Mitigation of ground borne noise in rock railway tunnels—Part I: Track design and simulation

Abstract

Railway trafc in shallow depth rock tunnels can give unacceptable levels of ground borne noise in buildings above the tunnel. For such a tunnel under construction in Norway a project involving full scale testing was commissioned by the Norwegian Rail Administration (JBV), with the aim of designing the most cost effective track that satised the prescribed residential sound levels. Evaluation of various track designs was based upon the results of a numerical model of the wagon-track-tunnel system. This model and the corresponding input parameters are the focus of this rst part of a two part paper; the second part concentrates on the full scale tests. The numerical model presented herein is a one dimensional model of the suspended railcar, rail, sleeper, railway substructure (ballast, ballast mats and backll) and tunnel oor. The model comprises mechanical mass-spring-damper elements and geolayer elements embodied by the one dimensional wave equation. Verication against results from other contributors is presented, and the model is shown to give high quality results with a modicum of computation. The properties of the constituent track materials are also discussed in this paper, with particular attention paid to the in-situ stress conditions.