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Investigation of cracking mechanism of the first tunnel lining during double-arch tunnel co.struction

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Underground Space 2024年第1期14卷 1-17页

作者： Yi Sui Xiaohui Cheng Zuozhou Zhao Weibin Ma railway Engineering research institute China Academy of Railway Sciences Corporation LimitedBeijing 100081China School of Civil Engineering Tsinghua UniversityBeijing 100084China

To solve the engineering problem of the first tunnel lining cracking caused by the seco.d tunnel co.struction of double-arch highway tunnels,a research method co.bining distributed optical-fibre monitoring,inversion analysis and numerical simulation that can reflect lining cracking was *** fibres were laid on opposite sides of the steel arches inside the first tunnel *** optical-fibre monitoring was co.ducted co.tinuously during the seco.d tunnel *** on the fibre-optic strain profile,the lining cracking was deduced and warned in *** mechanical behaviour of the steel arch was investigated by the inversion analysis,which took into co.sideration the integrated impact of axial force and flexural moment.A two-dimensional(2D)load-structure method–based numerical model was established,co.sidering the influence of different load distributions in each co.struction *** total strain rotating crack co.stitutive model was applied to reflect the cracking behaviour of co.crete lining in the simulation,and the model was calibrated and verified in the *** analysis between the simulated strain distribution and the distributed optical-fibre monitoring results was carried *** deformation mode and crack distribution of the lining were *** cracking mechanism was ***,the seco.d tunnel co.struction led to the loading at the top of the middle partition wall and the release of rock pressure in the first *** these load changes,the seco.dary lining of the first tunnel cracked on the inner side of the top of the middle partition wall owing to tension,and co.pression-bending failure occurred near the right arch ***,the influence of the parameters on the lining force was analysed,and a co.struction optimisation scheme was proposed.

关键词： Double-arch tunnel Cracking mechanism Distributed optical-fibre sensing Inversion analysis Total strain rotating crack model Loadstructure method

Fabricating functionally graded Fe-Cr-co.permanent magnetic alloys via laser powder bed fusion

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Journal of Iron and Steel research International 2024年第3期31卷 729-737页

作者： Ya-zhou He Ya-qing Hou Peng Shen Hao Zhang Dong Zhou Hang Su Central Iron and Steel research institute co. Ltd.Beijing 100081China Material Digital R&D Center China Iron and Steel Research Institute Group Co.Ltd.Beijing 100081China

Laser powder bed fusion(LPBF)in-situ alloying technology offers the possibility to co.struct gradient materials with varied structures and *** graded Fe-Cr-co.permanent magnetic alloys were fabricated by LPBF and in-situ alloying mixed powders of Fe,Cr,and co.*** effects of different Fe,Cr and co.co.tents on the microstructure,magnetic properties and hardness of Fe-Cr-co.alloys prepared by LPBF were *** as-built Fe-Cr-co.alloys present a single body-centered-cubic phase and have a homogeneous distribution of *** mechanical properties and magnetic properties of the co.positionally graded sample show a gradient *** the increase in Cr co.tent,the Vickers hardness of the sample increases,and the saturation magnetization of the sample *** optimal magnetic properties in an isotropic state are given as co.rcivity HcB=21.65 kA/m,remanence Br=0.70 T and energy product(BH)_(max)=5.35 kJ/m^(3),which are co.parable to or higher than the reported magnetic properties in an isotropic state prepared by traditional powder *** in-situ alloying technology has the potential to further explore Fe-Cr-co.magnetic materials,such as those co.sisting of multiple or more co.stituent elements,and to maximize the co.positional flexibility of magnetic materials.

关键词： Fe-Cr-co.alloy Laser powder bed fusion In-situ alloying Functional material Magnetic property

Chemical oxygen demand oxidation via sustained-release persulfate balls: a rate-co.patibility study of flow velocity, releasing, and oxidation

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第9期25卷 749-762页

作者： Bate BATE Danting ZHANG Jianshe YE Min XIA Yixin YANG Shuai ZHANG institute of Geotechnical Engineering Zhejiang UniversityHangzhou 310058China Shanghai Envirunion Eco.technology co. Ltd.Shanghai 201106China china railway Eryuan Engineering Group East china Survey and Design co. LtdHangzhou 310043China The Architectural Design&research institute of Zhejiang University co Ltd.Hangzhou 310027China

Identification of chemical oxygen demand(co.)in municipal solid waste(MSW)landfill leachates is a challenging *** paper investigated the feasibility of using sodium persulfate(PS),a strong oxidant,as a permeable reactive barrier(PRB)filling ***,sustained-release persulfate balls were manufactured to adjust the release rate of persulfate,the oxidation *** addition,Fe(II)-loaded activated carbon(Fe-AC)was used to help with an even distribution of Fe(II)in the porous medium(PRB in this case).Then,the oxidation efficiency and kinetic rate of co. removal by the sustained-release balls were subjected to batch tests.A mass ratio of 1:1.4:0.24:0.7 for PS:cement:sand:water was the most efficient for co. removal(95%).The breakthrough curve for a 5 mm sustained-release ball revealed that the retardation factor was 1.27 and that the hydrodynamic dispersion co.fficient was 15.6 cm^(2)/*** co.responding half-life of co. oxidation was 0.43 d,which was co.parable with the half-life of PS release from sustained-release balls(0.56 d).The sustained-release persulfate balls were shown to be an eco.omical material with a simple recipe and production method when catalyzed by *** with cutting-edge methods,sustained-release balls used in PRBs offer significant advantages in terms of both effectiveness and eco.omy for the preparation of sustained-release and catalytic *** results verified the feasibility of using sustained-release persulfate balls as a PRB material for co. removal.

关键词： Chemical oxygen demand(co.) Sodium persulfate(PS) Sustained-release balls Permeable reactive barrier(PRB) Fe(II)-loaded activated carbon(Fe-AC)

Effect of Lightweight Aggregates Inco.poration on the Mechanical Properties and Shrinkage co.pensation of a Cement-Ground Granulated Blast Furnace Slag-Phosphogypsum Ternary System

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Fluid Dynamics & Materials Processing 2024年第8期20卷 1773-1784页

作者： Yu Wang Mengyang Ma Yong Long Qingxiang Zhao Zhifei Cheng State Key Laboratory of Bridge Intelligent and Green co.struction China Railway Major Bridge Engineering Group Co.Ltd.Wuhan430034China china railway Bridge Science research institute. Ltd.Wuhan430034China

Shrinkage-induced cracking is a co.mon issue in co.crete structures,where the formation of cracks not only affects the aesthetic appearance of co.crete but also potentially reduces its durability and *** this study,the effect of ceramsite sand addition on the properties of a ternary system of cement-ground granulated blast furnace slag(GGBFS)-phosphogypsum(PG)is *** particular,the fluidity,rheology,hydration heat,co.pressive strength,autogenous shrinkage,and drying shrinkage of the co.sidered mortar specimens are *** results indicate that an increase in PG co.tent leads to a decrease in fluidity,higher visco.ity,lower exothermic peak,and lower co.pressive ***,the shrinkage of the mortar specimens is effectively *** inco.poration of internal curing water from ceramsite sand improves fluidity,decreases both yield stress and visco.ity,enhances the degree of hydration,and induces mortar ***,the inferior mechanical properties of the ceramsite sand generally produce a decrease in the co.pressive strength.

关键词： Phosphogypsum ceramsite sand internal curing mechanical property shrinkage

Atomistic mechanism of high ionic co.ductivity in lithium ytterbium-based halide solid electrolytes:A first-principles study

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Journal of Rare Earths 2024年第1期42卷 155-162,I0006页

作者： Limin Wang Wei Xiao Lu Sun Rong Yang Jinqiu Yu Ligen Wang State Key Laboratory of Nonferrous Metals and Processes China GRINM Group Co.Ltd.Beijing100088China GRIMAT Engineering institute co. Ltd.Beijing101407China General research institute for Nonferrous Metals Beijing100088China china Automotive Battery research institute co. Ltd.Beijing101407China Rare Earth Functional Materials(Xiong'an)Innovation Center co. Ltd.Xiong'an071700China

As the next generation of co.mercial automotive power batteries begins replacing liquid lithium batteries,many look towards all-solid-state batteries to pioneer the ***-so lid-state batteries have attracted the attention of co.ntless researchers around the world because of their high safety and high energy *** recent times,halide solid-state electrolytes have beco.e a research hotspot within solid-state electrolytes because of their potentially superior *** this paper,in the framework of DFT,we investigated the atomic mechanisms of improving the ionic co.ductivity and stability of Li_(3)YbCl_(6).Our calculations show that both trigonal and orthorhombic Li_(3)YbCl_(6) exhibit wide electrochemical windows and metastable properties(100 meV/atom>Ehull>0 meV/atom).However,the orthorhombic Li_(3)YbCl_(6) can be stabilized at high temperatures by taking the vibrational entropy into acco.nt,which is supported by the experimental ***,it is expected that because of the Yb/Li synergistic interactions that,due to their strong mutual co.lomb repulsion,influence the Li^(+)transport behavior,the orthorhombic Li_(3)YbCl_(6) might have superior ionic co.ductivities with appropriate Li+migration paths determined by the Yb^(3+) ***,higher ionic co.ductivities can be obtained by regulating the random distribution of Li^(+) *** Li^(+)-deficiency can also largely increase the ionic co.ductivity by invoking *** study helps gain a deeper understanding of the laws that govern ionic co.ductivities and stabilities and provides a certain theoretical reference for the experimental development and design of halide solid-state electrolytes.

关键词： Halide solid-state electrolytes Phase stability Ionic co.ductivity First-principles calculations Rare earths

Technical innovation in the “Beishan No. 1” hard rock tunnel boring machine for high-gradient spiral tunnels

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Frontiers of Engineering Management 2024年第1期11卷 175-179页

作者： Ju WANG Mengxue QI Bin LONG Hongsu MA Beijing research institute of Uranium Geology Beijing 100029China china railway 18th Bureau Group Tunnel Engineering co. Ltd.Chongqing 400700China china railway co.struction Heavy Industry co. Ltd.Changsha 410100China

1 Project overview The“Beishan No.1”,the world’s first-ever hard rock Tunnel Boring Machine(TBM)tailored for high-gradient spiral tunnels,co.stitutes a pivotal element within the Beishan Underground research Laboratory(URL)initiative in *** URL,the first URL for geological disposal of high level radioactive waste(HLW)in china,is a national key co.struction project listed in the“13th Five-Year Plan”.In 2019,subsequent to receiving approval from the china Atomic Energy Authority,the Beijing research institute of Uranium Geology(BRIUG),serving as the project’s owner,initiated its *** underground facility,categorized as a“third generation”URL for HLW disposal,i.e.,area-specific URL,was located in Beishan,Jiuquan City,Gansu Province,china,following more than three decades of rigorous research on site selection.

关键词： tunnel boring machine extremely hard rock co.tinuous small-radius curves high gradient equipment technology innovation

Solidification behaviour and hot cracking susceptibility of a novel Ni-based superalloy

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Journal of Iron and Steel research International 2024年第4期31卷 956-966页

作者： Yue Chen Shao-min Lv Xing-fei Xie Xiao-can Wen Jng-long Qu Jin-hui Du High-Temperature Materials institute China Iron and Steel Research Institute Group Co.Ltd.Beijing 100081China Beijing GAONA Materials and Technology co. Ltd.Beijing 100081China Sichuan CISRI-GAONA Forging co. Ltd.Deyang 610000SichuanChina

A novel Ni-based superalloy GH4151,with a γ′ volume fraction of about 55%and a service temperature capability up to 8oo oC,was *** to the different co.ling co.ditions of various regions during the solidification of ingots,significant co.ling rate variations may lead to the occurrence of hot *** scanning laser microsco.e was utilised to investigate the solidification process and phase precipitation behaviour of the GH4151 under wide range co.ling *** characteristics of L→γ transformation were analysed,and the growth rates of at each stage were *** segregation behaviour was predicted using the Scheil equation,and the predicted results match well with the experimental *** sensitivity co.fficient for hot cracking was modified,and cracking sensitivity co.fficient values for the alloy under different co.ling rates were co.puted,revealing that the alloy is most susceptible to hot cracking at 10℃/min co.ling ***,co.trolling the co.ling rate can reduce the possibility of hot cracking in ingot.

关键词： Ni-based superalloy Solidification behaviour In-situ observation Clyne and Davies's criterion:Hot cracking susceptibility

Damage Evolution of Ballastless Track co.crete Exposed to Flexural Fatigue Loads:The Application of Ultrasonic Pulse Velocity,Impact-echo and Surface Electrical Resistance Method

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Journal of Wuhan University of Technology(Materials Science) 2024年第2期39卷 353-363页

作者：杨志强李化建 WEN Jiaxing DONG Haoliang HUANG Fali WANG Zhen YI Zhonglai railway Engineering research institute China Academy of Railway Science Corporation LimitedBeijing 100081China State Key Laboratory for Track System of High-Speed railway Beijing 100081China School of Civil Engineering Beijing Jiaotong UniversityBeijing 100044China

In order to clarify the fatigue damage evolution of co.crete exposed to flexural fatigue loads,ultrasonic pulse velocity(UPV),impact-echo technology and surface electrical resistance(SR) method were *** variable based on the change of velocity of ultrasonic pulse(Du) and impact elastic wave(Di)were defined acco.ding to the classical damage *** influences of stress level,loading frequency and co.crete strength on damage variable were *** experimental results show that Du and Di both present a three-stages trend for co.crete exposed to fatigue *** impact elastic wave is more sensitive to the microstructure damage in stage Ⅲ,the critical damage variable,i e,the damage variable before the final fracture of co.crete of Di is slightly higher than that of ***,the evolution of SR of co.crete exposed to fatigue loads were analyzed and the relationship between SR and Du,SR and Di of co.crete exposed to fatigue loads were *** is found that the SR of co.crete was decreased with the increasing fatigue cycles,indicating that surface electrical resistance method can also be applied to describe the damage of ballastless track co.crete exposed to fatigue loads.

关键词： ballastless track fatigue damage ultrasonic pulse velocity impact-echo surface electrical resistance

co.trollable co.densation of Aromatics and Its Mechanisms in Carbonization

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china Petroleum Processing & Petrochemical Technology 2024年第1期26卷 34-46页

作者： Fan Xi Wang Chunlu Luo Yang Ren Qiang Shen Haiping Long Jun Sinopec research institute of Petroleum Processing co. Ltd.Beijing 100083China

In order to obtain liquefied products with higher yields of aromatic molecules to produce mesophase pitch,a good understanding of the relevant reaction mechanisms is *** molecular dynamics simulations were used to study the thermal reactions of pyrene,1-methylpyrene,7,8,9,10-tetrahydrobenzopyrene,and mixtures of pyrene with 1-octene,cyclohexene,or *** reactant co.version rates,reaction rates,and product distributions were calculated and co.pared,and the mechanisms were analyzed and *** results demonstrated that methyl and naphthenic structures in aromatics might improve the co.version rates of reactants in hydrogen transfer processes,but their steric hindrances prohibited the generation of high *** naphthenic structures co.ld generate more free radicals and presented a more obvious inhibition effect on the co.densation of polymers co.pared with the methyl side *** was disco.ered that when different olefins were mixed with pyrene,1-octene primarily underwent pyrolysis reactions,whereas cyclohexene mainly underwent hydrogen transfer reactions with pyrene and styrene,mostly producing superco.jugated biradicals through co.densation reactions with *** the mixture systems,the olefins scattered aromatic molecules,hindering the formation of pyrene trimers and higher *** to the reactive molecular dynamics simulations,styrene may enhance the yield of dimer and enable the co.trolled polyco.densation of pyrene.

关键词： carbonization co.trollable co.densation aromatics mechanisms molecular simulation