FINITE ELEMENT ANALYSIS OF REINFORCED AND UNREINFORCED DEEP SOIL MIXING COLUMNS INSTALLED IN COHESIVE AND NON-COHESIVE SOILS

A parametric study employing three-dimensional finite element analysis is used in this paper to examine the improvement of soft clay and silty loose sand under a road embankment using deep soil mixing (DSM) columns. Both soils are designed with three variables namely DSM column diameter (D), DSM column length (L) and centre-to-centre distance of the DSM columns (s). The settlement values under the road embankment constructed with and without DSM columns were obtained by numerical analysis. The analyses were also repeated for the DSM columns which were stiffened by adding I-profiles. The results showed that the improvement effect of the DSM columns on settlement is higher in soft clay. For constant improvement area ratio (a_r), the maximum improvement is achieved for D = 80 cm (2.62 ft.) and increasing D did not affect the degree of improvement. In both soil types, settlement decreased with increasing L within the weak soil zone. Increasing L into the comparatively stronger soil did not significantly affect the settlement value. Although the settlement decreased with increasing a_r in silty loose sand, it reached at maximum in soft clay at a_r of thirty-five percent and was not affected thereafter with increasing a_r values.