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Determination of time-dependent strengths of salt pillars based on strain energy principle

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International Journal of Mining Science and Technology 2019年第2期29卷 273-279页

作者： Prapasiri Junthong Supattra Khamrat Suratwadee Sartkaew Kittitep Fuenkajorn geomechanics Research Unit Institute of Engineering Suranaree University of Technology

The objective of this study is to determine the time-dependent strengths of salt mine pillars in the Maha Sarakham formation, northeast of Thailand. Strain rate-controlled triaxial compression tests have been performed on salt specimens under confining pressures from 0 MPa to 12 MPa. The strain rates are from 10^(-7) s^(-1) to 10^(-4) s^(-1). The axial stresses and lateral strains are monitored through the strain-softening region. The results indicate that the strengths and elastic moduli increase exponentially with the strain rates. The power creep law parameters are calibrated with the test results, and hence allows constructing series of strain-time curves for the salt pillars under different depths and extraction ratios. The strain energy density principle is applied to develop a strength criterion for the salt pillars. Combining this criterion with the series of the strain-time curves the time-dependent strengths of the salt pillars for different extraction ratios can be predicted.

关键词： Dilation Failure Elastic modulus Strain rate Time-dependency

Two-dimensional numerical manifold method with multilayer covers

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Science China(Technological Sciences) 2016年第4期59卷 515-530页

作者： LIU ZhiJun ZHENG Hong State Key laboratory of geomechanics and Geotechnical engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences Key laboratory of Urban Security and Disaster engineering Ministry of Education Beijing University of Technology

In order to reach the best numerical properties with the numerical manifold method(NMM),uniform finite element meshes are always favorite while constructing mathematical covers,where all the elements are *** the presence of steep gradients or strong singularities,in principle,the locally-defined special functions can be added into the NMM space by means of the partition of unity,but they are not available to those complex problems with heterogeneity or nonlinearity,necessitating local refinement on uniform *** is believed to be one of the most important open issues in *** this study multilayer covers are proposed to solve this *** addition to the first layer cover which is the global cover and covers the whole problem domain,the second and higher layer covers with smaller elements,called local covers,are used to cover those local regions with steep gradients or strong *** global cover and the local covers have their own partition of unity,and they all participate in the approximation to the *** advantageous over the existing procedures,the proposed approach is easy to deal with any arbitrary-layer hanging nodes with no need to construct super-elements with variable number of edge nodes or introduce the Lagrange multipliers to enforce the continuity between small and big *** no limitation to cover layers,meanwhile,the creation of an even error distribution over the whole problem domain is significantly *** typical examples with steep gradients or strong singularities are analyzed to demonstrate the capacity of the proposed approach.

关键词： numerical manifold method finite element method covers hanging nodes structured local refinement short cracks

Micromechanics of rock damage: Advances in the quasi-brittle field

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Journal of Rock Mechanics and Geotechnical engineering 2017年第1期9卷 29-40页

作者： Qizhi Zhu Jianfu Shao Key laboratory of Ministry of Education for geomechanics and Embankment engineering Hohai University laboratory of Mechanics of Lille UMR8107 CNRS University of Lille

Constitutive models play an essential role in numerical modeling and simulation of nonlinear deformation, progressive damage and failure of rock-like materials and structures. Recent advances in the quasi-brittle field show that upscaling methods by homogenization have provided a new efficient way to derive macroscopic formulations of rocks from their microstructure information and local properties and then to model nonlinear mechanical behaviors identified at laboratory. This paper aims first at relating the mechanical phenomena on sample scale to their respective mechanisms on microscale. Main focus is put on unilateral effects due to crack’s opening/closure transition, material anisotropy induced by crack growth in some preferred directions and multiphysical coupling at microcracks. After a brief introduction to the linear homogenization method and its application to crack problems, we present some recent advances achieved in the combined homogenization/thermodynamics framework, including anisotropic unilateral damage-friction coupling, theoretical failure prediction in conjunction with deformation analyses, poromechanical coupling, analytical solutions and numerical implementation with application to typical brittle rocks.

关键词： Micromechanics Damage-friction coupling Unilateral effects Induced anisotropy Failure criterion Brittle rocks

An improved three-dimensional spherical DDA model for simulating rock failure

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Science China(Technological Sciences) 2015年第9期58卷 1533-1541页

作者： JIAO YuYong HUANG GangHai ZHAO ZhiYe ZHENG Fei WANG Long State Key laboratory of geomechanics and Geotechnical engineering Institute of Rock and Soil Mechanics Chinese Academy of Sciences School of Civil and Environmental engineering Nanyang Technological University

In this paper, a discontinuous numerical model, namely SDDARF3D(three-dimensional spherical discontinuous deformation analysis for rock failure), is proposed for simulating the whole process of rock failure. Firstly, within the framework of the classical discontinuous deformation analysis(DDA) method, the formulation of three-dimensional spherical DDA(3D SDDA) is deduced; secondly, a bonding and cracking algorithm is constructed and the SDDARF3 D model is proposed; thirdly, corresponding VC++ calculation code is developed and some verification examples are calculated. The simulated results can intuitively reproduce the failure phenomena of rock mass, indicating that the proposed SDDARF3 D numerical model is correct and effective.

关键词： rock failure three-dimensional spherical discontinuous deformation analysis crack propagation bonding and cracking algorithm

Vertical drainage capacity of new electrical drainage board on improvement of super soft clayey ground

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Journal of Central South University 2015年第10期22卷 4027-4034页

作者：沈扬励彦德黄文君徐海东胡品飞 Key laboratory of Ministry of Education for geomechanics and Embankment engineering Hohai University Huahong Full Electro-osmosis Technologies Co. Ltd

As an advanced polymer composites electro-kinetic geosynthetics, the electro-osmotic vertical drainage(EVD) board could drain water quickly and accelerate consolidation process. However, the drainage rate was mainly impacted by the vertical drainage capability. Therefore, vertical drainage capability at the top of EVD board was theoretically analyzed. Basic requirements for drainage at the top of the board were summed up, as well as the formula of anode pore pressure when losing the vertical drainage capability. Meanwhile, a contrast test on the top and bottom drainage capacities was conducted. In use of the advanced EVD board, the voltage potential and pore pressure of anode were measured. Moreover, the derived formulas were verified. The result shows that the decrease of electric force gradient had an observable impact on the drainage capability. There was nearly no difference between the energy consumption for the two drainage methods. Although a little less water was discharged, the top drainage method had more advantages, such as high initial drainage velocity, few soil cracks, low anode water content and high soil strength. All of these show that the super soft soil ground could be consolidated quickly in use of the advanced EVD board through the top drainage. The top drainage method could efficiently improve the drainage effect, decrease the energy consumption and speed up the project proceeding.

关键词： electro-osmotic vertical drainage(EVD) board vertical drainage capacity potential gradient pore pressure around anode

Traction rheological properties of simulative soil for deep-sea sediment

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Journal of Oceanology and Limnology 2019年第1期37卷 62-71页

作者： QI Cailing RAO Qiuhua LIU Qi MA Wenbo College of Civil engineering and Mechanics Xiangtan University Hunan Key laboratory of geomechanics and engineering Safety Xiangtan University School of Civil engineering Central South University

The traction capacity of the mining machine is greatly in?uenced by the traction rheological properties of the deep-sea sediments. The best simulative soil was prepared for substituting the deep-sea sediment based on the deep-sea sediment collected from the Paci?c C-C mining area. Traction rheological properties of the simulative soil were studied by a home-made test apparatus. In order to accurately describe the traction rheological properties and determine traction rheological parameters, the Newtonian dashpot in Maxwell body of Burgers model was replaced by a self-similarity spring-dashpot fractance and a new rheological constitutive model was deduced by fractional derivative theory. The results show the simulative soil has obvious non-attenuate rheological properties. The transient creep and stable creep rate increase with the traction, but they decrease with ground pressure. The fractional derivative Burgers model are better in describing non-attenuate rheological properties of the simulative soil than the classical Burgers model. For the new traction rheological constitutive equation of the simulative soil, the traction rheological parameters can be obtained by ?tting the tested traction creep data with the traction creep constitutive equation. The ground contact length of track and walking velocity of the mining machine predicted by the traction rheological constitutive equation can be used to take full advantages of the maximum traction provided by the soil and safely improve mining effciency.

关键词： simulative soil traction rheological properties constitutive model rheological parameters ground contact length of track walking velocity

Seismic safety assessment with non-Gaussian random processes for train-bridge coupled systems

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Earthquake engineering and engineering Vibration 2024年第1期23卷 241-260页

作者： Zhao Han Gao Lei Wei Biao Tan Jincheng Guo Peidong Jiang Lizhong Xiang Ping Key laboratory of geomechanics and Embankment engineering of Ministry of Education Hohai UniversityNanjing 210024China School of Civil engineering Central South UniversityChangsha 410075China

Extensive high-speed railway(HSR)network resembled the intricate vascular system of the human body,crisscrossing *** events,known for their unpredictability,pose a significant threat to both trains and bridges,given the HSR’s extended operational ***,ensuring the running safety of train-bridge coupled(TBC)system,primarily composed of simply supported beam bridges,is *** methods like the Monte Carlo method fall short in analyzing this intricate system ***,efficient algorithm like the new point estimate method combined with moment expansion approximation(NPEM-MEA)is applied to study random responses of numerical simulation TBC *** of the NPEM-MEA’s feasibility is conducted using the Monte Carlo *** analysis confirms the accuracy and efficiency of the method,with a recommended truncation order of four to six for the ***,the influences of seismic magnitude and epicentral distance are discussed based on the random dynamic responses in the TBC *** methodology not only facilitates seismic safety assessments for TBC systems but also contributes to standard-setting for these systems under earthquake conditions.

关键词： train-bridge coupled(TBC)system random vibration new point estimate method(NPEM) seismic safety assessment moment expansion approximation(MEA) non-Gaussian distributions

Deformation control of asymmetric floor heave in a deep rock roadway:A case study

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International Journal of Mining Science and Technology 2014年第6期24卷 799-804页

作者： Sun Xiaoming Wang Dong Feng Jili Zhang Chun Chen Yanwei State Key laboratory of geomechanics and Deep Underground engineering School of Mechanics and Civil engineering China University of Mining & Technology

In order to control asymmetric floor heave in deep rock roadways and deformation around the surrounding rock mass after excavation, in this paper we discuss the failure mechanism and coupling control countermeasures using the finite difference method （FLAC^3D） combined with comparative analysis and typical engineering application at Xingcun coal mine, It is indicated by the analysis that the simple symmetric support systems used in the past led to destruction of the deep rock roadway from the key zone and resulted in the deformation of asymmetric floor heave in the roadway. Suitable rein- forced support countermeasures are proposed to reduce the deformation of the floor heave and the potential risk during mining. The application shows that the present support technology can he used to better environmental conditions. The countermeasures of asymmetric coupling support can not only effectively reduce the discrepancy deformation at the key area of the surrounding rock mass, hut also effectively control floor heave, which helps realize the integration of support and maintain the stability of the deep rock roadways at Xingcun coal mine.

关键词： Deep rock roadway Asymmetric floor heave Numerical simulation Asymmetric reinforced support

Seismic behavior of outrigger truss-wall shear connections using multiple steel angles

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Earthquake engineering and engineering Vibration 2016年第2期15卷 197-208页

作者： Li Xian Wang Wei Lü Henglin Zhang Guangchang State Key laboratory for geomechanics & Deep Underground engineering China University of Mining and Technology Jiangsu Key laboratory of Environmental Impact and Structural Safety in Civil engineering School of Mechanics and Civil Engineering China University of Mining and Technology

An experimental investigation on the seismic behavior of a type of outrigger truss-reinforced concrete wall shear connection using multiple steel angles is presented. Six large-scale shear connection models, which involved a portion of reinforced concrete wall and a shear tab welded onto a steel endplate with three steel angles, were constructed and tested under combined actions of cyclic axial load and eccentric shear. The effects of embedment lengths of steel angles, wall boundary elements, types of anchor plates, and thicknesses of endplates were investigated. The test results indicate that properly detailed connections exhibit desirable seismic behavior and fail due to the ductile fracture of steel angles. Wall boundary elements provide beneficial confinement to the concrete surrounding steel angles and thus increase the strength and stiffness of connections. Connections using whole anchor plates are prone to suffer concrete pry-out failure while connections with thin endplates have a relatively low strength and fail due to large inelastic deformations of the endplates. The current design equations proposed by Chinese Standard 04G362 and Code GB50011 significantly underestimate the capacities of the connection models. A revised design method to account for the influence of previously mentioned test parameters was developed.

关键词： anchor truss suffer welded reinforced stiffness tensile desirable properly frames