VIBRATION EMISSION FROM RAILWAY LINES IN TUNNEL - PART 2: PREDICTION

A method for characterizing and predicting vibration emission from railway lines in tunnels is presented in two companion papers: This paper corresponds to Part 2 and concentrates on how to predict a new situation from a measured existing one, while Part 1 is mainly focused on experimentally characterizing an existing situation. The transfer of an existing situation to a new one is performed using two different simplified 2D models representing the train/track/tunnel system: one is analytical (software S-RIV, developed at SYSTRA) with the train represented by a set of springs and masses, and the other is based on the wave approach (software VibraFer, developed at CSTB) with the train represented by its un-sprung mass. The situation change is expressed in terms of difference in the force density applied to the tunnel invert between the original and the new situations, the source being characterized by a line of un-correlated forces. An existing situation has been experimentally characterized (see Part 1) through measurements of both a set of track and tunnel transfer mobilities, as well as the track and tunnel vibration responses during train pass-by events. The track models are first calibrated from these measurements and then used to estimate the difference in force density applied to the tunnel between a new situation and the original one. A new situation can include changes in train types, train speed, rail/wheel unevenness, track system and tunnel mobility.