5.9 PECULIARITIES OF THE CONSTRUCTION OF THE TOP STRUCTURE OF THE JOINTLESS TRACK

Abstract

In this article the materials on the structures of the top structure of the jointless track are given. Elements of rail braids and schemes of jointing of jointless track on reinforced concrete sleepers are described.

Key words: jointless track, rail braid, equalising span, reinforced concrete sleeper, block section, insulating joint.

The rail whip is the main element of the upper structure of the jointless track. Rail improvement is carried out in the course of a complex of interrelated measures carried out in the following main directions: increase of rail mass, improvement of its cross profile, improvement of manufacturing quality, as well as improvement of conditions of its operation on the track and improvement of the rail management system. Rail mass, transverse profiles, chemical composition of rail steel, and the technology of their manufacture are interrelated and together determine the operational qualities of the rail as an element of trackless track [1].

Rail whips of the jointless track of out-of-class lines and lines of the 1st and 2nd classes are made by electric contact welding from new heat-strengthened rails of R65 type with the length of 25 m without bolt holes. For the 3rd class lines, the spans can be welded from old-aged R65 rails that have undergone comprehensive repair; for the 4th and 5th class lines - from old-aged rails, including those that have been repositioned without repair.

Fig. 1. High-strength insulating joint: 1 - bolt; 2 - insulating sleeve; 3 - rail; 4 - metal lining; 5 - insulating gasket; 6 - nut; 7 - washer; 8 - adhesive paste; 9 - metal shell

At rail-welding plants, rails 25 m long are welded into bundles up to 800 m long. Welded joints are marked on the rail neck inside the track with two vertical stripes symmetrically with respect to the axis of the joints at a distance of 10 cm from them. In the middle of the whip, a vertical stripe is marked on the rail neck.

In order to create rail splices of the designed length, splices up to 800 m long are transported to the crossing and welded by a track rail-welding machine (TRWM). The joints after such welding are heat treated. The length of rail shoulders set by the project depends on local conditions: location of switches, bridges, tunnels, curves with radius less than 350 m, etc.

At present the lengths of railway track shoulders can be:

- from station to station (length of the crossing from 2 to 4 km) on sections with tonal rail chains or at welding of rail inserts with high-strength insulating joints (Fig. 1) with resistance to rupture not less than 2.5 MN;

- equal to the lengths of block-partitions (in the absence of tonal interlocking), as a rule, not less than 400 m.