Factors Affecting the Development of MSE Wall Reinforcement Strain

The grade raising associated with the construction of a new runway at Seattle-Tacoma International Airport required construction of two near vertical tall reinforced earth walls that included the two tier 26 m North wall and the four tier 46 m tall West wall. Twenty reinforcement strips at critical wall cross-sections were instrumented with approximately 550 strain gages, and performance data were obtained during initial installation and backfill placement. The performance data facilitated the assessment of factors affecting the development of strains within the MSE walls. A simplified method to determine the amount of reinforcement strain due to installation of the reinforcement strip and subsequent compaction of fill is presented. Estimates of the initial reinforcement strain, fill thickness up to which compaction effects were noted, and the initial and geostatic reinforcement strain rate in terms of microstrain per meter of fill placed are tabulated and discussed. The local reinforcement stiffness contributes to the accumulation of initial reinforcement strain, but is found to play a significant role in controlling the rate of strain due to normal geostatic stresses. Implications for the design of very tall MSE walls are also given.