The influence of effective consolidation stress on the normalized extension strength properties of resedimented Boston blue clay

The ability to accurately determine the undrained shear strength of cohesive soil is of particular importance to the practice of geotechnical engineering. Ladd & Foot (1974) presents a method to determine the undrained shear strength based on the concept of normalized soil parameters; called the SHANSEP (Stress History and Normalized Soil Engineering Properties) method. Recent research at MIT has discovered a consistant variation of undrained shear parameters during triaxial compression. Undrained triaxial compression tests on RBBC (Resedimented Boston Blue Clay) have shown that the soil stiffness and strength is dependant on the vertical consolidation effective stress and that the strength behaviour does not strictly conform to a normalized framework. The aim of this study is to explore the trend between vertical consolidation stress and the undrained shear strength behaviour in extension for cohesive soils to determine whether the normalized soil parameter concept (and hence SHANSEP) is still applicable at vertical consolidation stresses ranges of [sigma]'v 2 =/>10 ksc (1.OMPa). To do this, a series of Ko-consolidated undrained triaxial extension tests were performed at vertical consolidation consolidation stresses ranging from 1.5 ksc (0.15 MPa) to 20 ksc (2.0MPa). Results from these tests clearly show that the undrained shear strength decreases with vertical effective stress. The undrained shear strengths decreased from 0.17 ksc to 0.15 ksc, and the friction angle decreased from 45° to 31.1° corresponding to an increase in vertical consolidation stress level.

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

2009

Author dc:creator

• Moniz, Safia R

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/1721.1/53072

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/53072