Instrumentation and construction performance monitoring for I-15 reconstruction project in Salt Lake City, Utah

The I-15 reconstruction project in Salt Lake City, Utah, involves the widening and rebuilding of 27 km of urban Interstate on alluvial and lacustrine deposits. In some locales, these soils have low shear strength and require up to 2 to 3 years to complete primary consolidation settlement. The aggressive 4-year construction schedule required much of the embankment and foundation work to be completed in the first 12 to 18 months, including the time required to complete primary settlement. To meet these rigorous schedule constraints, the geotechnical construction made extensive use of prefabricated vertical drains, ground modification, staged embankment construction, lightweight fill, mechanically stabilized earth walls, and pile foundations. Also, because of rigid time constraints, initial foundation treatments and embankment construction proceeded as parallel activities with the geotechnical design. Instrumentation and construction performance monitoring played a vital role in affirming initial design assumptions and developing a better understanding of strength, deformation, and consolidation characteristics of the foundation soils. Discussed are the instrumentation program and how performance monitoring was implemented to control construction processes and improve the geotechnical design.