Abstract: The collapsibility of loess soil fill materials was evaluated based on the sitespecific engineering geology and hydrogeological characteristics of an airport project. The effect of dynamic compaction on the collapsible loess fills was evaluated throughout the laboratory soil tests, field standard penetration test and insitu direct shear test. The results from the insitu direct shear tests were used to evaluate the stability safety of the slope of a high fill embankment. The following conclusions can be summarized: (1) The optimum number of blows of dynamic compaction was 6 and the accumulated settlement was about 40cm through trial test zone; (2) The density if the loess was apparently improved after the dynamic compaction. The blow counts of standard penetration test increased almost linearly along the depth. (3) The loess soil layer in the field is characterized by the low liquid limit loesslike silt, slightly wet, dense, low compressibility. (4) After the ground improvement by dynamic compaction, the collapsibility of loess in the field was eliminated. (5) After the dynamic compaction, the internal friction angle of loess samples become less variable with a significantly variable cohesion values from the insitu direct shear test result. The insitu tested shear strength values could be used for the slope stability evaluation of the high fill embankment. It is concluded that stability of the loess fill embankment met the design requirement.

Key words: Collapsible Loess, Dynamic Compaction, Direct Shear Tests, Standard Penetration Tests, Laboratory Tests of Soils, Slope Stability