The observational method, used so successfully by Terzaghi in applied soil mechanics, often permits maximum economy and assurance of safety, provided the design can be modified as construction progresses. The essential features of the method are set forth and examples are given of its application. The method is not without its pitfalls and limitations. It should not be used unless the designer has in mind a plan of action for every unfavourable situation that might be disclosed by the observations. The observations must be reliable, must reveal the significant phenomena, and must be so reported as to encourage prompt action. The possibility of progressive failure may introduce a serious element of uncertainty. In spite of the limitations, the potential for savings of time and money without sacrifice of safety is so great that every engineer who deals with applied soil mechanics needs to be informed of its principal features. © 1969, Thomas Telford Ltd. All rights reserved.
