Abstract: Because of its special pile technology and compaction effect, screw pile can effectively improve the mechanical properties of soil between piles and eliminate the collapsible of loess. In order to study the effect of screw pile on eliminating the collapsibility of loess foundation, the compaction effect of screw pile on loess under the condition of different pile center distance is studied and analyzed systematically. Test results show that the loess composite foundation treated with screw pile has a better compaction effect between pile and soil, and the collapsibility of loess is eliminated obviously. The dry density decreases with increase of the horizontal distance of the pile side due to particularity of the pile forming technology, and further the smaller the pile core distance is, the more obvious the compaction effect is. The collapsible coefficient decreases with the increase of depth and saturation. It is suggested therefore that the volumetric water content of soil instead of mass water content should be used as the influence factor of screw pile in the evaluation of collapsible loess compaction effect. Among those factors affecting the compaction effect of the screw pile in collapsible loess, the saturation focuses on the influence of soil pressure, and the liquid index mainly considers the influence of voids in the soil.

Key words: collapsible loess, screw pile, foundation treatment, saturation, liquidity index, coefficient of collapsibility