Settlement Analysis on Glacio-Lacustrine Clays using Observational Method for a New Interchange in Winnipeg, Manitoba
A new interchange located at the north end of Winnipeg, MB, was substantially completed in the fall of 2018 after 3 years of construction. This interchange included seven bridge structures and embankments heights up to 9 m above original elevation. The embankments were constructed on 8 to 15 m of compressible clay. Wick drains were installed in the clay to accelerate settlement and meet the project requirements that 90% and 95% consolidation occurs before placing granular base course and paving, respectively. Instrumentation installed throughout the site included 60 settlement plates, 9 ShapeArrays (SAAs), over 40 piezometers, and over 15 Inclinometers. At times during construction, differing magnitudes of settlement between the settlement plates versus the SAAs lead to difficulty calibrating numerical models. Thus commonly practiced methods to estimate degree of consolidation were employed. These methods included Root Time and Asaoka (1978) methods. An exponential function using regression analysis was fitted to the available settlement data to assist with predicting degrees of consolidation across the site. Porewater pressure dissipation was also reviewed. This paper presents a summary of the data at key locations and a comparison to settlements predicted prior to construction.
Dave Kurz, Ph.D., P.Eng. is a Geotechnical Engineer with KGS Group in Winnipeg, Manitoba.