Buttressing Berms for Stability of Cantilever Sheet Piles – Limit Equilibrium and Finite Element Approaches-Paper

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The study examines the use of soil buttressing berms to improve the stability of cantilever sheet-pile walls and reduce excessive deformation. Berms increase passive earth pressure in front of the wall, potentially allowing a shorter embedment or a less robust sheet-pile section.<br /><br />The authors conducted a parametric limit-equilibrium analysis for excavation depths of 2–5 m, soil friction angles of 25° and 30°, and varying berm heights and widths. They developed design charts showing the effects on embedment depth, maximum bending moment, and wall-top deflection. Selected cases were also modeled using finite-element analysis with Plaxis for comparison.<br /><br />Both approaches showed that increasing berm height generally reduces required embedment, bending moments, and wall-top deflection. Even a modest berm can produce substantial improvement, though the benefit diminishes as berm height increases. Increasing berm width also helps, but only up to a critical width; beyond that, further widening provides little additional reduction. For the modeled conditions, a berm width near the excavation depth was suggested as a practical rule of thumb. Finite-element analyses generally predicted lower maximum moments than limit-equilibrium analyses, and taller berms could cause the wall top to move away from the excavation.<br /><br />The design charts can support preliminary design decisions, cost reduction, or emergency response to excessive wall movement. However, they are screening tools based on specific assumptions—including dry, cohesionless sand, limited soil properties, and modeled geometries—and should not replace project-specific detailed analysis.

Keywords

soil buttressing berms

cantilever sheet-pile walls

passive earth pressure

embedment depth

wall deformation

limit-equilibrium analysis

finite-element analysis

Plaxis

bending moment

excavation stability