Abstract: To reveal the deformation characteristics of the Ili loess in westerly wind regions, we conduct laboratory tests on its collapsibility with different dry densities and water contents using the double line method and a YS-I high-pressure consolidation apparatus, focusing on the characteristics of its compressibility and collapsibility. Results show that higher water content or smaller dry density leads to smaller yield stress, larger compression coefficient a1-2, and stronger softening on the δs-p curve. And collapsibility coefficient has negative linear correlation with water content or dry density, and it diminishes to nearly zero when the dry density is bigger than 1.6 g/cm3. We derive an expression of compressibility with the parameter of dry density and reveal that under different water contents, the normalized compressibility curve can be characterized using an exponential relationship of e/e0 versus lg(p/pc). For typical collapsible curves, we construct a four-parameter model that better reflects the softening characteristics of collapsible deformation curves, and present a normalized model formula including the parameters of dry density and water content. This work may be helpful to engineering construction in the westerly wind loess region of Central Asia.

Key words: compression test of soil, Ili loess, high-pressure consolidation apparatus, double line method, dry density, water content, collapsibility model