ABSTRACT

Sediments from the continental slope and shelf edge in the northwest Gulf of Mexico were tested to determine their strength, stability, and consolidation characteristics. Consolidation tests for Sabine River delta samples and abyssal plain samples were used to aid in the interpre tation of the shelf and slope samples. To approximate in situ conditions, a direct shear-test machine was used to measure shear strength, and an Anteus Back-Pressure Consolidometer was used to determine consolidation.

The topography of this area has been attributed to local slumping of unconsolidated and unstable marine sediments. Although the Sabine River delta samples were underconsolidated, the continental shelf and slope samples were all overconsolidated. The overconsolidation of these samples and the high values of shear strength are assumed to be the result of low deposition rates and incipient cementation of the mineral grains. Analysis of the void ratio versus log-pressure consolidation curves indicated that the sediments were "sensitive," and therefore, relatively undisturbed by the sampling process.

The shear strength ranged from 0.05 TSF for the upper meter of sediment to over 0.5 TSF for a simulated depth of 20 meters. The shear strength tests indicate that the slope sediments should be stable to great thicknesses on even higher slopes than exist in this area.