Deep settlement study

5 August 2011

Engineers from the Tongji University and CCCC Second Highway Consultants Co have published findings of a study into the causes, effects and patterns of deep settlement during TBM tunnelling projects. The work not only considered ground loss, such as by TBM overcutting, but also dispersal of excess pore pressure, shrinkage of grouting slurry, surcharge and building gravity loads above the tunnel.

The study’s findings established five typical patterns of deep settlement distribution by various combinations of these factors. Some of the factors combined and some counteracted each other. Multi-position extensometers were used to monitor the effects of the shield machine passing beneath a building.

The work, which was supported by Shanghai Science and Technology Development Funds and the Shanghai Leading Academic Discipline Project, was carried out by Shao-Ming Liao and Yao-Yao Fan of Tonji University, and Jin Li of CCCC Second Highway Consultants Co. A report appears as the paper ‘Deep settlement patterns for evaluating environmental impact of shield tunnelling in soft ground’, presented to the World Tunnel Congress in May in Helsinki pp. 1009-1017.