Investigating property damage along Dublin Port Tunnel alignment

During the winter of 2002/2003, Dublin City Council received various complaints regarding aesthetic and serviceability damage of several residential buildings located within the highly populated residential area of Marino (1ṡ8 km north-east of Dublin centre, in the Republic of Ireland) allegedly caused by rock-tunnelling operations of the southwards tunnel-boring machine in the northbound tunnel carried out in execution of the Dublin Port Tunnel scheme. A holistic engineering–geological ground model for the area north of Dublin centre shows that structural elements crossing the bedrock have markedly affected the geological evolution and post-glacial drainage of the site, including the formation of buried valleys. A review of groundwater monitoring and tunnel construction records has allowed the causes of settlement at ground level to be identified. These include volume loss of the ground due to deformation and local failure of the tunnel excavation, dewatering of the bedrock and of coarse strata embedded in the Boulder Clay, resulting in the removal of fine soil particles, vibro-densification due to tunnel-boring machine ground-borne vibrations, and slow production and possibly consolidation of clayey strata. A comparison between the position of the properties where damages are being claimed and that of post-glacial rivulets and lakes, backfilled in the 1920s following a rapid expansion of Dublin suburbs, clearly indicates a direct linkage between the two.