عنوان مقاله [English]
Ground improvement using stone columns is a popular technique for foundation of structures and embankments on soft grounds. However, due to the lack of sufficient lateral confinement for the columns and greater required bearing capacity, this technique may not be effective for improvement of soft soils. In order to provide lateral confinement and increase the bearing capacity of stone columns, installed in soft soils, the stone columns are usually reinforced by layers of geosynthetics (i.e. geotextiles or geogrids) or encased with geosynthetics. In this research, the effect of unreinforced and reinforced stone column in the loose soil bed using Triaxial Test was investigated. Number of twelve independent Triaxial Tests and numerical simulation using Abaqus
software were performed on specimens with diameter of 100 mm and height of 200 mm. Five of the tests were repeated twice to examine the performance of the apparatus, the accuracy of the measurements and the repeatability of the system. The stress-strain variation of two repeated tests having the same test conditions, gave a close match with a maximum difference in results of around 7\%. In the reinforced test, two forms of reinforcement (1) geotextile as encasement and (2) laminated disks were used. Reinforcement of stone column by one, two, three, and four layers of geotextile (i.e., laminated disks) was investigated, and its performance was compared to that of the stone column reinforced by geotextiles encasement, in terms of bearing capacity improvement, construction, and economy. The results indicated that the stone column improved the strength of sample about 200\% as compared with loose soil bed. The results of numerical studies are in good agreement with experimental results. The comparative investigations imply that in order to achieve a specified improvement in strength of reinforced specimens, less mass of geosynthetic material would be used in a geotextile layers implementation compared to an encasement geotextile one at 60\% of stone column's length. In the example given in this paper, four layers of geotextile achieved a similar performance to an encasement geotextile that contained three times as much mass of geotextile material.