Settlement and Vertical Load Transfer in Column-Supported Embankments

Abstract

Column-supported embankments (CSEs) with or without a load-transfer platform (LTP) can reduce settlements, improve stability, and prevent damage to adjacent facilities when embankments are constructed on ground that would otherwise be too weak or compressible to support the new load. CSEs function by transferring the embankment load to the columns through stress redistribution above and below the foundation subgrade level. Mobilization of load-transfer mechanisms to the columns requires differential settlement at the base of the embankment between the stiff columns and foundation soils. This paper presents the load-displacement compatibility (LDC) analysis method, which estimates the transfer of vertical loads by (1) arching within the embankment fill, (2) the vertical component of tension developed in the geosynthetic reinforcement within the LTP, and (3) negative skin friction acting along the column. The LDC method incorporates the vertical displacements that accompany load transfer by considering nonlinear consolidation of the soft foundation soil, elastic compression of the columns, out-of-plane deformation of geosynthetic layers, and settlement of the embankment surface in compliance with the differential settlement at the embankment base. This paper also presents recommendations for estimating the critical height of the embankment, which is the minimum embankment height above the columns to avoid poor ride quality resulting from differential settlement at the surface of the embankment produced by differential settlements at the base of the embankment. Estimates of load transfer and reinforcement strain using the LDC method are compared to measurements from 15 full-scale embankments.