An end bearing stone column is one of the most common types of stone columns, which completely penetrates through a layer of soft clay soils, resting on much stiffer soils. This article presents a numerical model (analyses) of the stone column used to strengthen the soft clay soil. The analyses were performed using a three-dimensional model in FLAC3D. To investigate the effect of the stone column on strengthening soft clay soils, a dimensionless parameter called the settlement improvement ratio (Ks) is used. The results show that, the settlement improvement ratio (Ks) increases with an increasing diameter of the stone column. The lateral deformation of the stone column decreases with the increasing stone column diameter, and the maximum lateral deformation was occurred at approximately (1.0 to 1.5) diameter from the top of the surface.

The article presents the results of numerical analysis of the development of negative skin friction forces of a single pile by lowering the level of the groundwater ta-ble in soft clay soils. The analysis is conducted with a three-dimensional model (3D) us-ing the ABAQUS software package. Results from the present work are found to be in congruent with the available published results. Moreover, the influence of lowering of the groundwater table in distribution of negative skin friction and axial forces on the pile as well as the maximum relative displacement between the soil and pile at various stages has been observed. The compression of the pile material is also taken into con-sideration in the study. Based on the results of the current numerical analysis, an equa-tion has been proposed for estimating the additional load on the pile, which is caused by negative frictional forces.

Currently, geotechnical engineers use stone columns to strengthen weak soils. The usage of stone columns to strengthen soft soil has proven successful, increasing their bearing capacity, reducing the settlement and decreasing the consolidation time. The present study was carried out to investigate the impact of the length of stone columns on the behaviour of soft soils and determine the effective length of stone columns, within which they have the greatest impact on the process of settlement of the soft clay layer. The analysis was performed utilizing a three-dimensional limited distinction numerical model FLAC3D. The results of the study confirmed that with the increase in the length of the stone columns, the settlement of the clay layer decreases. This decrease in settlement is significant to a depth corresponding to the relative length of the piles (L/d) = 10, after that the decrease in settlement practically stops.