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Experimental study on unloading induced shear performances of 3D saw-tooth rock fractures

International Journal of Mining Science and Technology 2023年第4期33卷 463-479页

作者： Qian Yin Xinxin Nie Jiangyu Wu Qi Wang Kaiqi Bian hongwen jing State Key Laboratory for Geomechanics&Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China State Key Laboratory of High Performance Civil Engineering Materials Jiangsu Research Institute of Building Science Co.Ltd.Nanjing 210008China Department of Materials University of OxfordOxford OX13PHUK State Key Laboratory for Geomechanics&Deep Underground Engineering China University of Mining and Technology-BeijingBeijing 100083China

A fractal model governing saw-tooth fractures was first introduced to replicate sandstone samples containing an inclined 3D penetrating rough fracture surface with various joint roughness coefficients(JRC).In conventional triaxial compression,the peak strength for fractured samples increased with both confining pressure and JRC.During the unloading confining pressure process,the normal stress of fractures declined but the shear stress increased,resulting in shear sliding of fractures.The shear displacement of fractures exponentially increased,and the positive normal displacement decreased gradually to negative values under coupling effects of shear contraction caused by normal stress and shear dilation due to climbing effects of fractures.Transition from quasi-static to dynamic sliding of the fractures was identified.The sliding resistance duration increased with confining pressure but decreased with JRC.After prepeak unloading,the fracture surfaces presented a more significant surface wear response and JRC values decreased by 1.70%–59.20%due to more remarkable asperity degradation compared with those after conventional triaxial compression.The theoretical model for shear strength of fractures was established through improving the Ladanyi&Archambault model by introducing the relations between normal stress and surface wear ratios of fractures,which agreed well with the experimental results.

关键词： Saw-tooth fracture surfaces Pre-peak unloading Shear sliding Normal displacement JRC values

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Effect of the mineral spatial distribution heterogeneity on the tensile strength of granite:Insights from PFC3D-GBM numerical analysis

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第5期15卷 1144-1160页

作者： Tao Zhang Liyuan Yu Yuxuan Peng hongwen jing Haijian Su Jiangbo Wei State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China College of Geology and Environment Xi’an University of Science and TechnologyXi’an710054China

The mechanical characteristics of crystalline rocks are affected by the heterogeneity of the spatial distribution of minerals.In this paper,a novel three-dimensional(3D)grain-based model(GBM)based on particle flow code(PFC),i.e.PFC3D-GBM,is proposed.This model can accomplish the grouping of mineral grains at the 3D scale and then filling them.Then,the effect of the position distribution,geometric size,and volume composite of mineral grains on the cracking behaviour and macroscopic properties of granite are examined by conducting Brazilian splitting tests.The numerical results show that when an external load is applied to a sample,force chains will form around each contact,and the orientation distribution of the force chains is uniform,which is independent of the external load level.Furthermore,the number of high-strength force chains is proportional to the external load level,and the main orientation distribution is consistent with the external loading direction.The main orientation of the cracks is vertical to that of the high-strength force chains.The geometric size of the mineral grains controls the mechanical behaviours.As the average grain size increases,the number of transgranular contacts with higher bonding strength in the region connecting both loading points increases.The number of high-strength force chains increases,leading to an increase in the stress concentration value required for the macroscopic failure of the sample.Due to the highest bonding strength,the generation of transgranular cracks in quartz requires a higher concentrated stress value.With increasing volume composition of quartz,the number of transgranular cracks in quartz distributed in the region connecting both loading points increases,which requires many high-strength force chains.The load level rises,leading to an increase in the tensile strength of the numerical sample.

关键词： Rock mechanics Tensile strength Spatial distribution of minerals Three-dimensional(3D)grain-based model (GBM) Transgranular contact

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Estimates of strength and cracking behaviors of pre-flawed granite specimens treated by chemical corrosion under triaxial compression tests

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Frontiers of Earth Science 2022年第2期16卷 411-434页

作者： Zhicong LI Richeng LIU Shuchen LI hongwen jing Xiaozhao LI Liyuan YU State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China

Four types of granite specimens were prepared and treated by chemical corrosion for 5 and 30 days,which were then used to carry out triaxial compression tests under different confining pressuresσ_(3).Type A is the intact sample with no preexisting flaws.Types B and C are the samples containing two relatively low-dip flaws and two relatively high-dip flaws,respectively.Type D is the sample including both relatively low-dip and relatively high-dip flaws.The influences of pH value of chemical solutions,flaw distribution,corrosion time andσ_(3) on triaxial stress-strain curves and ultimate failure modes are analyzed and discussed.The results show that the pH value of the chemical solution,corrosion time and the arrangement of preexisting flaws play crucial roles in the cracking behaviors of granite specimens.Type A specimens have the largest peak axial deviatoric stress,followed by Type C,Type D,and Type B specimens,respectively.It is because the decrease in the inclination of preexisting flaws induces the weakening effect due to the decrease in the shadow area along the compaction direction.Under aσ_(3) of 5 MPa,the peak axial deviatoric stress drops by approximately 40.89%,29.08%,4.08%,and 23.53%for pH=2,4,7,and 12,respectively.For intact granite(Type A)specimens,the ultimate failure mode displays a typical shear mode.The connection of two secondary cracks initiated at the tips of preexisting cracks is always the ultimate failure and crack coalescence mode for Type B specimens.The ultimate failure and crack coalescence mode of Types C and D specimens are significantly affected by pH value of the chemical solution,corrosion time andσ_(3),which is different from those of Types A and B specimens due to the differences in flow distributions.

关键词： granites preexisting flaws chemical corrosion triaxial compression strength cracking behavior

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Molecular mechanism of fly ash affecting the performance of cemented backfill material

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International Journal of Minerals,Metallurgy and Materials 2023年第8期30卷 1560-1572页

作者： Shuo Yang Jiangyu Wu hongwen jing Xinguo Zhang Weiqiang Chen Yiming Wang Qian Yin Dan Ma State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou 221116China Shandong Key Laboratory of Mining Disaster Prevention and Control Shandong University of Science and TechnologyQingdao 266590China State Key Laboratory of High Performance Civil Engineering Materials Jiangsu Research Institute of Building Science Co.Ltd.Nanjing 210008China Department of Materials University of OxfordParks RdOxfordOX13PHUnited Kingdom Department of Mechanical Aerospace and Civil EngineeringSchool of EngineeringThe University of ManchesterManchester M139PLUnited Kingdom School of Mines China University of Mining and TechnologyXuzhou 221116China

The great challenge of cemented tailings backfill(CTB)is difficult simultaneously maintaining its excellent mechanical properties and low cost.Fly ash(FA)can potentially address this problem and further replace cement in favor of low carbon development.However,its mechanism on CTB with low cement dosage and low Ca system remains unclear.Consequently,this study conducted uniaxial compression,Xray diffraction(XRD),and scanning electron microscopy(SEM)-energy dispersive spectrometer(EDS)tests to investigate the effect of FA dosage on the mechanical property and microstructure of CTB.A molecular model of FA-CSH was constructed to reproduce the molecular structure evolution of CTB with FA based on the test results.The influences of FA dosage and calcium/silica molar ratio(Ca/Si ratio)on the matrix strength and failure model were analyzed to reveal the mechanism of FA on calcium silicate hydrated(C-S-H).The results show that the strength of CTB increases initially and then decreases with FA dosage,and the FA supplement leads to a decrease in Ca(OH)_(2) diffraction intensity and Ca/Si ratio around the FA particles.XRD and SEM-EDS findings show that the Ca/Si ratio of C-S-H decreases with the progression of hydration.The FA-CSH model indicates that FA can reinforce the silica chain of C-S-H to increase the matrix strength.However,this enhancement is weakened by supplementing excessive FA dosage.In addition,the hydrogen bonds among water molecules deteriorate,reducing the matrix strength.A low Ca/Si ratio results in an increase in water molecules and a decrease in the ionic bonds combined with Ca^(2+).The hydrogen bonds among water molecules cannot withstand high stresses,resulting in a reduction in strength.The water absorption of the FA-CSH model is negatively correlated with the FA dosage and Ca/Si ratio.The use of optimal FA dosage and Ca/Si ratio leads to suitable water absorption,which further affects the failure mode of FA-CSH.

关键词： fly ash cemented tailings backfill calcium/silica ratio microstructure molecular dynamics simulation

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Shear sliding of rough-walled fracture surfaces under unloading normal stress

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第10期15卷 2658-2675页

作者： Qian Yin Chun Zhu Jiangyu Wu Hai Pu Qi Wang Yuanchao Zhang hongwen jing Tianci Deng State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China School of Earth Sciences and Engineering Hohai UniversityNanjing210098China State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Chengdu University of TechnologyChengdu610059China State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology(Beijing)Beijing100083China College of Civil Engineering Fuzhou UniversityFuzhou350108China

Through high-precision engraving,self-affine sandstone joint surfaces with various joint roughness coefficients(JRC=3.21e12.16)were replicated and the shear sliding tests under unloading normal stress were conducted regarding various initial normal stresses(1e7 MPa)and numbers of shearing cycles(1 e5).The peak shear stress of fractures decreased with shear cycles due to progressively smooth surface morphologies,while increased with both JRC and initial normal stress and could be verified using the nonlinear Barton-Bandis failure criterion.The joint friction angle of fractures exponentially increased by 62.22%e64.87%with JRC while decreased by 22.1%e24.85%with shearing cycles.After unloading normal stress,the sliding initiation time of fractures increased with both JRC and initial normal stress due to more tortuous fracture morphologies and enhanced shearing resistance capacity.The surface resistance index(SRI)of fractures decreased by 4.35%e32.02%with increasing shearing cycles due to a more significant reduction of sliding initiation shear stress than that for sliding initiation normal stress,but increased by a factor of 0.41e1.64 with JRC.After sliding initiation,the shear displacement of fractures showed an increase in power function.By defining a sliding rate threshold of 5105 m/s,transition from“quasi-static”to“dynamic”sliding of fractures was identified,and the increase of sliding acceleration steepened with JRC while slowed down with shearing cycles.The normal displacement experienced a slight increase before shear sliding due to deformation recovery as the unloading stress was unloaded,and then enhanced shear dilation after sliding initiation due to climbing effects of surface asperities.Dilation was positively related to the shear sliding velocity of fractures.Wear characteristics of the fracture surfaces after shearing failure were evaluated using binary calculation,indicating an increasing shear area ratio by 45.24%e91.02%with normal stress.

关键词： Unloading normal stress Rough fracture surface Shear sliding Normal displacement Shear wear characteristics

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Deformation and failure characteristics of anchorage structure of surrounding rock in deep roadway

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International Journal of Mining Science and Technology 2020年第5期30卷 593-604页

作者： hongwen jing Jiangyu Wu Qian Yin Ke Wang State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhouJiangsu 221116China School of Mechanics and Civil Engineering China University of Mining and TechnologyXuzhouJiangsu 221116China

This paper investigated the stress evolution,displacement field,local deformation and its overall distribution,and failure characteristics of the anchorage structure of surrounding rock with different rockbolt spacing through the model experiments.The influences of the pre-tightening force and spacing of rockbolt on the support strength of the anchorage structure of surrounding rock were analyzed by the simulation using FLAC3D numerical software.The support scheme of the excavated roadway was then designed,and the effectiveness of this support scheme was further verified by the displacement measurement of the roadway.The results showed that the maximum displacement between the roof and floor of the west wing track roadway in Kouzidong coal mine,China is about 42 mm,and the maximum displacement between its both sides is about 72 mm,indicating that the support scheme proposed in this study can ensure the stability and safety of the excavated roadway.

关键词： Deep roadway Anchorage structure Deformation failure Stress evolution Loading capacity

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Strength and deformation behaviors of bedded rock mass under bolt reinforcement

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International Journal of Mining Science and Technology 2018年第4期28卷 591-597页

作者： Wenxin Zhu hongwen jing Lijun Yang Bing Pan Haijian Su State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology School of Traffic and Civil Engineering Shandong Jiaotong University

The mechanism of bolt support is an important topic in mining engineering and slope treatment. The artificial material and loading system were self-developed to study the influence of bedding cohesion and bolt number on the anchoring behavior of bedded rock mass. The results show that, both peak strength and elasticity modulus increase gradually with the increase of bedding cohesion and bolt number. The axial stress–strain curve of bedded rock mass under the reinforcement of bolts presents the features of strain-softening and secondary strengthening. Finally, anchoring behavior of bedded rock mass with different bolt numbers was simulated by using FLAC3 D numerical program and the results were compared with the experimental results. This study can provide certain bases to the stability control and support design of bedded rock mass in roadway.

关键词：岩石质量行为 FLAC3D 床上用品稳定性控制采矿工程装载系统弹性模量

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Numerical simulation of oxide nanoparticle growth characteristics under the gas detonation chemical reaction by space-time conservation element-solution element method

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Particuology 2017年第6期15卷 78-83页

作者： Ning LUO Hua Shen hongwen jing Zhangguo Ma Weiming Yang State Key Laboratory for Geo-mechanics and Deep Underground Engineering School of Mechanics and Civil Engineering China University of Mining and Technology Xuzhou 221116 China Laboratory for Precision and Nano Processing Technologies School of Mechanical and Manufacturing Engineering The University of New South Wales Sydney 2052 Australia Department of Mechanics and Engineering Science College of Engineering Peking University Beijing 100871 Chino

Under harsh conditions （such as high temperature, high pressure, and millisecond lifetime chemical reaction）, a long-standing challenge remains to accurately predict the growth characteristics of nanosize spherical particles and to determine the rapid chemical reaction flow field characteristics, The growth characteristics of similar spherical oxide nanoparticles are further studied by successfully introducing the space-time conservation element-solution element （CE/SE） algorithm with the monodisperse Kruis model. This approach overcomes the nanosize particle rapid growth limit set and successfully captures the characteristics of the rapid gaseous chemical reaction process. The results show that this approach quantitatively captures the characteristics of the rapid chemical reaction, nanosize particle growth and size distribution. To reveal the growth mechanism for numerous types of oxide nanoparticles, it is very important to choose a rational numerical method and particle physics model.

关键词： Oxide nanoparticles Growth characteristics Space-time conservation element-solutionelement method Kruis model Gas detonation

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Stability Control of Gob-Side Entry Retaining in Fully Mechanized Caving Face Based on a Compatible Deformation Model

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Computer Modeling in Engineering & Sciences 2020年第7期124卷 315-343页

作者： Xinshuai Shi hongwen jing Jianguo Ning Zhenlong Zhao Junfu Zhu State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and TechnologyXuzhou221116China College of Mining and Safety Engineering Shandong University of Science and TechnologyQingdao266510China.

The stability control of gob-side entry retaining in fully mechanized caving face is a typical challenge in many coal mines in China.The rotation and subsidence of the lateral cantilever play a critical role in a coal mine,possibly leading to instability in a coal seam wall or a gob-side wall due to its excessive rotation subsidence.Hence,the presplitting blasting measures in the roof was implemented to cut down the lower main roof and convert it to caved immediate roof strata,which can significantly reduce the rotation space for the lateral cantilever and effectively control its rotation.Firstly,the compatible deformation model was established to investigate the quantitative relationship between the deformation of the coal seam wall and the gob-side wall and the subsidence of the lateral cantilever.Then,the instability judgments for the coal seam wall and gob-side wall were revealed,and the determination method for the optimal roof cutting height were obtained.Furthermore,The Universal Distinct Element Code numerical simulation was adopted to investigate the effect of roof-cutting height on the stability of the retained entry.The numerical simulation results indicated that the deformation of the roadway could be effectively controlled when the roofcutting height reached to 18 m,which verified the theoretical deduction well.Finally,a field application was performed at the No.3307 haulage gateway in the Tangan coal mine,Ltd.,Shanxi Province,China.The field monitoring results showed that the blasting roof cutting method could effectively control the large deformation of surrounding rocks,which provided helpful references for coal mine safety production under similar conditions.

关键词： Gob-side entry retaining fully mechanized caving face lateral cantilever

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Strength and deformation behaviors of veined marble specimens after vacuum heat treatment under conventional triaxial compression

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Acta Mechanica Sinica 2017年第5期33卷 886-898页

作者： Haijian Su hongwen jing Qian Yin Liyuan Yu Yingchao Wang Xingjie Wu State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology

The mechanical behaviors of rocks affected by high temperature and stress are generally believed to be significant for the stability of certain projects involving rocks, such as nuclear waste storage and geothermal resource exploitation. In this paper, veined marble specimens were treated to high temperature treatment and then used in conventional triaxial compression tests to investigate the effect of temperature, confining pressure, and vein angle on strength and deformation behaviors. The results show that the strength and deformation parameters of the veined marble specimens changed with the temperature, presenting a critical temperature of 600 . The triaxial compression strength of a horizontal vein () is obviously larger than that of a vertical vein (). The triaxial compression strength, elasticity modulus, and secant modulus have an approximately linear relation to the confining pressure. Finally, Mohr-Coulomb and Hoek-Brown criteria were respectively used to analyze the effect of confining pressure on triaxial compression strength.

关键词： Veined marble Conventional triaxial compression High temperature Vein angle Hoek-Brown criterion

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