Letteratura scientifica selezionata sul tema "GEOGRID REINFORCED BALLAST"
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Articoli di riviste sul tema "GEOGRID REINFORCED BALLAST"
1
Jing, Guo Qing, Xi Haier Luo e Zi Jie Wang. "Micro-Analysis Ballast-Geogrid Pull out Tests Interaction". Applied Mechanics and Materials 548-549 (aprile 2014): 1716–20. http://dx.doi.org/10.4028/www.scientific.net/amm.548-549.1716.
Testo completoAbstract (sommario):
The discrete element method was used to simulate geogrid-reinforced ballast by pull out tests. Ballast particle was made of irregular clumps where its size and shape were considered by bonded spheres. The response of the ballast reinforced with geogrid under loading agrees with pull out experimental results. The micro-interaction between ballast particle and geogrid analyzed by microscopic parameters, contact force chain, force-displacement of the pull out tests was presented. It was also proved that the shape of granular particles, geogrid size and friction played an important role in ballast-geogrid system.
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Fu, Jianjun, Junfeng Li, Cheng Chen e Rui Rui. "DEM-FDM Coupled Numerical Study on the Reinforcement of Biaxial and Triaxial Geogrid Using Pullout Test". Applied Sciences 11, n. 19 (27 settembre 2021): 9001. http://dx.doi.org/10.3390/app11199001.
Testo completoAbstract (sommario):
The key to modeling the interlocking of geogrid-reinforced ballast is considering both the continuous deformation characteristics of the geogrid and the discontinuity of the ballast particles. For this purpose, pullout tests using biaxial and triaxial geogrids were simulated using the coupled discrete element method (DEM) and finite difference method (FDM). In this coupled model, two real-shaped geogrid models with square and triangular apertures were established using the solid element in FLAC3D. Meanwhile, simplified shaped clumps were used to represent the ballast using PFC3D. The calibration test simulation showed that the accurately formed geogrid model can reproduce the deformation and strength characteristics of a geogrid. The pullout simulation results show that the DEM-FDM method can well predict the relationship between pullout force and displacement, which is more accurate than the DEM method. For ballast particles of 40 mm in size, both the experiment and simulation results showed that the triaxial geogrid of 75 mm is better than the 65-mm biaxial geogrid. In addition, the DEM-FDM method can study the interaction mechanism between the particles and the geogrid from a microscopic view, and also reveal the similar deformation behavior of the geogrid in the pullout process. Therefore, the DEM-FDM coupled method can not only investigate the interlocking mechanism between the ballast and particles but can also provide a great method for evaluating the performance of different types of geogrids.
3
Ji, Danyang, Zheng Ma, Junjie Zhou, Yajun Li e Shuai Shao. "A Coupled Discrete-Finite Element Method for Shear Strength Analysis of Geogrid-Reinforced Railway Ballast". Advances in Materials Science and Engineering 2021 (31 dicembre 2021): 1–11. http://dx.doi.org/10.1155/2021/3685709.
Testo completoAbstract (sommario):
This paper presents a coupled discrete-finite element method for the investigation of shear strength of geogrid-reinforced ballast by direct shear tests and pull-out tests. The discrete element method (DEM) and finite element method (FEM) are employed to simulate ballast and geogrid, respectively. Irregularly shaped ballast particles are modeled with clumps, and the nonlinear contact force model is used to calculate contact force between particles. Continuum geogrid is modeled by a two-node beam element with six degrees of freedom. A contact algorithm based on the static equilibrium is proposed at the geogrid-ballast contact surface. The simulation results indicate that shear strengths increase with the installation of geogrid. Moreover, ballast particle displacements and nominal volumetric strains are analyzed to provide a microscopic view on the mechanism of the reinforcement effect of geogrid.
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Li, Jing, Ya-Fei Jia, Chen-Xi Miao e Ming-Xing Xie. "Discrete Element Analysis of the Load Transfer Mechanism of Geogrid-Ballast Interface under Pull-Out Load". Advances in Civil Engineering 2020 (10 ottobre 2020): 1–12. http://dx.doi.org/10.1155/2020/8892922.
Testo completoAbstract (sommario):
Geogrids have been extensively used in subgrade construction for stabilization purposes of unconfined ballast. Based on well-calibrated microparameters, a series of geogrid-reinforced ballast models with different geogrid sizes and particular structures were developed to reproduce the mechanical behavior of the geogrid under pull-out load in this paper. And the rationality of the DEM model is verified by comparing the evolution law pull-out force measured by laboratory tests and numerical simulations under comparable conditions. Moreover, the macro pull-out force and the internal force distribution of the geogrid were analyzed, and the contact force statistical zones of the particle system were divided accurately according to the results. Meanwhile, both the force transfer mechanism in the geogrid-ballast interface and the sectionalized strain of the geogrid were discussed. And results unveil that the pull-out load is transmitted along the longitudinal ribs to the transverse ribs, and nearly 90% of the load is transmitted to the contact network (in statistical zone 1) in front of the first transverse rib, resulting in strong interlocking between the particles occurs in statistical zone 1. And the second transverse rib is the strength dividing line between strong and weak contact forces. Then, additional pull-out tests on the control groups were conducted, and the sectionalized strain of the geogrid and the peak pull-out force, as well as the energy dissipation were systematically analyzed. In addition, the proposed method used in simulation holds much promise for better understanding of the reinforcement mechanism and further optimizing the performance of geogrid-reinforced structures.
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Abrashitov, A., A. Sidrakov e A. Zaitsev. "Construction and Current Maintenance of the Reinforced Ballast Layer of the Railway Track". IOP Conference Series: Earth and Environmental Science 988, n. 2 (1 febbraio 2022): 022045. http://dx.doi.org/10.1088/1755-1315/988/2/022045.
Testo completoAbstract (sommario):
Abstract The article presents the ideas for the construction and the current maintenance of the reinforced plastic geogrid top ballast composed of crushed solid rock. Meanwhile, the reinforced ballast material acquires new properties, which lead to the formation of a composite material with new properties. In the reinforced material, only micro-deformations occur under the dynamic load, which is intrinsic to solid rock. In this case, laboratory simulation of reinforced ballast with a cyclic load showed that multilayer stabilization with three geogrids reduces settelment by 67% and does not require cleaning during the entire service life of the reinforced top ballast. The construction and the current maintenance of the composite structure make a real difference from the ballastless structure of the railway track as the work techniques with geosynthetics in the ballast subgrade are properly developed, and they are widely used during the repairs of railway track, because the development of the technology for the creation of reinforced geocomposite will not cause any problem.
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Abrashitov, Alexander, e Andrei Sidrakov. "Laboratory study of ballast material reinforced by flat geogrid under the dynamic load". MATEC Web of Conferences 265 (2019): 01006. http://dx.doi.org/10.1051/matecconf/201926501006.
Testo completoAbstract (sommario):
Ballast material suffers from continuous degradation under cyclic load. This leads to rail track settlement and necessitates its constant maintenance. It is serious problem that costs Russia millions of dollars every year. Easily accessible plastic geogrid was proposed to reinforce ballast and to prevent its rapid degradation. However, the optimal parameters of geogrid (its mesh size, geometry and number of layers) remains an open question. In current work effects of number of geogrid layers and geogrid mesh size on ballast settlement are studied by laboratory dynamic load tests.
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Li, Lihua, Yanan Fang, Bowen Cheng, Na Chen, Mi Tian e Yiming Liu. "Characterisation of Geogrid and Waste Tyres as Reinforcement Materials in Railway Track Beds". Materials 14, n. 15 (27 luglio 2021): 4162. http://dx.doi.org/10.3390/ma14154162.
Testo completoAbstract (sommario):
The engineering behaviour of ballast is an important factor to determine the stability and safety of railway tracks. This paper examines the stress–strain, shear strength, peak deflection stress and reinforcement strength ratio of different reinforcement materials and reinforcement locations in ballast track bed layers based on large scale static triaxial shear tests. The results show that geogrid and waste tyre reinforcement have a significant effect on the peak deviator stress of railway track bed layers and the stress–strain relationship is strain-hardened. The peak deviator stress and shear strength of geogrid reinforcement are greater under the same conditions compared with waste tyres. The reinforcement of geogrid and waste tires increases the shear strength of the track bed significantly. The more layers of geogrid reinforcement, the more energy is required for the deformation of the track bed. The energy required for deformation is greater in the centre of the waste tyre than in the other reinforced forms, and the energy required for deformation is minimal in the fully reinforced form. Excessive tyre reinforcement changes the stiffness of the track bed layer, leading to an increase in the settlement rate. The reinforcement strength ratio between geogrid and waste tyre increases significantly with the increasing of the confining pressure and reinforcement layers. Moreover, the reinforcement strength ratio of the geogrid is significantly higher than that of the waste tyre.
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Zhao, Jian-bin, Jie Li, Xiao-hong Bai, Chen-xi Miao e Jun Zhang. "Influence of Particle Orientation on the Performance of Geogrid Reinforced Ballast". Advances in Materials Science and Engineering 2020 (27 dicembre 2020): 1–12. http://dx.doi.org/10.1155/2020/6758059.
Testo completoAbstract (sommario):
To explore the initial orientation effect of ballast assembly on the reinforcement performance of the geogrid reinforced ballast, particles with random orientation and five prescribed rotational orientations were developed through particle flow code (PFC3D). The evolution laws of the pullout force and the principal directions of the normal contact force were systematically compared and analyzed. Furthermore, the mechanical responses such as pullout force, distribution of axial force, displacement vectors, force chain, and mesoscopic fabric were discussed. According to the displacement vectors of the ballast particles, the average thickness of the stable shear band is determined. The inherent relationships among the force chain, the rotational angle of the normal contact force, and the mesoscopic fabric parameters are revealed. The results show that the pullout force of specimens with the initial orientation of 45° increases monotonously during the pullout process, and the peak value of pullout force appears at the end of the test. The mesostructural analysis also confirms that the evolution of the principal direction of contact normal force is relatively steady during the pullout process, indicating that the specimen with 45° orientation possesses higher systematic stability and ductility. Moreover, the optimum interval from 56.68° to 57.30° is observed to remain in a self-adapting state for ballast assembly.
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Fischer, Sz, e F. Horvát. "Investigation of the reinforcement and stabilisation effect of geogrid layers under railway ballast". Slovak Journal of Civil Engineering 19, n. 3 (1 settembre 2011): 22–30. http://dx.doi.org/10.2478/v10189-011-0015-y.
Testo completoAbstract (sommario):
Investigation of the reinforcement and stabilisation effect of geogrid layers under railway ballastThis paper deals with the issue of the stabilization of railway track geometry. It details the published results in numerous international journals. Having analysed the cited publications the paper deals with a new research topic related to geogrid-reinforced railway ballast. A research team of the Department of Transport Infrastructure and Municipal Engineering at the Szechenyi Istvan University would like to continue working on this research topic.
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Hussaini, Syed Khaja Karimullah, Buddhima Indraratna e Jayan S. Vinod. "Performance assessment of geogrid-reinforced railroad ballast during cyclic loading". Transportation Geotechnics 2 (marzo 2015): 99–107. http://dx.doi.org/10.1016/j.trgeo.2014.11.002.
Testo completoTesi sul tema "GEOGRID REINFORCED BALLAST"
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Sinmez, Bugra. "Characterization of Geogrid Reinforced Ballast Behavior Through Finite Element Modeling". Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7946.
Testo completoAbstract (sommario):
Recently, the railway pavement structure system, as an integral part of the transport infrastructure, has been under fast development in some countries such as China, Turkey, and some European Union countries, particularly for the use of high-speed trains. In designing and constructing the railway pavement structure, it is necessary to take into account the infrastructure demand of the High-Speed Railway Lines (HSRL). Compared to traditional railway trains, HSRL can cause more significant problems to the ballast or base layer of commonly used ballasted railway pavements. The deteriorated ballast or base layer may further result in substructure degradation that may cause safety issues and catastrophic accidents. As a consequence, heavy goods or high-speed trains will affect railway efficiency. As a countermeasure, a railway pavement structure may be reinforced by geosynthetic materials in the ballast or base layer. In the literature, however, there is still a need to quantify the effect of geosynthetic materials, geogrid in particular, on the mechanical responses of railway pavement structures to HSRL loads, which is necessary knowledge in supporting the selection of appropriate material and placement location of geogrid. Therefore, the goal of this study is to investigate how a geogrid reinforcement layer can change the essential characteristics of a ballasted railway pavement structure, with focus on the material type and placement location of geogrid that can help minimize the rate of deterioration of the railway pavement structure system. This research attempts to validate the advantage of geogrid reinforcement through numerical simulation in a realistic railway setting.
All technical literature on the use of geogrids in the railway system has been studied. A three-dimensional (3D) finite element model was constructed for the numerical simulation, in which three different types of geogrid placed at two different locations (i.e., within the ballast layer, between the ballast and the sub-ballast layer) within a railway pavement structure were analyzed under a range of vertical wheel loads. Therefore, four possible applications of geogrid reinforcement systems (G0: no-reinforcement; G1: reinforced with geogrid having the lowest density and Young’s modulus; G2: reinforced with geogrid having the intermediate Young’s modulus and density; G3: reinforced with geogrid having the highest density and Young’s modulus) were modeled to represent different situations in ballasted railway systems. Railway mechanical responses, such as vertical surface deflection, maximum principal stress and strain, and maximum shear stress were analyzed and compared among the four geogrid reinforcement scenarios and under four vertical wheel load levels (i.e., 75, 100, 150 and 200 kN). The advantages of such geosynthetics in ballast are indicated by result difference in the mechanical responses of railway pavement structures due to the use of different geogrid materials. The results also show that the reinforced structures have lower vertical surface deflection, lower maximum shear stress at the interface of sleeper and ballast, and maximum principal stress at the bottom of the ballast layer than a non-reinforced railway pavement structure.
Consequently, the addition of geogrid into the ballast layer, and between the ballast and sub-ballast layer has been shown to reduce critical shear and principal stresses and vertical surface deflection in a ballasted railway pavement structure. Besides that, the results of the analysis confirm that geogrid reinforced layers exhibit higher resistance to deformation than the non-reinforced layers.
2
Chen, Cheng. "Discrete element modelling of geogrid-reinforced railway ballast and track transition zones". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13399/.
Testo completoAbstract (sommario):
Track deterioration has a serious influence on the safety and efficiency (speed restriction) of train operations. Many expensive, disruptive and frequent repair operations are often required to maintain the ballast characteristics due to the problem of settlement. Because of this, a geogrid solution that has proved to be a simple and economical method of reinforcing track ballast is widely used. This project presents an evaluation of the behaviour of geogrid-reinforced railway ballast. Experimental large box pull-out tests were conducted to examine the key parameters influencing the interaction between ballast and the geogrid. The experimental results demonstrated that the triaxial geogrid with triangular apertures outperforms the biaxial geogrid with square apertures and the geogrid aperture size is more influential than rib profile and junction profile. The discrete element method (DEM) has then been used to model the interaction between ballast and geogrid by simulating large box pull-out tests and comparing with experimental results. The DEM simulation results have been shown to provide good predictions of the pull-out resistance and reveal the distribution of contact forces in the geogrid-reinforced ballast system. The discrete element method has also been used to simulate cyclic loading of geogrid-reinforced ballast under confined and unconfined conditions. For the confined condition, box tests have been simulated on unreinforced samples and reinforced samples with different geogrid positions and geogrid apertures. The response of the ballast layer reinforced with geogrid under repeated loading agrees with experimental results. It was found that the optimum location of geogrid is 100 mm depth from base, and the triaxial geogrid outperforms biaxial geogrid. For the unconfined condition, cyclic loading of a trough of ballast has also been simulated, and the sample with the geogrid at 50mm from the sub-ballast layer performs best. It was also found that the used of two geogrids at both 50mm and 150mm from the sub-ballast gave a smaller settlement than using a single layer geogrid, or the unreinforced ballast. The geogrid reinforcement limits the lateral displacement in reinforced zone, which is approximately 50mm above and below the geogrid. Previous investigations have shown that the abrupt stiffness change in track support is often associated with accelerated rates of deterioration of track geometry, high maintenance demand, and poor ride quality. However, at present, there is no detailed understanding of the mechanisms of track geometry deterioration at transition zones. This work provides insight into the factors that can cause or accelerate track degradation at the transition zones, in order to identify and evaluate appropriate mitigation design. A simple track transition model with dimensions 2.1m x 0.3m x 0.45m was simulated by using PFC3D. In order to identify and evaluate appropriate mitigation methods, two kinds of transition patterns, including a single step change and a multi step-by-step change for subgrade stiffness distribution were tested. The influence of the train direction of travel and speed on the transition were also investigated. In addition, geogrid was used in the ballast layer to examine the effects of geogrid reinforcement.
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Laryea, Sydney N. K. B. "An investigation into the performance of railway sleeper types and geogrid-reinforced ballast". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/49708/.
Testo completoAbstract (sommario):
Reliability and safety represent key features of any successful railway system and compromising either has undeniable ramifications. Railway industry practitioners are continually challenged to deliver reliability and performance improvements whilst facing ever increasing service demands. These improvements are typically achieved through track maintenance and renewal activities, which have to be balanced against a requirement to reduce whole life-cycle costs. Research focusing on the optimisation of railway track components, which can then be translated to field practice, presents a real opportunity to reduce the frequency of disruptive and often costly track maintenance activities and ultimately prolong the life span of a railway track. A laboratory study of track performance with particular emphasis on railway sleeper type and geogrid type as the main variables has been undertaken. The types of sleepers investigated were the concrete monoblock, twin-block, timber, plastic, and steel sleepers. The geogrids variants tested were the SSLA30 biaxial and TX130 triaxial geogrids with square and triangular apertures respectively. Testing undertaken involved the application of low frequency cyclic loads to railway sleeper sections and full-size sleepers installed on a 300 mm thick ballast with and without geogrid reinforcement. Bending tests, friction tests and hardness tests were initially performed to characterise the material and mechanical properties of the sleepers investigated. Preliminary cyclic tests were conducted with a Box Test apparatus and Composite Element Test (CET) apparatus to approximate field conditions. Full scale tests were subsequently performed with the Nottingham Railway Test Facility (RTF) which is designed to provide a closer representation of field conditions and simulate the passage of an axle load over three sleepers. The outer sleepers in the test facility provided the necessary boundary conditions for the middle sleeper, which was the primary focus of the tests performed. Measures of track performance included vertical track settlement, trackbed stiffness and formation pressure. Additional measurements were made of the differential deflection along the length of the middle sleeper to ascertain if sleeper bending occurred during the tests. Linear elastic and finite element analysis to determine the pressure on top of the subgrade and at the sleeper-ballast interface respectively were performed for idealised sleeper support conditions. The results of the numerical analysis were compared with the RTF pressure plate measurements and estimates of subgrade pressure calculated using empirically derived equations. The results showed that sleeper type influences the permanent settlement that develops in a railway track as well as the magnitude of transient live loads that is transmitted to an underlying subgrade. In line with the permanent settlement results, it is also apparent that trackbed stiffness is a function of sleeper bending stiffness. Measurements of formation pressure and resilient sleeper deflection revealed differences between sleeper types with regards to their ability to retain the as-built geometry of a trackbed, underlining the importance of the sleeper-ballast interface characteristics and sleeper bending stiffness. Traditionally used empirical equations for determining subgrade pressure were found to be conservative compared to subgrade pressures determined using linear elastic analysis and measurements of made of the same using pressure plates in the RTF. Finite element analysis to determine the pressure distributions at the base of different sleepers for a range of support conditions found the shape and magnitude of pressures determined to be consistent with the sleepers’ bending stiffnesses suggesting that sleeper properties should be an important consideration when predicting track performance. The use of the biaxial geogrid installed 100 mm above the base of the ballast reduced permanent settlement for all sleeper types without any significant bias towards any one sleeper type. Additionally, the use of the biaxial geogrid resulted in the delayed deterioration of sleeper support for all sleeper types. The application of the TX130 geogrid resulted in increased settlement and increased deterioration of the as-built trackbed geometry for all sleeper types owing to the grid aperture which proved unsuited to the standard Network Rail ballast gradation. It was proposed that a triaxial geogrid with a larger aperture may offer better results. It was also suggested that sleeper choice that includes consideration for the relative performance of sleeper types is possible for railway practice although it must be commensurate with the intended use of the track with due regard to cost and safety. The research concluded that the concrete monoblock sleeper, which is currently the prevalent sleeper type in the UK (with and without the biaxial geogrid), for the conditions simulated, presents the best opportunity to minimise the maintenance requirements of a railway track.
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SINGH, VEER VIKRAM. "NUMERICAL ANALYSIS OF RAILWAY FORMATION WITH GEOGRID REINFORCED BALLAST AND BLANKET LAYER FOR HIGH-SPEED RAIL". Thesis, 2023. http://dspace.dtu.ac.in:8080/jspui/handle/repository/20067.
Testo completoAbstract (sommario):
India will launch a high-speed rail project to improve the travel time between cities in the
upcoming years. Upgrading its current speed of 180 km/h to a high speed of 360 km/h
will be a turning point in railway transportation. The Vande Bharat Express is the current
high-speed train that travels at a speed of 180 km/hr. India intends to start its first bullet
train by 2026. But as the travel speed increases, the stresses will increase on the existing
soil formation. The strains on India's railway subgrade component would significantly
rise with the addition of high-speed railways and bullet trains. The strains may cause
failure in more brittle soil. For thousands of years, soils are mixed with different fibers,
fabrics, and vegetation to improve quality and stability. Geosynthetics which are polymer
products are used in Civil engineering for decades. Utilizing geo-synthetics in the lengths
of currently weak formations is an alternate strategy to reduce the number of stress.
This paper gives a numerical analysis of the behavior of railway embankments built on
sand. Finite element software was used to simulate the model. Using the finite element
software PLAXIS 3D, a railway embankment's vertical deformations and stresses are
calculated under a moving train load of 90 kN. The speeds of the moving train are taken
as 180 km/h and 360 km/h for the modeling. Geogrid is installed as per the
recommendations by RDSO (2018). The blanket layer and ballast layer are reinforced
with geogrids at different depths. It was observed that on using geogrid in the different
layers, the deformations and the stresses could be reduced up to certain levels. After
analyzing the model, it can be concluded that Geogrids are beneficial in restricting the
deformations and the stresses at particular sections but further studies are required to
check the suitability of geogrids for the long run.
Capitoli di libri sul tema "GEOGRID REINFORCED BALLAST"
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Gu, Qiusheng, Kaihui Shi, Xuecheng Bian e Sindy He. "Behavior of Geogrid-Reinforced Railway Ballast Under Train Traffic Loads". In Lecture Notes in Civil Engineering, 689–701. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-77234-5_57.
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Ngo, Ngoc Trung, e Buddhima Indraratna. "Interface Behavior of Geogrid-Reinforced Sub-ballast: Laboratory and Discrete Element Modeling". In Lecture Notes in Civil Engineering, 195–209. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-6713-7_16.
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Fattah, Mohammed Y., Mahmood R. Mahmood e Mohammed F. Aswad. "Experimental and Numerical Behavior of Railway Track Over Geogrid Reinforced Ballast Underlain by Soft Clay". In Sustainable Civil Infrastructures, 1–26. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-61627-8_1.
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Chen, Cheng, G. McDowell e N. Thom. "Investigating geogrid-reinforced ballast using laboratory pull-out tests and discrete element modelling". In Advances in Transportation Geotechnics 2, 667–72. CRC Press, 2012. http://dx.doi.org/10.1201/b12754-101.
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Ngo, N., B. Indraratna e C. Rujikiatkamjorn. "A study of the behaviour of fresh and coal fouled ballast reinforced by geogrid using the discrete element method". In Geomechanics from Micro to Macro, 559–63. CRC Press, 2014. http://dx.doi.org/10.1201/b17395-100.
Testo completoAtti di convegni sul tema "GEOGRID REINFORCED BALLAST"
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Liu, Shushu, Hai Huang e Tong Qiu. "Behavior of Geogrid-Reinforced Railroad Ballast Particles Under Different Loading Configurations During Initial Compaction Phase". In 2017 Joint Rail Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/jrc2017-2218.
Testo completoAbstract (sommario):
A railroad ballast or subballast layer is composed of unbound granular particles. The ballast/subballast initial compaction phase occurs immediately the construction or maintenance of a track structure is finished. The particles are densified into a more compact state after certain load repetitions. Geogrids are commonly used in railroad construction for reinforcement and stabilization. Currently heavy haul trains are increasing the loads experienced by the substructural layers, which changes behavior of reinforced granular particles. This paper presents a series of ballast box tests to investigate the behavior of geogrid-reinforced unbound granular particles with rectangular (BX) and triangular (TX) shaped geogrids during the compaction phase. Three types of tests were conducted: one without geogrid as a control, one with a sheet of rectangular shaped geogrid, and the other one with a sheet of triangular shaped geogrid. The geogrid was placed at the interface between subballast and subgrade layers. A half section of a railroad track structure consisting of two crossties, a rail, ballast, subballast and subgrade was constructed in a ballast box. Four wireless devices - “SmartRocks”, embedded underneath the rail seat and underneath the shoulder at the interface of ballast-subballast, and subballast-subgrade layers, respectively, to monitor particle movement under cyclic loading. The behavior of the unbound aggregates in the three sections under two different loading configurations were compared. The results indicated that the inclusion of the geogrid significantly decreased accumulated vertical displacement on the ballast surface, ballast particle translation and rotation under a given repeated loading configuration. The results also demonstrated the effectiveness of the SmartRock device and its potential for monitoring behavior of ballast particles in the field.
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Mahmud, S. M. Naziur, Debakanta Mishra e David O. Potyondy. "Effect of Geogrid Inclusion on Ballast Resilient Modulus: The Concept of ‘Geogrid Gain Factor’". In 2018 Joint Rail Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/jrc2018-6126.
Testo completoAbstract (sommario):
Geogrid reinforcement of railroad ballast improves its structural response under loading, limits lateral movement of ballast particles, and reduces vertical settlement through effective geogrid-ballast interlocking. This improved performance can be linked to improved shear strength and resilient modulus properties. An ongoing research study at Boise State University is focusing on investigating the effects of different specimen and test parameters on the mechanism of geogrid-ballast interaction. A commercially available Discrete Element Modeling (DEM) program (PFC3D®) is being used for this purpose, and the effect of geogrid inclusion is being quantified through calculation of the “Geogrid Gain Factor”, defined as the ratio between resilient-modulus of a geogrid-reinforced ballast specimen and that of an unreinforced specimen. Typical load-unload cycles in triaxial shear strength tests are being simulated, and parametric studies are being conducted to determine the effects of particle-size distribution, geogrid aperture size, and geogrid location on railroad-ballast modulus. This paper presents findings from the research study, and presents inferences concerning implications of the study findings on design and construction of better-performing ballast layers.
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Qian, Yu, Erol Tutumluer, Debakanta Mishra e Hasan Kazmee. "Behavior of Geogrid Reinforced Ballast at Different Levels of Degradation". In Geo-Shanghai 2014. Reston, VA: American Society of Civil Engineers, 2014. http://dx.doi.org/10.1061/9780784413401.033.
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