Evaluating Bending Failure of Floating Soil-Cement (SC) Columns under Road Embankments Using 3D FEA-Paper

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The study examines bending failure of soil-cement (SC) columns supporting highway embankments on soft ground. Conventional design methods generally assume shear failure through a composite of columns and soil, but centrifuge tests and numerical studies show that lateral soil movement can bend columns and cause failure.<br /><br />Three-dimensional finite element analyses were used to investigate how embankment loading, ground strength and stiffness, column area-improvement ratio, diameter, and length affect bending moments. Results show that bending moments decrease as the area-improvement ratio, ground stiffness, or undrained shear strength increases. Column length had little effect on maximum bending moment for end-bearing columns.<br /><br />The authors propose a design procedure for floating columns. It uses an existing design chart to estimate bending moments for end-bearing columns, then applies a second chart relating the moments in floating and end-bearing columns according to the depth-improvement ratio. Predicted bending moments are converted to tensile stresses and compared with the SC column’s tensile strength to assess bending failure.<br /><br />The method was applied to a full-scale embankment in Saga, Japan. It predicted a factor of safety of 1.58 against bending failure, consistent with the reported absence of column failure in the field. The authors conclude that the method can support the design of floating SC columns in soft ground.

Keywords

soil-cement columns

bending failure

highway embankment

soft ground

finite element analysis

lateral soil movement

area-improvement ratio

undrained shear strength

floating columns

design procedure