Cast-in-place pile construction method

The invention relates to the technical field of housing building and provides a cast-in-place construction method to solve the problem that a concrete contaminated soil layer has a large range. The cast-in-place construction method includes: (1) leveling a site; (2) drilling a hole, wherein the diameter of a pre-pile hole is less than that of a pile hole in a design drawing; (3) expanding the hole, to be specific, placing a water bag into the pre-pile hole at the premise that the outer diameter of the water bag is equal to the diameter of the pile hole in the design drawing and the length of the water bag is equal to the depth of the pile hole in the design drawing, injecting water into the water bag until water pressure is greater than 1 MPa, allowing standing for at least 10 min, relieving the pressure, drawing water, and removing the water bag to form a finished pile hole; (4) sinking a reinforcement cage inside; (5) casting concrete; (6) removing a pile head by breaking. The diameter of the pre-pile hole