Experimental study of ground improvement by using encased stone columns

The application of stone columns increases the stiffness of soft soils which contributes to its load carrying capacity and accelerates the process of consolidation leading to reduction in settlement. However, under external loading, squeezing of adjacent soil into the columns not only compromises the integrity of the columns but also reduces its stiffness, strength and drainage properties. The present study investigates the use of vertically and horizontally reinforced stone columns, as a remedial measure for ordinary unreinforced stone columns. The vertical reinforcement is done by encasing the stone columns in geotextile and horizontally by placing geotextile circular discs within the columns at regular interval. Model tests on group of 3 and 4 unreinforced and reinforced stone columns have been conducted in weak sandy soil. The load–settlement response and failure modes for both reinforced and unreinforced groups have been studied. It is observed that reinforced group of stone columns depict better load bearing capacity as compared to unreinforced group. Moreover, bearing capacity for vertically encased and horizontally reinforced is almost similar, with horizontally reinforced group of 4 stone columns depicting slightly higher (1–2%) bearing capacity for a settlement of 30 mm. The experimental results are also validated with theoretical results and are found to be in good agreement.