Physical FCV modeling of a stone column in sandy ground with a soft lens
ٔNiyousha Bazazzadegan
1
(
Department of Civil Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
)
Navid Ganjian
2
(
epartment,faculty,Islamic Azad University, Science and Research Branch, Tehran,Iran
)
3
(
Department of Civil Engineering, Shahr-e-Qods Branch, Islamic Azad University, Tehran, Iran
)
Keywords: Stone column, Frustum confined vessel (FCV), Soft lens, Bearing capacity, Stress concentration ratio, Geotextile,
Abstract :
The use of stone columns is an effective method to modify the behavior of problematic ground. When the ground contains a soft lens, the combined use of a stone column with a surrounding reinforcement improves the efficiency of this method for layered ground. The current study examined the efficiency and behavior of unreinforced and geotextile-reinforced stone columns embedded in sandy ground containing a soft lens. Physical modeling of ground with soft lenses of different thicknesses and placement levels was done in a Frustum confined vessel (FCV) under real stress conditions. The results of FCV testing on the bearing capacity, failure mode and stress concentration ratio revealed that a decrease in the soft lens thickness considerably increased the bearing capacity of the unreinforced and geotextile-encased columns. The absence of a soft lens increased the bearing capacity of the columns up to three-fold. While the unreinforced stone column underwent bulging failure in the soft lens range, geotextile encasement prevented bulging failure. As the lens depth increased, the bearing capacity of unreinforced and reinforced stone columns increased by about 40% and 10%, respectively. The occurrence of bulging in the soft lens range decreased the stress concentration ratio of the unreinforced stone column by 50% compared to the reinforced one.
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