Revised requirements for stiffness of ballast mats in new Norwegian railway lines

Abstract

In the Oslo region new railway lines which include many and long tunnels below dwelling areas, now are constructed and planned. All the tunnel tracks are ballasted track. Ballast mats are the preferred remedial actions for reduction of ground
borne noise. In the paper the work which lead to revised requirements for ballast mats are presented. Ballast mats having a stiffness of Cdyn,3 Hz = 0.01 N/mm3 have been installed in the most critical sections of the new tunnels. The required thickness of ballast for this track is 550 mm between sleeper underside and ballast mat surface. In the paper the definition and measurement method for maximum structure borne noise levels are given. The paper also shortly presents the results of a social survey on annoyance from this kind of noise, the calculation methods for structure borne noise transmission, and a method for measuring the vibration transmission from the tunnels before the track is installed.