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An alternative approach to improve the compatibility of PCE in cement paste blend with coal gangue powder

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Waste Disposal and Sustainable Energy 2024年第1期6卷 139-150页

作者： Zonglin Xie Yuxuan Li Dahui Sun Yi Tian Jinyuan Hu Qiang Yuan Zheng Chen School of Civil Engineering Central South UniversityChangshaChina china railway NO.9 Group co. LTDShenyangChina National Engineering Research Center for High-Speed railway construction Technology ChangshaChina Guangxi Key Laboratory of Disaster Prevention and Engineering Safety Guangxi UniversityNanningChina

coal gangue(CG)is an environmental waste that faces an urgent demand for disposal in china.The utilization of CG in construction materials has broad application prospects and gained increasing interest.However,the poor compatibility of polycarboxylate superplasticizer(PCE)with CG powder hinders its efficiency in a wide range of applications.Here,this paper attempts to improve the compatibility of PCE with CG powder in cement paste based on the regulation of aggregation and the adsorption behavior of PCE.Dynamic light scattering(DLS)and fluorescence spectroscopy tests were carried out to understand the improved mechanism.The results indicated that the addition of CG powder increases the ionic strengths of the cement liquid phase,which makes PCE tend to aggregate at a lower concentration compared with no CG powder introduction.Adding(CH_(3)coO)_(2)Cu is beneficial for enhancing the workability of cement paste by reducing PCE aggregation while maintaining the compressive strength of cement specimens.Therefore,(CH_(3)coO)_(2)Cu extra addition can be regarded as an effective and sustainable way to improve the workability of cement paste with CG powder.

关键词： coal gangue powder Polycarboxylate superplasticizer compatibility Aggregation

Review on frost resistance and anti-clogging of pervious concrete

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Journal of Traffic and Transportation Engineering(English Edition) 2024年第3期11卷 481-496页

作者： Zhuo Wang Zhichen Liu Feng Zeng Kun He Shuaicheng Guo china railway construction Group co. Ltd.Beijing 100040China State Key Laboratory of Bridge Safety and Resilience College of Civil EngineeringHunan UniversityChangsha 410082China

Pervious concrete is a special type of concrete that is of high porosity and contains no or a small amount of fine aggregate,and it is an important basic material for sponge city construction.The presence of a large number of connected pores inside pervious concrete leads to a marked difference in durability failure mechanism compared with that of ordinary concrete.In this study,the frost resistance and anti-clogging of pervious concrete were introduced in detail,and the methods to improve their performance were summarized systematically.The cracking pattern of pervious concrete is influenced by geometric characteristics and three-dimensional morphological features of pores,resulting in its crack generation,development,and geometry being significantly different from those of ordinary concrete,thus leading to different freeze-thaw cycle mechanisms.In addition,due to its different pore structure compared to ordinary concrete,three types of clogging mechanisms,affecting the long-term permeability of pervious concrete were elaborated systematically(i.e.,physical clogging,biological clogging,and chemical clogging).And the ways to improve the anti-clogging of pervious concrete are systematically presented from multiple perspectives.Finally,in order to broaden the engineering applications of pervious concrete,some research proposals are presented in this study.

关键词： Pervious concrete connected pore Frost resistance Clogging mechanism

Research on virtual coupling technology in rail transit train collision protection

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Transportation Safety and Environment 2024年第1期6卷 40-46页

作者： Gaosong Li Jinbai Zou Weijie Ma Meng Lan School of railway Transportation Shanghai Institute of TechnologyShanghai 201418China Shanghai Metro First Operation co. LtdShanghai 201418China

In the research on the new generation of intelligent rail transit system,the prevention of train collision accidents is still a focus.Virtual coupling technology controls the running speed and interval distance of two or more trains cooperatively through Trainto-Train(T2T)direct communication technology.The aim is to form a coordinated logical system and jointly complete the train control and dispatching.In this paper,a virtual coupling train formation control method based on the model predictive control(MPC)framework is proposed.From the establishment of the virtual coupling system,the construction of an MPC model and decoupling method,how to integrate virtual coupling technology into the rail transit train collision protection is studied.The safety and reliability of the system are calculated through fault tree and the method of constructing reliability function.The research shows that if virtual coupling technology is used for train collision protection,the overall safety and reliability of the train control system is improved.

关键词： virtual coupling model predictive control collision protection

Application of GNSS-PPP on Dynamic Deformation Monitoring of Offshore Platforms

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china Ocean Engineering 2024年第2期38卷 352-361页

作者： YU Li-na XIONG Kuan GAO Xi-feng LI Zhi FAN Li-long ZHANG Kai Institute of Ocean Energy and Intelligent construction Tianjin University of TechnologyTianjin 300384China china railway construction Bridge Engineering Bureau Group co.ltd Tianjin 300300China School of Civil Engineering Tianjin UniversityTianjin 300072China Department of Land Surveying and Geo-Informatics The Hong Kong Polytechnic UniversityHong KongChina State Key Laboratory of Precision Blasting Jianghan UniversityWuhan 430056China

The real-time dynamic deformation monitoring of offshore platforms under environmental excitation is crucial to their safe operation.Although Global Navigation Satellite System-Precise Point Positioning(GNSS-PPP)has been considered for this purpose,its monitoring accuracy is relatively low.Moreover,the influence of background noise on the dynamic monitoring accuracy of GNSS-PPP remains unclear.Hence,it is imperative to further validate the feasibility of GNSS-PPP for deformation monitoring of offshore platforms.To address these concerns,vibration table tests with different amplitudes and frequencies are conducted.The results demonstrate that GNSS-PPP can effectively monitor horizontal vibration displacement as low as±30 mm,which is consistent with GNSS-RTK.Furthermore,the spectral characteristic of background noise in GNSS-PPP is similar to that of GNSS-RTK(Real Time Kinematic).Building on this observation,an improved complete Ensemble Empirical Mode Decomposition with Adaptive Noise(CEEMDAN)has been proposed to de-noise the data and enhance the dynamic monitoring accuracy of GNSS-PPP.Field monitoring application research is also undertaken,successfully extracting and analyzing the dynamic deformation of an offshore platform structure under environmental excitation using GNSS-PPP monitoring in conjunction with improved CEEMDAN de-noising.By comparing the de-noised dynamic deformation trajectories of the offshore platform during different periods,it is observed that the platform exhibits reversible alternating vibration responses under environmental excitation,with more pronounced displacement deformation in the direction of load action.The research results confirm the feasibility and potential of GNSS-PPP for dynamic deformation monitoring of offshore platforms.

关键词： GNSS-PPP offshore platform dynamic deformation monitoring improved CEEMDAN de-noising

A method for support stiffness failure identification in a steel spring floating slab track of urban railway: a case study in china

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第3期25卷 206-222页

作者： Junyuan ZHENG Caiyou ZHAO Duojia SHI Ping WANG Jian WANG Bolong JIANG Xi SHENG Key Laboratoryof High-speed railway Engineering Ministry of EducationSouthwest Jiaotong UniversityChengdu 60031China School of Civil Engineering Southwest Jiaotong UniversityChengdu 610031China 01 DYNA(Qingdao)Test&Data co. Ltd.Qingdao 266000China Rail Transit Digital construction and Measurement Technology National Engineering Research Center China Railway Design CorporationTianjin300308China Institute of Urban Smart Transportation&Safety Maintenance Shenzhen UniversityShenzhen 518060China

The extensive use of steel spring floating slab tracks has effectively addressed the challenge of alleviating the environmental vibrations induced by urban rail transit systems.However,under the combined action of train dynamic loads and complex environmental factors,problems,such as the fracture of steel spring vibration isolators and suspension vibrations induced by the uneven settlement of the base,often occur.The failure of isolator support stiffness is often hidden in its early stages and is challenging to identify by conventional detection methods.At the same time,it will aggravate the wheel-rail interaction,accelerate the deterioration of track structure,and even affect the driving safety.This study first establishes a detailed coupled train-floating slab track-foundation analytical model.Then the influence of the vibration isolator support stiffness failure on the dynamic indices of the floating slab track system response is analyzed.A set of defect identification methods that can detect the number of failed steel springs,severity of damage,and their location is proposed.Finally,an intelligent monitoring system for support stiffness of floating slab track is built by combining the density-based spatial clustering of applications with noise algorithm and statistical data analysis and is applied to a rail line in southern china.During a three-year monitoring campaign,a suspension failure and a fracture of a steel spring were each successfully detected and detailed failure information was obtained.Field investigation results were consistent with the damage identification results.After repair,the track structure dynamic response returned to the average pre-damage level and further deterioration had been arrested.The proposed damage identification methods and monitoring system provide an approach for intelligent identification of track structure support stiffness failures.

关键词： Floating slab track Support stiffness Detailed analytical model Failure identification Monitoring system

Failure mechanism and infrared radiation characteristic of hard siltstone induced by stratification effect

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Journal of Mountain Science 2024年第3期21卷 1058-1074页

作者： CHENG Yun SONG Zhanping XU Zhiwei YANG Tengtian TIAN Xiaoxu School of Civil Engineering Yancheng Institute of TechnologyYancheng 224051China School of Civil Engineering Xi'an University of Architecture and TechnologyXi'an 710055China Shaanxi Key Laboratory of Geotechnical and Underground Space Engineering Xi'an 710055China china railway construction Bridge Engineering Bureau Group co. Ltd.Tianjin 300300China

The deformation in sedimentary rock induced by train loads has potential threat to the safe operation of tunnels. This study investigated the influence of stratification structure on the infrared radiation and temporal damage mechanism of hard siltstone. The uniaxial compression tests, coupled with acoustic emission(AE) and infrared radiation temperature(IRT) were conducted on siltstones with different stratification effects. The results revealed that the stratigraphic structure significantly affects the stress-strain response and strength degradation characteristics. The mechanical parameters exhibit anisotropy characteristics, and the stratification effect exhibits a negative correlation with the cracking stress and peak stress. The failure modes caused by the stratification effect show remarkable anisotropic features, including splitting failure(Ⅰ: 0°-22.50°, Ⅱ: 90°), composite failure(45°), and shearing failure(67.50°). The AE temporal sequences demonstrate a stepwise response characteristic to the loading stress level. The AE intensity indicates that the stress sensitivity of shearing failure and composite failure is generally greater than that of splitting failure. The IRT field has spatiotemporal migration and progressive dissimilation with stress loading and its dissimilation degree increases under higher stress levels. The stronger the stratification effect, the greater the dissimilation degree of the IRT field. The abnormal characteristic points of average infrared radiation temperature(AIRT) variance at local stress drop and peak stress can be used as early and late precursors to identify fracture instability. Theoretical analysis shows that the competitive relationship between compaction strengthening and fracturing damage intensifies the dissimilation of the infrared thermal field for an increasing stress level. The present study provides a theoretical reference for disaster warnings in hard sedimentary rock mass.

关键词： Hard siltstone Failure mechanism Stratification effect Infrared radiation characteristic Temporal-damage mechanism Dissimilation

Engineering classification recycling of spent lithium-ion batteries through pretreatment:a comprehensive review from laboratory to scale-up application

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Rare Metals 2024年第3期43卷 915-941页

作者： Shu-Xuan Yan You-Zhou Jiang Xiang-Ping Chen Lu Yuan Ting-Ting Min Yu Cao Wan-Li Peng Tao Zhou Hunan Provincial Key Laboratory of Chemical Power Sources College of Chemistry and Chemical EngineeringCentral South UniversityChangsha 410083China college of Chemistry and Chemical Engineering Hunan Normal UniversityChangsha 410083China School of Public Policy and Management Tsinghua UniversityBeijing 100084China china Nonferrous Metal industry's Foreign Engineering and construction co. LtdBeijing 100029China

The lithium-ion batteries(LIBs)have been widely equipped in electric/hybrid electric vehicles(EVs/HEVs)and the portable electronics due to their excellent electrochemical performances.However,a large number of retired LIBs that consist of toxic substances(e.g.,heavy metals,electrolytes)and valuable metals(e.g.,Li,co)will inevitably flow into the waste stream,and their incineration or landfill treatment will cause severe risks to ecosystem and human beings.The sustainable and efficient treatment or recycling of valuable resources from spent LIBs should be fully recognized for environmental and resource security.As one of the most important processes for spent LIBs recycling,the pretreatment is an indispensable step,which is directly related to the subsequent metal extraction and separation processes.Although considerable progresses have been made regarding the pretreatment technologies,there are few summarized reports concerning critical processes of spent LIBs recycling,especially combination of currently available recycling technologies with industrialized applications during pretreatments.Therefore,comprehensive review of the current prevailing pretreatment technologies in laboratory to existing scale-up applications is quite necessary to reveal cutting-edge development in the field of pretreatment.In this review,the current pretreatment technologies are systematically categorized and introduced,along with critical discussions.This review focused on the various options for pretreatment processes itself,instead of general spent LIBs recycling technologies without the focused topics that have been sophisticatedly reviewed by previous studies.Here,the deactivation,discharge,dismantling,separation,liberation of active material and electrolyte treatment have been summarized with the in-depth discussion of the technology development and current status of each category.Finally,current states of industrial development are also reviewed and discussed for the development of efficient and environmentally friendly recyclin

关键词： Spent lithium-ion batteries(LIBs) Recycling Pretreatment Valuable metals Cutting-edge technologies Industrialized application

Prediction of vibration response based on BP artificial neural network for simply supported beam bridge structures

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Regression Method for Rail Fastener Tightness Based on Center-Line Projection

Shenyang Gongye Daxue Xuebao/Journal of Shenyang University of Technology 2024年第3期46卷 347-352页

作者： Zhao L. Department of Civil and construction Engineering National Taiwan University of Science and Technology Taipei 10607 Taiwan Third Engineering co. Ltd. China Railway 19th Bureau Group Liaoning Shenyang 110136 China

To address the problems of large workload, time-consuming calculation and inability to achieve rapid prediction of structural response in finite element models, a structural stress and displacement prediction model based on BP neural network algorithm for simply supported beam bridge was proposed. Taking a simply supported beam bridge as the engineering background, a three-dimensional finite element model of the beam system was established by using Midas/Civil finite element software. Taking into account parameter uncertainty, a comprehensive training and testing sample dataset was obtained by using the finite element model, and an artificial-neural-network-based bridge structure response prediction model was established. The research results show that the artificial neural network prediction model can achieve rapid prediction of structural response on the prerequisite of satisfying prediction accuracy. The maximum error between the measured value of load test and the predicted value by the model is within 12.46%, and the goodness of fit is above 0.9. This prediction model can be combined with the bridge health monitoring system in the later stage to achieve real-time analysis of the structural response of simply supported beam bridges, and can be applied to the structural response evaluation of simply supported beams. © 2024 Shenyang University of Technology. All rights reserved.

关键词： artificial neural network finite element model simply supported beam bridge stress structural evaluation structural response

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Chinese Journal of Mechanical Engineering 2024年第2期37卷 356-371页

作者： Yuanhang Wang Duxin Liu Sheng Guo Yifan Wu Jing Liu Wei Li Hongjie Wang Robotics Research Center School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China china construction Industrial&Energy Engineering Group co. Ltd.Nanjing 210023China

In the railway system,fasteners have the functions of damping,maintaining the track distance,and adjusting the track level.Therefore,routine maintenance and inspection of fasteners are important to ensure the safe operation of track lines.Currently,assessment methods for fastener tightness include manual observation,acoustic wave detection,and image detection.There are limitations such as low accuracy and efficiency,easy interference and misjudgment,and a lack of accurate,stable,and fast detection methods.Aiming at the small deformation characteristics and large elastic change of fasteners from full loosening to full tightening,this study proposes high-precision surface-structured light technology for fastener detection and fastener deformation feature extraction based on the center-line projection distance and a fastener tightness regression method based on neural networks.First,the method uses a 3D camera to obtain a fastener point cloud and then segments the elastic rod area based on the iterative closest point algorithm registration.Principal component analysis is used to calculate the normal vector of the segmented elastic rod surface and extract the point on the centerline of the elastic rod.The point is projected onto the upper surface of the bolt to calculate the projection distance.Subsequently,the mapping relationship between the projection distance sequence and fastener tightness is established,and the influence of each parameter on the fastener tightness prediction is analyzed.Finally,by setting up a fastener detection scene in the track experimental base,collecting data,and completing the algorithm verification,the results showed that the deviation between the fastener tightness regression value obtained after the algorithm processing and the actual measured value RMSE was 0.2196 mm,which significantly improved the effect compared with other tightness detection methods,and realized an effective fastener tightness regression.

关键词： railway system Fasteners Tightness inspection Neural network regression 3D point cloud processing