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A comparative study for determining rock joint normal stiffness with destructive uniaxial compression and nondestructive ultrasonic wave testing

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第7期15卷 1700-1712页

作者： Zhenghu Zhang jianbo zhu Jianhui Deng School of Civil Engineering Dalian University of TechnologyDalian116024China Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong KongChina Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization College of Civil and Transportation EngineeringShenzhen UniversityShenzhen518060China State Key Laboratory of Hydraulics and Mountain River Engineering College of Water Resources and HydropowerSichuan UniversityChengdu610065China

Rock joints are one of the vital discontinuities in a natural rock mass.How to accurately and conveniently determine joint normal stiffness is therefore significant in rock mechanics.Here,first,seven existing methods for determining joint normal stiffness were introduced and reviewed,among which MethodⅠ(the indirect measurement method),MethodⅡ(the direct determination method),MethodⅢ(the across-joint strain gauge measurement method)and MethodⅣ(the deformation measuring ring method)are via destructive uniaxial compression testing,while MethodⅤ(the best fitting method),MethodⅥ(the rapid evaluation method)and MethodⅦ(the effective modulus method)are through wave propagation principles and nondestructive ultrasonic testing.Subsequently,laboratory tests of intact and jointed sandstone specimens were conducted following the testing requirements and pro-cedures of those seven methods.A comparison among those methods was then performed.The results show that Method I,i.***.the benchmark method,is reliable and stable.MethodⅡhas a conceptual drawback,and its accuracy is acceptable at only very low stress levels.Relative errors in the results from MethodⅢare very large.With MethodⅣ,the testing results are sufficiently accurate despite the strict testing environment and complicated testing procedures.The results from MethodⅤare greatly unstable and significantly dependent on the natural frequency of the transducers.The joint normal stiffness determined with MethodⅥis stable and accurate,although data processing is complex.MethodⅦcould be adopted to determine the joint normal stiffness corresponding to the rock elastic deformation phase only.Consequently,it is suggested that MethodsⅠ,ⅣandⅥshould be adopted for the mea-surement of joint normal stiffness.The findings could be helpful in selecting an appropriate method to determine joint normal stiffness and,hence,to better solve discontinuous rock mass problems.

关键词： Normal stiffness Rock joint Uniaxial compression Ultrasonic wave

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Failure strength and fracture characteristics of rock with discontinuity under indirect tension

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第6期14卷 1810-1822页

作者： Dongya Han jianbo zhu Yat-Fai Leung School of Resources and Safety Engineering Central South UniversityChangshaChina Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong KongChina Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization Institute of Deep Earth Sciences and Green EnergyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhenChina

Large-scale discontinuities can significantly affect the mechanical properties of rock masses.However,the tensile behavior of rock discontinuities is often less investigated.To study the statistical characteristics of failure strength and fracture characteristics of rock discontinuities,Brazilian disc tests were conducted on limestone specimens with a single natural discontinuity at different load-discontinuity angles(β).In this study,β=0°andβ=90°correspond to the discontinuity parallel and perpendicular to loading direction,respectively.The results show that Brazilian failure strength(BFS)can reasonably represent the tensile strength of rock with discontinuities,by comparing the BFS and tensile stress in the disc center at peak force.The two-parameter Weibull distribution can capture the statistical BFS characteristics of rock discontinuities parallel to loading direction(β=0°)and at different loaddiscontinuity angles(β≠0°).All specimens with discontinuity at different load-discontinuity angles show more plastic deformational behaviour than intact rock specimen.With increasingβ,the mean BFS of limestone with discontinuity increases before reaching a plateau atβ=45°.The single plane of weakness theory best explains the BFS of fractured limestone withβ.Only a specific segment of preexisting rock discontinuity could affect the fracture process.Whenβ=0°,interfacial cracks and alternative cracks formed.Whenβ≠0°,mixed failure mode with shear and tensile failure occurred,particularly whenβ=30°andβ=60°.The findings can contribute to better understanding the failure and fracture characteristics of rock with discontinuities,particularly the interaction of pre-existing discontinuities with stress-induced fracturing.

关键词： Brazilian failure strength(BFS) Weibull distribution Rock discontinuity Anisotropy

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A serologic investigation of epizootic hemorrhagic disease virus in China between 2014 and 2019

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Virologica Sinica 2022年第4期37卷 513-520页

作者： Yingliang Duan Zhenxing Yang Pei zhu Lei Xiao Zhanhong Li zhuoran Li Le Li jianbo zhu Yunnan Tropical and Subtropical Animal Virus Diseases Laboratory Yunnan Animal Science and Veterinary InstituteKunming650000China

Epizootic hemorrhagic disease virus(EHDV)is a member of the genus Orbivirus,family Sedoreoviridae.It was firstly recognized in 1955 to cause a highly fatal disease of wild white-tailed deer in America.So far,EHDV was detected and isolated in many wild or domestic ruminants,and widely distributed all over the world.Although the domestic cattle and sheep infected by EHDV were usually asymptomatic or subclinical,several outbreaks of epizootic hemorrhagic disease(EHD)in deer and cattle had been reported.Many EHDV strains were isolated and sequenced in last two decades in China,which promoted a general serologic investigation of EHDV in China.In this study,18,122 sera were collected from asymptomatic or subclinical domestic ruminants(cattle,cow,yaks,sheep,goats,and deer)in 116 regions belonging to 15 provinces in China.All the sera were tested by EHDV CELISA,and the results were obtained by big data analysis.EHDV infections were detected in the 14 of 15provinces,and only Tibet(average altitude≥4000 m)which was the highest province in China was free of EHDV.The numbers of seropositive collections in both bovine and goat/sheep were in an inverse proportion to the latitude.However,the seropositive rates in bovine were ranged from 0%to 100%,while the seropositive rates in goat/sheep were no more than 50%.The results suggested that bovine was obviously more susceptive for EHDV infection than goat and sheep,therefore might be a major reservoir of EHDV in China.The prevalence of EHDV was consistent with the distribution of Culicoides which were known as the sole insect vectors of EHDV.In particular,the seropositive rates of EHDV were very high in the southern provinces,which required the enhanced surveillance in the future.

关键词： Epizootic hemorrhagic disease virus(EHDV) Prevalence Ruminant China

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A novel fractal-statistical scaling model of rocks considering strain rate

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第11期15卷 2831-2841页

作者： Changtai Zhou Heping Xie Zhihe Wang Tao Zhou jianbo zhu Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization Institute of Deep Earth Sciences and Green EnergyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhen518060China Shenzhen Key Laboratory of Deep Underground Engineering Sciences and Green Energy Shenzhen UniversityShenzhen518060China

The scaling-dependent behaviors of rocks are significant to the stability and safe operation of the structures built in or on rock masses for practical engineering.Currently,many size effect models are employed to connect laboratory measurements at small scales and engineering applications at large scales.However,limited works consider the strain rate effect.In this study,an fractal-statistical scaling model incorporating strain rate is proposed based on a weakest-link approach,fractal theory and dynamic fracture mechanics.The proposed scaling model consists of 8 model parameters with physical meaning,i.***.rate-dependent parameter,intrinsic material parameter,dynamic strain rate,quasi-static strain rate,quasi-static fracture toughness,micro-crack size,micro-crack intensity and fractal dimension,enabling the proposed scaling model to model the scaling behaviors under different external conditions.Theoretical predictions are consistent with experimental data on red sandstone,proving the reliability and effectiveness of the proposed scaling model.Thus,the scaling behaviors of rocks under dynamic loading conditions can be captured by the proposed fractal-statistical scaling model.The sensitivity analysis indicates that the nominal strength difference becomes more obvious with a higher strain rate,larger fractal dimension,smaller micro-crack size or lower micro-crack intensity.Therefore,the proposed scaling model has the potential to capture the scaling behaviors considering the thermal effect,weathering effect,anisotropic characteristic etc.,as the proposed scaling model incorporated model parameters with physical meaning.The findings of this study are of fundamental importance to understand the scaling behaviors of rock under dynamic loading condition,and thus would facilitate the appropriate design of rock engineering.

关键词： Size effect Strain rate Uniaxial compressive strength(UCS) Dynamic fracture mechanics

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Experimental investigation on crack initiation and damage stresses of deep granite under triaxial compression using acoustic methods

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第11期15卷 3071-3078页

作者： Xiaoling Zhao Tao Zhou Tianqi Zhai Yang Ju jianbo zhu State Key Laboratory of Hydraulic Engineering Simulation and Safety School of Civil EngineeringTianjin UniversityTianjin300350China Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization Institute of Deep Earth Sciences and Green EnergyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhen518060China State Key Laboratory of Coal Resources and Safe Mining China University of Mining and TechnologyBeijing100083China

Crack initiation stress and crack damage stress are two critical indices for assessing the fracture strength of rock mass.However,understanding the stress characteristics of crack initiation and damage under triaxial compression remains still immature.To address this problem,by acoustic monitoring,i.***.ultrasonic wave transmission and acoustic emission(AE),the integrated triaxial compression experiments were carried out on granitic specimens.The crack initiation and damage stresses were determined by wave velocity,wave amplitude and AE methods,respectively.The discrepancy of stresses for crack initiation and damage identified by these methods were examined.Results showed that the confinement affected the peak stress and corresponding strain,and these two parameters increased with increasing confining pressure.The ultrasonic wave velocity and wave amplitude first increased and then remained relatively stable,and finally decreased with increasing axial compressive stress.The number of AE events stayed at a relatively low extent until axial stress approached the peak;after that,the AE accumulative counts skyrocketed to the maximum.It also shows that for a given confinement,the stresses for crack initiation and damage identified by the wave amplitude method were the smallest,followed those by AE method and wave velocity method.Moreover,the stresses for crack initiation and crack damage identified by these methods increased generally with confining pressures.However,the rate of increment of these two crack stresses decreased with increasing confining pressure.In addition,the slight decrease in these two crack stresses ratios was noticed with increasing confining pressure.The findings are helpful to understand the crack stresses of deep rocks,in terms of support of deep underground engineering.

关键词： Crack stress Ultrasonic wave Acoustic emission(AE) Triaxial compression

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Strength and failure characteristics of marble spheres subjected to paired point loads

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第9期15卷 2280-2290页

作者： Rui Zhao Ming Tao Wenzhuo Cao Kun Du jianbo zhu School of Resources and Safety Engineering Central South UniversityChangshaChina Department of Earth Science and Engineering Imperial College LondonLondonUK Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and Utilization College of Civil and Transportation EngineeringShenzhen UniversityShenzhenChina

Failure of irregular rock samples may provide implications in the rapid estimation of rock strength,which is imperative in rock engineering practice.In this work,analytical,experimental and numerical investigations were carried out to study the mechanical properties and failure characteristics of rock spheres under paired point loads.Analytical solutions indicted that with the increase in sample size(contact angle)and decrease in Poisson’s ratio,the uneven tensile stress in theta direction decreased.Then laboratory experiments were carried out to investigate the load characteristics and failure mode of spherical marble samples with different sizes subjected to a pair of diametral point loads.The discrete element method(DEM)was adopted to study the failure process of rock spheres.The effect of the sphere diameter on the point load contact angle was examined in terms of peak load,crushed zone distribution and energy dissipation.Experimental and numerical results showed that the samples primarily fail in tension,with crushed zones formed at both loading points.With increase in the sample size,the contact angle,crushed area and total work increase.As the specimen diameter increases from 30 mm to 50 mm,the peak load on the specimen increases from 3.6 kN to 8.8 kN,and the percentage of crushed zone(ratio of crushing zone to sample radius,d/r)increased from 0.191 to 0.262.The results of the study have implications for understanding the failure of irregular rock specimens under point loading conditions and their size effects.

关键词： Rock sphere Point load Contact angle Energy dissipation Failure analysis

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Multi-fluid Eulerian simulation of mixing of binary particles in a gas-solid fluidized bed with a cohesive particle-particle drag model

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Particuology 2020年第2期18卷 95-104页

作者： Liping Wei Guodong Jiang Haipeng Teng Jun Hu jianbo zhu School of Chemical Engineering Northwest UniversityChemical Engineering Research Center of the Ministry of Education for Advanced Use Technology of Shanbei Energyand Shaanxi Research Center of Engineering Technology for Clean Coal ConversionXi'an 710069ShaanxiChina

A particle-particle(p-p)drag model is extended to cohesive particle flow by introducing solid surface energy to characterize cohesive collision energy loss.The effects of the proportion of cohesive particles on the mixing of binary particles were numerically investigated with the use of a Eulerian multiphase flow model incorporating the p-p drag model.The bed expansion,mixing,and segregation of Geldart-A and C particles were simulated with varying superficial velocities and Geldart-C particle proportions,from which we found that the p-p drag model can reasonably predict bed expansion of binary particles.Two segregation types of jetsam-mixture-flotsam and mixture-flotsam processes were observed during the fluidization processes for the Geldart-A and C binary particle system.The mixing processes of the binary particle system can be divided into three scales:macro-scale mixing,meso-scale mixing,and micro-scale mixing.At a constant superficial velocity the optimal mixing was observed for a certain cohesive particle proportion.

关键词： Fluidization Cohesive particle Particle-particle drag model Mixing index Binary particles

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Achieving High Thermoelectric Performance in Rare-Earth Element-Free CaMg_(2)Bi_(2) with High Carrier Mobility and Ultralow Lattice Thermal Conductivity

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Research 2020年第1期2020卷 824-833页

作者： Muchun Guo Fengkai Guo jianbo zhu Li Yin Qian Zhang Wei Cai Jiehe Sui National Key Laboratory for Precision Hot Processing of Metals Harbin Institute of TechnologyHarbin 150001China Department of Materials Science and Engineering Harbin Institute of TechnologyShenzhenGuangdong 518055China

CaMg_(2)Bi_(2)-based compounds,a kind of the representative compounds of Zintl phases,have uniquely inherent layered structure and hence are considered to be potential thermoelectric materials.Generally,alloying is a traditional and effective way to reduce the lattice thermal conductivity through the mass and strain field fluctuation between host and guest atoms.The cation sites have very few contributions to the band structure around the fermi level;thus,cation substitution may have negligible influence on the electric transport properties.What is more,widespread application of thermoelectric materials not only desires high ZT value but also calls for low-cost and environmentally benign constituent elements.Here,Ba substitution on cation site achieves a sharp reduction in lattice thermal conductivity through enhanced point defects scattering without the obvious sacrifice of high carrier mobility,and thus improves thermoelectric properties.Then,by combining further enhanced phonon scattering caused by isoelectronic substitution of Zn on the Mg site,an extraordinarily low lattice thermal conductivity of 0.51Wm^(-1) K^(-1) at 873 K is achieved in(Ca_(0.75)Ba_(0.25))_(0.995)Na_(0.005)Mg_(1.95)Zn_(0.05)Bi_(1.98) alloy,approaching the amorphous limit.Such maintenance of high mobility and realization of ultralow lattice thermal conductivity synergistically result in broadly improvement of the quality factorβ.Finally,a maximum ZT of 1.25 at 873K and the corresponding ZTave up to 0.85 from 300 K to 873K have been obtained for the same composition,meanwhile possessing temperature independent compatibility factor.To our knowledge,the current ZTave exceeds all the reported values in AMg_(2)Bi_(2)-based compounds so far.Furthermore,the low-cost and environmentfriendly characteristic plus excellent thermoelectric performance also make the present Zintl phase CaMg_(2)Bi_(2) more competitive in practical application.

关键词： alloying substitution Rare

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Research progress and application of deep in-situ condition preserved coring and testing

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International Journal of Mining Science and Technology 2023年第11期33卷 1319-1337页

作者： Heping Xie Yunqi Hu Mingzhong Gao Ling Chen Ru Zhang Tao Liu Feng Gao Hongwei Zhou Xiaobo Peng Xiongjun Li jianbo zhu Cunbao Li Ruidong Peng Yanan Gao Cong Li Jianan Li Zhiqiang He State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering College of Water Resource and HydropowerSichuan UniversityChengdu 610065China State Key Laboratory of Intelligent Construction and Health Operation and Maintenance of Deep Earth Engineering Guangdong Provincial Key Laboratory of Deep Earth Sciences and Geothermal Energy Exploitation and UtilizationInstitute of Deep Earth Sciences and Green EnergyCollege of Civil and Transportation EngineeringShenzhen UniversityShenzhen 518060China School of Mechanical Engineering Sichuan UniversityChengdu 610065China Institute of New Energy and Low-Carbon Technology Sichuan UniversityChengdu 610065China Frontier Science Research Center for Fluidized Mining of Deep Underground Resources China University of Mining and TechnologyXuzhou 221116China State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology-BeijingBeijing 100083China

With the depletion of shallow resources,the exploration of deep earth resources has become a global strategy.The study of the different patterns in the physical mechanical properties of rocks at different occurrence depths is the basis for exploring deep into the earth,with the core and premise being the acquisition and testing of deep in-situ core specimens.Based on the original idea of deep in-situ condition preserved coring(ICP-Coring)and testing,combined with theoretical modeling,numerical analysis,test platform development,indoor testing and engineering application,the principles and technologies of deep ICP-Coring are developed.This principle and technology consists of five parts:in-situ pressurepreserved coring(IPP-Coring),in-situ substance-preserved coring(ISP-Coring),in-situ temperaturepreserved coring(ITP-Coring),in-situ light-preserved coring(ILP-Coring),and in-situ moisturepreserved coring(IMP-Coring).The theory and technology of temperature and pressure reconstruction at different occurrence depths and in different environments are proposed,and prototype trial production was completed by following the principle of displacement and tests based on the in-situ reconstructed environment.The notable advances are as follows:(1)Deep in-situ coring system:A pressure-preserved controller with an ultimate bearing capacity greater than 140 MPa,highperformance(temperature-resistant,pressure-resistant,and low thermally conductive)temperaturepreserved materials,an active temperature control system,and high-barrier quality-preserved membrane materials were developed;a deep ICP-Coring capacity calibration platform was independently developed,a deep in-situ coring technology system was developed,and the acquisition of deep in-situ cores was realized.(2)In-situ storage displacement system:Following the dual-circuit hydraulic design idea,a single-drive source push-pull composite grabbing mechanism was designed;the design of the overall structure for the deep in-situ displacement storage system and ultrahigh pressure ca

关键词： Deep mining Deep in-situ Coring Displacement Test

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Electronic Orbital Alignment and Hierarchical Phonon Scattering Enabling High Thermoelectric Performance p-Type Mg_(3)Sb_(2) Zintl Compounds

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Research 2022年第4期2022卷 107-118页

作者： Jinsuo Hu jianbo zhu Fengkai Guo Haixu Qin Yijie Liu Qian Zhang Zihang Liu Wei Cai Jiehe Sui State Key Laboratory of Advanced Welding and Joining Harbin Institute of TechnologyHarbin 150001China Department of Materials Science and Engineering Harbin Institute of TechnologyShenzhen 518055China

Environmentally friendly Mg_(3)Sb_(2)-based materials have drawn intensive attention owing to their promising thermoelectric performance.In this work,the electrical properties of p-type Mg_(3)Sb_(2) are dramatically optimized by the regulation of Mg deficiency.Then,we,for the first time,found that Zn substitution at the Mg2 site leads to the alignment of px,y and pz orbital,resulting in a high band degeneracy and the dramatically enhanced Seebeck coefficient,demonstrated by the DFT calculations and electronic properties measurement.Moreover,Zn alloying decreases Mg1(Zn)vacancies formation energy and in turn increases Mg(Zn)vacancies and optimizes the carrier concentration.Simultaneously,the Mg/Zn substitutions,Mg vacancies,and porosity structure suppress the phonon transport in a broader frequency range,leading to a low lattice thermal conductivity of~0.47 W m^(-1) K^(-1) at 773 K.Finally,a high ZT of~0.87 at 773 K was obtained for Mg_(1.95)Na_(0.01)Zn_(1)Sb_(2),exceeding most of the previously reported p-type Mg_(3)Sb_(2) compounds.Our results further demonstrate the promising prospects of p-type Mg_(3)Sb_(2)-based material in the field of mid-temperature heat recovery.

关键词： alloying Orbital exceeding

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