Geotechnical characterization of sediments from Hydrate Ridge, Cascadia Continental Margin

Eight whole core sediment samples were obtained from ODP Site 1244, Hydrate Ridge, Cascadia Continental Margin with the goal of understanding the stress history, consolidation behavior and strength characteristics of the soil. A series of Constant Rate of Strain Consolidation (CRSC) and Ko- Consolidated Undrained triaxial (CKoU) tests were performed in order to study the behavior. In addition, Atterberg limits and x-ray diffraction were performed in order to better classify the material. One of the key issues regarding this soil is the level of disturbance imparted during sampling and transportation. Evidence of the disturbance are cracks and voids in x-rays, as well as highly rounded compression curves. Established soil quality criteria have shown the soil to have poor quality. A new criterion comparing the initial loading to the reload cycle shows that soil quality varies, but has no pattern with depth. Nonetheless, highly disturbed samples and trimmings from previous tests were resedimented to produce better quality specimens for consolidation and strength testing. Conventional application of the strain energy method yielded high preconsolidation pressures that indicate the soil is normal to overconsolidated (1<OCR<8). An alternative method used to estimate the pre-consolidation stress based on extrapolation of the virgin consolidation curve to the in-situ void ratio predicts that samples shallower than 33 mbsf are near normally consolidated (OCR-1.2) whereas deeper sediments are underconsolidated (OCR<1). However, analysis of the stress path history from a horizontally-oriented CRSC sample gives evidence that the in-situ horizontal effective stress is greater than the vertical effective stress.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Civil and Environmental Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Tan, Brian B. (Brian Bautista), 1979-

Advisor dc:contributor.advisor

• John T. Germaine.

• Civil and Environmental Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/29396

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/29396