Lessons learned from field measurements in tunnelling

Over the past two decades, various numerical methods of analysis have become popular in the field of geotechnical engineering. However, the accuracy of numerical analyses varies considerably, primarily because of the uncertainties involved in modelling ocmplex geological formations with the complex geomechanical characteristics of soils and rocks. Field measurements carried out during construction can be used to overcome this difficulty. The author reviews ways of using measurement results to improve numerical analyses, including the determination of a “hazard warning level” for each measurement item prior to the start of construction, the use of back analysis. The importance of choosing a proper model is also discussed.