Buckling of Rail Track

Buckling of Track

A rail track is liable to get distorted, particularly in hot weather when the compressive forces in the track exceed the lateral or longitudinal resistance of the track. The buckling of the track is a matter of grave concern as it may lead to derailments and even serious accidents.

1 Causes

A track can buckle due to the following reasons.

(a)  Inadequate resistance to track due to deficiencies in the ballast

(b) Ineffective or missing fastenings

(c)  Laying, destressing, maintaining, or raising the track outside the specified rail temperature range, especially is hot weather

(d) Failure to lubricate the SEJs in time

(e)  Excessive creep, jammed joints, sunken portions in a welded track

2 Symptoms

Buckling in a track becomes noticeable when the track displays the following symptoms.

(a)  Presence of kinks in the track

(b) Absence of gaps in the SWR portion of the track in the morning hours of hot days.

(c)  Expansion/contraction at SEJ is ±20 mm more than the theoretical range given in the LWR manual

(d) High percentage of hollow sleepers

3 Precautions

Buckling can be avoided by taking the following precautions.

(a)  Proper expansion gaps as specified in the manual should be provided in the SWR portion of the track.

(b) As buckling is likely to occur between the 11th and 17th hour of the day,

rosters of key men should be so adjusted that there is proper patrolling of the LWR portions of the track when the temperature exceeds t_m + 20 o C.

(c)  No work of track maintenance including packing, laying, aligning, major/ minor realignment of tracks, screening of ballast should be done outside the specified temperature.

(d) Wherever the track structure is weak and vulnerable to buckling, immediate action should be taken to strengthen by the provision of extra shoulder ballast, increase in sleeper density, provision of adequate anticreep fastenings, replacement and tightening of missing and loose fastenings, etc.

4 Actions

As soon as a tendency towards buckling is detected in the track, traffic should be suspended and the track should be fully protected. The track should be stabilized by heaping the ballast on the shoulders up to the top of the web of the rail. When buckling takes place, traffic on the affected track should be suspended and remedial work should be carried out in the following stages under the personal supervision of a PWI.

a)     The temperature of the rail is brought down as far as possible by pouring water on the rails.

b)    Emergency or permanent repairs and destressing should be carried as specified in the LWR manual.

c)     In the case of fish-plated or SWR tracks, a gentle reverse curve may be provided in the rear of the buckled track to ease out the stress. The buckled rail should then be cut at two places that are more than 4 m apart. The track should then be slewed to correct the alignment and rails of the required lengths should be cut and inserted to close the gaps.