Finite element analysis of highway construction in peat bog

Abstract

Parts of a U.S. Route 44 relocation project span across cranberry bog areas with deep peat deposits. The peat in the proposed roadway side was completely excavated and backfilled with granular soils, and using sheet pile walls as retaining structures. As peat exhibits low strength, high compressibility, and significant creep behavior, the long-term performance of the sheet pile walls was a great concern. To monitor the development of sheet pile deflections and total lateral earth pressures in peat, selected sheet piles located in peat deposits were instrumented with pressure cells and inclinometer casings. Furthermore, to understand the soil–structure interaction mechanism during roadway construction, the finite element (FE) code PLAXIS was employed to continuously model roadway construction in peat deposits. Peat was simulated by a soft soil creep (SSC) model, which can account for creep effects. One of the challenges in this simulation was how to model deep dynamic compaction (DDC), since the enormous momentum induced by DDC would cause local failure of the soil body and consequently result in termination of the program. This problem was satisfactorily solved by using a dynamic approach presented in this paper, and the FE-calculated results were compared with the field measurements. The comparison indicated that FE modeling yields predictions in a good agreement with field measurements and also could provide some reasonable explanations for the field observations.