Abstract: The Grades II~IV Collapsible loess soils are widely deposited in Zhuanglang County, Gansu Province, along the alignment of Construction segment of Pingtian of PingliangMianyangExpressway Project. The compacted soillime mixed column method was selected to effectively eliminate the collapse when wetted, to improve the bearing capacity of the improved soils and to minimize the potential differential settlement of foundations. The effect of the soil improvement method was first evaluated in stations between K112+262 and 292. The evaluation results indicate that, the compacted soillime mixed columns can effectively increase the natural unit weight of the collapsible soils, reduce the initial moisture content and improve the bearing capacity of native soils. The key points of the column installations and lessons learned during the construction are also summarized in the paper.

Key words: collapsible loess, soil improvements, soillime mixed columns, plate loading tests