The observational method—learning from projects Available to Purchase

Simplicity is at the heart of the observational method. Its basis is straightforward and it is an inherently natural approach to address uncertainty. The focus on prediction, monitoring, feedback, and teamwork also creates a strong opportunity for learning. Applications typically involve underground construction and temporary works. The objectives are to save cost or time while maintaining an acceptable level of safety. Application of the method was pioneered by Terzaghi and the principles were formally set down by Peck in his 1969 Rankine lecture. Possible modes of failure must be carefully assessed and controlled, particularly those of a sudden or brittle nature, or those that could lead to progressive collapse. Safety is essential and a high degree of certainty in project performance and schedule is generally required. The observational method overcomes the limitations of conventional design by evaluating feedback from actual conditions. This paper describes how simple measurements were central to resolving complexity and controlling risk. It presents three recent case histories featuring the ‘progressive modification’ approach which removed barriers that may have prevented the opportunity to apply the observational method.