Abstract: The differential foundation settlements often occur in collapsible loess area due to the fluctuations of the groundwater, which will affect the long-term use of buildings. Quick lime columns are a common method for the retrofitting and strengthening foundations in these areas. Combination of bagged quick lime column and micro-pile are proposed to solve the shortcomings of traditional quick lime piles. The concept was applied in Shanxi Province. According to the expansion tests, the volume ratio of filling material of the column was set quick lime: dry plain soil: medium-coarse sand: cement 75:15:7:3; the maximum water injection amount was set 0.834 times of the mass of filling materials. Numerical simulation and field monitoring showed that the proposed micro-pile is feasible for the retrofit and reinforcement of building foundations. The settlements of the foundation tended to stabilize in 100 days from construction of the columns, and maximum settlement of the building foundation was less than 24.0mm.

Key words: Loess, Micropiles, Tilting Retrofit and Reinforcement, Lime Columns