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Particle aggregation and breakage kinetics in cemented paste backfill

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International Journal of Minerals,Metallurgy and Materials 2024年第9期31卷 1965-1974页

作者： Liuhua Yang Hengwei Jia Aixiang Wu Huazhe Jiao Xinming Chen Yunpeng Kou Mengmeng Dong school of civil and engineering Henan Polytechnic UniversityJiaozuo 454000China school of civil and Environmental engineering University of Science and Technology BeijingBeijing 100083China

The macroscopic flow behavior and rheological properties of cemented paste backfill(CPB)are highly impacted by the inherent structure of the paste *** this study,the effects of shear-induced forces and proportioning parameters on the microstructure of fresh CPB were *** size evolution and distribution of floc/agglomerate/particles of paste were monitored by focused beam reflection measuring(FBRM)technique,and the influencing factors of aggregation and breakage kinetics of CPB were *** results indicate that influenced by both internal and external factors,the paste kinetics evolution covers the dynamic phase and the stable *** the mass content or the cement-tailings ratio can accelerate aggregation kinetics,which is advantageous for the rise of average floc ***,the admixture and high shear can improve breaking kinetics,which is beneficial to reduce the average floc *** chord length resembles a normal distribution somewhat,with a peak value of approximate 20μ*** particle disaggregation con-stant(k_(2))is positively correlated with the agitation rate,and k_(2) is five orders of magnitude greater than the particle aggregation constant(k1).The kinetics model depicts the evolution law of particles over time quantitatively and provides a theoretical foundation for the micromechanics of complicated rheological behavior of paste.

关键词： cemented paste backfill particle kinetics admixture rheology

Bond-Slip Behavior of Steel Bar and Recycled Steel Fibre-Reinforced Concrete

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Journal of Renewable Materials 2024年第1期12卷 167-186页

作者： Ismail Shah Jing Li Nauman Khan Hamad R.Almujibah Muhammad Mudassar Rehman Ali Raza Yun Peng school of Architecture and civil engineering Yunnan Agricultural UniversityKunming650000China Institute of Mountain Hazards and Environment Chinese Academy of SciencesChengdu610041China Yunnan International Joint R&D Center of Smart Agriculture and water Security Yunnan Agricultural UniversityKunming650201China school of water Conservancy Yunnan Agricultural UniversityKunming650201China school of civil engineering Guizhou UniversityGuiyang550025China Department of civil engineering College of EngineeringTaif UniversityP.O.Box 11099Taif City21974Saudi Arabia school of civil engineering Zhengzhou UniversityZhengzhou450001China

Recycled steel fiber reinforced concrete is an innovative construction material that offers exceptional mechanical properties and *** is considered a sustainable material due to its low carbon footprint and environmental friendly *** study examines the key influencing factors that affect the behavior of this material,such as the steel fiber volume ratio,recycled aggregate replacement rate,concrete strength grade,anchorage length,and stirrup *** study investigates the bond failure morphology,bond-slip,and bond strength constitutive relationship of steel fiber recycled *** results show that the addition of steel fibers at 0.5%,1.0%,and 1.5%volume ratios can improve the ultimate bond strength of pull-out specimens by 9.05%,6.94%,and 5.52%,*** replacement rate of recycled aggregate has minimal effect on the typical bond strength of pull-out ***,the ultimate bond strengths of pull-out specimens with concrete strength grades C45 and C60 have improved compared to those with C30 *** specimens with longer anchorage lengths exhibit lower ultimate bond strength,with a reduction of 33.19%and 46.37%for anchorage lengths of 5D and 7D,respectively,compared to those without *** restraint of 1φ8 and 2φ8 improves the ultimate bond strength by 5.29%and 6.90%,*** fibers have a significant effect on the behavior of concrete after it cracks,especially during the stable expansion stage,crack instability expansion stage,and failure stage.

关键词： Recycled coarse aggregates(RCA) steel fiber bonding performance bond-slip environmental challenges

Dynamic Response Impact of Vehicle Braking on Simply Supported Beam Bridges with Corrugated Steel Webs Based on Vehicle-Bridge Coupled Vibration Analysis

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Computer Modeling in engineering & Sciences 2024年第6期139卷 3467-3493页

作者： Yan Wang Siwen Li Na Wei school of civil engineering Zhengzhou UniversityZhengzhou450001China

A novel approach for analyzing coupled vibrations between vehicles and bridges is presented,taking into account spatiotemporal effects and mechanical phenomena resulting fromvehicle *** modeling and solution of bridge vibrations induced by vehicle deceleration are realized using this *** method’s validity and reliability are substantiated through numerical examples.A simply supported beam bridge with a corrugated steel web is taken as an example and the effects of parameters such as the initial vehicle speed,braking acceleration,braking location,and road surface roughness on the mid-span displacement and impact factor of the bridge are *** results show that vehicle braking significantly amplifies mid-span displacement and impact factor responses in comparison to uniform vehicular motion across the ***,the influence of wheelto-bridge friction forces is of particular significance and cannot be *** the vehicle initiates braking near the middle of the span,both the mid-span displacement and impact factor of the bridge exhibit substantial increases,further escalating with higher braking *** favorable road surface conditions,the midspan displacement and the impact factor during vehicle braking may exceed the design values stipulated by *** is important to note that road surface roughness exerts a more pronounced effect on the impact factor of the bridge in comparison to the effects of vehicle braking.

关键词： Corrugated steel web girder bridges simply supported beam bridges vehicle-bridge coupled vibration braking impact factor

Effect of Size Change on Mechanical Properties of Monolayer Arsenene

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Journal of Wuhan University of Technology(Materials Science) 2024年第1期39卷 206-212页

作者：郭娟刘贵立孙震宇 school of Architecture and civil engineering Shenyang University of TechnologyShenyang 110870China

The Young's modulus, shear modulus and Poisson's ratio of monolayer arsenene with different sizes were calculated by finite element method, so as to explore the influence of dimension and orientation on the mechanical properties of monolayer arsenene. The calculation results show that the small size has a significant effect on the mechanical properties of the monolayer arsenene. The smaller the size, the larger the Young's modulus and Poisson's ratio of the monolayer arsenene. The size change has a great influence on the Young's modulus of the arsenene handrail direction, and the Young's modulus of the zigzag direction is not sensitive to the size change. Similarly, the size change has a significant effect on the shear modulus of arsenene in the handrail direction, while the shear modulus in the zigzag direction has no significant effect on its size change. For the Poisson's ratio, the situation is just the opposite, and the effect of the size change on the Poisson's ratio of the arsenene zigzag direction is greater than that of the handrail direction.

关键词： finite element method arsenene size change mechanical properties

Multiscale modeling of gas-induced fracturing in anisotropic clayey rocks

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Journal of Rock Mechanics and Geotechnical engineering 2024年第6期16卷 2091-2110页

作者： Jianxiong Yang Jianfeng Liu Zhengyuan Qin Xuhai Tang Houquan Zhang State Key Laboratory of Hydraulics and Mountain River engineering College of Water Resource and HydropowerSichuan UniversityChengdu610042China school of resources and Safety engineering Wuhan Institute of TechnologyWuhan430073China school of civil engineering Wuhan UniversityWuhan430072China State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground engineering China University of Mining and TechnologyXuzhou221116China

In the context of repositories for nuclear waste,understanding the behavior of gas migration through clayey rocks with inherent anisotropy is crucial for assessing the safety of geological disposal *** primary mechanism for gas breakthrough is the opening of micro-fractures due to high gas *** occurs at gas pressures lower than the combined strength of the rock and its minimum principal stress under external loading *** investigate the mechanism of microscale mode-I ruptures,it is essential to incorporate a multiscale approach that includes subcritical microcracks in the modeling *** this contribution,we derive the model from microstructures that contain periodically distributed microcracks within a porous *** damage evolution law is coupled with the macroscopic poroelastic system by employing the asymptotic homogenization method and considering the inherent hydro-mechanical(HM)anisotropy at the *** resulting permeability change induced by fracture opening is implicitly integrated into the gas flow *** examples are presented to validate the developed model step by *** analysis of local macroscopic response is undertaken to underscore the influence of factors such as strain rate,initial damage,and applied stress,on the gas migration *** examples of direct tension tests are used to demonstrate the model’s efficacy in describing localized failure ***,the simulation results for preferential gas flow reveal the robustness of the two-scale model in explicitly depicting gas-induced fracturing in anisotropic clayey *** model successfully captures the common behaviors observed in laboratory experiments,such as a sudden drop in gas injection pressure,rapid build-up of downstream gas pressure,and steady-state gas flow following gas breakthrough.

关键词： Deep geological repositories Mode-I microcracks Time-dependent damage Fracturing process Anisotropic rock

Rainfall-triggered waste dump instability analysis based on surface 3D deformation in physical model test

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Journal of Mountain Science 2024年第5期21卷 1549-1563页

作者： LI Hanlin JIN Xiaoguang HE Jie XUE Yunchuan YANG Zhongping school of civil engineering Chongqing UniversityChongqing 400038China

Landslide is the second largest natural disaster after earthquake. It is of significance to study the evolution laws and failure mechanism of landslides based on its surface 3D deformation information. Based on the rainfall-triggered waste dump instability model test, we studied the failure mechanisms of the waste dump by integrating surface deformation and internal slope stress and proposed novel parameters for identifying landslide stability. We developed a noncontact measurement device, which can obtain millimeter-level 3D deformation data for surface scene in physical model test;Then we developed the similar materials and established a test model for a waste dump. Based on the failure characteristics of slope surface, internal stress of slope body and displacement contours during the whole process, we divided the slope instability process in model test into four stages: rainfall infiltration and surface erosion, shallow sliding, deep sliding, and overall instability. Based on the obtained surface deformation data, we calculated the volume change during slope instability process and compared it with the point displacement on slope surface. The results showed that the volume change can not only reflect the slow-ultra acceleration process of slope failure, but also fully reflect the above four stages and reduce the fluctuations caused by random factors. Finally, this paper proposed two stability identification parameters: the volume change rate above the slip surface and the relative velocity of volume change rate. According to the calculation of these two parameters in model test, they can be used for study the deformation and failure mechanism of slope stability.

关键词： Waste dump stability Physical model test Surface 3D deformation Stability identification

An extended numerical model of the first exothermic peak for three dimensional printed cement-based materials

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Frontiers of Structural and civil engineering 2024年第1期18卷 80-88页

作者： Wei JIANG Wenqian LI Xi CHEN school of Materials Science and engineering Tongji UniversityShanghai 200092China school of civil engineering Tongji UniversityShanghai 200092China

The first exothermic peak of cement-based material occurs a few minutes after mixing,and the properties of three dimensional(3D)printed concrete,such as setting time,are very sensitive to *** this background,based on the classical Park cement exothermic model of hydration,we propose and construct a numerical model of the first exothermic peak,taking into account the proportions of C_(3)S,C_(3)A and quicklime in *** calculated parameters are calibrated by means of relevant published exothermic test *** is found that this developed model offers a good simulation of the first exothermic peak of hydration for C_(3)S and C_(3)A proportions from 0 to 100% of cement clinker and reflects the effect of quicklime content at 8%-10%.The unique value of this research is provision of an important computational tool for applications that are sensitive to the first exothermic peak of hydration,such as 3D printing.

关键词： 3D printed cement-based materials cement hydration the first exothermic peak liquid quick-setting agent numerical model

Mechanistic insight into Cr(Ⅵ)retention by Si-containing ferrihydrite

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Journal of Environmental Sciences 2024年第5期139卷 217-225页

作者： Ying Hu Qiang Xue Honghan Chen Huaming Guo Kenneth C.Carroll Song Wang MOE Key Laboratory of Groundwater Circulation and Environmental Evolution School of Water Resources and EnvironmentChina University of Geosciences(Beijing)Beijing 100083China Beijing Key Laboratory of water resources and Environmental engineering School of Water Resources and EnvironmentChina University of GeosciencesBeijing 100083China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China Plant&Environmental Science New Mexico State UniversityNM 88003USA Institute of Theoretical Chemistry College of ChemistryJilin UniversityChangchun 130023China

Hexavalent chromium[Cr(Ⅵ)]causes serious harm to the environment due to its high toxicity,solubility,and ***(Fh)are the main adsorbent and trapping agent of Cr(Ⅵ)in soils and aquifers,and they usually coexist with silicate(Si),forming Si-containing ferrihydrite(Si-Fh)***,the mechanism of Cr(Ⅵ)retention by Si-Fh mixtures is poorly *** this study,the behaviors and mechanisms of Cr(Ⅵ)adsorption onto Si-Fh with different Si/Fe molar ratios was *** electron microscope,Fourier transform infrared spectroscopy,X-ray diffraction,X-ray photoelectron spectroscopy,and other techniques were used to characterize Si-Fh and Cr(Ⅵ)-loading of *** results show that specific surface area of Si-Fh increases gradually with increasing Si/Fe ratios,but Cr(Ⅵ)adsorption on Si-Fh decreases with increasing Si/Fe *** is because with an increase in Si/Fe molar ratio,the point of zero charge of Si-Fh gradually decreases and electrostatic repulsion between Si-Fh and Cr(Ⅵ)***,the complexation of Cr(Ⅵ)is enhanced due to the increase in adsorbed hydroxyl(A-OH-)on Si-Fh with increasing Si/Fe molar ratio,which partly counteracts the effect of the electrostatic ***,the increase in the electrostatic repulsion has a greater impact on adsorption than the additional complexation with *** functional theory calculation further supports this observation,showing the increases in electron variation of bonding atoms and reaction energies of inner spherical complexes with the increase in Si/Fe ratio.

关键词： Hexavalent chromium Ferrihydrite Si/Fe ratio Cr(Ⅵ)Adsorption

Effect of Low-Temperature Thermal Oxidation on the Capillary Performance of Sintered Copper Powder Wicks

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Journal of Thermal Science 2024年第1期33卷 29-40页

作者： ZHU Minghan FANG Runquan HU Yanxin ZHANG Jiangyun SHAO Dan HUANG Jin school of Material and Energy Guangdong University of TechnologyGuangzhou 510006China school of Electric Power engineering Guangdong Polytechnic of Water Resources and Electric EngineeringGuangzhou 510006China Research into Artifacts Guangdong Key Laboratory of Battery SafetyGuangzhou Institute of Energy testingGuangzhou 511447China

In this study,a composite powder capillary wick is prepared,manufactured by sintering copper powder and surface treated by low-temperature thermal *** is used to improve the performance of the capillary *** forced flow method and infrared imaging method are used to test the permeability and capillary performance of the *** effects of different oxidation temperatures on the performance of capillary wick are *** experimental results show that the wetting performance of the oxidized samples is significantly *** the increase of oxidation temperature,the permeability *** capillary height and velocity of the thermally oxidized samples are significantly higher than those of the untreated capillary ***,the oxidation temperature needs to be adjusted to obtain the best capillary *** highest capillary performance is found at oxidation temperature of 300℃,with an increase of 46% compared to the untreated *** with other composite wicks show that the sample with an oxidation temperature of 300℃ has competitive capillary performance,making it a favorable alternative to two-phase heat transfer *** study shows that combining low-temperature thermal oxidation technology with powder sintering is a convenient and effective method to improve the capillary performance of powder wicks.

关键词： low-temperature thermal oxidation capillary performance copper powder permeability