An analytical study of tunnel-pile interaction

Tunnelling under the foundations of structures is becoming more common because of the lack of available space for infrastructure, both above and below ground. The interaction between newly constructed tunnels and existing piled foundations is an important issue. This paper presents results obtained using a computationally efficient analytical approach which aims to estimate the effect that constructing a new tunnel will have on an existing pile. The method uses a spherical cavity expansion analysis to evaluate the end-bearing capacity of the pile, and cylindrical cavity contraction to estimate the decrease in the confining pressure and resulting reduction in pile capacity caused by tunnel volume loss. The paper extends previously published work using this method by considering the effect of tunnel location on the tunnel-pile interactions, examining different possible assumptions of soil stiffness used in the analysis, and by considering the effect that tunnel cavity contraction has on the friction along the pile shaft. (C) 2014 The Authors. Published by Elsevier Ltd.