Sea-Floor Characteristics and Dynamics Affecting Geotechnical Properties at Shelf-Slope Breaks: ABSTRACT

Abstract

Shelf-break geotechnical and sea-floor stability investigations are rare but such studies offer challenging scientific and engineering opportunities in a unique sea-floor environment. The uniqueness stems from the highly variable sea-floor properties, morphology, and dynamic processes. Some characteristics and processes at the break are nonexistent in nearshore environments where most of our understanding and experience exists. The geotechnical properties and stability of submarine deposits are strongly influenced by the nature of the geologic environment, dynamic processes, sediment type, and sea-floor slope. Sediment properties and sea-floor morphology at the break can be highly variable over relatively short horizontal and vertical distances. The outer shelves and slopes off Cape May, New Jersey, and the Mississippi delta are among the few geotechnically investigated continental margins. Off Cape May, mobile shelf sands contribute to sandy silts overlying the upper slope muds which occasionally exhibit structures and geochemical properties suggesting slope-creep processes. In contrast, the Mississippi delta's shelf-slope break is characterized by clays and silty clays that mobilize as mudflows which encroach upon the upper slope. Geotechnical properties such as shear strength and water content display striking differences between the two areas as a function of regionally differing dynamic processes, sedimentation rate, type, and texture. End_of_Article - Last_Page 899------------