure, we propose that granular matter is intrinsically multiscale, i.e. microscale of particle size, mesoscale of force chain, and macroscale of the bulk of granular matter. The correlations among difference scales would be crucial. The mesoscale force chain network is determined by both particle properties and macroscopic boundary conditions. The evolution of the force the chain network contributes to macroscopic mechanical properties of granular matter. In addition, we discuss the drawbacks in simplifying contact forces in the current models, and the difficulties in analyzing the interaction of interstitial fluid in wet granular matter. As an appropriate application of granular matter, debris flow can be studied with granular matter mechanics; meanwhile, debris flow brings more challenges which certainly motivate future studies on granular matter.

关键词： Granular matter Multiscale mechanics force chain Contact mechanics Debris flow

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force fluctuations in sheared granular disks

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Frontiers of Structural and Civil Engineering 2013年第1期7卷 46-49页

作者： Mingbo YUAN Qicheng SUN Feng JIN Shandong College of Electronic Technology Jinan 250014China State Key Laboratory of Hydroscience and Engineering Tsinghua UniversityBeijing 100084China

The internal structure established within granular materials,often observed as force chains,is dominant in controlling bulk mechanical *** designed a two-dimensional Hele-Shaw cell to contain photoelastic disks,and two servos were used on the top and right boundaries *** experimentally monitored the fluctuations in force on the top plate while slowing the shearing of the well-confined disks and keeping the right boundary at a contactconfined force of 0.2 *** particle rearrangements were found to correspond to bulk force drops and were observed in a localized zone with a length of approximately 5 particle *** results help reveal the structure and mechanics of granular materials,and further investigations are ongoing.

关键词： granular matter force chain stick and slip

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Visualization of force networks in 2D dense granular materials

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Frontiers of Structural and Civil Engineering 2010年第1期4卷 109-115页

作者： Jianguo LIU Qicheng SUN Feng JIN State Key Laboratory of Hydroscience and Engineering Department of Hydraulic EngineeringTsinghua UniversityBeijing 100084China

Dense granular matter is a conglomeration of discrete solid and closely packed *** subjected to external loadings,the stress is largely transmitted by heavily stressed chains of particles forming a sparse network of larger contact *** understand the structure and evolution of force chains,a photoelastic technique was improved for determining stresses and strains in the assemblies of photoelastic granular disks in this paper.A two-dimensional vertical slab was *** contains 7200 polydispersed photoelastic disks and is subjected to a localized probe penetrating at the top of the slab to mimic the cone penetration *** interparticle contact force distribution was found a peak around the mean value,a roughly exponential tail for greater force and a dip toward zero for smaller *** force chain network around the probe tip was depicted,and the contact angle distribution of particles in force chains was found to be well aligned in the directions of major principal stress.

关键词： granular matter force chain multiscale modeling

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