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A laboratory study on improvement of railway ballast using geosynthetics

Indraratna, Buddhima (Department of Civil Engineering, University of Wollongong); Khabbaz, Hadi; Salim, Wadud Source: Geotechnical Special Publication, n 126 I, Geotechnical Engineering for Transportation Projects: Proceedings of Geo-Trans 2004, 2004, p 617-626

ISSN: 0895-0563 CODEN: GSPUER

Conference: Geotechnical Engineering for Transportation Projects: Proceedings of Geo-Trans 2004, Jul 27-31 2004, Los Angeles, CA, United States Sponsor: American Society of Civil Engineers, Geo-Institute, ASCE

Publisher: American Society of Civil Engineers

Abstract: The classical railway track basically consists of a flat framework made up of rails and sleepers, which are supported on ballasted track formation. Ballast particles breakdown and deteriorate progressively under heavy cyclic rail loading. Moreover, excessive consolidation settlement and progressive shear failure may occur in soft track formation under repetitive stresses. In order to rectify these problems, frequent maintenance operations are generally required in ballasted track. In order to minimize the deterioration of track substructure and also to reduce maintenance cost, the use of various types of geosynthetics including recycling of waste ballast have been studied in the laboratory. The prospective use of three types of geosynthetics (i.e. geogrids, geotextiles and geocomposites) in enhancing the performance of fresh and recycled ballast has been examined. The aspects of deformation and degradation of ballast under cyclic loading have been studied using a large-scale prismoidal triaxial rig. The research findings reveal that recycled ballast stabilized with geosynthetic reinforcement has a good potential for resilient track construction and for reducing the cost of track maintenance. The experimental findings may be beneficial to the railway engineers and encourage them to upgrade current tracks based on these innovative techniques. (8 refs.)









The Nottingham railway test facility, UK

Brown, S.F. (Nottingham Centre for Pavement Engineering, School of Civil Engineering, University of Nottingham); Brodrick, B.V.; Thom, N.H.; McDowell, G.R. Source: Proceedings of the Institution of Civil Engineers: Transport, v 160, n 2, May, 2007, p 59-65

ISSN: 0965-092X

Publisher: Thomas Telford Services Ltd
Abstract: A major new full-scale laboratory test facility for railway trackbeds is described. The equipment was designed and developed by the research team at the University of Nottingham, and has been used initially for two projects concerned with the performance of railway ballast. One dealt with the application of geogrid reinforcement to reduce the rate of settlement under repeated vehicle loading, and the other was concerned with ballast degradation both under loading and tamping. The facility allows application of cyclic loads of up to 94 kN directly to the sleepers using a loading system constructed in a laboratory test pit. Three sleepers are involved, and loads are applied by servo-controlled hydraulic actuators with their inputs phased to simulate a moving wheel. A tamping bank can be attached to the loading frame to perform the normal maintenance operation. Instrumentation is used to measure the permanent track settlement and the transient deflection of the central sleeper. Earth pressure cells can be installed in the subgrade to monitor transient stresses. Facilities are incorporated to determine the degree of particle degradation and to control the subgrade water table level. The design and performance of the equipment are described, together with some typical results from early experiments. (6 refs.)





Environmental values

Anon Source: Highways, v 72, n 9, November, 2003, p 30-31

ISSN: 0142-6168 CODEN: HGHWEM

Publisher: Alan Limited
Abstract: Glynn Valley A38 stabilization project was discussed. Engineering consultant, Mott MacDonald, used Tensar geogrids to reinforce the road structure and provide a secure steep vegetated slope to the embankment. After excavation of the loose embankment material the exposed slope supporting the railway was reinforced with 8 m long soil nails. The embankment face was finished by wrapping the ends of the Tensar geogrid reinforcement around topsoil filled hessian bags, seeded with grass.







Strain measurement of geogrids using a video-extensometer technique

Shinoda, Masahiro (Railway Technical Research Institute, Found. and Geotechnical Engineering, Structures Technology Division); Bathurst, Richard J. Source: Geotechnical Testing Journal, v 27, n 5, September, 2004, p 456-463

ISSN: 0149-6115 CODEN: GTJODJ

Publisher: American Society for Testing and Materials

Abstract: The paper describes a novel technique to record displacements and compute local strains at the surface of typical geogrid soil reinforcement products using a noncontact high resolution digital CCD camera (video-extensometer) technique. Specimens of biaxial polypropylene (PP) geogrid, knitted polyester (PET) geogrid, and uniaxial high-density polyethylene (HDPE) geogrid were subjected to in-isolation wide-width strip tensile loading under constant rate of strain (CRS), constant load (creep), and stress relaxation load paths. The specimens were gripped using a set of split roller clamps. Targets painted on the surface of the specimens were tracked in both vertical and horizontal directions using a commercially available CCD camera with ancillary hardware and software. The paper examines repeatability of the test methodology and demonstrates the ability of the method to record strains at high resolution up to rupture and to identify nonuniform distribution of axial and lateral strains in geogrid specimens. © 2004 by ASTM International. (16 refs.)








FEM-analysis and dimensioning of a sinkhole overbridging system for high-speed trains at Grobers in Germany

Alexiew, Dimiter (Huesker Synthetic GmbH and Co. KG); Elsing, Andreas; Ast, Wolfgang Source: Rail International, v 33, n 11, December, 2002, p P4-P13

ISSN: 0020-8442 CODEN: RAIIAF

Publisher: International Railway Congress Association
Abstract: Roads and railroads crossing sinkhole areas are a problem of increasing importance. The range of possible solutions is dominated by geosynthetic reinforced systems. Although some analytical procedures are available for design, for an increasing number of cases they are not precise enough or not applicable. Numerical procedures provide some help. Based on the project Grobers on the new high-speed rail link Leipzig-Halle such a case is discussed. The bearing system bridging sinkholes consists of a cement-stabilized soil block with basal geogrid reinforcement. The main problems of design were to check both serviceability and stability of the system for a pre-failure and a partial post-failure state as well. A commercially available FEM-code could not solve all problems, e. g. the post-failure analyses. Thus, analytical procedures were developed and applied. An overview of all checks and corresponding FEM and analytical calculations is shortly presented. The final project specifications were based on the design described. The bearing system is already built. (13 refs.)



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