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Experimental and numerical settlement analysis of railway track over geogrid reinforced ballast

Railway Sciences 2024年第3期3卷 311-331页

作者： Mohammed Y.Fattah Mahmood R.Mahmood Mohammed F.Aswad Department of Civil Engineering UOTBaghdadIraq

Purpose-The main objective of the present research is to investigate the benefits of using geogrid reinforcement in minimizing the rate of deterioration of ballasted rail track geometry resting on soft clay and to explore the effect of load amplitude,load frequency,presence of geogrid layer in ballast layer and ballast layer thickness on the behavior of track system.These variables are studied both experimentally and numerically.This paper examines the effect of geogrid reinforced ballast laying on a layer of clayey soil as a subgrade layer,where a half full scale railway tests are conducted as well as a theoretical analysis is performed.Design/methodologylapproach-The experimental tests work consists of laboratory model tests to investigate the reduction in the compressibility and stress distribution induced in soft clay under a ballast railway reinforced by geogrid reinforcement subjected to dynamic load.Experimental model based on an approximate half scale for general rail track engineering practice is adopted in this study which is used in Iraqi railways.The investigated parameters are load amplitude,load frequency and presence of geogrid reinforcement layer.A half fuli-scale railway was constructed for carrying out the tests,which consists of two rails 800 mm in iength with three w00den sleepers(900 mm×90 mm×90 mm).The ballast was overlying 500 mm thick clay layer.The tests were carried out with and without geogrid reinforcement,the tests were carried out in a well tied steel box of 1.5 m length X 1 m width X 1 m height.A series of laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid.Settlement in ballast and clay,was measured in reinforced and unreinforced ballast cases.In addition to the laboratory tests,the application of numerical analysis was made by using the finite element program PLAXIS 3D 2013.Findings-It was concluded that the settlement increased with increasing the simulated train load amplitude,there is a sha

关键词： Track ettlement ballast Finiteelements

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Angle of repose in the numerical modeling of ballast particles focusing on particle-dependent specifications:Parametric study

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Particuology 2022年第6期20卷 39-50页

作者： Peyman Aela Lu Zong Morteza Esmaeili Mohammad Siahkouhi Guoqing Jing School of Civil Engineering Beijing Jiaotong UniversityBeijing 100044China School of Railway Engineering Iran University of Science and TechnologyTehran 16846-13114Iran

The discrete element method(DEM)is widely used in the realistic simulation of the shapes of particles.Researchers have considered the simplification of particle shapes owing to the high computational cost of such simulation.In this regard,the modeling of calibrated particles is a major challenge owing to the simultaneous effects of particle properties.The angle-of-repose test is a standard test method used to calibrate the bulk behavior of simulated particles.In the present study,the hollow-cylinder(slump)test was modeled for the verification of discrete element simulations.In this regard,a sensitivity analysis was conducted for all effective parameters,namely the static friction,rolling friction,restitution coefficient,sphericity,roundness,particle size distribution,and number of ballast particles.The results indicate that the rolling friction,roundness,number of particles,and size of particles are the most important parameters in the determination of the angle of repose(AOR).For particles in the range of ballast(20-60 mm),the effect of the number of particles on the angle of repose is reduced when the number is greater than 426.Additionally,it is concluded that angular particles can be replaced with sub-angular particles(R≈0.2-0.45)with a higher rolling friction coefficient(μ_(r)>0.14).

关键词： ballast Angle of repose Calibration Hollow cylinder test Friction coefficients Shape factors

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Stress distribution from railway track over geogrid reinforced ballast underlain by clay

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Earthquake Engineering and Engineering Vibration 2019年第1期18卷 77-93页

作者： Mohammed Y.Fattah Mahmood R.Mahmood Mohammed F.Aswad Civil Engineering Department University of TechnologyBaghdad Iraq Civil Engineering Department University of TechnologyBaghdad IraqAssistant

Railway ballast forms a major component of a conventional rail track and is used to distribute the load to the subgrade, providing a smooth running surface for trains. It plays a significant role in providing support for the rail track base and distributing the load to the weaker layer underneath. ballast also helps with drainage, which is an important factor for any type of transportation structure, including railroads. Over time, ballast progressively deforms and degrades under dynamic loading and loses its strength. In this study, extensive laboratory tests were conducted to investigate the effect of load amplitude, geogrid position, and number of geogrid layers, thickness of ballast layer and clay stiffness on the behavior of the reinforced ballast layer and induced strains in a geogrid. A half full-scale railway was constructed for carrying out the tests, which consisted of two rails 800 mm in length with three wooden sleepers(900 mm × 10 mm × 10 mm). Three ballast thicknesses of 200, 300 and 400 mm were used in the tests. The ballast was overlying 500 mm thickness clay in two states, soft and stiff. The tests were carried out with and without geogrid reinforcement; the tests were performed in a well-tied steel box of 1.5 m length ×1 m width ×1 m height. Laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid. Settlement in ballast and clay, soil pressure and pore water pressure induced in the clay were measured in reinforced and unreinforced ballast cases. It was concluded that the amount of settlement increased as the simulated train load amplitude increased, and there was a sharp increase in settlement up to cycle 500. After that, there was a gradual increase that leveled out between, 2500 to 4500 cycles depending on the frequency used. There was a slight increase in the induced settlement when the load amplitude increased from 0.5 to 1 ton but it was higher when the load amplitude increased to 2 tons. The increased amoun

关键词： ballast geogrid reinforcement clay stress pore water pressure dynamic load

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Breakage and shape analysis of ballast aggregates with different size distributions

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Particuology 2017年第6期15卷 84-92页

作者： Yifei Sun Changjie Zheng Key Laboratory ofMinistryof Education for Geomechanics and Embankment Engineering College of Civil and Transportation Engineering Hohai University Nanjing 210098 China School of Civil Mining and Environmental Engineering University ofWollongong Wollongong NSW2522 Australia Key Laboratory of New Technology for Consgruction of Cities in Mountain Area Ministry of Education School of Civil Engineering Chongqing University Chongqing 400045 China

Particle breakage usually alters the size and shape of ballast aggregates, which significantly influences the long-term performance of rail tracks. This study reports an investigation on the breakage and shape characteristics of ballast aggregates subjected to monotonic and cyclic triaxial tests with two different load frequencies. The results show that particle breakage is not only influenced by the particle size distribution but also by the relative density. Breakage indices defined by breakage potential and grading entropy fail to characterize the breakage extent of ballast with multiple initial particle size distributions, while the Marsal breakage index exhibits a general decrease with increasing coefficient of uniformity for ballast with similar relative densities. Higher breakage extent is observed in ballast subjected to a higher load frequency. Particle shape varies with load frequency because of breakage. A slightly higher value of each shape index is observed for ballast subjected to a higher load frequency, implying that ballast aggregates become increasingly regular with the increase of load frequency,

关键词： Breakage Breakage potentia Grading entropy Particle shape ballast

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Micromechanical experiments using a new inter-granule loading apparatus on gravel to ballast-sized materials

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Friction 2020年第1期8卷 70-82页

作者： Chitta Sai SANDEEP Kostas SENETAKIS City University of Hong Kong Hong Kong SARChina

Micromechanical and tribological studies of geological materials with a particular focus on their contact-mechanics behavior at the grain scale are currently a major interest in the engineering and geoscience disciplines. In this study, a new robust micromechanical apparatus developed at the City University of Hong Kong is described;it is capable of conducting inter-granule(or inter-particle) loading tests on fine gravel to ballast-sized materials of sizes as small as 5-10 mm to granules(or ballast) as big as 50 mm. The focus of our study is the description of the major technical features of the new apparatus and its performance and repeatability in conducting experiments on reference grains of chrome steel balls and glass balls;in addition, we conducted a preliminary set of experiments on crushed granitic rock, which is a material widely used in geotechnical and transportation infrastructure. The representative results of these experiments are presented in terms of the normal force-displacement relationship, friction, and tangential stiffness. The newly developed large-size apparatus is further compared with a well-established apparatus that can conduct micromechanical tests on sand-sized materials.

关键词： experimental micromechanics contact mechanics linear bearings inter‐particle friction granite debris flow ballast

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Fracture toughness estimation of ballast stone used in Iranian railway

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第5期9卷 892-899页

作者： I.Ferestade P.Hosseini Tehrani R.Heidary Railway Engineering Iran University of Science and Technology Tehran Iran

ballast is a layer composed of crushed stone basically with diameters of 20-60 mm,on which sleepers and rails are set.ballast is used to withstand vertical,horizontal and lateral forces applied on sleepers and to hold the line in operative conditions.ballast deterioration induced by crashed stones is a major issue of track instability as the ballast layer quality depending on the materials used and their densities should be focused on.Therefore,ballast should be resistant against loads applied,and the fracture toughness of ballast stone is of great importance.For this purpose,the fracture toughness of two kinds of ballast stones used in Iranian railway,i.e.Gaduk(limestone) and Anjylavnd(andesite),is investigated experimentally in this paper.The quality of ballast stone is evaluated in different weather conditions.Numerical results shown that the Anjylavnd stone is more appropriate for rainy and cold weather when there is a probability of fracturing due to frozen water captured in ballast.

关键词： ballast Fracture toughness Crack Freezing

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Study on the Elasticity-Plasticity-Stickiness of the Railway Crushed Stone ballast

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上海交通大学学报 2004年第Z2期38卷 67-72页

作者： Gao Liang School of Civil Engineering and Architecture Beijing Jiaotong University Beijing100044 China

This paper is mainly aimed at the mechanics characteristic elas of ticity-plasticitystickiness existed in the CWR (continuously welded rails) track plane of the railway crushed stone ballast. As an important mechanics parameter of the CWR track plane, the ballast resistance is mainly influenced by this mechanics characteristic. Through the systematic experimental research and the theoretical analysis, this mechanics characteristic of the ballast resistance is revealed and a reasonable theoretical model is built for it. This study set a sound foundation for further studying the CWR track deformation property. It will be beneficial to the development of high-speed railway in China.

关键词： elasticity-plasticity-stickiness crushed stone ballast constitutive model CWR track

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Identification of ballast grading for rail track

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第5期9卷 945-954页

作者： Yifei Sun Chen Chen Sanjay Nimbalkar Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering College of Civil and Transportation EngineeringHohai University School of Civil Miningand Environmental EngineeringUniversity of Wollongong School of Civil and Environmental Engineering University of Technology Sydney

Grading has long been recognised to critically influence the mechanical behaviour of ballast.To identify the ballast grading for heavy-haul rail track,monotonic and cyclic triaxial tests are conducted to assess the performances of different gradings.Permanent deformations,aggregates degradation,resilience,shear resistance,maximum and minimum densities are recorded and analysed.The grading is found to affect the behaviour of ballast in that coarser gradings exhibit relatively better strength,resilience and therefore less permanent deformation.However,ballast degradation increases with the overall aggregate size.Therefore,to identify the grading for ballast with different performance objectives,a grey relational theory is used to convert the multi-objective into single-objective,i.***.grey relational grade.A relatively optimal grading that provides the highest grey relational grade is thus suggested for the improved ballast performance.

关键词： ballast Deformation Grading Grey relational analysis

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Cooling effect of ballast revetment on the roadbed of Qinghai-Tibetan Railway

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Science China Earth Sciences 2004年第Z1期47卷 161-167页

作者： HU Zeyong CHENG Guodong QIAN Zeyu WANG Jiemin WEI Guoan HOU Xuhong GU Lianglei YAN Yuping Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

The data obtained through the roadbed surface thermal regime experiment (ROBSTREX), which was carried out at Beiluhe test section of Qinghai-Tibetan Railway from October to December in 2002, were used to estimate the cooling effect of ballast revetment on the roadbed. The results show that both riprap rock ballast revetment and crushed stone ballast revetment can reduce the temperature of the roadbed. But the cooling effect of riprap rock ballast revetment is better than that of crushed stone ballast revetment when the temperature of roadbed is higher. The cooling effect of crushed stone ballast revetment is better than that of riprap rock ballast revetment when the temperature of the roadbed is lower, especially at deeper roadbed layers. In the frozen season, the heat release from the roadbed also shows that the cooling effect of ballast revetment on the roadbed is obvious, and the cooling effect of crushed stone-ballast revetment on the roadbed is much evident than that of riprap rock ballast revetment.

关键词： Qinghai-Tibetan Railway, ballast revetment, cooling effect.

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Survivorship characteristics and adaptive mechanisms of phytoplankton assemblages in ballast water

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Journal of Oceanology and Limnology 2019年第2期37卷 580-588页

作者： WU Huixian SHEN Chen WANG Qiong Richard B. ARONSON CHEN Chen XUE Junzeng College of Marine Ecology and Environment Shanghai Ocean University Shanghai 201306 China ballast Water Detecting Lab Shanghai Ocean University Shanghai 201306 China Department of Biological Sciences Florida Institute of Technology Melbourne Florida 32901 USA

Phytoplankton diversity and abundance were determined in ballast water from 26 vessels in the Shanghai Yangshan Deep-Water Port from April 2015 to January 2016. In total, 84 species of phytoplankton were identified, belonging to 43 genera and 5 phyla. Bacillariophyta (75.0%, including 30 genera and 63 species) were the dominant algae in the ballast water. Their density ranged from (5.55±9.62) SD to (1.878±0.872)×10 3 cells/L, with a mean of 410.1 cells/L. Nine potentially harmful phytoplankton taxa were detected: Ceratium furca , Ce . marcroceros , Leptocylindrus danicus , Coscinodiscus radiatus , Co . granii , Prorocentrum micans , Melosira sulcata , Meuniera membranacea and Skeletonema costatum . Our survey and identification results showed that Microcystis aeruginosa , Ankistrodesmus falcatus and Scenedesmus survived in the high-salinity ballast water, even though they are freshwater species. We identified the common features of surviving phytoplankton and impacts on the phytoplankton assemblage of ballast water age and source. Our goal was to understand the adaptative mechanisms of phytoplankton in ballast water, providing statistical and theoretical support for future ballast water research and suggesting a scientific basis of ballast water management and inspection of vessels entering the port.

关键词： diversity abundances Yangshan Port dominant algae ballast water age source

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