Pile-forming construction method under liquefied fly ash and loose pebble stratum condition in coastal area

The invention discloses a pile forming construction method under the liquefied fly ash and loose pebble stratum condition in a coastal area. The pile forming construction method comprises the steps that a precipitation well is formed in a pile foundation construction area so as to lower the underground water level of the pile foundation construction area to the position below a fly ash stratum; the variable-frequency long spiral drilling machine is in place and drills to the hole bottom elevation; after the variable-frequency long spiral drilling machine stops drilling, concrete is poured while the drill rod is lifted; hoisting a reinforcement cage and placing the reinforcement cage in the plain concrete pile position, and keeping the perpendicularity of the reinforcement cage after the reinforcement cage sinks stably by utilizing the self weight of the reinforcement cage; and an eccentric vibratory hammer is started, and the reinforcement cage is put into the plain concrete pile by a designed depth. The meth