Normalized mechanical properties of resedimented Gulf of Mexico clay from Integrated Ocean Drilling Program Expedition Leg 308

Abstract

During Integrated Ocean Drilling Program (IODP) Expedition Leg 308, many Whole Core Samples were recovered from the Ursa Basin in the Gulf of Mexico. Post-cruise geotechnical testing found these samples to be highly disturbed due to the sampling process. This research will determine mechanical properties of laboratory Resedimented samples created using recovered Leg 308 sediment. A seven triaxial compression tests, Ko consolidated, were performed to ascertain these mechanical properties as a function of consolidation stress. Consolidation stress for these specimen ranges from 150 kPa up to 1,200 kPa. Axial strain induced on the soil during laboratory consolidation was approximately 60%. Results show that with an increase in Ko values there is a decrease in undrained shear strength, which is in accord with research completed on resedimented Boston Blue clay (RBBC) at MIT and also intact material that was recovered from this expedition. Undrained shear strength of the material is between 0.24 and 0.27, which is weaker than what is expected, according to SHANSEP. Friction angle of the material ranges from approximately 220 to 260. There is not any apparent relationship between Ko and modulus, friction angle or consolidation stress. Reaching end of primary proved to be a difficult task, concluding that it is reached after approximately five days. CRS data was used to corroborate values such as Cv, (0.0004 cm2/sec) and to more clearly map compression behavior. The results will provide a data base perform analysis and design of offshore structures and calibrate soil models.