Effect of Coupling on A-Walls for Slope Stabilization-PDF

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The report investigates how coupling between upslope and downslope piles through an A-Wall’s capping beam affects slope-stabilization performance. Earlier design methods analyzed the piles separately, potentially missing force transfer between them.<br /><br />Researchers developed two-dimensional finite-element models linking battered piles with a stiff capping beam and representing soil interaction through lateral p-y and axial t-z relationships. They calibrated the models against measurements from two instrumented A-Walls—at Littleville, Alabama, and SUM 271, Ohio—and compared results with uncoupled analyses.<br /><br />Coupled models produced bending-moment and axial-force profiles that generally agreed with field measurements. A single calibration, using a lateral-resistance modifier of 0.3 and an axial-resistance factor of 0.5, worked for both sites. These values were more realistic than the substantial, case-specific resistance reductions required by the uncoupled method. Coupling particularly improved predictions near the capping beam and for axial forces, and captured pile-head forces and moments without artificial boundary conditions. The findings indicate that the capping beam can materially affect force development in both piles. Coupled analysis can also help determine capping-beam design demands.<br /><br />For the two cases, which involved relatively deep sliding surfaces (about 30 ft) and small ground movements, uncoupled analysis still gave reasonable estimates of resistance at the sliding surface. The authors therefore consider it suitable for deep slides, while recommending coupled analysis for shallower slides, where the cap is likely to play a larger role. Published adjustments for pile batter worsened agreement in these deep-slide cases, suggesting batter effects may diminish with depth.<br /><br />The study is limited by its reliance on two case histories. The authors recommend collecting additional field data, especially for shallow slides and larger movements, and further investigating how pile-batter effects vary with depth.
Keywords
A-Wall
capping beam
upslope piles
downslope piles
slope stabilization
finite-element model
p-y relationship
t-z relationship
pile coupling
bending moment