Construction and Long-Term Performance of Transportation Infrastructure Constructed Using EPS Geofoam on Soft Soil Sites in Salt Lake Valley ,
The Utah Department of Transportation (UDOT) and the Utah Transit Authority (UTA) have made extensive use of EPS embankment for several major interstate, light rail, and commuter railway embankments in Salt Lake Valley, Utah. Constructed between 1998 and 2001, the Interstate 15 Design Build Reconstruction Project involved the widening of interstate embankments within a 27 km narrow corridor and limited right-of-way. Approximately, 100,000 m of EPS fill was placed at various locations to minimize post-construction settlements of deep, compressible lake deposits. This paper presents results of long-term monitoring of EPS fills and comparison with other geotechnologies. Geofoam embankments had the best overall settlement performance of the technologies monitored. Gap closure and deformation of the geofoam embankment due to placement of the load distribution slab and overlying roadway materials was about 1% of the embankment height. In addition, at 3300 South Street, the foundation soil settled about 15 mm due to placement of the embankment and overlying loads. The face of the embankment settled an additional 25 mm in a 5-year period due to additional pressure of a 1.5m toe berm placed at the base of the tilt-up wall. Total post-construction settlement (foundation settlement and geofoam creep) is expected to be about 50 mm at the wall face for a 10-year postconstruction period. The trend of post-construction settlements suggest that geofoam embankments are performing as designed and will meet the 50-year post-construction deformation limit of 1% creep strain. Overview of the I-15 Reconstruction Project The Utah Department of Transportation (UDOT) togeth er with Wasatch Constructors finished the $1.6 billion reconstruction of Interstate 15 (I -15) that runs through Salt Lake City, Utah in 2001 just prior to the start of the 2002 Winter Oly mpics. The interstate embankment was widened from eight lanes to ten general-purpose lan s, plus two high occupancy vehicle lanes, within an existing north-south alignment that runs through the middle of the densely populated Salt Lake Valley. In this area, parts of the I-15 a lignment are located atop extensive deposits of relatively compressible lake sediments. Collateral consolidation settlement along this widened alignment had to be minimized to prevent differenti al settlement damage and subsequent
Bridge Foundations Supported by EPS Geofoam Embankments on Soft Soil
EPS geofoam can be used to support highway bridge structures without the aid of deep foundations. The development of this technology is important to accelerate construction on soft compressible soil. EPS geofoam allows for the rapid construction of bridge foundations on such soils without the time and cost involved in installing traditional foundations. Because EPS geofoam is an extremely light weight fill, it can be used to avoid settlement impacts at bridge approaches. In Norway, bridges have been directly supported by EPS geofoam. Norwegian Public Roads Administration has pioneered this application for a few bridges underlain by soft, clayey deposit where the bridge structure rests solely on EPS geofoam blocks. Investigating bridge foundations supported by EPS geofoam embankments is a joint effort starting summer 2013 between the University of Utah, University of Memphis and Norwegian Public Roads Administration. This paper includes some tasks and conceptual designs that address development of performance goals, design criteria, material testing, prototype analyses, numerical modeling and constructability of this innovative bridge support system.
Evaluating the Seismic Stability and Performance of Freestanding Geofoam Embankment
The Utah Department of Transportation has made extensive use of expanded polystyrene (EPS) geofoam embankment at select locations on the I-15 Reconstruction Project in Salt Lake City, Utah. This paper presents a method to evaluate the seismic response and stability of a geofoam embankment for a nearby M7.0 earthquake. The recommended approach uses a finite difference numerical model implemented in FLAC (Fast Lagrangian Analysis of Continua) to evaluate the dynamic and deformation response of the geofoam embankment undergoing interlayer sliding and horizontal sway with rocking. The evaluations were performed in a coupled fashion using both the horizontal and vertical components of strong motion of a representative set of acceleration time histories for a nearby M7.0 earthquake. The analyses indicate that interlayer sliding is initiated in some cases and the amount of interlayer sliding displacement depends on the characteristics of the long-period strong motion and the interface properties used in the model. Shear keys strategically placed within the embankment are recommended where the estimated sliding displacements are potentially damaging. The numerical model also suggests that internal deformation caused by rocking and sway can cause local tensile yielding of some blocks within the embankment, usually near the base. In some cases, this yielding can propagate upward and cause the embankment to begin to decouple dynamically. Consideration should be given to using blocks with higher strengths than Type VIII geofoam in the basal zones of geofoam embankments undergoing high levels of strong motion.