Experimental Study on Behavior of Soft Clay Strengthened by Geogrid Encased Stone Columns

Abstract

Treatment of soft unsaturated soil using stone columns provides the most satisfactory results in terms of bearing improvement and settlement reduction under monotonic loading conditions, as compared to the untreated soil. The present work deals with improvement of soft clay by single stone column under circular foundation 10 cm in diameter. The evaluation of that method is based on the amount of increase in bearing capacity and the reduction in settlement as compared to the untreated soil. The proposed method of treatment of soft clay requires determination of the affecting factors, the method is illustrated by using geogrid reinforced stone columns at different diameters (3, 5 and 7) cm of different lengths (1/3, 1/2 and 1) the model sample height (40 cm). It was concluded that the variation of IF (influence factor) was found between 3 and 88 % depending on the ratio of D/L, L (where D is the diameter of stone column and L is the length of embedded stone column) and the stiffness of geogrid. The stone column's length has a greater influence on settlement reduction and bearing capacity improvement than its diameter. The geogrid stiffness and pattern affects considerably the stone column's efficiency, as the geogrdid stiffness increases, the influence factor increases too. The settlement influence factor for encased stone columns is decreased by about 60 to 75% when the stone column diameter is increased from 3 to 7 cm.