Abstract: The treatment of collapsible loess foundation has always been an engineering challenge. The working mechanism of the Cement Flyash Gravel (CFG) column composite foundation for the ground improvement of collapsible loess is demonstrated by the brief discussion of the role of CFG columns strengthening the collapsible loess. This paper also presents a case history of installing CFG column in collapsible loess soils using a long flight auger. The installation methods are discussed with problem solving on the site-specific subsurface conditions. Both laboratory and the field quality assurance test results indicate that the bearing capacity and the deformation are met the design requirements. The CFG column is a cost-effective solution in the ground improvement of collapsible loess soils.

Key words: Collapsible Loess, Cement Flyash Gravel Columns, Cast-in-Place Concrete Pile by Long-Flight Auger, Construction Technique