Mechanically Stabilized Earth Walls and Uneven Reinforcement Lengths (Trapezoidal Walls) – Design Development and Challenges

A composite trapezoidal MSE-embankment system was designed and constructed to support the embankment widening project at a Highway Bridge in New Zealand. The widening necessitated the construction of retaining walls on the existing abutment slopes and under the existing bridge. To suit the constructability and achieve a customized cost effective solution, the use of traditional rectangular MSE reinforcement lengths, which would require vertical excavation into the existing abutment slope, was replaced by the use of Trapezoidal-shaped reinforcement lengths. This paper assesses the consideration of a designed and constructed Trapezoidal Wall for a highway Bridge abutment, and variations on the conventional assessment of failure mechanisms to ensure the wall achieved the design intent. A few options are discussed and compared. Numerical analysis is carried out to establish the achievement of wall stability and serviceability requirements. The successful application of this wall is demonstrated by observed stability and the monitoring during and post-construction.