The Effect of Overburden Pressure on Chloride and Water Movement in Swelling Clay Soil

Abstract

AbstractThis study was conducted to evaluate the influence of overburden pressure on the movement of water and Cl‐ through short undisturbed cores of swelling clay soil. When overburden pressure was removed from the cores, saturated flow rates increased. Subsequent miscible displacement studies revealed that the percent soil water excluding Cl‐ was also reduced. When soil cores were loaded with overburden pressure, the amount of soil water excluding Cl‐ was approximately 50%. When overburden pressure was removed, the amount of soil water excluding Cl‐ was 33%, about the same value as measured in disturbed soil cores of approximately the same water content. Differences in the quantity of soil water excluding Cl‐ between loaded and unloaded cores were due to an interaction between soil structure and the negative charge on the clay in the loaded cores. Apparently, when overburden pressure was removed, smaller pores increased in diameter, which allowed Cl‐ to diffuse more freely into these spaces.