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This study examines the small-strain stress-strain properties during cyclic loading of Lanzhou loess deposits, characterized by a very high void ratio (>0.9). Torsional resonant column (RC) tests are performed in order to investigate the effect of water content, confining pressure, consolidation time and soil structure strength on the small-strain stiffness ( G 0 ) and damping (D min ) of loess. It is proved that shear modulus G 0 at low strain levels is very sensitive to water content while the effect of water content on small-strain damping D min is relatively small. As water content W approaches the plastic limit PL, there is a dramatic decrease of G 0 compared to drier loess specimen; G 0 has the tendency to reach a stable or constant value with further increase of water content which is more than the PL of loess. The small strain damping D min decreases continuously with water content for unsaturated loess and then tends to increase slightly for almost fully saturated loess. A linear relationship between G 0 and confining pressure σ′ m in log-log coordinates for different water contents is observed for Lanzhou loess. Similarly, D min decreases linearly with σ′ m . A power function is proposed to describe the relationship between G 0 and confining pressure σ′ m where the exponent m varies with the water content of loess. G 0 is also affected by the consolidation duration and a power function is proposed between normalized G 0 and normalized consolidation time. G 0 is finally strongly affected by the structure of loess and the type of specimen. For undisturbed loess samples, G 0 is always higher than reconstituted ones and the difference decreases with the degree of saturation; for fully saturated samples the influence of the structure strength between undisturbed and reconstituted samples becomes insignificant. Likewise, D min of undisturbed loess is higher than that for remolded loess under the same confining pressure and the difference between them reduces with the degree of saturation as well. [ABSTRACT FROM AUTHOR]

Loess is a kind of world-recognized problematic soil and, as a consequence, it is a major hazard in geotechnical engineering. This study examines the small to medium strain dynamic properties of Lanzhou intact and recompacted loess through a set of resonant column (RC) tests. The influence of soil structure on the small-strain shear modulus G 0 , the variations of G / G 0, and damping ratio DT(%) with shear strain γ were analyzed and discussed. The test results show that the structure has an important influence on the dynamic properties of dry loess at small and medium strain, whereas, with the increase of moisture, its effect weakens. It is proved that a normalized correlation between G / G 0 and γ/γ 0.7 is practically identical for undisturbed and recompacted loess in Lanzhou, irrespective of soil structure, which may be useful in practical applications. • The small to medium strain dynamic properties of Lanzhou loess with metastable structure were examined. • Structure effect reduces the ductility in dynamic response for Lanzhou loess. • The correlations between G / G 0 and γ/γ 0.70 could be normalized well for Lanzhou loess, irrespective of structure effect. [ABSTRACT FROM AUTHOR]