Hole forming method for repeated utilization of main hole and casing pipe of curtain grouting cluster well drill hole

The invention discloses a hole forming method for repeated utilization of a main hole and a casing pipe of a curtain grouting cluster well drill hole. The method comprises the following steps that a ground directional drilling machine is used for constructing a first layer curtain horizontal directional drill hole; the technical casing is sealed in a positive circulation mode in a ground grouting mode; drilling a horizontal section, and carrying out grouting curtain operation; the hole is swept to the position, without cement, of an annulus of the deflecting section, the secondary-opening technical casing is cut open in the drilling deflecting section through a casing cutter, and the cut technical casing is pulled out to the ground through a drilling machine; thick cement grout is adopted to seal the drill hole to the hole opening, and solidification is reasonable for the first time; and deflecting construction is carried out again for curtain directional drilling at different layers, and the steps are circul