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Numerical Simulation of Desiccation Cracking in Clayey Soil Using a Multifield Coupling discrete-element model

JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING 2022年第2期148卷 04021183-04021183页

作者： Le, Tian-Cheng Liu, Chun Tang, Chao-Sheng Zhang, Xiao-Yu Shi, Bin Nanjing Univ Sch Earth Sci & Engn Nanjing 210023 Jiangsu Peoples R China

Desiccation cracking in clayey soil, which may lead to soil erosion, geotechnical engineering accidents, or even environmental pollution, is a serious problem nowadays. This research proposed a multifield coupling discrete-element model of clayey soil, in which each element represented a certain volume of soil. Meanwhile, the uneven distribution and transfer of moisture were also achieved. By establishing the relationships between water content and element radius, Young's modulus, and tensile strength, respectively, the model coupled the moisture field with the stress field. Through a discrete-element simulation of desiccation cracking in a thin clay layer, the gradual development of crack network was successfully reproduced, and the proposed model was validated. The uneven moisture distribution in the numerical specimen indicates that cracks can intensify evaporation by increasing the area of soil-air interface. Layer thickness, evaporation intensity, soil-base interaction, and compressive strength are proved to have significant impacts on crack pattern by influencing the equilibrium between desiccation shrinking and cracking. This research provides a new means to study the mechanism of desiccation cracking under multifield coupling effects.

关键词： Clayey soil Desiccation cracking Multifield coupling discrete-element model MatDEM

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A coupled fluid-solid model for problems in geomechanics: Application to sand production

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INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS 2011年第9期35卷 997-1018页

作者： Boutt, D. F. Cook, B. K. Williams, J. R. Univ Massachusetts Dept Geosci Amherst MA 01003 USA Sandia Natl Labs Albuquerque NM 87185 USA MIT Dept Civil & Environm Engn Cambridge MA 02139 USA

Some of the most challenging problems in geomechanics involve the coupling between fluid flow and solid deformation. In this paper we briefly present an overview of existing coupling methods to problems involving fluid flow and deformation and describe testing of a new discrete-based coupling method for problems in porous media. modeled permeability and porosity distributions are compared to idealized packed assemblies and results are presented for simulations of steady flow through porous media. Previously published results for the coupled model focused on few or multiple particles in a fluid, whereas our results show good agreement to packed assemblies of particles (i.e. porous media). Finally, the two-dimensional model is applied to sand production, a common problem in geomechanics. Sand production is defined as the co-production of both a fluid and solid phase in oil and gas wells. In our models, we capture initial sand production associated with early-time drawdown. Later-time results show episodic sanding rates associated with formation stability and instabilities. Both observations are qualitatively consistent with laboratory and field observations. We find that high confining pressure inhibits the production of sand, through elevated interparticle contact forces. It is argued that these physically based models have a use in testing and evaluating competing hypotheses of sand production but their applicability is currently limited to small spatial and temporal scales. We believe these models bridge an important gap between the underlying physics of micro-mechanical interactions of fluid and solid grains and the continuum descriptions of those systems. Copyright (C) 2010 John Wiley & Sons, Ltd.

关键词： fluid-solid mechanics porous media flow sand production discrete-element model

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discrete and continuum modeling of granular flow in silo discharge

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Particuology 2018年第1期16卷 127-138页

作者： Tian Tian Jinglin Su Jinhui Zhan Shujun Geng Guangwen Xu Xiaoxing Liu State Key Laboratory of Multi-Phase Complex System Institute of Process Engineering Chinese Academy of Science Beijing 100190 China University of Chinese Academy ofSdences Beijing 100049 China Sino-Danish Center for Education and Research Beijing 100190 China

Granular material discharge from a flat-bottomed silo has been simulated by using continuum modeling and a three-dimensional discrete-element method （DEM）. The predictive abilities of three commonly used frictional viscosity models （Schaeffer, S-S, and μ（I）） were evaluated by comparing them with the DEM data. The funnel-flow pattern （type C） and the semi-mass-flow pattern （type B） that was predicted by DEM simulations can be represented when the Schaeffer orμ（I） model is used, whereas the S-S model gives a consistent type-B flow pattern. All three models over-estimate the discharge rate compared with the DEM. The profiles of the solids volume fraction and the vertical velocity above the outlet show that the larger discharge rates given by the Schaeffer and μ（I） model result from an over-estimation of volume fraction, whereas the deviation in the S-S model stems from the failure to predict a solid vertical velocity and a volume fraction.

关键词： Silo Flow pattern Discharge rate discrete-element model Frictional viscosity model

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Unified Mechanistic Approach for modeling Tests of Unbound Pavement Materials

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JOURNAL OF TRANSPORTATION ENGINEERING 2012年第9期138卷 1091-1098页

作者： Hill, Kimberly Yohannes, Bereket Khazanovich, Lev Univ Minnesota Dept Civil Engn Minneapolis MN 55455 USA

Several tests are used for the characterization of unbound materials for pavement applications. The resilient modulus has been one of the most common tests for design specification of unbound materials. The California bearing ratio (CBR) is another laboratory test that is frequently used. The dynamic cone penetrometer (DCP) test is a more common test for in situ quality assessment/quality control of unbound materials. For better connection between design and quality assurance (QA)/quality control (QC), it would be helpful to have a reliable, mechanistic method for correlating test results. This is particularly true for the use of new materials, for which there is not an extensive body of data to empirically draw such connections. This paper presents a framework for a unified approach for modeling these tests. A discrete-element method (DEM) is used to simulate the CBR test, the DCP test, and the resilient modulus test. An initial evaluation demonstrated that the simulations can account for the effect of aggregate shape, size, gradation, friction, and stiffness. As such, this methodology shows promise for the development of mechanistic-based correlation between test results. These results are presented, along with some limitations of the current model and challenges for the future. DOI: 10.1061/(ASCE)TE.1943-5436.0000411. (C) 2012 American Society of Civil Engineers.

关键词： Unbound pavement materials DCP test Resilient modulus test discrete-element model Granular materials

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Using the discrete element method to assess the seismic vulnerability of aggregated masonry buildings

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BULLETIN OF EARTHQUAKE ENGINEERING 2015年第10期13卷 3135-3150页

作者： Ulrich, Thomas Negulescu, Caterina Ducellier, Ariane Bur Rech Geol & Minieres F-45060 Orleans 2 France

The seismic vulnerability of masonry aggregates is assessed with an approach based on the discrete element method. In that purpose, a quasi-static push-over procedure has been developed, in which a load pattern, based on the building first mode of vibration, is applied to the studied structure. Using this approach, the magnitude of the horizontal load to be applied for the building to collapse is obtained after a short computation time, as well as a detailed description of the failure mechanism. These results can be useful, for instance, for identifying the weakness of a structure or for comparing quantitatively the vulnerability of different structures. The beneficial and negative effects on the seismic response of the aggregation are assessed by subjecting isolated and aggregated buildings to both in-plane and transverse loads. As observed by engineers during post-seismic field missions, the buildings at the extremities of the aggregate are more prone to damage, because, contrary to the buildings inside the aggregate, they are not efficiently braced by the neighboring structures.

关键词： Masonry Aggregate Cluster Seismic vulnerability discrete-element model DEM Numerical modeling Push-over Collapse mechanism

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Temperature Changes of Interlaminar Bonding Layer in Different Seasons and Effects on Mechanical Properties of Asphalt Pavement

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INTERNATIONAL JOURNAL OF PAVEMENT RESEARCH AND TECHNOLOGY 2022年第3期15卷 589-605页

作者： Xu, Junjie Li, Ning Xu, Tao Nanjing Forestry Univ Coll Civil Engn 159 Longpan Rd Nanjing 210037 Jiangsu Peoples R China

In this study, the discrete-element model (DEM) of asphalt pavement is established to discuss the effects of temperature changes of interlaminar bonding layer on mechanical responses of asphalt pavement in different seasons. Calculated and test results indicate that the temperature within the depth range of 0-5 cm in asphalt pavement is obviously affected by ambient temperature. The heat is accumulated within the pavement depth range of 2-5 cm, greatly affecting the interlaminar bonding state. In addition, lower temperature in winter increases the continuity of asphalt pavement layers, reducing the compressive stress in upper layer. In addition, higher temperature in summer weakens the interlaminar bond, increasing the horizontal tensile stress in upper layer and at the interlaminar interface. Further, lower interlaminar bonding strength increases the maximum shear stress at the interlaminar interfaces between asphalt pavement layers, as well as at the interface between asphalt mortar and aggregate. As the pavement depth is increased, the horizontal shear stress is increased. Finally, the high temperature increases the tensile strain near the bottom of upper layer. The displacement directions of more aggregate particles move vertically downward at low temperature, but move to two lateral sides at high temperature.

关键词： discrete-element model Interlaminar bond Seasonal temperature Temperature distribution Mechanical responses Stress distribution

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Wave-Induced Surge Motion and Collisions of Sea Ice Floes: Finite-Floe-Size Effects

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JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS 2018年第10期123卷 7472-7494页

作者： Herman, A. Univ Gdansk Inst Oceanog Gdansk Poland

Plain Language Summary Among many mechanisms potentially contributing to wave energy attenuation in sea ice are wave-induced ice floe collisions. At present, little is known about collision patterns and their phase-averaged effects under different combinations of sea ice properties (ice thickness, floe size, etc.) and wave forcing (wavelength and steepness). The existing parameterizations of collision-related effects are therefore based on several simplifying, unverified assumptions. In this work, wave-induced motion and collisions of ice floes are analyzed numerically with a model based on momentum equations for an arbitrary number of floes, with source terms computed by integrating local forcing (wave-induced dynamic pressure, surface drag, etc.) over the surface area/volume of each floe. It is shown that this simple model, with prescribed wave forcing (i.e., no wave-ice interactions), is capable of reproducing observed surge amplitudes up to floe sizes comparable with wavelength. A full Hertzian contact model is used instead of a simple hard-disk algorithm, which makes the model suitable for simulating both rapid collisions and prolonged contact between floes. The model equations are used to formulate heuristic collision criteria based on relative floe size, ice concentration, and wave steepness. The model is then run for different combinations of those three parameters, together with different restitution and drag coefficients, in order to analyze possible motion/collision patterns within the multidimensional parameter space, and phase-averaged effects of collisions: kinetic and contact stress, granular temperature, and work done by forces acting on the ice. The outer region of a sea ice-covered ocean, neighboring open water, is called marginal ice zone (MIZ). It is a very dynamic environment, and one of its defining properties is sea ice-wave interactions: waves entering MIZ from the ocean move and bend the ice, breaking it into smaller floes, and the ice floes

关键词： sea ice ice-wave interactions sea ice floes ice floe collisions sea ice stress discrete-element model

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discrete-element, individual-based and agent-based models: Tools for interdisciplinary enquiry in geography?

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GEOFORUM 2008年第2期39卷 625-642页

作者： Bithell, Mike Brasington, James Richards, Keith Univ Cambridge Dept Geog Cambridge CB2 3EN England

discrete-element, individual-based and agent-based modelling techniques represent the interactions of individuals or entities with one another and their environments by sets of computational rules. These methods are now being used in geophysics, ecology, zoology, and increasingly in the social sciences. A characteristic is that the "agents" are embedded in an environment with which they interact, so that joint evolution of physical, ecological and socio-economic systems can be studied;this makes them of interest in integrated geographical investigation. Of particular interest is the fact that they allow the study of macro-scale emergent behaviour generated by multiple individual actions. discrete techniques have the potential to create integrated models that cross disciplines. Similar computational methods can be employed to control the spatial search process, deal with irregular or changing boundaries, and to track the evolution of systems where preservation of heterogeneity across space and time is important. The complex series of feedbacks between the different types of system can thus be modelled within a single computational framework. Humans modelled in this way as "agents" can allow the collective effect of many interacting individuals to generate emergent structures at the community scale. The structural characteristics of their social and natural environments will influence their behaviour, while at the same time constituting emergent consequences of their actions. The principal challenge of the latter is to find those sets of rules that represent the beliefs and desires of real human agents, accurately reflecting the cultural context, while allowing us to explore the social and economic limitations of agents to take action. This paper reviews and illustrates discrete methods applicable to a range of geographical enquiries, and with particular reference to individual- and agent-based methods, assesses the rich diversity of approaches that must be combined t

关键词： discrete-element model individual-based model agent-based model environment society

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Failure of topologically interlocked structures - a Level-Set-DEM approach

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EUROPEAN JOURNAL OF MECHANICS A-SOLIDS 2024年 103卷

作者： Feldfogel, Shai Karapiperis, Konstantinos Andrade, Jose Kammer, David S. Swiss Fed Inst Technol Inst Bldg Mat Zurich Switzerland Swiss Fed Inst Technol Dept Mech & Proc Engn Zurich Switzerland Caltech Dept Mech & Civil Engn Pasadena CA USA

Topological Interlocking Structures (TIS) are assemblies of interlocking building blocks that hold together solely through contact and friction at the block interfaces and thus do not require any connective elements. This salient feature makes them highly energy-absorbent, resistant to crack propagation, geometrically versatile, and reusable. It also gives rise to failure mechanisms that, differently from ordinary structures, are governed by multiple contact interactions between blocks and frictional slip at their interfaces. Commonly-used modeling tools for structural analysis struggle to capture and quantify these unusual failure mechanisms. Here, we propose a different approach that is well-suited for modeling the complex failure of slab-like TIS. It is based on the Level-Set-discrete-element-Method, which was originally developed for granular mechanics applications. After introducing the basic assumptions and theoretical concepts underlying our model, we show that it accurately captures the slip-governed failure of slab-like TIS panels as observed in the literature, that it can closely estimate the force-displacement curves, and that it is can be used to explore important features governing the structural mechanics of TIS. The theoretical foundation, together with the results of this study, provide a proof-of-concept for our new approach and point to its potential to improve our ability to model and understand the behavior of interlocked structural forms.

关键词： Topologically interlocked structures Level-set discrete-element model

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Research on Asphalt Mixture Bending Test and Micromechanical Evolution Based on 2D discrete-element Method

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JOURNAL OF MATERIALS IN CIVIL ENGINEERING 2021年第8期33卷 04021179-04021179页

作者： Zhao, Guofang Wang, Qizhi Yan, Zhanyou Hebei Coll Ind & Technol Dept Comp Technol Shijiazhuang 050091 Hebei Peoples R China Shijiazhuang Traff Construct Expressway Construct Pingzan Branch Shijiazhuang 050000 Hebei Peoples R China Shijiazhuang Tiedao Univ Sch Civil Engn Shijiazhuang 050043 Hebei Peoples R China

The damage of asphalt mixture is closely related to its internal material heterogeneity and discontinuity. The mechanical evolution of asphalt mixture is analyzed by meso-mechanics theory, which is very important for revealing the failure mechanism of asphalt pavement. In this paper, the two-dimensional (2D) bending discrete-element model of asphalt mixture was established based on the meso parameters and pictures of the model determined by practical experiments. The process of meso-crack formation and propagation between particles of asphalt mixture under a certain load rate was analyzed. The distribution and transmission of stress and the evolution of the displacement field were also analyzed. The results show that the error between the model bending test and the actual standard test is within 10% (maximum bending strength and maximum bending strain). The model test results show that the discrete-element method can simulate discontinuous and heterogeneous materials well. Under the action of external load, the vertical displacement of coarse aggregate particles is much larger than the horizontal displacement. The displacement of asphalt cement granules is slightly larger than that of coarse aggregate granules. The number of microcracks in the model increases slowly in the early stage and quickly in the later stage. Finally, macroscopic cracks are generated. These macroscopic cracks generally extend along the edges of coarse aggregate particles and where the adhesion of asphalt mortar particles is weak. The force chain diagram between particles in the discrete-element model had both regularity and great discreteness. The results showed that the discrete-element method could not only obtain the internal stress and displacement of the asphalt mixture, but also reveal the mechanical evolution behavior between the particle flows of the asphalt mixture.

关键词： Bending test discrete-element model Mesoscopic parameters Crack evolution Stress and displacement

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