Abstract

London has one of the most extensive network and oldest sections of subway tunnels in the world. Deterioration of the linings and change in earth pressures with time is of great concern. In particular, the engineering condition of old cross passages between adjacent cast-iron tunnels is found to be critical by recent assessment. To evaluate the behaviour of underground structures, tunnel engineers usually rely on conservative analytical solutions but may overly underestimate the lining performance. In this study, two series of 3D numerical analyses on tunnel behaviour were conducted: 1) Structural analyses and 2) Geotechnical analyses. The structural finite element (FE) analyses considered tunnel structure in a detailed manner, aiming to produce a more realistic simulation on segmental lining behaviour subjected to load. On the other hand, the geotechnical study performed a soil-fluid coupled 3D numerical model of a cast iron cross passage. It was proposed to answer another question: how much actual soil load is applied on the tunnel linings both in short-term and long-term. Both series of analyses built up from their basic models and then gradually undertook to investigate more complicated engineering behaviours. The combined work of the structural / geotechnical analyses developed a deeper understanding of the long-term behaviour of underground structures.