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Failure Mode Characteristic of Rocks Containing a Weak Interlayer with Different Thickness and Dip Angles Based on discrete-element method

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INTERNATIONAL JOURNAL OF GEOMECHANICS 2025年第3期25卷

作者： Wei, Xu Huang, Wenqi Su, Xiaopeng Mei, Ao Yang, Hongyun Zuo, Jianping Chongqing Jiaotong Univ Sch Civil Engn Chongqing 400074 Peoples R China China Univ Min & Technol State Key Lab Coal Resources & Safe Min Beijing 100083 Peoples R China

Both the integrity and the strength of a rock mass are influenced by weak interlayers. In order to study the failure modes of a rock mass with a weak interlayer under uniaxial compression load, based on the discrete-element method, in this paper, a rock mass with different thicknesses and dip angles of a weak interlayer was constructed for uniaxial compression simulation by using particle flow code 2D (PFC2D version 5.00.25). The simulation results showed that cracks mostly distributed in the interlayer. Models with 0 degrees and 15 degrees interlayers bulged outward along the inclination of the interlayer at the interlayer, while the slip failure at the interlayer was the main cause of failure of the interlayer at 30 degrees, 45 degrees, and 60 degrees. The model with a 90 degrees interlayer was dominated by split damage, with cracks distributed randomly in the rock matrix and the interlayer. Combining the number and distribution of cracks in the interlayer with the deterioration of the rock mass strength after failure, the index of interlayer crack failure was defined, based on which the failure modes were categorized into three types: material failure, combination failure, and structural plane failure. The results of the failure mode classification of the test and simulation based on this index were similar. The index reveals the relationship between the deterioration of the rock mass strength after failure and the percentage of interlayer fractures and failure modes. This study offers a novel perspective and a scientific foundation for the quantitative classification of rock failure modes, thereby providing guidance for the stability assessment of rock structures in engineering applications.

关键词： Weak interlayer discrete-element method Failure mode classification Interlayer crack failure index

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Mesoscopic Freeze-Thaw Damage Model of Residual Soil Using a discrete-element method under a Laminated-Wall Flexible-Boundary Condition

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INTERNATIONAL JOURNAL OF GEOMECHANICS 2025年第3期25卷

作者： Que, Yun Chen, Yining Fu, Yuanshuai Huang, Weifeng Lin, Yiqian Jiang, Zhenliang Fuzhou Univ Coll Civil Engn Fuzhou 350108 Peoples R China

Freeze-thaw processes can cause slope instability in areas with short-term frozen (STF) soil, resulting in potential safety risks and huge financial losses to a certain extent, as these processes affect the physical and mechanical properties of the soil. However, their adverse effect on the mesoscopic-level mechanical properties of residual soil has not been adequately investigated. To gain an effective understanding in this regard, a laminated-wall approach was adopted to create a flexible boundary for a triaxial-shear test. Simulated stress-strain curves closely matched experimental results, with a maximum relative error of 7.81% at the peak. Moreover, the experimental data collected from real soil subjected to freeze-thaw cycles were used to calibrate the relation between the macroscopic and mesoscopic parameters. The deterioration of the macromechanical and micromechanical parameters of residual soil primarily occurred in the first four freeze-thaw cycles. For eight freeze-thaw cycles, the damage degree of each microparameter remained the same, reaching approximately 0.37. A freeze-thaw damage model of the mesoscopic parameters of residual soil was then constructed through parameter fitting. Using this model, the impact of frost-thaw on slope deformation behaviors was analyzed. A simulation revealed that displacement primarily occurred at the slope toe and the area of influence expanded with an increasing number of freeze-thaw cycles. As freeze-thaw cycles increased, the stress distribution in the X-direction along the top and surface of a slope became more concentrated, impacting mesoscopic parameters. Conversely, the stress in the Z-direction on the slope dispersed across three slopes after four to eight freeze-thaw cycles, with considerable influence during the initial four cycles. The flexible boundary created using the laminated-wall approach and the freeze-thaw damage model of the mesoscopic parameters facilitated an effective understanding of the freeze-t

关键词： Laminated wall Flexible boundary Freeze-thaw Residual soil Mesoscopic damage parameters discrete-element method

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discrete-element method for particle capture by a body in an electrostatic field

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INTERNATIONAL JOURNAL FOR NUMERICAL methodS IN ENGINEERING 2010年第13期84卷 1589-1612页

作者： Liu, G. Marshall, J. S. Li, S. Q. Yao, Q. Univ Vermont Sch Engn Burlington VT 05405 USA Tsinghua Univ Dept Thermal Engn Key Lab Thermal Sci & Power Engn Minist Educ Beijing 100084 Peoples R China

A discrete-element method is developed for applications involving interaction of spherical particles with a body of arbitrary shape in an electrostatic field. The electric field is induced both by charged particles and by other 'macroscopic' bodies (e.g. electrodes). The electric field due to macroscopic bodies is computed using a boundary-element method that accounts for the particle influence. An algorithm using approximate particle images is introduced to improve electric field resolution for particles lying close to the body surface. The long-range electric field induced by particles is computed using an optimized, adaptive multipole expansion method. The method is applied to the formation of chain-like particle aggregates, with long-range particle attraction governed by the electric field and particle adhesion by van der Waals forces. The method is illustrated by simulation of the capture of uncharged particles on a cylindrical electrode. A local panel subdivision method is developed to mitigate particle drift toward panel edges induced by panel discretization errors. The particle deposition pattern at different cylinder surface charge levels is studied, which shows that long straight particle chains are formed under strong electric fields. The predicted particle capture efficiency agrees well with the experimental data. Copyright (C) 2010 John Wiley & Sons, Ltd.

关键词： discrete-element method dielectrophoretic force boundary-element method electrostatic field

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Effects of model size and particle size on the response of sea-ice samples created with a hexagonal-close-packing pattern in discrete-element method simulations

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Particuology 2018年第1期16卷 106-113页

作者： Shaocheng Di Yanzhuo Xue Xiaolong Bai Qing wang College of Shipbuilding Engineering Harbin Engineering University Harbin 150001 China

We investigated the effects of model size and particle size on the simulated macroscopic mechanical properties, uniaxial compressive strength, Young＇s modulus, and flexural strength of sea-ice samples, using the discrete-element method （DEM） with a bonded-particle model. Many different samples with a hexagonal-close-packing pattern and a unique particle size were considered, and several ratios of particle size to sample dimension （D/L） were studied for each sample. The macroscopic mechanical properties simulated by the DEM decrease monotonously with an increase in D/L. For different samples with different particle sizes, the macroscopic mechanical properties will be identical when D/L is constant. The quanti- tative relationships between macroscopic mechanical properties and ratio of particle size to sample size are important aspects in engineering applications of the DEM method. The results provide guidance on the choice of a particle size in the DEM simulation for numerical samples with a hexagonal-close-packing pattern.

关键词： discrete-element method Bonded-particle model Sample size Particle size Size effect

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Evaluation Indices of an Asphalt-Mixture Digital Specimen Based on the discrete-element method

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JOURNAL OF TESTING AND EVALUATION 2016年第2期44卷 812-819页

作者： Liu, Weidong Li, Liming Tian, Bo Liu, Fei Cheng, Yongzhen Southeast Univ Sch Transportat Nanjing Jiangsu Peoples R China Hunan Univ Sci & Engn Yongzhou Hunan Peoples R China Highway Minist Transport Res Inst Beijing 100088 Peoples R China

To evaluate the generation method of a digital asphalt-mixture specimen based on the discrete-element method, an algorithm for generating three-dimensional coarse aggregates is presented in this study. The simulation result shows that this algorithm can reflect the actual geometry (e.g., shape, size, fracture surface, and angularity) of aggregate particles. The digital three-dimensional specimen generated using this algorithm can model the three-phase system of coarse aggregates, air voids, and asphalt mastic for asphalt mixtures well. To estimate the distribution of coarse aggregates, both in the digital specimen and real asphalt mixture, the position and quantity of the coarse aggregates within a two-dimensional section of the asphalt mixture were adopted as evaluation indices. The results showed that the digital asphalt-mixture specimen was in good agreement with the real asphalt mixture, and the evaluation indices could be used to quantitatively analyze whether the digital specimen could reflect the real asphalt mixture. The proposed approach based on the discrete-element method can be used as a supplemental tool to evaluate the uniformity of asphalt mixtures for micromechanical analysis.

关键词： discrete-element method digital specimen asphalt mixture coarse aggregate image processing

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Analysis of initial stage of liquid-phase sintering by combined multi-phase-field/discrete-element method

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CERAMICS INTERNATIONAL 2024年第19期50卷 37300-37307页

作者： Shinagawa, Kazunari Kyushu Univ Fac Engn Dept Mech Engn 744 MotookaNishi Ku Fukuoka 8190395 Japan

A combined multi-phase-field/discrete-element method in two dimensions is applied to the liquid phase sintering process of blended elemental powders. The boundary migration, diffusion of elements, and phase transformation between two dissimilar particles are calculated using a multi-phase-field method for sintering based on Gibbs energy functions. The sintering shrinkage is computed with the discrete-element method taking account of the neck size and sintering force, which are obtained from a multi-phase-field simulation. In this study, a pair or small cluster consisting of two elemental powders in a binary eutectic alloy is used as a model system. First, the formation of a liquid phase around the contact area between two dissimilar particles above the eutectic temperature of the system, and the motions of the particles due to grain boundary sliding along the liquid films are confirmed. Second, an Sn-Bi system is selected as the real eutectic system, and the sintering behavior of powder compacts with various mixing ratios of Sn and Bi particles is demonstrated. Finally, transient liquid-phase sintering of Sn-Bi system is simulated, that is, the generation and extinction of the liquid phase due to interdiffusion between Sn and Bi particles are calculated.

关键词： Liquid-phase sintering Multi-phase-field method discrete-element method Blended elemental powders Eutectic system

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Algorithms for Generating Three-Dimensional Aggregates and Asphalt Mixture Samples by the discrete-element method

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JOURNAL OF COMPUTING IN CIVIL ENGINEERING 2013年第2期27卷 111-117页

作者： Zhang, Dong Huang, Xiaoming Zhao, Yongli Southeast Univ Sch Transportat Nanjing 210096 Jiangsu Peoples R China

An algorithm for generating three-dimensional aggregates was developed first in this study. This algorithm can model the various shapes, sizes, and angularity of coarse aggregates. The shapes, sizes, and angularity of the generated aggregates can be correlated to those of actual aggregates. Then, algorithms were developed to model coarse aggregate gradation accurately and place the coarse aggregates randomly within the sample. Finally, algorithms were developed to generate the asphalt mastic. The triaxial compression test of the discrete-element sample of the asphalt mixture with the nominal maximum aggregate size of 16 mm was simulated to predict its dynamic modulus. The results indicate that the discrete-element model generated using the algorithms developed in this paper can predict the mixture modulus across a range of loading frequencies. DOI: 10.1061/(ASCE)CP.1943-5487.0000210. (C) 2013 American Society of Civil Engineers.

关键词： discrete-element method Algorithms Aggregates Asphalt mastic Asphalt mixtures

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Liquid-Bridge Contact Model of Unsaturated Granular Materials and its Application in discrete-element method

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INTERNATIONAL JOURNAL OF GEOMECHANICS 2021年第9期21卷

作者： Cai, Guoqing Li, Jian Liu, Shaopeng Li, Jiguang Zhao, Chenggang Beijing Jiaotong Univ Minist Educ Key Lab Urban Underground Engn Beijing 100044 Peoples R China Beijing Jiaotong Univ Sch Civil Engn Beijing 100044 Peoples R China CCCC Highway Consultants Co Ltd Beijing 100088 Peoples R China

In the past, the capillary effect is rarely considered for microcontact models when two adjacent particles are separated by a certain distance. In this paper, a liquid-bridge contact model of unsaturated particles is presented, which is applied to the discrete-element software PFC. Based on this, simulations of uniaxial tensile for unsaturated soils under (2D) situation are carried out, and influence of a water retention angle on uniaxial tensile strength are studied. The simulation results show that the uniaxial tensile strength of unsaturated soil decreases gradually with the increase of the water retention angle, obvious cracks generate at both ends of the soil samples, and the soil sample possesses a residual strength. According to the particle displacement field, velocity field, and contact force chain, the failure forms of samples with different water retention angles are determined. Based on the rose diagram of normal contact force, the changes of its direction and value during failure process are observed directly, so as to analyze the evolution law of contact force for unsaturated soils.

关键词： Unsaturated soil discrete-element method Uniaxial tensile strength Liquid-bridge contact model Water retention angle

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Breakage Characteristics and Crushing Mechanism of Cement Materials Using Point-Loading Tests and the discrete-element method

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JOURNAL OF MATERIALS IN CIVIL ENGINEERING 2014年第5期26卷 992-1002页

作者： Wang, Xiao-bo Xu, Wen-jie Zhang, Bing-yin Tsinghua Univ Dept Hydraul Engn State Key Lab Hydrosci & Hydraul Engn Beijing 100084 Peoples R China

A point-loading device was used to research the breakage characteristics of single particles and to study their crushing mechanism. A series of point-loading tests were completed on the basis of cement ellipsoid particles modeled in various sizes and strengths with cement pastes. A close-packing method of equal spheres with several close-packed assemblies was generated, and the corresponding numerical models for cement ellipsoid particles were established by the discrete-element method. Experimental and numerical tests show that the high-strength materials are brittle, whereas the low-strength materials are ductile, and vice versa. A comparison of the experimental and numerical results show reasonable, rational results, and indicate that the force-displacement relationship is approximately linear for this type of granular material. A measurement-sphere method was used to trace the energy and stress distribution in the particle samples. The accumulation of dilatant deformation causes the collapse of the local skeleton structures in the cement ellipsoid particles.

关键词： Point-loading tests Crushing mechanism discrete-element method Cement ellipsoid particles

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Stress Responses Associated with Earth Pressure Balance Shield Tunneling in Dry Granular Ground Using the discrete-element method

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INTERNATIONAL JOURNAL OF GEOMECHANICS 2019年第7期19卷 1-9页

作者： Wang, Shuying Qu, Tongming Fang, Yong Fu, Jinyang Yang, Junsheng Cent S Univ Sch Civil Engn Changsha 410002 Hunan Peoples R China Southwest Jiaotong Univ Key Lab Transportat Tunnel Engn Minist Educ Chengdu 610031 Sichuan Peoples R China

This study investigates stress responses associated with earth pressure balance (EPB) shield tunneling in dry granular ground. A numerical model using the discrete-element method (DEM) was employed to simulate both the advancement of EPB shield and the discharge of muck from the chamber. Some critical ground stress variations associated with tunneling were thus effectively captured. Numerical results show that the responses of the principal stress in dry granular ground, namely changes of magnitude and rotation angle, significantly depend on both the discharge rate of muck and the distance from tunnel face. The average value and distribution features of stress at the tunnel face are also subjected to the discharge rates of muck in the shield chamber. To be specific, in the case without muck discharge out of the chamber, the average stress at the tunnel face first increases with increases in advancement distance and subsequently tends toward a stable value. But for the case of discharging muck with an upper limit rate, the stress first decreases rapidly to a minimum value and subsequently increases to a stable value. Further, a significant stress release area is also found in the proximity of the tunnel face, and the changes in the contact forces among soil particles are far less than those in the case without muck discharge.

关键词： EPB shield tunnel Stress response Principal stress Dry granular ground discrete-element method

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