The invention discloses a
microorganism soil-reinforcement
cement fly-ash gravel (CFG)
pile composite foundation and a construction method. The construction method comprises the steps that a, a
pile pipe is pressed into a foundation; b,
microorganism bacterium liquid is injected into the
pile pipe at the same time, and the
microorganism bacterium liquid is made to diffuse towards the foundation around the pile
pipe; c, the microorganism bacterium liquid is pumped out, and a cementing solution is injected into the pile pipe and made to diffuse to the foundation around the pile pipe and reacts with the microorganism bacterium liquid to generate
calcium carbonate crystals, and incompact sandy soil or floury soil is cemented; d, the step b and the step c are executed repeatedly till the soil around the pile pipe meets the reinforcement requirement; e, pipe-drawing pile formation is conducted while
cement-ash stabilized aggregates are poured; and f, a
bed course is laid, so that the CFG pile composite foundation is formed. According to the microorganism soil-reinforcement CFG pile, the soil around the pile pipe is reinforced through
calcium carbonate generated through reaction between the microorganism bacterium liquid and the cementing solution, so that the strength of the soil around the pile pipe is improved, and the quality problems of
necking, pile breakage, soil carrying and the like in the pile forming process are solved; in addition, a reinforced soil body can be combined with a pile for bearing, and the
bearing capacity of the single pile is effectively improved.