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A combined experimental and DEM investigation of grain interlocking in sheared granular assemblies

Particuology 2024年第7期90卷 436-451页

作者： Rui Lu Qiang Luo Tengfei Wang David P.Connolly Tao Xie School of civil engineering Southwest Jiaotong UniversityChengdu 610031China Key Laboratory of High-Speed Railway engineering(Southwest Jiaotong University) Ministry of EducationChengdu 610031China School of civil engineering University of LeedsLeeds LS29JTUK department of civil engineering McMaster UniversityHamiltonONCanada

Compacted granular material,integral to geotechnical engineering,undergoes translation,rotation,and interlocking when subject to shear displacements or external *** present study focuses on the interlocking of heterogeneous granular materials,a complex behavior influenced by gradation,compaction,and varying particle geometry,and has consequently received limited attention in existing *** address this research gap,we conducted an analysis on the effect of grain interlocking on the shear resistance of granular assemblies,using a combination of laboratory testing and the discrete element method(DEM).Initially,large-scale direct shear tests were conducted on gravel−sand mixes with varying degrees of compaction and normal *** of the mixes also underwent subsequent shear reversal to explore the differences in grain interlocking between the two shearing processes on the shear *** analyzing the laboratory results,a mesoscopic scale investigation was performed by replicating the test using discrete element *** facilitate this,granular particle geometries were measured using 3D laser scanning based on the physical lab ***,based on these scans,discrete element R-block and ball models were utilized to construct both the coarse and fine particles within the *** vibro-compaction was employed to regulate the degree of *** results indicate that an increase in vertical pressure,coupled with a zero dilatancy angle,results in a rising stress ratio,indicative of grain *** interlocking exhibits a positive correlation with both the coarse content and the degree of compaction,and varies depending on the shear *** interlocking progresses,the shear band,induced by particle movement,expands and is associated with reduced particle rotation near the shear *** study further reveals a consistent positive correlation between interlocking and the principal orientation angle of strong normal c

关键词： Granular material Interlocking Shear resistance Direct shear Discrete element method Vibro-compaction

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A bounding surface visco-plasticity model considering generalized spacing ratio of soils

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Journal of Rock Mechanics and Geotechnical engineering 2024年第5期16卷 1832-1846页

作者： Xiaosen Kang Hongjian Liao Qiangbing Huang Jianbing Peng department of Geological engineering Chang’an UniversityXi’an710054China department of civil engineering Xi’an Jiaotong UniversityXi’an710049China

The non-unique critical state of soils with time-dependent behaviors is a significant issue in geotechnical engineering ***,previous bounding surface plasticity models cannot predict accurately the non-unique critical state of soils,because the distance between the compression line and critical state line charged by strain-rate effect is basically *** fill this gap,a generalized spacing ratio of soils is defined in the elasto-viscoplastic framework,and a bounding surface visco-plasticity model is formulated and verified,which can consider the generalized spacing ***,the generalized spacing ratio of soils reflects the distance between the compression line and the critical state line of soils with time-dependent ***,the generalized spacing ratio is introduced into an improved anisotropic bounding surface.A new expression of the visco-plastic multiplier is derived by solving the consistency equation of an anisotropic bounding *** the expression,a strain rate index is proposed to account for the strain-rate effect on visco-plastic strain increment,and a visco-plastic hardening modulus is derived to predict the visco-plastic response of soils in overconsolidation *** model is then verified through constant strain rate tests and creep ***,it can capture the non-unique critical states of soils with time-dependent behaviors due to the generalized spacing ratio and the creep rupture of soils due to the visco-plastic multiplier that considers the stress ratio and visco-plastic strain rate.

关键词： Soil Constitutive model Visco-plastic behavior Strain rate Creep Anisotropic

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Online learning-based model predictive trajectory control forconnected and autonomous vehicles: Modeling and physical tests

Journal of Intelligent and Connected Vehicles

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Journal of Intelligent and Connected Vehicles 2024年第2期7卷 86-96页

作者： Qianwen Li Peng Zhang Handong Yao Zhiwei Chen Xiaopeng Li School of Environmental CivilAgricultural and Mechanical EngineeringUniversity of GeorgiaAthens 30602USA department of civil and Environmental engineering University of Wisconsin–MadisonMadison 53706USA department of civil Architecturaland Environmental EngineeringDrexel UniversityPhiladelphia 19104USA

Motivated by the promising benefits of connected and autonomous vehicles (CAVs) in improving fuelefficiency, mitigating congestion, and enhancing safety, numerous theoretical models have been proposed to plan CAVmultiple-step trajectories (time–specific speed/location trajectories) to accomplish various operations. However, limitedefforts have been made to develop proper trajectory control techniques to regulate vehicle movements to follow multiplesteptrajectories and test the performance of theoretical trajectory planning models with field experiments. Without aneffective control method, the benefits of theoretical models for CAV trajectory planning can be difficult to harvest. This studyproposes an online learning-based model predictive vehicle trajectory control structure to follow time–specific speed andlocation profiles. Unlike single-step controllers that are dominantly used in the literature, a multiple-step model predictivecontroller is adopted to control the vehicle’s longitudinal movements for higher accuracy. The model predictive controlleroutput (speed) cannot be interpreted by vehicles. A reinforcement learning agent is used to convert the speed value to thevehicle’s direct control variable (i.e., throttle/brake). The reinforcement learning agent captures real-time changes in theoperating environment. This is valuable in saving parameter calibration resources and improving trajectory control accuracy.A line tracking controller keeps vehicles on track. The proposed control structure is tested using reduced-scale robot *** adaptivity of the proposed control structure is demonstrated by changing the vehicle load. Then, experiments on twofundamental CAV platoon operations (i.e., platooning and split) show the effectiveness of the proposed trajectory controlstructure in regulating robot movements to follow time-specific reference trajectories.

关键词： connected and autonomous vehicles(CAVs) reinforcement learning physical tests time-specific speed and location longitudinal and lateral control

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Seismic control of multi-degrees-of-freedom structures by vertical mass isolation method using MR dampers

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Earthquake engineering and engineering Vibration 2024年第2期23卷 503-510页

作者： Mohamad Shahrokh Abdi Masoud Nekooei Mohammad-Ali Jafari department of civil engineering Marivan BranchIslamic Azad UniversityMarivan ***Iran department of civil engineering Science and Research BranchIslamic Azad UniversityTehran ***Iran Structural department of Transmission and Distribution Research Center Niroo Research Institute(NRI)Tehran ***Iran

Vertical mass isolation(VMI)is one of the novel methods for the seismic control of *** this method,the entire structure is assumed to consist of two mass and stiffness subsystems,and an isolated layer is located among *** this study,the magnetorheological damper in three modes:passive-off,passive-on,and semi-active mode with variable voltage between zero and 9 volts was used as an isolated layer between two ***-degrees-of-freedom structures with 5,10,and 15 floors in two dimensions were examined under 11 pairs of near field *** each level,the displacement of MR dampers was taken into *** responses of maximum displacement,maximum inter-story drift,and maximum base shear in controlled and uncontrolled buildings were compared to assess the suggested approach for seismic control of the *** to the results,the semi-active control method can reduce the response by more than 12%compared to the uncontrolled mode in terms of maximum displacement of the mass subsystem of the *** method can reduce more than 16%and 20%of the responses compared to the uncontrolled mode in terms of maximum inter-story drift and base shear of the structure,respectively.

关键词： seismic control vertical mass isolation base shear magnetorheological damper semi-active control

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Theoretical investigation on axial cyclic performance of monopile in sands using interface constitutive models

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Journal of Rock Mechanics and Geotechnical engineering 2024年第7期16卷 2645-2662页

作者： Pan Zhou Jingpei Li Kaoshan Dai Stefan Vogt Seyedmohsen Miraei department of Geotechnical engineering Tongji UniversityShanghai200092China department of civil Geo and Environmental EngineeringTechnical University of MunichFranz-Langinger-Str.10München81245Germany department of civil engineering Sichuan UniversityChengdu610065China

Cyclic loads generated by environmental factors,such as winds,waves,and trains,will likely lead to performance degradation in pile foundations,resulting in issues like permanent displacement accumulation and bearing capacity *** paper presents a semi-analytical solution for predicting the axial cyclic behavior of piles in *** solution relies on two enhanced nonlinear load-transfer models considering stress-strain hysteresis and cyclic degradation in the pile-soil *** parameters are calibrated through cyclic shear tests of the sand-steel interface and laboratory geotechnical testing of sands.A novel aspect involves the meticulous formulation of the shaft loadtransfer function using an interface constitutive model,which inherently inherits the interface model’s advantages,such as capturing hysteresis,hardening,degradation,and particle *** semi-analytical solution is computed numerically using the matrix displacement method,and the calculated values are validated through model tests performed on non-displacement and displacement piles in *** results demonstrate that the predicted values show excellent agreement with the measured values for both the static and cyclic responses of piles in *** displacement pile response,including factors such as bearing capacity,mobilized shaft resistance,and convergence rate of permanent settlement,exhibit improvements compared to non-displacement piles attributed to the soil squeezing *** methodology presents an innovative analytical framework,allowing for integrating cyclic interface models into the theoretical investigation of pile responses.

关键词： Piles Cyclic degradation Load-transfer models Interface constitutive model Semi-analytical solution Model tests

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High-efficiency Carbonation Modification Methods of Recycled Coarse Aggregates

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Journal of Wuhan University of Technology(Materials Science) 2024年第2期39卷 386-398页

作者：张美香 YANG Xiaolin 丁亚红 SUN Bo ZHANG Xianggang LÜXiuwen department of civil engineering Henan Polytechnic UniversityJiaozuo 454150China College of Architectural engineering Xinyu UniversityXinyu 336500China

To solve the problem of only surface carbonation and realize high-efficiency carbonation of recycled coarse aggregate,the method of carbonated recycled coarse aggregate with nano materials pre-soaking was first put *** carbonation effect of modified recycled coarse aggregate with three different carbonation methods was evaluated,and water absorption,apparent density and crush index of modified recycled coarse aggregate were *** with XRD,SEM,and MIP microscopic analysis,the high-efficiency carbonation strengthening mechanism of modified recycled coarse aggregate was *** experimental results show that,compared with the non-carbonated recycled coarse aggregate,the physical and microscopic properties of carbonated recycled coarse aggregate are *** method of carbonation with nano-SiO_(2) pre-soaking can realize the high-efficiency carbonation of recycled coarse aggregate,for modified recycled coarse aggregate with the method,water absorption is reduced by 23.03%,porosity is reduced by 44.06%,and the average pore diameter is 21.82 *** high-efficiency carbonation strengthening mechanism show that the pre-socked nano-SiO_(2) is bound to the hydration product Ca(OH)_(2) of the old mortar with nano-scale C-S-H,which can improve the CO_(2) absorption rate,accelerate the carbonation reaction,generate more stable CaCO_(3) and nano-scale silica gel,and bond to the dense three-dimensional network structure to realize the bidirectional enhancement of nano-materials and pressurized *** is concluded that the method of carbonation with nano-SiO_(2) pre-soaking is a novel high-efficiency carbonation modification of recycled coarse aggregate.

关键词： recycled coarse aggregate pressurized carbonation high-efficiency carbonation nano-SiO2 strengthening mechanism

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Experimental and numerical study on dynamic mechanical behaviors of shale under true triaxial compression at high strain rate

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International Journal of Mining Science and Technology 2024年第2期34卷 149-165页

作者： Xiaoping Zhou Linyuan Han Jing Bi Yundong Shou School of civil engineering Wuhan UniversityWuhan 430072China College of civil engineering Guizhou UniversityGuiyang 550025China

High-energy gas fracturing of shale is a novel,high efficacy and eco-friendly mining technique,which is a typical dynamic perturbing *** effectively extract shale gas,it is important to understand the dynamic mechanical properties of *** experiments on shale subjected to true triaxial compression at different strain rates are first conducted in this *** dynamic stress-strain curves,peak strain,peak stress and failure modes of shale are *** results of the study indicate that the intermediate principal stress and the minor principal stress have the significant influence on the dynamic mechanical behaviors,although this effect decreases as the strain rate *** characteristics of compression-shear failure primarily occur in shale subjected to triaxial compression at high strain rates,which distinguishes it from the fragmentation characteristics observed in shale under dynamic uniaxial ***,a numerical three-dimensional Split Hopkinson Pressure Bar(3D-SHPB),which is established by coupling PFC3D and FLAC3D methods,is validated to replicate the laboratory characteristics of *** dynamic mechanical characteristics of shale subjected to different confining stresses are systematically investigated by the coupling PFC3D and FLAC3D *** numerical results are in good agreement with the experimental data.

关键词： Dynamic behaviors True triaxial compression High strain rates Dynamic failure mechanism PFC3D-FLAC3D coupled method

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Mechanical Property and Microstructure of Cement Mortar with Carbonated Recycled Powder

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Journal of Wuhan University of Technology(Materials Science) 2024年第3期39卷 689-697页

作者：丁亚红张美香 YANG Xiaolin XU Ping SUN Bo GUO Shuqi department of civil engineering Henan Polytechnic UniversityJiaozuo 454150China College of Architectural engineering Xinyu UniversityXinyu 336500China

Carbonated recycled powder as cementitious auxiliary material can reduce carbon emissions and realize high-quality recycling of recycled *** this paper,microscopic property of recycled powder with three carbonation methods was tested through XRD and SEM,the mechanical property and microstructure of recycled powder mortar with three replacement rates were studied by ISO method and SEM,and the strengthening mechanism was *** results showed that the mechanical property of recycled powder mortar decreased with the increasing of replacement *** is suggested that the replacement rate of recycled powder should not exceed 20%.The strength index and activity index of carbonated recycled powder mortar were improved,in which the flexural strength was increased by 27.85%and compressive strength was increased by 20%at the *** powder can be quickly and completely carbonated,and the improvement effect of CH pre-soaking carbonation was the *** activity index of carbonated recycled powder can meet the requirements of Grade II technical standard for recycled *** results revealed the activation mechanism of carbonated recycled powder such as surplus calcium source effect,alkaline polycondensation effect and carbonation enhancement effect.

关键词： recycled powder carbonation activation compound carbonation activity index mechanical property microstructure

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Trombe walls with porous medium insertion and their influence on thermal comfort in flats in Cusco,Peru

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Energy and Built Environment 2024年第2期5卷 194-210页

作者： Patrick Facelli Sanchez Lisset Mercado Hancco department of civil engineering Faculty of Architecture and Civil EngineeringUniversidad Nacional de San Antonio Abad del Cusco08003 CuscoPeru

The Trombe wall is a passive indirect heating system which should be used in Cusco,Peru to improve thermal conditions against the typical frosts and low temperatures during winter in the high Andean *** to this problem,the use of a modified Trombe wall with insertion of porous medium is proposed to improve thermal comfort in flat buildings in *** research aims to analyse and compare the performance of dwellings without Trombe wall,with traditional Trombe wall,and with Trombe wall with glass and plastic pellets insertion in thermal comfort ***■CFD was used to simulate and analyse the *** simulation was performed with three prototype flats(55 m^(2),75 m^(2) and 95 m^(2))for six months of the *** the results obtained,the level of thermal comfort in the traditional scenarios is low with an average PMV of-1.86,in the scenarios with Trombe wall is good and in the scenarios with Trombe wall with insertion of porous medium is slightly better than the previous one,reaching an average PMV of+0.10 and a temperature of 21.90℃.The study carried out is important because it represents an efficient eco-sustainable heating alternative that improves the thermal comfort sensation in houses during the coldest months of the year.

关键词： Trombe wall thermal comfort porous medium residential buildings computational fluid dynamics

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Simplified seismic scenario analysis of existing masonry buildings accounting for local site effects

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Frontiers of Structural and civil engineering 2024年第2期18卷 309-318页

作者： Ayşe E.ÖZSOYÖZBAY Işıl SANRI KARAPINAR Zehra N.KUTLU İsmail E.KILIÇ department of civil engineering Maltepe UniversityIstanbul 34857Turkey School of engineering and Construction Oryx Universal CollegeDoha 12253Qatar

This study discusses the effects of local sites and hazard amplification on the seismic vulnerability assessment of existing masonry *** this context,a rapid seismic evaluation procedure was implemented on an old masonry building stock in the historical center Galata,located inİstanbul,to determine the seismic risk priority of the built *** scenarios were generated for all soil classes,different moment magnitudes,and source-to-site distances to obtain more accurate results for the seismic vulnerability assessment of the studied building ***,damage distributions estimated under nine different scenarios with/without site effects were compared and illustrated in maps to discuss changes in vulnerability owing to amplification *** this study,by re-examining the rapid seismic evaluation procedure by including geo-hazard-based assessment,the importance of site effects on the vulnerability and risk assessment of built heritage was *** proposed framework integrating field data and local site effects is believed to advance the current applications for vulnerability assessment of masonry buildings and provide an improvement in the application of rapid seismic assessment procedures with more reliable results.

关键词： masonry buildings seismic vulnerability assessment cultural heritage local site effect

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