Ballastless track on high-speed lines A guarantee for travel savety and comfort Prologue High–speed rail travel, as a fast connection between high-density population areas and as an alternative to frequently-overloaded air connections with an uncertain future, is gaining increasingly in significance all over the world. In the face of growing traffic density, critical views of life-cycle costs and significantly increa- sed requirements of the availability of railway tracks, there is an increasing demand for track systems which have a long lifetime, low service and maintenance costs and which also guarantee tra- vel safety and comfort. Ballastless tracks (BLT) have numerous advantages over the tradi- tional ballasted track, because of markedly reduced maintenance costs, longer duration of use, improved precision of the running track and the resultant quiet vehicle running. High speed and ballast The nature of the route requirements is changing, as a result of an increase in travel speed or axle loads. The load transported creates inertial forces and the particular more-frequent faults ari- sing from the rolling process are increasing dramatically. Altered deformation mechanisms with dynamic stimulation can result in major grain shifts during piling-up of ballast, which result in con- siderable impairment of the ballasted track and are responsible for uneven creeping and track displacement in the ballast bed. In addition, the track ballast stones are sucked up by vehicles at very high speeds (flying ballast) and may damage them. De- spite the choice of harder types of stone for ballast in high-speed traffic, maintenance costs are considerably higher. Maintenance expenses usually double for a route covered at 250 to 300 km/h as opposed to one covered at 160 to 200 km/h. Replacing the ballast on such routes becomes necessary after 300 million load tonnes (load tonnes = total of axle loads), instead of after 1 billion load tonnes previously. SSF Ingenieure GmbH Ingenieure SSF / Visualization ballastless track as prefabricated part design (Type Bögl FFB) in visualisierungen bit-better credits: Picture the Tunnel Katzenberg Ballastless track on earthworks in cutting area – Type Bögl FFB on new railway line Nuremberg – Ingolstadt Track axis Track axis (direction B) Train axis (direction A) Catenary mast Catenary mast made of concrete made of concrete 5.10 Distance of rails 4.50 5.075 4.77 at axis of deep drainage 4.77 at axis of deep drainage 4.40 4.40 4.00 catenary mast 4.00 catenary mast 3.80 3.80 3.70 at leading edge of catenary mast 3.70 at leading edge of catenary mast 3.25 3.25 2.80 2.80 1.625 1.625 Formation width 12.10 Superstructure ballastless track Superstructure ballastless track system Bögl system Bögl Surface of hydraulically bounded base layer and edges: Centre cover acc. to requirements bituminous emulsion (U70K) (asphalt, concrete and ballast) Lateral filling (ballast 32/56) Mineral aggregate mixture Rail UIC60 Cable trough, (gravel, sand, frost-resistant) Cable trough, size II Mineral aggregate mixture Rail fastener Ioarv 300 size II (gravel, sand, frost-resistant) Prefabricated slab TE MZR DN 250 acc. TE MZR DN 250 acc. to to hydraulic calculations hydraulic calculations Anti-freeze layer Anti-freeze layer Multipurpose tube PE-HD Soil formation Soil formation of filter material (drainage ballast 8/16), filter coating made of Geotextile Soil formation PFA 21 Tolerance Soil formation PFA 31/32 Tolerance Collective pipes DN 500 and concrete pipe socket joint The ballast bed is also sensitive to strong impurities which may night intervals. The track geometry can also be easily adjusted. It In addition, the standard types of construction for the ballastless as a result, track deformation at increasing speed, depend on the occur in the bulk transport of mineral ore and of coal, in heavy rail is a disadvantage that the track geometry is altered by the pas- track have a lower base height than the ballasted track. This is track geometry quality which is uneven along the track axis, be- transport. The lasting input of fine particles results in the ballast sage of the trains and has to be realigned periodically. This align- of particular advantage in minimising tunnel cross-sections or for cause of the different bearing elasticities of ballast and subgrade. components “floating” and this phenomenon has to be countered ment process causes the track to be raised and the rails have to structure clearances in the case of existing tunnel structures. It is by increased expenditure on ballast cleaning and tamping tasks. be installed at a lower height as in the case of a ballastless track. a disadvantage that the updating of an ballastless track cannot be In the case of the ballastless track, a multi-layered, largely rigid In this context, the term used is “lifting reserve”. The mechanised carried out during night intervals and that the type of construction supporting system is formed by differently-designed slabs and As a continuous, largely rigid transport system with clearly-spe- steps with heavy track maintenance machines also cause consi- is generally very sensitive to differential height alterations of the specified unbound base layers. The required track elasticity for cified storage conditions and uniform rigidity conditions, the bal- derable environmental stresses as a result of noise emissions and foundations, in view of the limited possibilities for adjustment of the distribution of the traffic loads and damping of the dynamic lastless track design does not possess these kinds of disadvantage dust formation.Ballastless tracks, which replace the maintenance- the rail support points. The initial investments are higher all-round effects is, in contrast to the ballasted track, achieved almost ex- and is thus primarily ideally suited to use both in high-speed rail intensive track ballast by a fixed design, guarantee a consistently than for the ballasted track. clusively by means of intermediate elastic layers in the rail faste- traffic and in heavy goods traffic under special conditions of use. good track geometry, and the maintenance of the highest stan- ning system or by elastically-supported sleeper bearing systems. dards in travel comfort at greatly-reduced maintenance expense. Functionality Thus a high level of homogeneity of vertical rigidity with precisely Comparison between ballasted and ballastless tracks Compared to the ballasted design, this design makes it possible In practical terms, the ballastless track’s functionality can be ex- definable and only slightly dispersing values is achieved in the The salient feature of the ballasted track is its low production cost. for greater lateral acceleration forces to be supported. The route plained by comparing it to the ballasted track. In the case of bal- design of the ballastless track. This is of the greatest importance The track can also largely be maintained automatically and during study can be more closely focussed and curve speeds increased. GmbH SSF Ingenieure credits: Picture lasted track the dispersion of vertical and horizontal stresses, and, for the interaction of vehicle and track in high-speed traffic. Ballastless track substructure Abutment of a viaduct with transition to earthworks The ballastless track design requires a foundation which is almost tively, an asphalt load-bearing layer, a frost-protection layer un- free of deformation and settlement. The ballastless track must derneath it and the bottom load-bearing layer (earth subgrade) normally be prepared to a depth of at least 2.5m beneath the slab with overall proven properties. by using suitable customised, quality-assured earthwork materi- The hydraulically-bound load-bearing layer or the asphalt one Construction pit for abutment and als. In cases of low load-bearing, soft or pulpy soil conditions, spe- protects the multi-layered system with the upper frost-protection launching truss construction cial foundation improvement measures are generally necessary to layer, by distributing the forces over a large area before dynamic E ≥ 120 MN/m2 v2 E ≥ 60 MN/m2 guarantee stability and usability or for settlement stability. stresses have their effect. The unbound load-bearing layer under- v2 With ballastless tracks on earthworks, an adequately-sized foun- neath the frost-protection layer consists of scarping, in the case of Partial excavation for Lean concrete C8/11 underneath abutment wing abutment construction constructed together with backfill dation in the form of a layered package is now provided for even specially documented embankments and as a foundation in cut- 2 Ev2 ≥ 45 MN/m and long-term low-deformation support for the track structure, tings, with equally documented properties, with soil replacement, consisting of a hydraulically-bound load-bearing layer or, alterna- if necessary. Topsoil removal around 0. 50 m, old ground formation E ≥ 45 MN/m2 v2 terracing of terrain, length approx. 5 m, height offset 1 – 1.5 m Earthwork requirements backfill and embankment Zone Permissible grain size Soil classification Compaction Bearing capacity Special requirements acc. to DIN 18196 1.I superstructure: KG 2 acc. to DBS 918 GW Dpr ≥ 1.0 E ≥ 120 MN/m2 on upper edge kf ≥ 1 x 10-5 m/s v2 Ballastless track on earthworks, in embankment area frost protection 062 (Germany railway earth formation layer standards) 2 1.II substructure max. thickness ≤ 20 mm GU, GT, SU, ST Dpr ≥ 1.0 Ev2 ≥ 60 MN/m on Soil binder mixture: base layer + after treatment of initial upper edge earth formation Binding agents ≥ 5 wt.% *) abutment filling material frost-resistant upper layer thickness ≥ 0.3 m, qu,M ≥ 0.8 MN/m2 qu,M ≥ 1.0 MN/m2 2 1.III substructure: max. thickness ≤ 20 mm GU*, GT*, ST*, SU*, Dpr ≥ 1.0 Ev2 ≥ 60 MN/m on Soil binder mixture: backfill after treatment of initial UL, UM, TL (TM, TA) and nA≤ 0.12 upper edge earth formation Binding agents ≥ 5 wt.% *) 7.12 7.12 material use acc.