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ABSTRACT The geogrid encased stone column (GESC) system, which increases the confinement effect, has been developed to improve the load carrying capacity of stone columns. This paper investigates improvement in load-carrying capacity and reduction in bulging of a geogrid cncasedstone column using field load tests. Also, to examine the effect of the geogrid encasement depth, GESC were for changing geogrid encasement depths from the upper part of 2D and 3D. It is found from load tests that geogrid encased stone columns have much higher load carrying capacity and less laterial bulging compared to conventional stone columns.
INTRODUCTION Recent research on the technology of reinforcing gravel piles or stone columns using geosynthetics has been active. This method is known to have the advantage of lessening the horizontal deformation and increasing the bearing capacity of sand compaction piles, gravel piles or stone columns (Al-Joulani, 1995; Wood et al, 2000; Kempfert, et al, 2002). Since the research on the geotextile encased column (GEC) method, which is the method of increasing the carrying capacity by encasing the sand in the soft ground with geotextile, was started in Germany in early 1994, extensive research on using geotextiles has continued (Kempfert, et al, 1999; Raithel, et al, 2001; Alexiew et al. 2003). The GEC method has been applied mainly to soft ground such as marine areas. It has the disadvantage of increasing construction cost because it uses sand as the filler, causing insufficiency of natural aggregate. By contrast, the geogrid-encased stone column method, which uses stones, waste concrete and recycled aggregates as the filler with a high strength geogrid, is more economical because it reinforces the weak part of the stone column unlike the GEC method which reinforces the entire sand column with geotextile.