Three-Dimensional Simulation of a Load Transfer Mechanism for Frictional and End Bearing CMC Supported Embankments on Soft Soil

Recently, the use of controlled modulus columns (CMC) has gained popularity in the support of rail and road bridge approach embankments on soft soils. If the columns are extended into a competent firm soil, and designed to take nearly all the vertical loads, they become rigid inclusions. The advantage of this design approach is that settlement will be controlled, but the drawback is that the columns will attract greater load, including bending moment and shear force in situations where non-uniform loading or ground conditions exist. The load on the composite soil-CMC is uniformly distributed by the upper layer of granular load transfer platform (LTP). In this paper, the effect of CMC length on the load transfer mechanism is numerically investigated. Coupled flow-deformation analysis has been performed for a long period to understand the system response in the long term, while interface elements capable of simulating gapping and sliding between CMC and the surrounding soil are considered. A geosynthetic reinforcement layer has been simulated using the inbuilt FLAC^3D geogrid element. The force in the reinforcement layer has been evaluated, and in particular, a clear comparison is made between the stresses in CMC and the ground settlement with floating and end-bearing columns.