C11/2003R Collapsing of railway bed in Urpia underpass site at Vantaa on 20 December, 2003
On Saturday December 20, 2003 a hazardous situation arose in train traffic at Vantaa, Finland when the railway bed had collapsed in a bridge worksite in the Urpia station underpass. A Pendolino train having left Helsinki at 5.30 hrs travelled past the site of the collapse at a speed of 30 km/h. On the place of the collapse the train ”made a low curtsey” but did not derail. The curtsey caused no personal injury or material damage in the train; the passengers only experienced an unpleasant feeling. The train driver immediately advised the remote controller of the situation by line-radio and asked him to close down the line. Also the adjacent track had to be closed at 13 hrs. The adjent track was reopened for traffic on Sunday at 14.00 hrs and the track on the collapsed bed, on Sunday at 20.15 hrs.
Already the evening preceding the incident, the railway bed in question displayed some irregularities: the passing trains communicated the remote controller notices of poor condition of the track. In fact as due to the poor condition of the track, a temporary speed limit was set up at the underpass. Then after midnight, the bed finally collapsed.
To repair the collapse of the railway bed, about 100 m of track had to be removed, and the collapsed support wall had to be dismounted and replaced by a new one. To reinforce the new support wall, a counterbed measuring a height of about 2.5 m and a width of about 15 m had to be constructed. The counterbed and the track understructure required about 450 m of soil to be transported to the site, as well as ballast for the bearing layer of the railway bed. In all, the upgrading and repair costs amounted to about €80,000.
The collapse of the railway bed that developed to a hazardous situation was caused by the lower part of the support wall of the bed having spread as the groundwater basin of the underpass had been constructed too close to the support wall. In fact the work of excavation of the groundwater basin had been commenced although this particular work phase failed to have an approved work plan. The system that monitors the condition of the track and train safety was unable to disclose the development of the settlement discovered in the track, to a collapse, and hence it could not prevent the travelling of the train to the site of the collapse.
In order to prevent corresponding hazardous situations and incidents, the Accident Investigation Board of Finland recommends that for each worksite an unambiguous written specification should be drawn up on the detailed responsibilities and obligations of the workers in terms of the operating condition of the track and on their rights to engage auxiliary personnel and set restrictions to traffic operation. Moreover the Accident Investigation Board recommends that in underpass and bridge worksites, for every work phase that impacts the stability of the railway bed and the track, an approved plan be required before the commencement of the work in question.