Comparison of 2D and 3D Anchor Analysis Methodologies-Paper

Paper

Pdf Summary

The paper compares two-dimensional (2D) and three-dimensional (3D) limit-equilibrium analyses of anchored slopes. In conventional 2D models, anchors are treated as continuous support, with their capacities adjusted for lateral spacing. A 3D model represents their discrete, point-load nature more realistically.<br /><br />The authors analyze homogeneous slopes and a complex stratified slope, with unsupported and reinforced cases. They use the General Limit Equilibrium method and search for critical slip surfaces in both dimensions. The examples include different slope geometries, soil layers, groundwater, surface loads, anchors, and micropiles.<br /><br />Across the cases studied, the calculated critical factor of safety (FOS) is higher in 3D than in 2D. Differences vary with slope geometry and slip-surface shape: in the homogeneous examples, 3D FOS differences range from about 8% to 21%; in the complex slope, they are 4.6% for the unsupported case and 6.2% for the reinforced case. The authors attribute some of the increase to 3D slip-surface geometry and some to representing supports as discrete loads rather than continuous support.<br /><br />The results suggest that 2D analysis can reasonably represent slopes with consistent cross sections and closely spaced anchors, but may not capture important 3D effects where geometry, loading, weak layers, or support patterns vary spatially. Concave or convex surfaces and external loads can produce lower-aspect-ratio slip surfaces with significant edge effects. The authors therefore recommend 3D evaluation when such field conditions may influence stability, while noting that the effect varies by project.

Keywords

2D vs 3D analysis

limit equilibrium

anchored slopes

factor of safety

critical slip surface

general limit equilibrium

slope stability

discrete anchors

micropiles

three-dimensional modeling