Effect of the Degree of Saturation on the Behavior of a Single Sand Column in Clay

Abstract

Researchers have extensively studied the Use of granular piles (sand columns) as a ground improvement technique under fully saturated conditions, but have paid limited attention to the influence of the unsaturated zone, which reflects soil conditions in arid and semi-arid regions. However, their behavior in partially saturated soils remains critical due to the complex interaction between soil suction and structural stiffness. The objective of this research is to assess the behavior of a single sand column in partially saturated soil by studying the effect of increasing the L/D ratio and the area replacement ratio on column efficiency. The study used 32 mm diameter columns with varying slenderness ratios (L/D = 8, 10, 12, and 15) at varying degrees of Saturation (60%, 80%, and 100%). Clay soil layers were placed in a 60×40×60 cm steel box, and a hydraulic jack applied axial load using square foundations of 9×9 cm and 6×6 cm, representing area ratios (as) of 0.09 and 0.22. Electrical matric potential sensors measured matric suction. The results show that column capacity varies significantly with Saturation, matric suction, and slenderness ratio. When Saturation decreased from 100% to 80% and 60%, the bearing capacity of the composite soil increased for all L/D ratios used. Further increases in the L/D ratio beyond a certain limit do not substantially enhance capacity at (Sr.=100%) and (Sr.=80%), where increases range from 1% to 6%. However, this percentage increases significantly at (Sr.=60%) up to 18% for the same (as=0.09), and becomes higher when (as) increases to (0.22). Additionally, increasing the area ratio from 0.09 to 0.22 significantly improves the bearing capacity.