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2012 3rd International Conference on Information Technology for Manufacturing Systems(ITMS 2012)

作者： Song Wei School of Construction Management and Real Estate Chongqing University

Laboratory experiments and numerical simulations, using particle flow code(PFC2D), were performed to study the behavior of marble under tri-axial loading and pre-existing fissure uniaxial *** laboratory tri-axial compression results of marble was analyzed, and the calibration of the micro-properties of BMP(Bonded particle model) in PFC2D with the test data was carried out *** pre-existing fissure was simulated by smooth joint contact, and the cracking propagation mode of pre-existing fissure was carried out with the calibrated BMP properties and single smooth joint *** simulation show that the tensile crack firstly initiated along the vertical direction to pre-existing fissure, and then gradually departs towards the direction of axial stress, and finally develops along the direction of axial during *** numerical simulation coincide with our understanding of fracture mechanics.

关键词： Numerical model Micromechanics Crack Propagation Pre-existing Fissure particle flow code Bonded particle model Smooth-Joint model

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Numerical simulation of the mechanical behaviour of porous concrete

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ENGINEERING COMPUTATIONS 2011年第7-8期28卷 984-1002页

作者： Lian, Chunqi Yan Zhuge Beecham, Simon Univ S Australia Sch Nat & Built Environm Brisbane Qld Australia Univ So Queensland Fac Engn & Surveying Brisbane Qld Australia

Purpose - Porous concrete is a mixture of open-graded coarse aggregate, water and cement. It is also occasionally referred to as no-fines concrete or pervious concrete. Due to its high infiltration capacity, it is viewed as an environmentally sustainable paving material for use in urban drainage systems since it can lead to reduced flooding and to the possibilities of stormwater harvesting and reuse. However, the high porosity is due in the main part to the lack of fine aggregate particles used in the manufacture of porous concrete. The purpose of this paper is to present a numerical method to understand more fully the structural properties of porous concrete. This method will provide a useful tool for engineers to design with confidence higher strength porous concrete systems. Design/methodology/approach - In the method, porous concrete is modelled using a discrete element method (DEM). The mechanical behaviour of a porous concrete sample subjected to compressive and tensile forces is estimated using two-dimensional particle flow code (PFC2D). Findings - Three numerical examples are given to verify the model. A comprehensive set of micro-parameters particularly suitable for porous concrete is proposed. The accuracy and effectiveness of simulation are confirmed by comparison with experimental results and empirical equations. Originality/value - The experimental investigations for porous concrete described in this paper have been designed and conducted by the authors. In addition, the type of two dimensional PFC analysis presented has rarely been used to model porous concrete strength characteristics and from the results presented in this paper, this analysis technique has good potential for predicting its mechanical properties.

关键词： Mechanical behaviour of materials Simulation Concretes Porosity Porous concrete Modelling Strength particle flow code PFC

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Analysis of reasonability of several assumptions used in typical limit equilibrium methods based on progressive failure feature of slope

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ROCK AND SOIL MECHANICS 2012年第SUPPL. 1期33卷 146-150页

作者： Zeng Zeng Zhang Ze-hui Yang Hong-li Yin Xiao-tao Dang Fa-ning Xian Univ Technol Inst Geotech Engn Xian 710048 Shaanxi Peoples R China Zhejiang Design Inst Water Conservancy & Hydroele Hangzhou 310002 Zhejiang Peoples R China Xian Changqing Technol Engn Co Ltd Xian 710018 Shaanxi Peoples R China Chinese Acad Sci Inst Rock & Soil Mech Wuhan 430071 Hubei Peoples R China

Progressive failure feature of slope is difficult for numerical simulation of slope. Also practical slope failure process is rarely a whole and sudden slipping one, is often step by step one from local deformation to final and overall instability, which is a chain domino style failures triggered by small disturbance under critical condition. Here by particle flow code(PFC), a numerical slope with cohesion between particles being 36 kPa, friction coefficient between particles being 0.36, 0.1m particle size and 10m height is designed, initial models damage will not occur under gravity condition. Slope failure is done by cohesion strength between particles reduced to half of initial one. Slope shapes of each 20 000 steps, total steps being 200 000, are obtained by monitoring change of vertical particle groups at horizontal intervals of 1m, which directly reveals progressive failure of slope. Found that failure is always beginning from local part, movement of slope body material results in secondary damage in slope, which forms final arc sliding surface. These account for sliding isn't a whole declining of slope body, the body isn't a rigid one. Stress conditions along slip surface don't reach limit state at the same time. Change of stress in slope body isn't a monotonous one, but a process with rises and falls. All these conclusions contradict assumptions in current limit equilibrium methods such as rigidity of finite slice, simultaneously reaching limit sate on slip surface, making statically indeterminate problem solved by force transfer mode between slices given, overall analytical method not presenting localization and progressive feature of failure, which hints future of slope computing method lies in discrete element methods can present dynamic practical problem and material real failure characteristics.

关键词： slope progressive failure limit equilibrium method assumption particle flow code numerical test

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Selecting Ore Pass-Finger Raise Configurations in Underground Mines

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ROCK MECHANICS AND ROCK ENGINEERING 2011年第3期44卷 291-303页

作者： Esmaieli, Kamran Hadjigeorgiou, John Golder Associates Geoengn Grp Montreal PQ Canada Univ Toronto Lassonde Min Inst Toronto ON Canada

Material transfer in underground mines often relies on ore and waste pass systems. In mines where ore pass systems transcend multiple production levels, finger raises are used to funnel material into the system. Empirical evidence, from several mines, suggests that the use of finger raises often results in damage in the immediate vicinity of finger raise-ore pass junctions. Of particular concern is damage on the ore pass walls as a result of impact loads generated by material flowing through the fingers on to the ore pass walls. The severity of damage is directly related to the rock mass quality of the excavation walls, material properties of transiting ore and the ore pass-finger raise configuration. This paper examines the influence of different configurations aiming to develop strategies to minimize ore pass wall damage. To these purposes the particle flow code was employed to undertake a series of numerical experiments. This involved dumping a batch of rock fragments, represented by a uniform distribution of disc-shaped particles, into a finger raise and allowed to flow into an ore pass. It has been clearly demonstrated that higher impact loads were generated when the angle of intersection between ore pass and finger raise was 140A degrees to 145A degrees. This configuration results in the most damage. The results of these numerical experiments were collaborated by observations at an underground mine in Canada.

关键词： Ore pass systems particle flow code Finger raise Impact loads

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Numerical study of mechanism of fold formation in a laminated rock

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JOURNAL OF EARTH SYSTEM SCIENCE 2011年第6期120卷 965-978页

作者： Saini, P. K. Kumar, T. Singh, T. N. Singh, N. Keshri, V. K. Indian Inst Technol Dept Earth Sci Bombay 400076 Powai India Banaras Hindu Univ Dept Min Engn Inst Technol Varanasi 221005 Uttar Pradesh India

A set of large deformation experiments are presented to simulate folding pattern at various energy states during formation. In order to numerically simulate this phenomenon, a rectangular layer of shale is generated and compressed at various strain rates. The results reveal the variation in distribution of stress along the length of the bed. The stress distribution during elastic behaviour of shale bed at low compression rate and the change in stress distribution leading to rupture at high compression rates is discussed. Wavelength, limb length, bulk shortening, stress distribution, displacement of particles along the length of the bed is considered for comparative study of the fold pattern generated at various compression rates. The nature and position of crack generated during the formation of fold is also explained. After rupture in shale bed, the generation of fault and stress distribution in limbs of fold sliding over one another is also described.

关键词： Discrete element method particle flow code folding bulk shortening compression rate

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The Numerical Simulation of the Triaxial Test of Cemented Coarse-grained Soils

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1st International Conference on Civil Engineering, Architecture and Building Materials (CEABM 2011)

作者： Xu Bin Luo Wei Zou Degao Kong Xianjing Zhou Yang Dalian Univ Technol State Key Lab Coastal & Offshore Dalian 116024 Peoples R China Dalian Univ Technol Fac infrastruct Engn Dalian 116024 Peoples R China

ISBN: (纸本)9783037851272

Cemented coarse-grained soils have both the properties of coarse-grained soils and concrete. This paper used discrete element method (DEM) to simulate of the drained monotonic load triaxial tests of coarse-grained soils and cemented coarse-grained soils respectively, the microscopic parameters of numerical models were calibrated based on the tests. The characteristics of the cemented coarse-grained soils and the microscopic mechanism were analyzed. The results showed that, the cemented coarse-grained soils have the higher modulus and strength compared with coarse-grained with adding the 3% cement in the specimens and appear the significant strain softening after the stress reaches the peak value;the deformation of the soil particles,the friction between soil particles and the crack of the cement bond are the mainly internal factors.

关键词： DEM particle flow code cemented coarse-grained soils numerical simulate

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Mesoscopic numerical simulation of acoustic emission experiments in rock failure

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International Symposium on Geomechanics and Geotechnics - From Micro to Macro

作者： Su, Hui Ma, Qiujuan HeBei Univ Engn Sch Water Resources & Hydropower HanDan Peoples R China

ISBN: (纸本)9780415612951

By using particle flow code (PFC2D), mesoscopic numerical simulation of rock failure in uniaxial compression is studied. The tests reproduce the process of rock failure and the rule of AE. By using FISH language embedded within PFC2D, the mesoscopic medium parameters is set. The nonlinear characteristics of rock are simulated;meanwhile the internal damage of the rock is demonstrated by reducing the contact stiffness. According to the hypothesis of consistency in AE and rock damage, the number of broken bonds was used as a measurement of AE events. It is shown that AE events are related to compressive strength in the process of rock failure. With the increase of heterogeneity, peak strength of rock specimens reduce and the total number of AE increases significantly. The spatial distribution of AE becomes more extensive. Meanwhile, AE of rock samples appear earlier and sustain for longer duration. The AE rates change dramatically in different stages. In the post-peak region, AE events stay evident and the AE characteristics depend on the failure type of rocks. The results illustrate the interdependence of stress, strain, acoustic and meso-fracture.

关键词： acoustic emission rock failure particle flow code rock heterogeneity

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Effects of Large Rock particles on Permeability of Soil and Rock Mixture

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1st International Conference on Civil Engineering, Architecture and Building Materials (CEABM 2011)

作者： Xiang, Xianchao Jiang, Guosheng China Univ Geosci Fac Engn Wuhan 430074 Peoples R China

ISBN: (纸本)9783037851272

The soil and rock mixture is widely spread in the world, which is much different from homogeneous and continuous soil, it is hard to get the permeability of the soil and rock mixture by theories, and it is also hard to get that from the large lab test as the difficulty in sampling. The particle flow code (PFC) method is used to study the permeability character influenced by large rock particles. The result shows that the seepage of the soil and rock mixture obeys the linearity of Darcy's law in low fluid velocity, but the large particles influence the local pore pressure evidently. The permeability increases while the ratio of rock to soil increase first, and decreases while the ratio enlarge to 0.5, then increases after the ratio enlarge to 0.7. The large rock particles jam the fluid path, but decrease the length of the pipe, the permeability is influenced by the two effects.

关键词： Permeability Pore pressure Soil and rock mixture particle flow code

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Sand meso analysis and numerical simulation

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International Symposium on Geomechanics and Geotechnics - From Micro to Macro

作者： Zhou, Jian Gao, Bing Tongji Univ Dept Geotech Engn Shanghai 200092 Peoples R China

ISBN: (纸本)9780415612951

The numerical simulation Method Discrete Element (DEM) is widely used in many engineering field. DEM is mainly used to explore micromechanics and macroscopic deformation behavior of granular shear zones. Such numerical experiments allow us to look inside deforming fault zones and identity controls on fault zone structure, mechanical strength, and rheology. A numerical simulation software particle flow code in 2-Dimension (PFC2D) based on DEM has been carried out to simulate many in-situ tests. In this paper, PFC is used to simulate lab direct-shear, in order to study the rules of shearing strength and internal friction angle on different graduation medium sand. At the end, with the data that the PFC offers, the law that the coefficient of variation of internal frictional angle will change corresponding to the changing graduation is found. The concrete results show that when d(50) and d(10) keep invariant, internal frictional angle increased with the increase of C-u;Under the condition of the stationary d(50) and C-u. internal frictional angle increased with the increase of C-u. The further result shows that the change of C-u has more influence on internal frictional angle than d(50).

关键词： particle flow code microscopic mechanics macroscopic response coefficient of variation

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Macro-response of rock mechanics behavior affected by its micro-parameters

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International Symposium on Geomechanics and Geotechnics - From Micro to Macro

作者： Yin, Xiaotao Ge, Xiurun Li, Chunguang Wang, Shuilin Chinese Acad Sci State Key Lab Geomech & Geotech Engn Inst Rock & Soil Mech Wuhan Peoples R China

ISBN: (纸本)9780415612951

Micro-parameters of rock and soil material are hard to determine with present technology. But their unique physical & mechanics characteristics and failure mechanism are controlled by them, heterogeneity and micro-structure. So, virtual uniaxial compression tests of rock are done by means of inner fish language in particle flow code. Four different kinds of computing scheme such as friction coefficient, contact radius multiplier, elastic modulus and micro-strength between material particles based on these numerical models are designed. And each kind of computing scheme contains three calculating conditions of great, medium and less, total conditions being twelve, aiming to study relation between micro-mechanics-parameters and macro-mechanics response of the rock and soil material. Found that the former three parameters can result in enhancement of material's modulus and strength, but micro-strength only increases macro-strength, that friction dominates post-peak strength of material, this friction effect is done after the micro-crack produced by micro-cohesion being overcome and under slipping condition. So the micro-cohesion only results in macro-strength change, but micro-friction-coefficient can cause changes in strength and deformation feature. Contact radius multiplier determines cohesion strength and contact area of particles and elastic modulus dominates slipping strain of particles, so these two micro-factors can cause changes in strength and deformation. All these illustrate the relation is the one between part and whole. Features of assembly are large than particles, whose relation is not simply summation.

关键词： particle flow code virtual test micro-parameter macro-response

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