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IDOT Trilevel Interchange

Owner: Illinois Department of Transportation (IDOT)
Client: CTE Engineers
Location: East St. Louis, Illinois
Services: Drilling, Geotechnical

Overview:
Geotechnology was contracted to provide a subsurface exploration for modifications to the I-55, I-64, I-70 Trilevel interchange as part of the new Mississippi River Bridge project between 2001 and 2005, and again in 2008 for design of a reconfigured interchange. This work is ongoing.

The original Trilevel interchange configuration included raising the three-level interstate highway interchange approximately 20 feet and maintaining traffic during construction. The Trilevel interchange included improvements and modifications to numerous bridge structures, approach embankments and retaining walls.

The Trilevel project was on a fast-track schedule within the overall Mississippi River Bridge project. Geotechnology’s fieldwork involved drilling approximately 215 exploratory soil borings, some of which included rock coring at depths of 120 feet below the ground surface. Borings were located on state right-of-way, as well as on private property. Coordination for drilling involved communication with IDOT personnel for utilities and mowing activities, private property owners and public utility clearance. Laboratory soil testing was completed in accordance with IDOT requirements and included index tests, unconfined compression tests on soil and rock samples, consolidation tests and multi-stage consolidated undrained triaxial shear tests.

The geotechnical report included discussions of liquefaction, slope stability, settlement and foundation recommendations for embankments and structures.

The reconfigured Trilevel interchange features an overall lower profile with shorter approach embankments and more reuse of existing structures. Geotechnology drilled 51 additional borings and prepared 16 structural geotechnical reports (SGR) and one subgrade report for the latest design effort.