Compressibility Behaviour of Peat Reinforced with Single and Multiple Deep Soil Mixing (DSM) Columns

Peat represents an extreme form of soft soil and it poses serious problems in construction due to its long-term consolidation settlement even when subjected to a moderate load. Hence, suitable geotechnical design parameters and construction techniques are needed for this type of ground condition. Deep soil mixing (DSM) method is one of the widely used chemical methods of ground improvement for soft clay. However, DSM technique is quiet new for peat. Hence, aim of this research was to study the compressibility behaviour of peat stabilized with fly ash using DSM technique. A series of Rowe Cell consolidation experiments was conducted on peat and peat stabilized with fly ash. For the stabilization, 50% of fly ash was added to peat and single and multiple deep mixing columns were formed. Based on the outcome of this research, it was noticed that compressibility parameters such as compression index (Cc) and swell index (Cs) reduce with the addition of fly ash. Percentage reductions in Cc by the addition of stabilized single and multiple columns (for column area ratio of 16%) were 27.3% and 39.4% respectively compared to raw peat, while the reductions in Cs were 37.6% and 62.5% respectively for single and multiple columns. In addition, it was noticed that shear strength parameters of peat (cu0027 and φu0027) can be significantly improved by stabilizing with fly ash. On the whole, DSM technique is applicable for peat, and for a given area ratio, multiple DSM columns are more effective in reducing the compressibility compared to asingle DSM column.