An experimental study on time-dependent behaviour of reconstituted clayey soils in 1D and triaxial compression

Accurate assessment of the safe performance of geotechnical structures against the time-dependent strength-deformation behaviour of soils relies on the knowledge acquired from laboratory and field experiments. Therefore, the focus of this research is to experimentally investigate the role of stress history, soil properties and loading system in the time-dependent strength-deformation behaviour of reconstituted clayey soils. The experimental program consists of oedometer and triaxial compression tests on compacted lightly overconsolidated natural soils (high plastic Regina clay and low plastic Calgary till) as well as on artificial soil mixtures made by mixing pure kaolinite or bentonite with crushed Opal, silt or Calgary till. Results of multiple-stage oedometer tests show that vertical stress level, clay content, size of the coarse particle, coarse particle type, clay type, and liquid limit affect the secondary compression behaviour of oils. Results of constant rate of strain tests in oedometer and triaxial conditions show that at a given strain level, faster strain rates always result in a higher effective vertical stress or deviatoric stress value for high plastic Regina clay. Thus, the behaviour is considered as isotach. However, low plastic Calgary till shows isotach behaviour only under overconsolidated or unsaturated conditions. Further, strain rate effect on shear strength is found to increase with liquid limit, OCR value, matric suction, and absolute magnitude of strain rate. In both oedometer and triaxial conditions, the ratio between relaxed stress at any time and the stress level at the beginning of the relaxation test is found to be linear with the logarithm of time after an initial time period. These linear segments are approximately parallel for stress relaxation tests conducted within or closer to the NC region/post-peak region of the stress-strain curve a soil. The gradient of these parallel segments is found to be independent of the soil structure and confining pressure but depends on the test condition and degree of saturation. Intercepts of fitted lines to these parallel segments can be used to correlate strain rate, stress relaxation behaviour and pre-consolidation pressure. Keywords: Time-dependent, secondary compression, stress relaxation, shear strength, isotach

Name thesis:degree_name

Doctor of Philosophy (PhD)

Discipline thesis:degree_discipline

Civil Engineering

Grantor dc:publisher.institution

Graduate Studies

Year dc:date.issued

2018

Author dc:creator

• Wickrama Kaluthota Hewage, Rajitha Eranga Wickramage

Advisor dc:contributor.advisor

• Wong, Ron

Committee members dc:contributor.committeemember

• Hayley, Jocelyn
• Wan, Richard
• Maini, Brij
• Siddiqua, Sumi

Statement dc:rights

• University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.

Language dc:language.iso

eng

DOI

http://dx.doi.org/10.11575/PRISM/33070

OAI identifier oai:identifier

oai:ucalgary.scholaris.ca:1880/108717