Experimental Study on Improvement of Bearing Capacity Using Geosynthetic Stone Column

Abstract

The coastal areas are covered with thick layers of very soft soil deposits which have low shear strength and high compressibility. The developmental activities in the coastal regions led to the use of such weak strata. Stone columns are one of the ground improvement techniques used for grounds with soft silts, clays and loose silty sands. The use of stone column has proved to be one of the economical and technically viable ground improvement techniques on soft soils like lithomargic clay (locally called as shedi soil). In the present study, experimental investigations were done on the basic properties of lithomargic clay. Tests were carried out on the behaviour of stone column surrounding clay. The diameter of stone column is maintained as 50 mm for all the tests, and granular fill of 12 mm down size coarse aggregate was used. Loading was done in two ways, entire area loading and column loading. Also, the stone column was encased with geotextile in order to prevent the lateral bulging. Length-to-diameter ratio equal to 4 (Dhanshree and Satyajit in Application of stone column for ground improvement: A review. College of Engineering, Pune, Maharashtra, 2015 [2]) was kept constant throughout the experiment. Effect of group of three stone columns encased with geotextiles was studied using larger mould by varying parameters like spacing-to-diameter ratio, taking S/D = 2, 3 and 4. It was observed that S/D = 2 gave optimum results and can be adopted in construction practices. Stone column is placed in groups and when loaded over the entire area, it undergoes less bulging than for a single stone column. The encasement increased the strength and stiffness of the stone column, thus enabling quicker and economical installation. It was found that the load-carrying capacity was increased by 67.4% for stone column without geotextile and 75.43% with geotextile for entire area loading. When load was applied on column area only, it was observed that the load-carrying capacity was increased by 87.37% using geotextile.