Using probabilistic methods to measure the risk of geotechnical site investigations

Abstract

The site investigation phase plays a vital role in foundation design where inadequate characterization of the subsurface conditions may lead to either an under-designed solution, resulting in failure, or an over-designed solution that is not cost-effective. Whether the design is for a building foundation or for a retaining wall for an unstable slope, an investigation of some form is required to predict the soil properties in order to estimate the soil response to applied loading. However, determining whether the scope and type of an investigation is suited to the site and the requireddesign situation is not a straightforward task. Typically, the type and scope of an investigation is determined by a senior geotechnical engineer within the budget and time constraints placed on a project. However, it is rarely known, in other than subjective terms, whether the type and scope of the investigation is adequate or suitable. In order to account for this, as well as for the complex nature of soil behavior under load, geotechnical engineers use higher factors of safety than are otherwise used in other forms of engineering, such as structural engineering.