COMPARATIVE STUDY OF LOAD DEFORMATION BEHAVIOUR OF SILTY CLAY BED REINFORCED WITH STONE COLUMN OF DIFFERENT DEPTH AND GRADATION

Abstract

Stone columns or granular piles can have widespread application in the field of ground improvement. It is a cost effective measure used to improve bearing capacity of weak soils for supporting a wide variety of structures such as residential, commercial and industrial buildings, raft foundations, oil storage tanks, highways and other applications. It also helps in reducing settlements. The stone columns derive its load carrying capacity mainly from confinement of the surrounding soil. In the present investigation, load versus settlement response of silty clay bed is compared with the load versus settlement response of silty clay bed reinforced with stone column for different aggregate mixes and different depth of stone column with and without encasement. The plate load tests were carried out on a single column in a large rectangular tank (1.5m×0.6m×0.9m). The test bed was prepared using locally available silty clay soil. Investigations were carried out by varying the size of aggregate in the stone column as well as mixing different size aggregates. The results from the tests indicated a clear improvement in load carrying capacity of silty clay bed due to stone column as well as a reduction in settlement. The bearing capacity improvement factors have been found out to be 1.11, 1.23, 1.32 for stone columns with 20mm aggregates; 1.08, 1.22, 1.31 for stone columns with 10mm aggregate; 1.15, 1.24,1.41 for stone columns with a mixture of 10mm and 20mm aggregates in the ratio of 1:1 by weight for depths of 250mm, 500mm and 750mm respectively at 25mm settlement. It has been observed that for encased stone column the bearing capacity improvement factors at 25mm settlement for full depth of silty clay bed i.e. 750mm has been observed as 1.87,1.83 and 1.91 for stone columns with 20mm, 10mm and a mixture of 10mm and 20mm aggregate respectively.