Effect of pore fluid on compressibility and collapse of clayey sand

In geoenvironmental engineering applications, the compacted fills often come in contact with hazardous chemical contaminants and are subjected to physico-chemical changes. These changes alter the mechanical behaviour of compacted soils due to the physico-chemical interactions at the clay particle level, which are reflected as a variation in the yield stress at the macrostructural level. Therefore, the current experimental investigation presents the effect of pore fluid osmotic suction on the compressibility and collapse behaviour of compacted clayey sand (red soil). Compaction of salt solution remoulded soil leads to the development of larger macropores owing to the microstructural contractions. The macroporosity increases with the increase in the pore fluid osmotic suction due to greater microstructural contractions. Thus, the yield stress decreases with the increase in the pore fluid suction, and the relationship between them was found to be logarithmic. The micro- and macro-structural changes occurring from the physico-chemical changes also affect the collapse, as the phenomenon of collapse is associated with macrostructural deformations. In order to eliminate the osmotic flow during collapse, no osmotic flow condition was adopted. Experimental results illustrate that the collapse increases with the increase in the pore fluid suction on account of increase in matric suction and macroporosity.