Method for constructing composite foundation through gravel piles and ballast drainage mode

The invention relates to the technical field of offshore dredger fill sludge foundation treatment construction, in particular to a construction method of a composite foundation with a hillstone layer covered on the upper portion and a sludge layer laid on the lower portion. The invention discloses a method for constructing a composite foundation through gravel piles and ballast drainage. The method comprises the steps that S1, upper covering layer guide hole construction is conducted; s2, constructing gravel piles on a lower silt layer; s3, piling a pile position drainage plate; s4, general ramming treatment of an upper covering layer; s5, shallowly burying a drainage filter screen pipeline; and S6, later settlement and drainage monitoring. According to the method, the composite foundation principle and the drainage consolidation principle are combined and complement each other, the repeated operation cost is reduced, the strength of the pile body and the surrounding soil body is further improved through drai