Effects of Structure on the Compression Behavior of Unsaturated Loess

The influence of structure plays a strong part in hydromechanical properties of soil. A series of suction-controlled oedometer tests have been conducted to explore the compression behavior of intact and compacted loess. The main findings show the following: (1) the yield stress of intact loess is higher than that of compacted loess at a given initial void ratio and under constant suction; (2) the slope of the normal compression line [λ(s)] of compacted loess is larger than that of intact loess; (3) the λ(s) value of intact loess initially increases sharply as suction increases and then trends to a slow decrease as suction increases further, while λ(s) of compacted loess continues to increase; (4) the λ(s) value of compacted loess can be fitted precisely with the Barcelona basic model; and (5) intact loess exhibits anisotropic behavior, in which a vertically trimmed specimen has a higher yield stress and λ(s) value than a horizontally trimmed specimen. The results showed that intact specimens and compacted specimens have different hydromechanical properties. Moreover, anisotropic behavior has also been found in unsaturated silty loess.