Abstract: A new city zone will be built on a large area of backfill, and according to the complex engineering geology conditions, the CFG pile composite foundation scheme was finally selected. The isolated foundation and strip foundation were calculated and piles were designed after comprehensive analysis and comparison on economy, technique and construction period of various approaches like natural foundation and compound foundation etc. The CFG pile composite foundation is a kind of composite foundation that consists of CFG pile, soil among the piles and broken stone underlay. The CFG pile body is of good quality, short construction period, fast construction speed and big bearing capacity which can be more than 350 kPa. The CFG pile composite foundation should be adopted,if the maximum load of a pile is not more than 4 000 kN or there is a sand and gravel bed which is of high hydraulic permeability in the soil stratum.

Key words: backfill, composite foundation, CFG pile