An overview of the observational method: development in cut and cover and bored tunnelling projects : A. J. Powderham, Geotechnique, 44(4), 1994, pp 619–636

Abstract

An overview of the observational method is presented starting with a review of the criteria set out by Peck (1969). Against this background, recent applications and development of the method are described. Reference is made to case histories drawn from major tunnelling projects in the UK: the Channel Tunnel, the Docklands Light Railway and the Limehouse Link. These projects involved complex soil-structure interaction and geometry, and variable ground conditions-primarily stiff overconsolidated clays and sands. The uncertainties in predicting performance in these soils enhanced the potential for the success of the observational method. Although the method imposes onerous requirements it has great potential and deserves wider application. The primary objectives are savings in time and cost and the assurance of safety. Important additional benefits are also noted. The development of the 'progressive modification' approach is described. Such applications can address the limitations imposed contractually and b...