Reducing the secondary consolidation of peat ground using vacuum consolidation

This paper discusses secondary consolidation of peat ground improved by vacuum consolidation method, and quantitatively presents the degree of reduction of the secondary consolidation. When an embankment is constructed for roads, river dykes or other purposes on peat ground, settlement after the construction due to remarkable secondary consolidation of peat ground is a serious problem. Therefore, to clarify the reduction effect on secondary consolidation obtained by using the vacuum consolidation method for peat ground, a trial embankment and elasto-viscoplastic finite-element (FE) analysis were performed. It was proved, with the trial embankment, that the surcharge effect by unloading vacuum pressure reduces the secondary consolidation. The coefficient of secondary consolidation (C_α) of peat ground improved by vacuum consolidation was approximately 30−50% that of non-improved peat ground. The trial embankment and the FE analysis revealed that the reduction effect could be expressed quantitatively in relation to the over-consolidation ratio (OCR), and C_α decreases hyperbolically with an increase of the OCR with the maximum curvature near an OCR of 1·3.