Geotechnical properties of near‐surface sediments from the Northwestern Alboran Sea slope (SW mediterranean): Influence of texture and sedimentary processes

20 pagesThe near-surface deposits of the NW Alboran Sea slope are grouped into two main textural types: clay-dominant and silt/sand-dominant. Clayey deposits underlie areas of open, very low gradient slopes (aug. 0.55°), whereas silty and sandy deposits occur on higher gradient slopes (aug. 2.65°) and near the walls and floors of submarine canyons and channels that incise the slope. These sediment types can also be distinguished on the basis of their geotechnical properties. Clayey sediments have high water content (avg. 70% of dry weight) and plasticity (avg. wL: 70%, lp: 45%) and low vane shear strength (avg. 6 kPa); they are highly compressible (avg. Cc: 0.45) and are overconsolidated (avg. OCR: 3.8). During triaxial compression, the clayey sediments show contractive behavior and have typical normalized undrained strength (avg. Su / σ‘c: 0.42) and effective friction angles (avg. ø’: 36°). In contrast, silty sediments have lower water content (avg. 30%) and plasticity (avg. wL: 35%, Ip : 10%), but only slightly higher vane shear strength (avg. 8 kPa). They are normally consolidated to slightly overconsolidated (avg. OCR: 2) and are almost incompressible (avg. Cc: 0.15). During triaxial compression the silty-sandy sediments show dilative behavior, have higher normalized undrained strength (avg. Su/σ‘c: 1.1), and have effective friction angles (avg. ø’: 39.5°) greater than the clayey sediments. Increased proportions of silt and sand critically influence the physical properties and geotechnical behavior of the sediment. Sedimentary processes responsible for each sediment type directly control their physical properties. Fine-grained sediments deposited from low density mass flows have open structures and plastic behavior and are dominated by matrix effects. In contrast, coarser grained, polimodal sediments, which result from high density flows, have a more rigid structure and are dominated by grain-to-grain interactions. © 1994 Taylor and Francis Group, LL