Abstract: In additional to the highly compressible, well developed porous system, the loess has its unique characteristics of collapse after wetting. The collapsibility of the collapsible loess is required to be eliminated and the other mechanical properties need to be improved for the construction of passenger rail projects. This paper presents a case history of loess soil improvement in Lanzhou West Passenger Station using cement mixed soil columns with expanded base formed by the percussive poundings. The results indicate that this expanded base columns can effectively improve the loess soil properties in the bearing capacity, eliminating the collapsibility. The test results also show that the compressibility coefficient of soil between columns can be reduced by 50% and the dry density can increase as high as 22.5%.

Key words: Cement Mixed Soils, Percussive Pounding formed Expanded Base Columns, Collapsible Losses, Compressibility Coefficient