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Impact and explosion resistance of NPR anchor cable:Field test and numerical simulation

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Underground Space 2023年第3期10卷 76-90页

作者： Manchao He Aipeng Guo Zhigang Meng Yuefeng Pan Zhigang Tao State Key Laboratory for Geomechanics and Deep Underground engineering Beijing 100083China School of Mechanics and civil engineering China University of Mining and Technology(Beijing)Beijing 100083China department of civil and Mineral engineering University of TorontoToronto M5S 1A4Canada NingboTech University Ningbo 315100China The PLA Rocket Force engineering Design and Research Institute Beijing 100011China

With the reduction of shallow resources,the degree of damage and the frequency of dynamic hazards,such as deep rock bursts and impact ground pressure,are increasing ***,the existing support materials are incapable of meeting the safety require-ments of the refuges and roadways under a strong impact *** effectively solve these problems,a novel negative Poisson’s ratio(NPR)anchor cable with excellent properties,such as impact resistance and the ability to withstand large deformation,is *** the present study,a series of field tests and numerical simulations are conducted to investigate the mechanical and support charac-teristics of NPR anchor cables under blast *** mechanical tests show that NPR anchor cables can maintain constant resistance and produce large deformation under the action of multiple drop hammer *** to the results of field tests,the roadway supported by conventional anchor cables was unable to endure the blast impact,while the roadway supported by NPR anchor cables was able to withstand the severe impact equivalent to a Class 3 mine *** dynamic response of the NPR anchor cable that supports the roadway under explosion is investigated using the innovative coupled modeling approach that combines the finite element method and the discrete element method,and the support effect of the NPR anchor cable is *** study shows that the NPR anchor cable has a superior impact and blast resistance performance,and a broad application prospect in the support of chambers and roadways that are at high risk of rock bursts and impact ground pressure.

关键词： Negative Poisson’s ratio(NPR)anchor cable Rock burst Tunnel support Field test Numerical simulation

Investigation of stability of a tunnel in a deep coal mine in China

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International Journal of Mining Science and Technology 2013年第4期23卷 567-577页

作者： Kulatilake P.H.S.W. Wu Qiong Yu Zhengxing Jiang Fuxing Geological engineering Program Department of Materials Science & Engineering University of Arizona Faculty of engineering China University of Geosciences China Academy of Safety Science and Technology School of civil and Environmental engineering University of Science and Technology Beijing

Stability level of tunnels that exist in an underground mine has a great influence on the safety,production and economic performance of *** of stability for soft-rock tunnels is an important task for deep coal mines located in high in situ stress *** the available information on stratigraphy,geological structures,in situ stress measurements and geo-mechanical properties of intact rock and discontinuity interfaces,a three-dimensional numerical model was built by using 3DEC software to simulate the stress conditions around a tunnel located under high in situ stress conditions in a coal rock mass in *** were conducted for several tunnel shapes and rock support *** obtained for the distribution of failure zones,and stress and displacement felds around the tunnel were compared to select the best tunnel shape and support pattern to achieve the optimum stability conditions.

关键词： Coal mine Tunnel stability High in situ stress Numerical modeling 3DEC

Mechanical Properties and ITZ Microstructure of Recycled Aggregate Concrete Using Carbonated Recycled Coarse Aggregate

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Journal of Wuhan University of Technology(Materials Science) 2018年第3期33卷 648-653页

作者：伍君勇张云升 ZHU Pinghua FENG Jincai 胡坤 Jiangsu Key Laboratory of Construction Materials School of Material Science and Engineering Southeast University department of civil engineering Changzhou University Laboratory of Construction Materials Swiss Federal Institute of Technology (EPFL)

The effect of carbonation treatment and mixing method on the mechanical properties and interfacial transition zone（ITZ） properties of recycled aggregate concrete（RAC） was investigated. Properties of recycled concrete aggregate（RCA） were tested firstly. Then, five types of concretes were made and slump of fresh concrete was measured immediately after mixing. Compressive strength and splitting tensile strength of hardened concrete were measured at 28 d. Meanwhile, the microstructure of RAC was analyzed by backscattered electron（BSE） image. It was found that the water absorption ratio of carbonated recycled concrete aggregate（CRCA） was much lower when compared to the untreated RCA. Comparatively, the apparent density of CRCA was not significantly modified. The concrete strength results indicate that the mix CRAC-2 prepared with CRCA by adopting two-stage mixing approach shows the highest compressive strength value compared to the other mixes. The microstructural analysis demonstrate that the mix CRAC-2 has a much denser old ITZ than the untreated RAC because of the chemical reaction between CO2 and the hydration products of RCA. This study confirms that the ITZ microstructure of RAC can be efficiently modified by carbonation treatment of RCA and encourages broadening the application of construction and demolition wastes.

关键词： recycled aggregate concrete compressive strength interfacial transition zone carbonation treatment two-stage mixing approach back scattered electron

Spatial memory enhances the evacuation efficiency of virtual pedestrians under poor visibility condition

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Chinese Physics B 2018年第3期27卷 560-567页

作者： Yi Ma Eric Wai Ming Lee Meng Shi Richard Kwok Kit Yuen Institute for Disaster Management and Reconstruction Sichuan University Chengdu 610207 China department of Architecture and civil engineering City University of Hong Kong Kowloon Hong Kong China

Spatial memory is a critical navigation support tool for disoriented evacuees during evacuation under adverse environ-mental conditions such as dark or smoky conditions. Owing to the complexity of memory, it is challenging to understand the effect of spatial memory on pedestrian evacuation quantitatively. In this study, we propose a simple method to quan- titatively represent the evacuee＇s spatial memory about the emergency exit, model the evacuation of pedestrians under the guidance of the spatial memory, and investigate the effect of the evacuee＇s spatial memory on the evacuation from theoretical and physical perspectives. The result shows that （i） a good memory can significantly assist the evacuation of pedestrians under poor visibility conditions, and the evacuation can always succeed when the degree of the memory exceeds a threshold （φ〉 0.5）; （ii） the effect of memory is superior to that of ＂follow-the-crowd＂ under the same environmental conditions; （iii） in the case of multiple exits, the difference in the degree of the memory between evacuees has a significant effect （the greater the difference, the faster the evacuation） for the evacuation under poor visibility conditions. Our study provides a new quantitative insight into the effect of spatial memory on crowd evacuation under poor visibility conditions.

关键词： crowd evacuation memory visibility social force model

Quantifying water quality and flow in multi-branched urban estuaries for a rainfall event with mass balance method

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Water Science and engineering 2020年第4期13卷 317-328页

作者： Joan Cecilia Casila Gubash Azhikodan Katsuhide Yokoyama College of engineering and Agro-Industrial Technology University of the Philippines Los BanosLos Banos 4031Philippines department of civil and Environmental engineering Tokyo Metropolitan UniversityTokyo 192-0397Japan

In this study,field observations were conducted after a heavy rainfall event in the Sumida and Shakujii rivers in Tokyo,*** flow dynamics and fluxes of salt,suspended sediment(SS),and dissolved oxygen(DO)were investigated with the mass balance *** fractions of fresh water and saltwater in seaward and landward flows were *** maximum salt flux in the Shakujii River was 53.8 kg/s during the flood tide,and those in the Sumida River were 680.3 kg/s at the upstream station and 703.7 kg/s at the downstream *** trends of SS and DO fluxes were similar in both *** the Shakujii River,the highest SS(3.1 kg/s)and DO(0.4 kg/s)fluxes appeared during the flood tide after *** the Sumida River,the maximum SS fluxes(6.1 and 6.3 kg/s at the upstream and downstream stations,respectively)and DO fluxes(1.15 and 1.21 kg/s at the upstream and downstream stations,respectively)appeared during the ebb *** mass balance method was used to estimate discharge,salinity,SS concentration,and DO concentration at a station with missing *** results show that the estimated salinity and SS concentration had a significant correlation with the on-site observations,with correlation coefficients(R)of 0.950 and 0.835,respectively,but not for DO concentration(R?0.638).The disparity between the computed and measured data may be explained by the differences in velocity,salinity,topography,sedimentation,and the presence of organic *** analysis based on the advective salt transport components found a lower salt flux per unit width in the Shakujii River(0.36 kg/(m·s))in comparison with that in the Sumida River(2.88 kg/(m·s)).This indicates a higher probability for salt retention in the Shakujii River.©2020 Hohai *** and hosting by Elsevier *** is an open access article under the CC BY-NC-ND license(http://***/licenses/by-nc-nd/4.0/).

关键词： Mass balance Water quality Flow Salt transport Sumida River Shakujii River Estuary

Case study of a driven pile foundation in diatomaceous ***:Pile installation,dynamic analysis,and pore pressure generation

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Journal of Rock Mechanics and Geotechnical engineering 2021年第2期13卷 446-456页

作者： Ehsan Yazdani Jiayao Wang T.Matthew Evans School of civil and Construction engineering Oregon State UniversityCorvallisOR97331USA

This paper presents the results from a case study highlighting the difficulties of pile driving in diatomaceous *** the companion(first)paper to this article,results of an extensive laboratory and in situ testing program were presented while the results from pile driving and further analysis of field observations were presented *** high pile rebound(HPR)was observed during driving of a closed-end pipe pile,with refusal occurring at a depth of less than 5 *** open-ended piles were thus *** and case pile wave analysis program(CAPWAP)data were collected during driving of both closed-and open-end *** data indicated that negative pore water pressures(PWPs)were generated while the closed-ended pile exhibited high *** from in situ tests indicated change in material stiffness and strong dilative tendencies near the depth of refusal.A hypothesis for observed behavior was proposed that considers the soil beneath the pile as a medium with an effectively infinite bulk modulus.

关键词： Diatomaceous soil Problematic soil Site characterization Laboratory testing

Multivariate adaptive regression splines and neural network models for prediction of pile drivability

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geoscience Frontiers 2016年第1期7卷 45-52页

作者： Wengang Zhang Anthony T.C.Goh School of civil and Environmental engineering Nanyang Technological UniversitySingapore 639798Singapore

Piles are long, slender structural elements used to transfer the loads from the superstructure through weak strata onto stiffer soils or rocks. For driven piles, the impact of the piling hammer induces compression and tension stresses in the piles. Hence, an important design consideration is to check that the strength of the pile is sufficient to resist the stresses caused by the impact of the pile hammer. Due to its complexity, pile drivability lacks a precise analytical solution with regard to the phenomena *** situations where measured data or numerical hypothetical results are available, neural networks stand out in mapping the nonlinear interactions and relationships between the system’s predictors and dependent responses. In addition, unlike most computational tools, no mathematical relationship assumption between the dependent and independent variables has to be made. Nevertheless, neural networks have been criticized for their long trial-and-error training process since the optimal configuration is not known a priori. This paper investigates the use of a fairly simple nonparametric regression algorithm known as multivariate adaptive regression splines（MARS）, as an alternative to neural networks, to approximate the relationship between the inputs and dependent response, and to mathematically interpret the relationship between the various parameters. In this paper, the Back propagation neural network（BPNN） and MARS models are developed for assessing pile drivability in relation to the prediction of the Maximum compressive stresses（MCS）, Maximum tensile stresses（MTS）, and Blow per foot（BPF）. A database of more than four thousand piles is utilized for model development and comparative performance between BPNN and MARS predictions.

关键词： Back propagation neural network Multivariate adaptive regression splines Pile drivability Computational efficiency Nonlinearity

Lithium Diffusion and Stress in a Polycrystalline Film Electrode

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Acta Mechanica Solida Sinica 2018年第3期31卷 290-309页

作者： YanFei Zhao Bo Lu Junqian Zhang department of civil engineering Shanghai University Materials Genome Institute Shanghai University and Shanghai Materials Genome Institute Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai Key Laboratory of Mechanics in Energy engineering Shanghai University department of Mechanics Shanghai University

In the present work, the two-dimensional analytical solution for Li diffusion in grains and grain boundaries of a polycrystalline film electrode is established with consideration of Li-segregation at the grain boundary. The stress field induced by the inhomogeneity of Li con- centration, called chemical stress here for brevity, is analyzed via the finite element simulation. The effects of the grain boundary including its size, its diffusion coefficient as well as the segrega- tion phenomenon on the solute concentration and the chemical stress are examined. It shows that grain boundaries can assist fast diffusion and significantly affect the stress profile in the whole film. It proves that tailoring the grain boundary size or other grain boundary-related parameters may provide an alternative strategy for improving the overall diffusivity and mechanical stability of battery electrodes.

关键词： Polycrystalline film Two-dimensional diffusion Grain boundary Segregation Chemical stress

Empirical Evidence for the Look-Ahead Behavior of Pedestrians in Bi-directional Flows

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Chinese Physics Letters 2012年第6期29卷 299-302页

作者： GUO Ren-Yong WONG SC XIA Yin-Hua HUANG Hai-Jun LAM William H.K. CHOI Keechoo College of Computer Science Inner Mongolia UniversityHohhot 010021 department of civil engineering The University of Hong KongPokfulam RoadHong Kong department of Mathematics University of Science and Technology of ChinaHefei 230026 School of Economics and Management Beijing University of Aeronautics and AstronauticsBeijing 100191 department of civil and Structural engineering The Hong Kong Polytechnic UniversityHong Kong department of Transportation engineering Ajou UniversitySan 5 Woncheon-DongYeongtong-KuSuwon442-749 Korea

Using the sample data obtained from a group of pedestrian experiments,a function formulating the velocitydensity relationship of pedestrians and linear regression is proposed to provide empirical evidence for the lookahead behavior of pedestrians in bi-directional *** find that the velocity of pedestrians is negatively correlated with not only the densities of the opposite-direction and the identical-direction pedestrians around them but also the densities of the same-direction pedestrians ahead of ***,the movement of pedestrians is most affected by other pedestrians moving in the same direction about 1 m ahead.

关键词： directional identical ahead