Application of geotechnical data to resource planning in southeast Alaska.

Abstract

Recent quantification of engineering properties and index values of dominant soil types in the Alexander Archipelago, southeast Alaska, have revealed consistent diagnostic characteristics useful to evaluating landslide risk and subgrade material stability before timber harvesting and low-volume road construction. Shear strength data are summarized and grouped by Soil Conservation Service soil series, by the Unified Soil Classification system, and by geologic origin. Such groupings allow the selection of strength parameters for slope and subgrade stability analyses based on existing knowledge of the terrain and on available inventory data. Parameters are expressed by mean and minimum values so that both average and conservative evaluations can be made, depending on management requirements. Engineering procedures were used to incorporate the parameters into planning and project-level investigations to identify areas of unstable terrain, to assess levels of landslide risk, and to define suitability of materials for road construction.