Effect of Cold Temperature on Shear Strength and Consolidation Properties of Deep Water Soft Marine Clays

Montana State University, Bozeman MT

Investigators

Abstract

In the Norwegian Sea and in many other extreme northern or southern latitude offshore areas, the temperature at the seabed in deep-water locations is continuously around 0 °C with the salt content of the pore fluid allowing the soil to remain unfrozen. The design of offshore facilities in these regions is generally governed by cases involving large lateral loads from waves or floating ice where the weak surficial soils become critical components. A precise estimate of soil strength and consolidation properties that avoids unnecessary conservatism can result in substantial construction and installation savings. Previous work has shown a significant effect of increasing preconsolidation pressure and increasing undrained shear strength with decreasing temperature for clay soils. Previous work has not, however, been performed on samples from cold temperature environments that have been maintained at cold in situ temperatures during sampling, storage and testing. Previous work indicates that allowing samples to warm to room temperature and then recooling to cold in situ temperatures may result in an overestimation of undrained shear strength and preconsolidation pressure. This project will compare the effect of temperature on laboratory strength and consolidation properties for samples taken from cold temperature environments that have been maintained at cold in situ temperature during sampling, storage and testing to those that have been stored at room temperature and then tested at both cold in situ temperature and room temperature. Two clays of different plasticity indices will be evaluated. This work will be done in collaboration with the Norwegian Geotechnical Institute, Oslo Norway, and has the potential to impact industry through reduced construction and installation costs by recognizing the effects of cold temperature on strength and consolidation properties. In addition, results from this project have the potential to impact engineering practice through sampling, handling, storage and testing practices that can account for the effect of cold temperature on soft clay properties.