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Mechanical properties and energy evolution of Beishan shallow-layer granite under different unloading paths

Journal of Mountain Science 2024年第5期21卷 1728-1744页

作者： WANG Chuanle LI Erbing ZHANG Dengke HAN Yang LU Hui HE Kang DU Guangyin School of Transportation Southeast UniversityNanjing 211189China College of Defense engineering Army Engineering University of PLANanjing 210007China Nanjing Urban construction Management Group Co. Ltd.Nanjing 210006China College of Field engineering Army Engineering University of PLANanjing 210007China

Rock has mechanical characteristics and a fracture damage mechanism that are closely related to its loading history and loading path. The mechanical properties, fracture damage features, acoustic emission(AE) characteristics, and strain energy evolution of the Beishan shallow-layer granite used in triaxial unloading tests were investigated in this study. Three groups of triaxial tests, namely, conventional triaxial compression test(Group Ⅰ), maintaining deviatoric stress synchronously unloading confining pressure test(Group Ⅱ), and loading axial pressure synchronously unloading confining pressure test(Group Ⅲ), were carried out for the cylindrical granite specimens. AE monitoring device was utilized in these tests to determine the degree to which the AE waves and AE events reflected the degree of rock damage. In addition, the crack stress thresholds of the specimens were determined by volumetric strain method and AE parameter method, and strain energy evolution of the rock was explored in different damage stages. The results show that the shallow-layer granite experiences brittle failure during the triaxial loading test and unloading test, and the rock has a greater damage degree during the unloading test. The crack stress thresholds of these samples vary greatly between tests, but the threshold ratios of all samples are similar in the same crack damage stage. The Mogi-Coulomb strength criterion can better describe the unloading failure strength of the rock. The evolution of the AE parameter characteristics and strain energy differs between the specimens used in different stress path tests. The dissipative strain energy is the largest in Group Ⅱ and the smallest in Group Ⅰ.

关键词： Beishan granite Unloading test Mechanical properties Damage mechanism Acoustic emission Strain energy

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A Simplified Method for the Stress Analysis of Underground Transfer Structures Crossing Multiple Subway Tunnels

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Computer Modeling in engineering & Sciences 2024年第6期139卷 2893-2915页

作者： Shen Yan Dajiang Geng Ning Dai Mingjian Long Zhicheng Bai College of Civil engineering Tongji UniversityShanghai200092China China construction 4th engineering Bureau 6th corp. Ltd.Shanghai201199China Department of Civil and Architecture engineering Hubei Polytechnic UniversityHuangshi435003China

According to the design specifications,the construction of extended piles involves traversing the tunnel’s upper region and extending to the underlying rock *** address this challenge,a subterranean transfer structure spanning multiple subway tunnels was *** on the function of piles in the transfer structure as springs with axial and bending stiffness,and taking into account the force balance and deformation coordination conditions of beams and plates within the transfer structure,we established a simplified mechanical model that incorporates soil stratification by combining it with the Winkler elastic foundation beam *** resolved established simplifiedmechanicalmodel employed finite difference technology and the Newton-Simpsonmethod,elucidating the mechanical mechanism of the transfer *** research findings suggest that the load carried by the upper structural columns can be transferred to the pile foundation beneath the beams through the transfer structure,subsequently reaching the deep soil layer and ensuring minimal impact on adjacent *** established simplified analysis method can be used for stress analysis of the transfer structure,concurrently considering soil stratification,pile foundation behavior,and plate *** pile length,pile section size,and beam section size within the transfer structure should account for the characteristics of the upper load,ensuring an even distribution of the beam bending moment.

关键词： Crossing tunnels transfer structure force mechanism simplify analysis layered soil mass

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Preparation and combustion properties of laminated sticks of B-CuO and B-Bi_(2)O_(3)

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Defence Technology（防务技术） 2024年第8期38卷 67-74页

作者： Haoyu Song Chenyang Li Fubing Gao Chongwei An Shijiao Li Xuan Zhan Jianchen He School of Environment and Safety engineering North University of ChinaTaiyuan 030051China Chongqing Military Agency of the army Chongqing 400060China

To explore the composite process of B-CuO and B-Bi_(2)O_(3) two-component laminated sticks,obtain the corresponding sticks with good printing effect,and explore the energy release *** this study,boron,copper oxide,and bismuth trioxide powders were dispersed in the dispersed phase (DMF) using F_(2602) as a binder,and the construction of two-component B-CuO,B-Bi_(2)O_(3),three-component microcomposite,and three-component macro-composite sticks were realized with the help of double nozzle direct ink writing (DIW) technique *** resulting sticks were ignited by a nichrome wire energized with a direct current,and a high-speed camera system was used to record the combustion behavior of the sticks,mark the flame position,and calculate the rate of *** results showed that the B-CuO stick burning rate (42.11 mm·s^(-1)) was much higher than that of B-Bi_(2)O_(3)(17.84 mm·s^(-1)).The formulation with the highest CuO content (ω_(CuO)=58.7%) in the microscale composite of the sticks also had the fastest burning rate of 60.59 mm·s^(-1),as the CuO content decreased (ω_(CuO)=43.5%,29.3%),its burning rate decreased to 34.78 mm·s^(-1),37.97 mm·s^(-1).The stick with the highest copper oxide content(ω_(CuO)=60%) also possessed the highest burning rate (48.84 mm·s^(-1)) in the macro-composite sticks,and the burning rates of the macro-composite sticks with component spacing of 0.1 mm,0.2 mm,and 0.5 mm were 43.34 mm·s^(-1),48.84 mm·s^(-1),and 40.76 mm·s^(-1).

关键词： Boron-based thermite Direct ink writing Linear burning rate Multi-component composite

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Experimental investigation of engineered geopolymer composite for structural strengthening against blast loads

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Defence Technology（防务技术） 2024年第2期32卷 496-509页

作者： Shan Liu Chunyuan Liu Yifei Hao Yi Zhang Li Chen Zhan Li Key Laboratory of Coast Civil Structure Safety of Ministry of Education Tianjin UniversityTianjin 300072China Tianjin Key Laboratory of Prefabricated Buildings and Intelligent construction Hebei University of TechnologyTianjin 300400China Institute of Defense engineering AMSPLABeijing 100850China engineering Research Center of Safety and Protection of Explosion&Impact of Ministry of Education Southeast UniversityNanjing 211189JiangsuChina State Key Laboratory of Disaster Prevention&Mitigation of Explosion&Impact Army Engineering University of the PLANanjing 210007JiangsuChina

The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil *** geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and ***,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are *** this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and *** experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of *** that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical *** tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact *** was found that EGC could effectively enhance the blast resistance of structural elements in different *** AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly *** plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.

关键词： Engineered geopolymer composites Fiber optimization Strengthening material Blast resistance Masonry wall Reinforced AAC panel Plain concrete slab

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Experimental and numerical study on protective effect of RC blast wall against air shock wave

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Defence Technology（防务技术） 2024年第1期31卷 567-579页

作者： Xin-zhe Nian Quan-min Xie Xin-li Kong Ying-kang Yao Kui Huang State Key Laboratory of Precision Blasting Jianghan UniversityWuhan430056China Hubei Key Laboratory of Blasting engineering Jianghan UniversityWuhan430056China Hubei(Wuhan)Institute of Explosion and Blasting Technology Jianghan UniversityWuhan430056China College of Defense engineering Army Engineering University of PLANanjing210007China Institute of Defense engineering AMSPLALuoyang471023China

Prototype experiments were carried out on the explosion-proof performance of the RC blast *** mass of TNT detonated in the experiments is 5 kg and 20 kg *** shock wave overpressure was tested in different *** above experiments were numerically simulated,and the simulated shock wave overpressure waveforms were compared with that tested and given by CONWEP *** results show that the numerically simulated waveform is slightly different from the test waveform,but similar to CONWEP *** dimensional analysis and numerical simulation under different working conditions,the equation for the attenuation rate of the diffraction overpressure behind the blast wall was *** to the corresponding standards,the degree of casualties and the damage degree of the brick concrete building at a certain distance behind the wall can be determined when parameters are *** above results can provide a reference for the design and construction of the reinforced concrete blast wall.

关键词： Blast wall Shock wave Diffraction Overpressure Protection

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双线盾构隧道开挖引起既有铁路路基沉降及盾构掘进参数研究:工程案例

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Journal of Central South University 2024年第1期31卷 272-287页

作者：刘翔张瑞房倩李倩倩姜谙男黎奎辰 College of Transportation engineering Dalian Maritime UniversityDalian 116026China Key Laboratory of Urban Underground engineering of Ministry of Education Beijing Jiaotong UniversityBeijing 100044China Beijing Urban Rapid Transit construction Administration corp. Beijing 100068China

为揭示盾构掘进参数对既有铁路路基沉降的影响规律,本文依托北京地铁16号线丰益桥南站至丰台站双线盾构隧道下穿既有铁路线路工程进行案例分析。将盾构掘进过程分为盾构穿越前、盾构穿越中和盾构穿越后三个阶段。实测数据表明,路基沉降... 详细信息

为揭示盾构掘进参数对既有铁路路基沉降的影响规律,本文依托北京地铁16号线丰益桥南站至丰台站双线盾构隧道下穿既有铁路线路工程进行案例分析。将盾构掘进过程分为盾构穿越前、盾构穿越中和盾构穿越后三个阶段。实测数据表明,路基沉降在盾构穿越前逐渐增大,在盾构穿越过程中急剧增大,在盾构穿越后趋于稳定。将盾构管片及时封闭成环,施作补偿注浆、二次注浆,有利于控制路基沉降。此外,盾构掘进参数对控制路基沉降具有至关重要的作用。研究结果表明:盾构掘进速度越快引起的路基沉降越大,继而引起较大的土仓压力,并伴随刀盘扭矩和盾构总推力的骤减;由于盾构过程中出土量易于控制,因此其对路基沉降影响不大;然而,如果同步注浆量控制不当,将导致既有路基向上隆起。本研究为盾构开挖下穿多条既有铁路线路引起的路基变形控制以及盾构掘进参数设置提供参考和指导。

关键词：路基沉降盾构掘进参数既有铁路盾构隧道

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Co-occurrence of per- and polyfluoroalkyl substances, heavy metals and polycyclic aromatic hydrocarbons and their composite impacts on microbial consortium in soil: A field study

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Pedosphere 2024年第4期34卷 736-748页

作者： Meng ZHANG Qing WANG Xin SONG Mukhtiar ALI Zhiwen TANG Xin LIU Zhuanxia ZHANG Shurong MA Jinhui BI Zhongyuan LI Key Laboratory of Saline-Alkali Vegetation Ecology Restoration Northeast Forestry UniversityHarbin 150040China Key Laboratory of Soil Environment and Pollution Remediation Institute of Soil ScienceChinese Academy of SciencesNanjing 210008China University of Chinese Academy of Sciences Beijing 100049China Center International Group Co. Ltd.Beijing 101160China China construction Eighth engineering Division corp. Ltd.Shanghai 200122China

This is the first study to report the co-occurrence of per-and polyfluoroalkyl substances(PFASs),heavy metals,and polycyclic aromatic hydrocarbons(PAHs)and their impacts on the native microbial consortium in soil due to the long-term *** PFASs,heavy metals,and PAHs were detected in soil samples collected at 2–6 m below the ground surface at different sampling locations in a steel-making *** total concentrations of PFASs varied from 6.55 to 19.79 ng g^(-1),with perfluorooctane sulfonate(PFOS),perfluorobutane sulfonate,and 6:2 chlorinated polyfluorinated ether sulfonate(alternative of PFOS)being the predominant *** concentrations of arsenic,cadmium,and lead were detected in the ranges of 4.40–1270.00,0.01–8.67,and 18.00–647.00 mg kg^(-1),respectively,and the concentration of total PAHs was detected in the range of 1.02–131.60 mg kg^(-1).The long-term exposure to mixed contaminants of PFASs,heavy metals,and PAHs led to lower richness and diversity of microbial communities in *** soil bacterial communities were mainly composed of Pseudomonas,norank_p_GAL15,Leptothrix,norank_o_Rokubacteriales,and *** between soil environmental factors and microbial communities indicated that cation exchange capacity and total phosphorus were two key factors in shaping the composition of native microbial ***,Arthrobacter,Leptothrix,and Sphingobium were found to be significantly positively correlated with PFAS concentrations,indicating that these genera could tolerate the stress exerted by PFASs,along with the stress imposed due to the presence of heavy metals or/and PAHs.

关键词： arsenic cation exchange capacity mixed contaminant native microbial community perfuorooctane sulfonate total phosphorus

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Designing Membrane Electrode Assembly for Electrochemical CO_(2)Reduction:a Review

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Transactions of Tianjin University 2024年第2期30卷 117-129页

作者： Xuerong Wang Shulin Zhao Tao Guo Luyao Yang Qianqian Zhao Yuping Wu Yuhui Chen State Key Laboratory of Materials-Oriented Chemical engineering and School of Energy Science and EngineeringNanjing Tech UniversityNanjing 211816China Jiangsu Academy of Environmental Industry and Technology corp Nanjing 210036China

Currently, the electrochemical CO_(2) reduction reaction (CO_(2) RR) can realize the resource conversion of CO_(2) , which is a promising approach to carbon resource use. Important advancements have been made in exploring the CO_(2) RR performance and mechanism because of the rational design of electrolyzer systems, such as H-cells, flow cells, and catalysts. Considering the future development direction of this technology and large-scale application needs, membrane electrode assembly (MEA) systems can improve energy use efficiency and achieve large-scale CO_(2) conversion, which is considered the most promising technology for industrial applications. This review will concentrate on the research progress and present situation of the MEA component structure. This paper begins with the composition and construction of a gas diff usion electrode. Then, the application of ion-exchange membranes in MEA is introduced. Furthermore, the eff ects of pH and the anion and cation of the anolyte on MEA performance are explored. Additionally, we present the anode reaction type in MEA. Finally, the challenges in this field are summarized, and upcoming trends are projected. This review should offer researchers a clearer picture of MEA systems and provide important, timely, and valuable insights into rational electrolyzer design to facilitate further development of CO_(2) electrochemical reduction.

关键词： CO_(2)reduction Electrocatalysis Membrane electrode assembly

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An improved LuGre model for calculating static steering torque of rubber tracked chassis

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Defence Technology（防务技术） 2022年第5期18卷 797-810页

作者： Kang Liang Qun-zhang Tu Xin-min Shen Zhong-hang Fang Xuan Yang Yong Zhang Hui-yu Xiang College of Field engineering Army Engineering University of PLANanjing210007China State Key Laboratory of Intelligent Manufacturing of Advanced construction Machinery Xuzhou Construction Machinery GroupXuzhou221004China

Tire and rubber track interchangeable chassis combines the advantages of tire and rubber track,which can greatly improve the maneuverability of military construction ***,there is almost no effective calculation model for the real-time static steering *** the relative sliding speed is greater than 0.01 m/s,the influence of friction heating can not be *** improved LuGre model is established to calculate the static real-time steering torque of tire and rubber track interchangeable ***,the friction heating model between rubber and ground is *** with the influence of temperature on the dynamic performance of rubber material,the influence of friction heating on the stiffness and friction coefficient of rubber track is analyzed,and the improved LuGre friction model is *** steering torque of tire and rubber track interchangeable chassis is affected by rubber material properties,steering speed,pavement type,and ambient *** with the original Lu Gre model,the improved LuGre model captures the change in friction torque during multiple in-situ turns due to frictional *** error with the experimental data is small,which verifies the effectiveness of the improved LuGre model.

关键词： Rubber track Static steering torque Friction model Chassis Maneuverability Vehicle

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Model test to investigate failure mechanism and loading characteristics of shallow-bias tunnels with small clear distance

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Journal of Central South University 2016年第12期23卷 3312-3321页

作者：雷明锋林大涌杨伟超施成华彭立敏黄娟 School of Civil engineering Central South University China construction Fifth engineering Division corp. Ltd.

Based on the similarity theory,a tunnel excavation simulation testing system under typical unsymmetrical loading conditions was *** this system,the failure mechanism of surrounding rock of shallow-bias tunnels with small clear distance was analyzed along with the load *** results show that:1) The failure process of surrounding rock of shallow-bias tunnels with small clear distance consists of structural and stratum deformation induced by tunnel excavation; Microfracture surfaces are formed in the tunnel surrounding rock and extend deep into the rock mass in a larger density; Tensile cracking occurs in shallow position on the deep-buried side,with shear slip in deep rock *** the meantime,rapid deformation and slip take place on the shallow-buried side until the surrounding rocks totally *** production and development of micro-fracture surfaces in the tunnel surrounding rock and tensile cracking in the shallow position on the deep-buried side represent the key stages of failure.2) The final failure mode is featured by an inverted conical fracture with tunnel arch as its top and the slope at tunnel entrance slope as its *** range of failure on the deep-buried side is significantly larger than that on the shallow-buried *** difference becomes more prominent with the increasing bias *** distinguishes it from the "linear fracture surface" model is that the model proposed has a larger fracture angle on the two ***,the bottom of the fracture is located at the springing line of tunnel arch.3) The total vertical load increases with bias *** with the existing methods,the unsymmetrical loading effect in measurement is more *** last,countermeasures are proposed according to the analysis results: during engineering process,1) The surrounding rock mass on the deep-buried side should be reinforced apart from the tunnel surrounding rock for shallow-buried tunnels with small clear distance;

关键词： shallow-bias tunnels with small spacing failure mechanism loading characteristics model test

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