Construction device and method for cast-in-situ bored pile at extremely thick silty-fine sand bottom layer

The invention provides a construction device and method for a cast-in-situ bored pile on a super-thick silty-fine sand bottom layer. The construction device comprises a pile hole formed in a construction area foundation, a reinforcement cage is arranged in the pile hole, a plurality of positioning and clamping mechanisms are arranged on the outer side of the pile hole, and every two adjacent positioning and clamping mechanisms are connected through a connecting mechanism; alternate use of the abutting plate and the steel bar clamp is achieved through the linkage assembly of the gear and the rack, so that in the lowering process of the steel bar cage, the abutting plate is moved to be close to a pile hole, the abutting plate is close to the steel bar cage and even makes contact with the steel bar cage, the lowering position of the steel bar cage is limited, and the problem that the steel bar cage deviates in the lowering process is solved; after the reinforcement cage is put down, the movable plate is moved to