Closure to “Assessment of Reinforcement Strains in Very Tall Mechanically Stabilized Earth Walls” by Armin W. Stuedlein, Tony M. Allen, Robert D. Holtz, and Barry R. Christopher

Abstract

In the course of analyzing data collected from two exceptionally tall mechanically stabilized earth (MSE) walls constructed for the third runway at Seattle-Tacoma International Airport (SeaTac), the authors failed to understand three fundamental points regarding MSE wall design: 1. The authors ignore both the mandated design friction angle and the fact that the actual backfill internal friction angle was not known when the wall was designed. Instead, they assess the accuracy of the MSE design methods using selected in-place values of the soil friction angle, 40 and 44 , which are substantially higher than the mandated design friction angle, 37 . 2. The authors also ignore the fact that MSE walls are designed for the finished condition, not for the partially constructed condition. Instead, they condemn the validity of the Coherent Gravity and Simplified design methods based on those methods’ underprediction of reinforcement loads at intermediate stages of construction. Postconstruction stresses in the soil reinforcements at SeaTac are consistent with those predicted by the Coherent Gravity and Simplified methods using the mandated design friction angle, 37 . 3. The earth pressure distribution behind an MSE wall is triangular, not trapezoidal as assumed by the K-Stiffness method.