Instrumented Mechanically Stabilized Earth Wall Reinforced with Polyester Straps

Abstract

A wall of mechanically stabilized earth (MSE) with large concrete panel facing, reinforced with polyester straps, is an emerging technology in the United States. To enable the design of this wall system through AASHTO's methodology, the system's classification of extensibility must be established. Therefore, a section of such a wall was instrumented as part of a newly constructed interchange on I-95 at Christiana, Delaware. The section was one of several similar walls that allow access to bridges composing the interchange. Monitoring included tensile force distribution at selected straps and force at the connection of a few straps to the large concrete panels. The recorded data were from April 2012, the beginning of construction of the instrumented wall, to June 2014, about 20 months after construction ended. When this reinforced wall system was classified as extensible, the maximum load in the straps and connections was about one-fourth the predicted value from using the AASHTO method, and the lengths of the reinforcing straps were adequate to enable the wall to sustain the required loads. The indicated conservatism of the measured versus the predicted maximum load in the reinforcements was attributed to significant underestimation of the reinforced soil strength in AASHTO's design and, potentially, to a large toe resistance. The data suggest that AASHTO's design, which is based on extensible reinforcement for this family of MSE walls, is adequate.