Since first reading about the Heathrow Express tunnel collapse, there have been references to elaborate monitoring equipment and virtually ignored readings.
I understand the reason there were no injuries or fatalities was not because of the equipment but a 'mark 1 eyeball', ie an experienced workman, who noticed untoward movements in the excavation just in time to get everybody out.
There is no point in installing monitoring unless a chain of command or plan of action is set out which ensures that: (a) the results are seen by someone who understands the readings and their implications; and (b) someone has the authority to act upon the results, sufficiently quickly, if and when a hazard is identified. In this respect, simpler monitoring with readings that are understood may be better than elaborate monitoring that is not.
I think it was John Dunnicliff, a frequent contributor to Ground Engineering, who recommended the 'green-amber-red' approach to viewing and appraising the results of monitoring.
Eric Gray, Warwickshire