In order to investigate the construction control parameters for treating collapsible loess foundation using lime-soil compaction piles and ensure the effectiveness of the treatment, focuses on the foundation treatment project of the Lan-Lin Expressway, through the physical and mechanical properties test studied the water content, pore characteristics, compression characteristics and collapsibility of collapsible loess foundation soil samples with spatial distribution before and after reinforcement, and the influence of dilatancy characteristics and initial stress on the radius of plastic zone was analyzed by using the theory of cavity expansion. The results indicate that moisture content in soil between piles increases with distance from piles but decreases with depth; dry density and compression modulus decrease with horizontal distance from piles, while porosity shows an opposite trend，collapsibility within a 0.7 m radius from pile bodies is eliminated， the radius of plastic zone increases with dilatancy parameter but decreases with depth increase. Results suggest that when lime content is 10% and pile diameter is 0.4m, a reasonable spacing for lime-soil compaction piles treating collapsible loess foundation is 1.3 m.