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The principal function of the Permanent Way (Track) is accepting the imposed dynamic and static loads as cars, locomotives and trains run over the track. Type of the track depends on the track class including traffic density and maximum speed indicators. According to traffic density all tracks are divided into 5 groups (A, B, C, D, E), and according to maximum speed – into 7 categories.

e.g. Track 2A4 means: 2 – class

A- group

4 – category

 

Permanent Way is the structure consisting of th e rails, fasteners, sleepers and ballast.

The rail is running surface, carrier and guiding element at the same time. The parts of the rail are known as the head, the web and the foot (also called the flange).

The rails must meet the following requirements:

-high resistance to wear

-high resistance to compression

-high resistance to fatigue

-high yield strengths, tensile strengths and hardness

According to weight and profile the rails are classified into three main types:

 

Type	Weight, kg/m
R 50	51,67
R 65	64,72
R 75	74,71

 

Sleepers are a very important part of the track structure. They are used to support the rails and keep them at the correct gauge and to transfer the loads from the rails to the ballast.

 

The basic requirements are:

- minimum initial and maintenance cost;

- moderate weight (easy to handle);

- fixing and removing of fastenings should be easy;

- ability to resist shocks and vibrations;

- track circuiting must be possible;

- sufficient bearing area.

 

Three types of sleepers are used in railways: wooden, concrete and steel. The advantages of wooden sleepers are the following: cheap, easy to manufacture and handle, suitable for track circuiting, good dampening effect and correction to alignment is easy. At the same time the wooden sleepers have some disadvantages: short service life due to decay wear and attack of vermin, decreasing availability of timber.

Concrete sleepers are preferred for use nowadays. They are progressively replacing wooden sleepers because of long service life (40-50 years), stability of the track (due to greater weight and size), smother running of trains, lower maintenance cost. On the other hand concrete sleepers have some disadvantages: difficult handling (due to greater weight), high rigidity and current conductivity.

Steel sleepers are commonly used in tropical countries. Principal technical difficulties are the unsuitability of steel sleepers on electrified lines because of current leakage.

 

Ballast has to provide the following functions:

- to transmit the sleeper pressure to the subsoil as evenly as possible;

- to have high resistance to longitudinal and lateral sleeper displacement;

- to ensure the track elasticity in order to minimize dynamic forces;

- to provide effective drainage;

- to enable corrective actions in the track tamping, lining.

 

Some of the more commonly used types of ballast are: crushed rock, gravel and crushed gravel, rock wool, crushed shells and sand.

 

 

ballast n	балласт
carrying capacity	пропускная способность
construction cost	стоимость строительства
durable a	долговечный
ensure safety	обеспечивать безопасность
ensure v	обеспечивать, гарантировать
fasteners n	скрепления
fix v	закреплять
gauge n	ширина колеи
handle v	управлять, обращаться
increase v	увеличивать
keep v	удерживать, содержать
lateral a	поперечный
longitudinal a	продольный
maintenance cost	эксплуатационные расходы
meet requirements	удовлетворять требованиям
rails n	рельсы
remove v	удалять
resistance n	сопротивление
resistant a	устойчивый
sleepers n	шпалы
speed n	скорость
strong a	прочный
support v	поддерживать
transfer v	перемещать
transmit v	передавать
traffic density	грузонапряженность