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A stable implicit nodal integration-based particle finite element method(N-PFEM)for modelling saturated soil dynamics

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Journal of Rock Mechanics and Geotechnical engineering 2024年第6期16卷 2172-2183页

作者： Liang Wang Xue Zhang Jingjing Meng Qinghua Lei department of earth Sciences ETH ZürichZürich8092Switzerland department of civil engineering and Industrial Design University of LiverpoolLiverpoolL693BXUK department of civil Environmental and Natural Resources EngineeringLuleåUniversity of TechnologyLuleå97187Sweden department of earth Sciences Uppsala UniversityUppsala75105Sweden

In this study,we present a novel nodal integration-based particle finite element method(N-PFEM)designed for the dynamic analysis of saturated soils.Our approach incorporates the nodal integration technique into a generalised Hellinger-Reissner(HR)variational principle,creating an implicit PFEM formulation.To mitigate the volumetric locking issue in low-order elements,we employ a node-based strain smoothing technique.By discretising field variables at the centre of smoothing cells,we achieve nodal integration over cells,eliminating the need for sophisticated mapping operations after re-meshing in the PFEM.We express the discretised governing equations as a min-max optimisation problem,which is further reformulated as a standard second-order cone programming(SOCP)problem.Stresses,pore water pressure,and displacements are simultaneously determined using the advanced primal-dual interior point method.Consequently,our numerical model offers improved accuracy for stresses and pore water pressure compared to the displacement-based PFEM formulation.Numerical experiments demonstrate that the N-PFEM efficiently captures both transient and long-term hydro-mechanical behaviour of saturated soils with high accuracy,obviating the need for stabilisation or regularisation techniques commonly employed in other nodal integration-based PFEM approaches.This work holds significant implications for the development of robust and accurate numerical tools for studying saturated soil dynamics.

关键词： Particle finite element method Nodal integration Dynamic saturated media Second-order cone programming(SOCP)

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Hydrodynamic Assessment of A New Nature-Based Armour Unit on Rubble Mound Breakwater for Coastal Protection

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China Ocean engineering 2024年第3期38卷 439-452页

作者： Ehsan SAFA Alireza MOJTAHEDI Abdolmajid MOHAMMADIAN Mohamad Ali Lotfollahi YAGHIN department of Water resources engineering Faculty of Civil EngineeringUniversity of TabrizTabriz ***Iran Faculty of civil engineering University of OttawaOttawa K1H 8M5Canada

This research proposes a novel nature-based design of a new concrete armour unit for the cover layer of a rubblemoundbreakwater. Armour units are versatile with respect to shape, orientation, surface condition details, and porosity.Therefore, a detailed analysis is required to investigate the exact state of their hydraulic interactions and structuralresponses. In this regard, the performance results of several traditional armour units, including the Antifer cube,Tetrapod, X-block and natural stone, are considered for the first step of this study. Then, the related observed resultsare compared with those obtained for a newly designed (artificial coral) armour unit. The research methodology utilizesthe common wave flume test procedure. Furthermore, several verified numerical models in OpenFOAM code areused to gain the extra required data. The proposed armour is configured to provide an effective shore protection as anenvironmental-friendly coastal structure. Thus it is designed with a main trunk including deep grooves to imitate thetypical geometry of a coral type configuration, so as to attain desirable performance. The observed results and ananalytic hierarchy process (AHP) concept are used to compare the hydraulic performance of the studied traditionaland newly proposed (artificial coral) armour units. The results indicate that the artificial coral armour unit demonstratesacceptable performance. The widely used traditional armour units might be replaced by newer designs for betterwave energy dissipation, and more importantly, for fewer adverse effects on the marine environment.

关键词： rubble mound breakwater hydraulic interaction armour unit analytic hierarchy process numerical model

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Insights into the changes in the surface properties of goethite with Ni in the lattice in the presence of salicylhydroxamic acid:Experimental and density functional theory studies

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International Journal of Minerals,Metallurgy and Materials 2024年第4期31卷 665-677页

作者： Levie Mweene Gilsang Hong Hee-Eun Jeong Hee-won Kang Hyunjung Kim department of earth resources and Environmental engineering Hanyang University222 Wangsimni-roSeongdong-guSeoul 04763Republic of Korea

Comparative experiments and theoretical analysis of the surface chemistry changes of goethite(GT)and goethite containing Ni(GTN)in the lattice in the presence of salicylhydroxamic acid(SA)were performed.It was revealed that in the presence of 100 g·t^(-1)of SA,the flotation recovery of GTN and GT increased with increasing pH,achieving a maximum recovery of 98.9%for both minerals at p H 8.3 and decreasing beyond that pH,with GTN having a slightly higher recovery than GT,except at pH 8.3.This was further confirmed by the higher complexation energies of GTN···SA(-883.87 kJ·mol^(-1))compared with GT···SA(-604.23 kJ·mol^(-1))resulting from covalent,closed-shell,and conventional hydrogen bonding.The higher adsorption of SA onto GTN relative to GT was due to the formation of aπ-hole in GTN,thereby promoting a higher interaction of the collector with the mineral.Thus,the presence of Ni in the GT lattice improves and decreases the adsorption and desorption of SA onto and from the mineral,respectively,compared with those onto and from GT.

关键词： nickel goethite adsorption salicylhydroxamic acid recovery

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Tensile strength and failure behavior of rock-mortar interfaces: Direct and indirect measurements

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Journal of Rock Mechanics and Geotechnical engineering 2024年第1期16卷 41-55页

作者： Ghasem Shams Patrice Rivard Omid Moradian civil engineering and Building engineering department Universitéde SherbrookeSherbrookeQuébecCanada department of earth Sciences Swiss Federal Institute of Technology(ETH)ZurichSwitzerland department of civil and Environmental engineering Colorado School of MinesGoldenCOUSA

The tensile strength at the rock-concrete interface is one of the crucial factors controlling the failure mechanisms of structures,such as concrete gravity dams.Despite the critical importance of the failure mechanism and tensile strength of rock-concrete interfaces,understanding of these factors remains very limited.This study investigated the tensile strength and fracturing processes at rock-mortar interfaces subjected to direct and indirect tensile loadings.Digital image correlation(DIC)and acoustic emission(AE)techniques were used to monitor the failure mechanisms of specimens subjected to direct tension and indirect loading(Brazilian tests).The results indicated that the direct tensile strength of the rock-mortar specimens was lower than their indirect tensile strength,with a direct/indirect tensile strength ratio of 65%.DIC strain field data and moment tensor inversions(MTI)of AE events indicated that a significant number of shear microcracks occurred in the specimens subjected to the Brazilian test.The presence of these shear microcracks,which require more energy to break,resulted in a higher tensile strength during the Brazilian tests.In contrast,microcracks were predominantly tensile in specimens subjected to direct tension,leading to a lower tensile strength.Spatiotemporal monitoring of the cracking processes in the rock-mortar interfaces revealed that they show AE precursors before failure under the Brazilian test,whereas they show a minimal number of AE events before failure under direct tension.Due to different microcracking mechanisms,specimens tested under Brazilian tests showed lower roughness with flatter fracture surfaces than those tested under direct tension with jagged and rough fracture surfaces.The results of this study shed light on better understanding the micromechanics of damage in the rock-concrete interfaces for a safer design of engineering structures.

关键词： Rock-mortar Rock-concrete Moment tensor inversion(MTI) Acoustic emission(AE) Digital image correlation(DIC) Tensile strength Direct tensile test Brazilian test

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A performance-based hybrid deep learning model for predicting TBM advance rate using Attention-ResNet-LSTM

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Journal of Rock Mechanics and Geotechnical engineering 2024年第1期16卷 65-80页

作者： Sihao Yu Zixin Zhang Shuaifeng Wang Xin Huang Qinghua Lei department of Geotechnical engineering College of Civil EngineeringTongji UniversityShanghaiChina Key Laboratory of Geotechnical and Underground engineering Ministry of EducationTongji UniversityShanghaiChina department of earth Sciences ETH ZürichZürichSwitzerland department of earth Sciences Uppsala UniversityUppsalaSweden

The technology of tunnel boring machine(TBM)has been widely applied for underground construction worldwide;however,how to ensure the TBM tunneling process safe and efficient remains a major concern.Advance rate is a key parameter of TBM operation and reflects the TBM-ground interaction,for which a reliable prediction helps optimize the TBM performance.Here,we develop a hybrid neural network model,called Attention-ResNet-LSTM,for accurate prediction of the TBM advance rate.A database including geological properties and TBM operational parameters from the Yangtze River Natural Gas Pipeline Project is used to train and test this deep learning model.The evolutionary polynomial regression method is adopted to aid the selection of input parameters.The results of numerical exper-iments show that our Attention-ResNet-LSTM model outperforms other commonly-used intelligent models with a lower root mean square error and a lower mean absolute percentage error.Further,parametric analyses are conducted to explore the effects of the sequence length of historical data and the model architecture on the prediction accuracy.A correlation analysis between the input and output parameters is also implemented to provide guidance for adjusting relevant TBM operational parameters.The performance of our hybrid intelligent model is demonstrated in a case study of TBM tunneling through a complex ground with variable strata.Finally,data collected from the Baimang River Tunnel Project in Shenzhen of China are used to further test the generalization of our model.The results indicate that,compared to the conventional ResNet-LSTM model,our model has a better predictive capability for scenarios with unknown datasets due to its self-adaptive characteristic.

关键词： Tunnel boring machine(TBM) Advance rate Deep learning Attention-ResNet-LSTM Evolutionary polynomial regression

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Parametric investigation on the novel and cost-effective nano fly ash impregnated geopolymer system for sustainable construction

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Frontiers of Structural and civil engineering 2024年第2期18卷 170-183页

作者： R.MOHANA S.M.Leela BHARATHI department of civil engineering Mepco Schlenk Engineering CollegeSivakasi 626123India

The hazardous environmental effects of greenhouse gas emissions and climate change demand alternative sources for cementitious materials in the construction industry.The development of geopolymer structures provides a way of producing 100%cement-free construction.In this research work,a novel and simple way of deriving nano particles from waste fly ash particles is promoted.The effect of adding the synthesized nano fly ash particles as a filler medium in geopolymer mortars was investigated by considering strength and durability properties.Parameter optimization was done by using regression analysis on the geopolymer mortar and the impact of adding nano fly ash particles was studied by varying different percentages of addition ranging from 0 to 7.5%by weight of binder content.From the results,it was observed that 1%nano fly ash acted not only as a filler but also as nano-sized precursors of the polymerization process,resulting in denser geopolymer medium.This can explain the extraordinary gain in strength of 72.11 MPa as well as the denser core with negligible level of chloride ion penetration,making the material suitable for the development of structures susceptible to marine environment.

关键词： geopolymer nano fly ash chloride ion penetration durability polymerization fillers

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Recent process developments in beneficiation and metallurgy of rare earths:A review

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Journal of Rare earths 2024年第4期42卷 629-642页

作者： Shaokai Cheng Wenbo Li Yuexin Han Yongsheng Sun Peng Gao Xiaolong Zhang School of resources and civil engineering Northeastern UniversityShenyang110819China National-local Joint engineering Research Center of High-efficient Exploitation Technology for Refractory Iron Ore resources Shenyang110819China

Rare earth elements(REEs)are irreplaceable materials supporting low-carbon technology and equip-ment,and their commercial demand and strategic position are becoming increasingly prominent.With the continuous depletion of rare earth(RE)resources,developing high-efficiency beneficiation and eco-friendly metallurgical processes has attracted widespread attention.This paper reviews the major minerals exploited for RE production and their deposits,as well as the beneficiation and metallurgical processes of RE minerals.Bastnaesite,monazite,mixed RE ores,and ion-adsorption clays are the main raw materials in the world to date.RE-bearing ores(except ion-adsorption minerals)are generally beneficiated by flotation,gravity and magnetic separation techniques.The mainstream metallurgical processes for bastnaesite,monazite and mixed RE concentrates are oxidation roasting-HCl leaching,caustic soda decomposition and high-temperature concentrated sulfuric acid roasting,respectively.Ion-adsorption clays are directly processed by in situ leaching-precipitation/solvent extraction.To achieve the sustainable development of RE resources,it is essential to further explore innovative techniques to achievecomprehensive utilization and cleaner production.

关键词： Rare earths Beneficiation processes Metallurgical processes Cleaner production

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Mechanical performance of cold mix asphalt containing cup lump rubber as a sustainable bio-modifier

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Journal of Traffic and Transportation engineering(English Edition) 2024年第3期11卷 424-440页

作者： Syed Abdul Ghafar Muhammad Naqiuddin Mohd Warid Norhidayah Abdul Hassan Zulfiqar Ali Jattak Ashraf Abdalla Mohammed Radwan Faculty of civil engineering Universiti Teknologi MalaysiaSkudai 81310Malaysia department of civil engineering Balochistan University of Information TechnologyEngineering&Management SciencesQuettaPakistan department of civil engineering Balochistan University of Engineering and TechnologyKhuzdarPakistan department of civil engineering Faculty of EngineeringUniversity of TripoliTripoliLibya

The road construction industry aims to contribute to the protection of already compromised environment.Cold mix asphalt(CMA)is a measure initiated by the road industry to protect the environment and preserve energy.Despite having additional benefits,CMA has attracted little attention due to its inferior performance.CMA's performance is enhanced using a sustainable binder bio-modifier,natural cup lump rubber(CLR)is one of them.This study evaluated the tensile properties,rutting,moisture susceptibility,and adhesion properties of CLR-modified CMA(CMA-CR).The tensile property was enhanced by 26%due to CLR modification.CMA-CR had excellent rutting resistance of less than 2 mm rut depth at 10,000 load cycles,showing 70%improvement compared with conventional CMA.Moisture susceptibility evaluation indicated that CMA-CR had tensile strength ratio(TSR)value of 104%,satisfying the minimum 80%requirement of AASHTO T283.It also retained more than 96%bitumen coating.The moisture damage resistance was improved by 12%and 10%in terms of TSR and stripping,respectively.The durability results revealed that the CMA-CR mixture prevented higher mass loss,representing 14%improvement compared with conventional CMA.

关键词： Cup lump rubber Cup lump modified cold mix asphalt Moisture damage Tensile property Rutting Digital imaging

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Auto-parametric resonance of a continuous-beam-bridge model under two-point periodic excitation:an experimental investigation and stability analysis

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earthquake engineering and engineering Vibration 2024年第2期23卷 445-454页

作者： Li Yuchun Shen Chao Liu Wei Li Dong department of Hydraulic engineering College of Civil EngineeringTongji UniversityShanghai 200092China

The auto-parametric resonance of a continuous-beam bridge model subjected to a two-point periodic excitation is experimentally and numerically investigated in this study.An auto-parametric resonance experiment of the test model is conducted to observe and measure the auto-parametric resonance of a continuous beam under a two-point excitation on columns.The parametric vibration equation is established for the test model using the finite-element method.The auto-parametric resonance stability of the structure is analyzed by using Newmark's method and the energy-growth exponent method.The effects of the phase difference of the two-point excitation on the stability boundaries of auto-parametric resonance are studied for the test model.Compared with the experiment,the numerical instability predictions of auto-parametric resonance are consistent with the test phenomena,and the numerical stability boundaries of auto-parametric resonance agree with the experimental ones.For a continuous beam bridge,when the ratio of multipoint excitation frequency(applied to the columns)to natural frequency of the continuous girder is approximately equal to 2,the continuous beam may undergo a strong auto-parametric resonance.Combined with the present experiment and analysis,a hypothesis of Volgograd Bridge's serpentine vibration is discussed.

关键词： auto-parametric resonance continuous beam bridge model two-point excitation experimental investigation stability analysis vibration of Volgograd Bridge

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Biodegradability of bioplastics in different aquatic environments:A systematic review

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Journal of Environmental Sciences 2024年第8期142卷 169-181页

作者： Maria Cristina Lavagnolo Valentina Poli Anna Maria Zampini Valentina Grossule department of civil Environmental and Architectural Engineering-Laboratory of Environmental EngineeringUniversity of PadovaLungargine Rovetta 8Padova 35100Italy

Bioplastics were first introduced as environmentally friendly materials,with properties similar to those of conventional plastics.A bioplastic is defined as biodegradable if it can be decomposed into carbon dioxide under aerobic degradation,or methane and CO_(2)under anaerobic conditions,inorganic compounds,and new cellular biomass,by the action of naturally occurring microorganisms.This definition however does not provide any information on the environmental conditions,timescale and extent at which decomposition processes should occur.With regard to the aquatic environment,recognized standards have been established to assess the ability of plastics to undergo biodegradation;however,these standards fail to provide clear targets to be met to allow labelling of a bioplastic as biodegradable.Moreover,these standards grant the user an extensive leeway in the choice of process parameters.For these reasons,the comparison of results deriving from different studies is challenging.The authors analysed and discussed the degree of biodegradability of a series of biodegradable bioplastics in aquatic environments(both fresh and salt water)using the results obtained in the laboratory and from on-site testing in the context of different research studies.Biochemical Oxygen Demand(BOD),CO_(2)evolution,surface erosion and weight loss were the main parameters used by researchers to describe the percentage of biodegradation.The results showed a large variability both in weight loss and BOD,even when evaluating the same type of bioplastics.This confirms the need for a reference range of values to be established with regard to parameters applied in defining the biodegradability of bioplastics.

关键词： Biodegradation Bioplastic Plastic Natural environment Plastic waste

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