TRACK SYSTEM

(BALLASTED TRACK vs. FIXED TRACK)

Introduction

As an alternative to common ballasted tracks, slab tracks were developed to meet the requirements for combined high-speed and heavy-load traffic.

This construction method allows replacing the old ballast layer by a load-spreading concrete base-plate.

The common ballasted track does not ensure stable track-position under present and expected future conditions with an acceptable amount of servicing.

Numerous tests concerning the comparison between fixed track and ballasted track have been made.

The tests showed that the ballasted track enables a more cost effective construction while the maintenance is costly, the fixed track construction is more expensive but reduces the maintenance costs.

One reason for the cost-exceeding of the fixed track for example is that the development of slab track constructions still on the way.

System “Ballasted Track”

The ballasted track is a tried and proven mature technology and is commonly used in major railway systems. The accuracy and permanence of track geometry is sufficient. The track resilience is hardly to exceed. The system will be designed to have a minimum life of 40 years, if the velocity of trains doesn’t exceed 160km/h.

Economical effects on the civil work portion concerning the necessity of an eventually slightly increased tunnel diameter by using the ballasted track should be considered due to greater execution height as well as larger cross sections of the structure beams due to its additional weight.

System Components

Ballast :

The ballast distributes transversal and longitudinal forces, damps rail-borne vibrations and drains occurring surface water.

It’s highly resistant against crushing, grinding and pounding. The material will be weather resistant and of a homogeneous structure.

The minimum height of the ballast is 30 cm between soil and sleeper-bottom.

Wooden Sleeper and Fastening :

Wooden sleepers and ballasted track is a common combination in track laying. These sleepers are hardwood-made (e.g. oak) and capable for recreation, when worn-out. The sleepers are impregnated against rottenness and parasitic infestation.

The sleepers will be designed for load characteristics consistent with the design of the passenger and service vehicles and with the performance requirements of the system. For increasing the horizontal track stability, sleeper anchors can be used.

The fastening system ensures permanent tension by means of elastic spring clips. All fastening components are already preassembled onto the sleeper, so the complete sleeper can be laid mechanically.

For quick replacement of the rail, tension clamps are easy to remove in preassembled position.

Concrete Sleeper and Fastening :

Concrete prestressed monoblock sleepers form the support for the ballasted track. They are designed to have a minimum life of 50 years.

The sleepers are used on ballasted track and designed for load charactistics consistent with the design of the passenger and service vehicles and with the performance requirements of the system hardwood timber sleepers. In addition, concrete sleepers are also foreseen to be equipped with anchors.

The rail fastening is an elastic system, which is capable of attenuation of rail borne vibrations. This consists of two parts :

l   the elastomeric pad

l   the elastic fastening

The rail rests directly on the concrete sleeper with only a plastic pad in between. The position of the rail is fixed by plastic angled guide plates. Positive permanent tightening between rail and sleeper is achieved by using tension clamps. Sleeper screws are inserted in plastic dowels, which have been preassembled while fabricated into the concrete sleeper.

Construction Operation

Installation :

The ballasted track system is a high mechanized construction. This ensures low costs and labour expenditure.

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