Double-pile-casing device for drilling deep and thick block stone backfill layer

The utility model discloses a double-pile-casing device for drilling of a deep and thick block stone backfill layer, and relates to the technical field of cast-in-place pile drilling. The pile casing comprises an outer pile casing and an inner pile casing, the inner diameter of the outer pile casing is larger than the outer diameter of the inner pile casing; the four pile bodies are used for positioning; a cover body is placed at the upper end of the outer pile casing; the upper end of the cover body is slidably connected with a telescopic rod; the other end of the telescopic rod is fixedly connected with a limiting ring; the axis of the limiting ring is fixedly connected with an axis block through a support. The upper end of the cover body is provided with a contrast line. The structure has the advantages that the problem of placing of the ultra-thick backfill rock block layer pile casing is solved, it is guaranteed that hole collapse does not occur in the pile casing placing process, cohesive soil is used o