Performance of MSE Walls Supporting Bridge Foundations

A consortium of contractors, engineers, and designers was assembled to plan, design, and construct an expansion of the Virginia Route 288 (VA 288) highway around Richmond's fast-growing western half. The project was approved for construction in December 2000 and construction started in April 2001. The project includes construction of approximately 17 miles of new highway with 23 bridges and overpasses. In keeping with the design-build spirit, the contractor proposed to shorten the bridge carrying Ramp G over Interstate 64 (I-64) by using high mechanically stabilized earth (MSE) walls. The north and south MSE walls needed to be 64 and 79 feet high, respectively. The construction of these walls reduced the number of bridge spans from five to two, saving an estimated $1 million in construction costs. The south wall, the highest abutment wall in Virginia, called for validation that it would adequately perform. To accomplish this validation, numerical analyses (using FB-Pier and FLAC) were performed to predict the short- and long-term behavior of both the walls and the bridge foundations. These analysis results were used to develop validation documentation necessary for final approval by the Virginia Department of Transportation and the Federal Highway Administration. An instrumentation and monitoring program was implemented during construction to evaluate the short- and long-term performance of the walls and pile foundations. Instrumentation included survey monitoring points, inclinometers, and strain gauges. Movement data collected from the instrumentation program indicate that the wall and bridge foundations are performing satisfactorily and within the general bounds of predicted movements.