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Mesoscopic study of interface properties of geogrid-reinforced soil

ROCK AND SOIL MECHANICS 2011年第SUPPL. 1期32卷 66-71页

作者： Chen Jian-feng Li Hui-li Liu Jun-xiu Zhou Jian Tongji Univ Minist Educ Key Lab Geotech & Underground Engn Shanghai 200092 Peoples R China Shanghai Inst Geol Survey Shanghai 200072 Peoples R China

A large-size reinforced soil pull-out test was carried out and was simulated by particle flow code(PFC) to investigate the microscopic properties of geogrid-soil interface. The results show that the behavior of trigonometric group particles developed based on "clump" inherent in PFC is close to that of practical sand particles. The upper and lower geogrid-soil interfaces are not symmetrical such that the disturbed area of lower interface is higher than that of upper interface. Under the condition of low compactness of sand as well as low normal stress, the thickness of geogrid-soil interface decreases with increase of normal stress, exhibiting negative linear relationship.

关键词： geogrid interface properties particle flow code pull-out test

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Analyzing of Functionally Graded Materials by Discrete Element Method

Analyzing of Functionally Graded Materials by Discrete Eleme...

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International Conference on Applied Mechanics and Mechanical Engineering

作者： Zhou Feng-xi Li Shi-rong Lai Yuan-ming Yang Yan Lanzhou Univ Technol Sch Civil Engn Lanzhou 730000 Gansu Peoples R China Chinese Acad Sci Cold & Arid Reg Enviromn Engn Res Inst Beijing 100864 Peoples R China Yangzhou Univ Sch Civil Sci & Engn Yangzhou 225009 Jiangsu Peoples R China

ISBN: (纸本)9780878492459

Based on discrete element method, the mechanical responses of a functionally graded cantilever beam are studied by using of two kinds of particle with different properties. The variation of material properties along the thickness direction is simulated by the different distribution of constituent particles in space. The method validity was tested, and the influence of material homogenous on deformation and stiffness of cantilever beam under mechanical load were studied make use of numerical examples. Method in this paper will provide a new way for analyzing of functionally graded materials and its optimizing design from micromechanism.

关键词： functionally graded materials discrete element method particle flow code beam

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Stability analysis of vertical excavations in hard rock by integrating a fracture system into a PFC model

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TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY 2009年第3期24卷 296-308页

作者： Hadjigeorgiou, John Esmaieli, Kamran Grenon, Martin Univ Laval Dept Min Met & Mat Engn Quebec City PQ G1K 7P4 Canada

This paper presents an implementation of a comprehensive engineering approach to the analysis of the stability of vertical excavations in rock. This approach relies in the generation of discrete fracture systems to better capture the structural complexity of the rock mass. The resulting fracture system is consequently linked into a distinct element stress analysis. The particle flow code was selected as it potentially allows greater flexibility in representing a fracture system. In the first example a 3D fracture system was linked into a 2D PFC model. Although this has allowed for an improved quantification of stress structure interaction it necessitated important simplifications which may not be necessarily appropriate. These have been overcome by providing a complete integration of a 3D fracture system to a 3D PFC model. This will potentially lead into a design tool that adequately account for the stress structure interaction on the stability of vertical or near vertical excavations in hard rock. (C) 2008 Elsevier Ltd. All rights reserved.

关键词： Fracture system Mining Vertical excavations particle flow code

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ANISOTROPIC STRENGTH CHARACTERISTICS OF JOINTED ROCK MASS

ANISOTROPIC STRENGTH CHARACTERISTICS OF JOINTED ROCK MASS

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2009 International Symposium on Rock Mechanics:"Rock Characterisation,Modelling and Engineering Design Methods"

作者： Chun-sheng Qiao Beijing Jiaotong University,Beijing Beijing Zhi-gang Zhang China Highway Planning and Design Institute Consultants.Inc. Beijing Xiao Li Institute of Geology and Geophysics Chinese Academy of Sciences Beijing

Rock masses are often intersected by discontinuities,such as regular bedding planes,fissures,fractures,joints or faults,producing many types of *** of the most important features of the joints in rock is that they introduce anisotropy in strength and *** the mass is not highly fractured and the joint system has only few sets（say five or less）,then the mass usually behaves anisotropically provided that no set has a dominant *** influence of the intrinsic anisotropy on rock mass failure strength is one of the basic data required for predicting rock mass *** many attempts have been made in the past to describe the strength anisotropy of jointed rock mass,no general methodology has emerged yet. To estimate strength anisotropy behavior of jointed rock mass quantitatively,the strength anisotropy of rock mass having one and two sets of joints is analyzed through numerical simulation of uniaxial and triaxial compression *** flow code in 3 Dimensions(PFC) is selected to be used in the simulations because it is a well-documented and commercially available tool for modeling the behavior of brittle rock material including fracture *** numerical models having a single joint or one and two sets of joints are *** the testing conditions include the uniaxial and triaxial compression accompanying the different joint *** valuable conclusions obtained are as follows. （1） Duo to presence of joints,the strength of the jointed rock is *** strength of the jointed rock is dependent on the inclination and persistence as well as number of the *** degree of strength anisotropy of the jointed rock is the highest at uniaxial compression condition and decreases with increasing confining pressure and persistence of the joints. （2） The strength-joint dip angle curves obtained from numerical simulation for the rocks having a single or one set of joints are different in shape and manner clearly with

关键词： jointed rock anisotropy strength particle flow code numerical simulation compressive test

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ANALYSIS OF THE MECHANICAL BEHAVIORS OF ROCK MASSES BY USING A NUMERICAL METHOD Paper No.253

ANALYSIS OF THE MECHANICAL BEHAVIORS OF ROCK MASSES BY USING...

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ISRM-Sponsored International Symposium on Rock Mechanics:"Rock Characterisation,Modelling and Engineering Design Methods"(SINOROCK2009)

作者： Eui-Seob Park Hee-Soon Shin Sung-Ho Bae Korea Institute of Geoscience & Mineral Resources(KIGAM) KIGAM

ISBN: (纸本)9789628014170

Although the evaluation of the mechanical properties and behavior of discontinuous rock masses is very important for the design of underground openings,it has always been considered the most difficult *** evaluation of rock mechanical properties such as deformation and strength properties can be achieved through the application of empirical relationships or by a theoretical approach based on numerical *** of the difficulties in describing the rock mass behavior is assigning the appropriate constitutive *** limitation may be overcome with the progress in discrete element software such as PFC(particle flow code),which does not need the user to prescribe a constitutive model for rock ***,the micro-scale properties of the intact rock and joints are defined and the macro-scale response results from those properties and the geometry of the problem. The methodology for the rock mechanical descriptive model was developed in Sweden,which is a combination and evaluation of the characterization of rock mass by means of empirical relationships and a theoretical approach based on numerical modelling. In this paper,the methodology developed in Sweden for the rock mechanics descriptive model was reviewed by applying it to two tunnel *** rock mass models were generated from 2D trace sections extracted from the 3D Discrete Fracture Network (DFN) model,which was generated by Fracman(?) for representing fracture patterns in three dimensions within a given rock volume at the test *** the numerical modeling was performed with the rock mass models for two-dimensional code PFC. To assess the rock mechanical considerations for a deep repository,the tunnel scale with resolution of 30 by 30 m in the numerical model is most likely sufficient to cover rock mechanical aspects in"the repository scale".So the model size of 30m×30 m was used in PFC computations to consider the mechanical behavior of intact rock and fractures and fracture geometry. In t

关键词： Mecahnical behavior particle flow code Rock Mechanics Descriptive Model Discrete Fracture Network Constitutive model

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ANISOTROPIC STRENGTH CHARACTERISTICS OF JOINTED ROCK MASS Paper No.259

ANISOTROPIC STRENGTH CHARACTERISTICS OF JOINTED ROCK MASS Pa...

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ISRM-Sponsored International Symposium on Rock Mechanics:"Rock Characterisation,Modelling and Engineering Design Methods"(SINOROCK2009)

关键词： jointed rock anisotropy strength particle flow code numerical simulation compressive test

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Discrete element method contact model for dynamic simulation of inelastic rock impact

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COMPUTERS & GEOSCIENCES 2007年第4期33卷 513-521页

作者： An, Baoquan Tannant, Dwayne D. Terracon Geotech Ltd Calgary AB T1Y 5R8 Canada Univ Alberta Dept Civil & Environm Engn Edmonton AB T6G 2W2 Canada Terracon Geotech Ltd 140 Calgary AB T1Y 5R8 Canada

A contact model for inelastic impact-rebound events such as those that occur when a rock bounces down a slope is developed for dynamic simulations using the discrete element method. Upon impact, the normal contact force follows a linear elastic relationship as a function of relative displacement up to a pre-set transition force, after which the contact force is fixed at the transition force until the relative velocity between the objects in contact reaches zero. Upon unloading (rebound), the contact force follows a power function that enables the contact model to remove, in a time-stepping manner, significant stored elastic energy from the contact thus reducing the rock's kinetic energy. The model automatically generates lower values of coefficient of normal restitution as the impact velocity increases. (c) 2006 Elsevier Ltd. All rights reserved.

关键词： discrete element method contact model particle flow code rock impact rock fall kinetic energy loss coefficient of normal restitution

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Numerical investigations of ore pass hang-up phenomena

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INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES 2007年第6期44卷 820-834页

作者： Hadjigeorgiou, J. Lessard, J. F. Univ Laval Dept Min Met & Mat Engn Quebec City PQ G1K 7P4 Canada

Material flow in ore pass systems is critical to the economic performance of mining operations. The design of ore passes, however, does not seem to receive the same engineering attention as other mining infrastructure. Quite often, it is only when ore pass systems fail to perform, and material flow is disrupted, that ore pass design and operation come under scrutiny. A survey of ore pass design and performance in 10 Quebec underground mines has shown that, while cohesive arching is also observed, interlocking hang-ups of coarse material are by far the most frequently observed phenomena in the surveyed mines. This paper summarizes work undertaken using the distinct element method to conduct a series of numerical experiments in order to investigate the influence of ore pass geometry, rock fragments shape and size distribution on material flow in an ore pass. The employed modelling methodology contributes to a better understanding of interlocking and provides a series of guidelines to help limit the occurrence of interlocking hang-ups in an ore pass. Better flow is achieved when using vertical ore passes with square cross sections. particle shape is an important element as demonstrated by using spherical as well as cubical particles. It is recognised that cubical particles provide more realistic results. (C) 2006 Elsevier Ltd. All rights reserved.

关键词： ore pass hang-ups interlocking arching fragment flow modelling particle flow code

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Study of the micro-mechanical behaviour of the Opalinus Clay:: an example of co-operation across the ground engineering disciplines

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BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT 2006年第2期65卷 195-207页

作者： Bock, Helmut Bluemling, Peter Konietzky, Heinz Q&S Consult Int Consulting Qual Control & Safety Management G D-48455 Bad Bentheim Germany NAGRA Natl Genossenschaft Lagerung Radioakt Abfalle CH-5430 Wettingen Switzerland ITASCA Consultants GmbH D-45886 Gelsenkirchen Germany

The high degree of scientific cross-fertilisation possible between the three geo-engineering disciplines soil mechanics, rock mechanics and engineering geology, is demonstrated by means of a micro-mechanical model of the Opalinus Clay. After a brief review of Terzaghi's effective stress principle and the importance of micromechanical models in general, a conceptual study of a micromechanical model of a claystone is presented in some detail. The model is based on the particle flow code (PFC) developed by Itasca Corp. It introduces into the model the pertinent composition and structure of the Opalinus Claystone established in the local engineering geology of Switzerland and SW Germany. This includes elongated clay platelets, various layers of densified water around the platelets, free water in the pores and a specific texture of the platelets after consolidation. The model is numerically subjected to a series of loading stages. It is shown that the micro-mechanical model reproduces a number of features which have been known for a long time in soil and rock mechanics but which are often intractable in conventional generic models. The features include non-linear stress-strain curves with pre-failure damage and post-failure strain softening, a non-linear increase of the particle contacts with loading, distinct clustering of deformations, clustering of micro cracks leading to the development of shear bands and hysteresis in cyclic loading. It is concluded that micro-mechanical models are promising tools for further development of our understanding of the mechanical behaviour of geological materials. They offer an excellent opportunity for scientific co-operation between engineering geologists and soil and rock mechanics engineers.

关键词： engineering geology soil mechanics rock mechanics discrete elements particle flow code opalinus clay micro-mechanical model

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ANALYSIS OF THE UPLIFT MECHANISM OF UNIFORM-SECTION PILES IN SANDS

ANALYSIS OF THE UPLIFT MECHANISM OF UNIFORM-SECTION PILES IN...

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中日岩土工程学术会议

作者： WEN-BAI LIU ZI-SHENG LIU and JIAN ZHOU Depart, of Communications and Transportation, Shanghai Maritime University, Shanghai 200135, China Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China

The bearing mechanism of piles on uplift load are analyzed and tested with particle flow code (PFC2D) numerical simulation of mcso-mechanics. PFC2D simulates and analyzes the uplift displacement of pile and particle distribution figure and force chains distribution figure of sand as well as the changes of them. Comparing with the results of material object tests, the relationship of uplift load and displacement of pile experiment are preferably analyzed. The distribution of pile shaft resistance and the formation of shear band are also studied in the paper. The macro mechanics phenomena of piles on uplift load are closely related to the changes of its meso-mechanics.

关键词： Uplift Load Pile particle flow code Meso-Mechanics Shear Band

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