68th Canadian Geotechnical Conference and 7th Canadian Permafrost Conference

SECONDARY COMPRESSION OF A COHESIVE SOIL IN NORTHERN ONTARIO: A CASE STUDY

Session: Soil Mechanics I / Mécanique des sols I

André Bom, Golder Associates (Canada)
J.Paul Dittrich, Golder Associates (Canada)
Matthew Thibeault, Golder Associates (Canada)
Greg Qu, Hatch Ltd. (Canada)
Keli Shi, Thurber Engineering (Canada)
Tony Sangiuliano, MTO Foundations (Canada)

Long-term field settlement data and short-term and long-term laboratory consolidation test data provide a comparison of typical values used in the assessment of secondary compression (creep) of a cohesive soil beneath a highway embankment crossing a swamp area south of Sudbury in Northern Ontario. Design of the approximately 10 m high embankment with surcharge over an approximately 23 m thick clay deposit was based on the standard Terzaghi primary and secondary compression concepts. The secondary compression design parameters, which are the focus of this paper, were based on standard 24 hour load increment, one-dimensional laboratory consolidation tests and embankment construction included wick drains, staged construction and a surcharge. Regular monitoring of the consolidation of the cohesive layer using Settlement Rods (SRs), Vibrating Wire Piezometers (VWPs) and deep settlement Profilers (PRs) was carried out during embankment construction and surcharge period and annual readings have been taken following completion of the highway and opening to traffic in 2009. Secondary compression indices back-calculated from the long-term, post-construction field data are compared to values derived from the short-term (standard) laboratory consolidation tests as well as from long-term laboratory consolidation tests that have been running for about 1.5 years.