Adaptive Management in Geotechnics

Among the many innovations developed by Karl Terzaghi and Ralph Peck in the early days of geotechnical engineering is the observational method, wherein construction and design procedures and details of a geotechnical project are adjusted based upon observations and measurements made as construction proceeds. The method has been applied to tunnels, embankments constructed over soft ground, and deep urban excavations, among other types of projects. Geotechnical uncertainties in these projects arise when predicting settlements caused by tunneling operations, rate of settlement of embankments constructed over soft soils, and ground movements arising during excavation. For example, when excavation support for a project in an urban area (Figure 1) is conducted under a design-bid-build contract, design-stage uncertainties related to prediction of ground movements include construction procedures and strength and stiffness of the affected soils. When attempting to predict rates of settlements — for example, when considering a staged process of embankment construction — there are substantial uncertainties in the field hydraulic conductivity as well as the compressibility of the affected soils. The observational approach allows for a design to be adjusted based on the observed performance of the actual construction process.