Recent Developments in the Pipe-in-Pipe Model for Underground-Railway Vibration Predictions

Abstract

The Pipe-in-Pipe (PiP) model is a fast-running model that calculates vibration levels from an underground railway within a layered halfspace. This model contains many simplifying assumptions, but its fast computation time makes it useful as an early design tool. Recent developments in PiP have focused on quantifying the effect of various features of the underground environment that are commonly disregarded in railway vibration models. We present a summary of the work done on seven such features: soil inhomogeneity; inclined soil layers; irregular contact at the tunnel-soil interface; track with discontinuous slabs; the presence of piled foundations; second (twin) tunnels; and sources of track roughness. All of these features can introduce inaccuracy of at least 5 dB into vibration predictions. Two examples of other uses of PiP are presented: a theoretical study of coupling effects between railways and buildings; and a manufacturer’s investigation into the effects of track resilience. Current and future research directions are also discussed.