BUDAPEST METRO LINE 4 FEASIBILITY STUDY

Oktober 1996

Track

Introduction

This chapter defines the main principles proposed for the design of the tracks of Budapest Metro line 4. It includes the following paragraphs:

• alignment,
• different types of tracks,
• points and crossings,
• conductor rail.

The main characteristics of the operating system are:

• train maximal operating speed: 80 km/h
• train maximal axle load: 16 tonnes
• train power supply: 750 volts DC and third rail,
• track gauge: 1.435 m.

The design criteria considered are those described Chapter C-2.

Definition of the different types of track laying

Tracks are mainly located in tunnel and very partly in open air and laid on a track bed delivered by the Civil Works.

In tunnel, the track is recommended to be of a ballastless an antivibrating type. In open air, the track bed can be, according to the choices of the Civil Works, a road bed or a concrete invert, at grade level, on which the tracks shall be laid on ballast, refer to the below Figures C-12 & 13.

Antivibrating ballastless track in tunnel

• Justification of the proposed ballastless track

The specified track is a track without rigid connection with the invert (no elements imbedded in the concrete of the invert) and using concrete sleepers, useless elements of the railway track.

Called "STEDEF track", it has been used by the Paris metro network since 1975 for all its new tracks in tunnel (about 60 km of single track in operation) after tests of different types of ballastless tracks (direct fastening on concrete with 1 or 2 elastic stages, Cologne Eggs, etc.). It is also world wide used by many other underground networks (of which recently Cairo City and Seoul) and railway tunnels, with a total of about 400 km of single track.

Compared to a conventional ballasted track, the vibratory speed reduction of the STEDEF track is about 10 dB; in some special cases it can increased to 14 dB by adding a second micro-cellular rubber pad.

Brief description of the proposed ballastless track (refer to Figure C-14)

The STEDEF ballastless track includes two elastic stages separated by an heavy inertia support.

The first stage, designed for medium frequency vibration damping, consists of an elastic pad placed under the rail. The rail is fixed by elastic clips fastened to the support. The heavy inertia support consists of usual concrete sleepers, preferably twin-block (2 concrete blocks linked by a steel bar).

The second elastic stage, designed for law frequency vibration damping, consists of a micro-cellular rubber pad placed beneath the block or the head of the sleeper. An elastic boot wraps the pad and the lower part of each sleeper block (or head) and is kept by an filling concrete up to 10 cm above the lower part of the sleeper. The track is set up in its final position by means of adjustable wedges giving a perfect stability and allowing to obtain the required geometrical precision.

The embedding concrete, put in place after the track adjustment, does not include any steel reinforcement or connection steel pin , except for possible steel bar or wire mesh for drainage of stray current.

Outside ballasted tracks

The ballasted track will be laid either on a subgrade of a road type or on a concrete invert whose profile, slope of embankment, ditches and materials will be defined by the Civil Works.

The track will be equipped with concrete sleepers (excepted in some short sections between points and crossings if they are equipped with wooden sleepers) and elastic fastenings allowing rail welding in CWR on main tracks.

Sleepers will be inserted in a ballast layer whose theoretical profile principle is defined by the below Figure C-10. The ballast normal thickness between the upper part of the subgrade and the lower part of the sleepers will be:

• 0.30 m for a track with concrete sleepers on a concrete bed,
• 0.25 m for a track with concrete sleepers on a subgrade,
• 0.20 m for a track with wooden sleepers on a subgrade,
• 0.15 m for the tracks in the workshops.
  

At the location between an underground ballastless track and an open-air ballasted track on a subgrade, the ballasted track will continue over 30 metres inside the tunnel.

Between a track laid in tunnel on a concrete invert and a track laid outside on subgrade with ballast, an inclined slab located under the ballast will ensure the rigidity transition.

Points and crossings

Introduction

Points and crossings are made up of turnouts which are used alone or in crossovers, simple or double (scissors crossings).

Three types of turnouts are defined:

• turnout for the main line,
• turnout for the workshops,
• turnout for possible diversion on a branch line.
  

As there are no international standards defining an unified range of points and crossings, the following characteristics could be replaced by those of similar equipment possibly used in Hungary. In this case, these characteristics shall be as similar as possible: same tangent, speed on the diverted track at least equal to the specified values, same technology.

General characteristics

The points and crossings shall be laid without cant. The layout of the diverted track shall be designed in order to limit the cant deficiency to 100 mm and the variation of cant deficiency to 90 mm/s. The design shall also allow their setting up in Continuous Welded Rails (CWR).

The foreseen general characteristics are given in the following Table C-9:

Use	Tangent	Radius of the diverted track m	Speed on the diverted track km/hr	Length m
Turnout on main line	1/8	250/150	35	29
Cross-over on main line	1/8	250/150	30	46
Turnout in workshops *	1/6	90	25	19
Turnout for branch line	1/14	760	60	60

* Except for the test track turnouts which should be of the tg 1/8 type.

Operation, locking and control of the points tongues

All the points shall be operated by electrical motors whose specification shall be carried out by the Signalling.

All the points and crossings crossed through by passengers trains facing the point, or by any train at a speed 40 km/hr, shall be equipped with individual, and untrailable, devices locking each tongue on its stockrail. The operation of the locking device shall be performed by the moving of the tongue, and the device shall also wedge each tongue in its open position.

Each tongue position shall be controlled by a device with electrical contacts allowing to make sure that each tongue is well in contact with its stockrail.

Conductor rail

Trains are supplied in 750 volts DC by a third rail. Vehicle collector shoes will come into contact with the lower part of the rail.

The conductor rail shall be a steel, law carbon rail fixed on the track by monobloc insulators and shall be provided with a protective cover fastened on the rail itself in order to give a maximum protection against accidental contact.

The rolling stock underframe gauge shall be specially designed in order to take into account that the ends approaches of the third rail are going upwards