Variable-diameter arch frame for supporting reserved filling air return duct of mine

The utility model provides a variable diameter arch frame for mine reserved filling air return duct support, which comprises an arch frame unit, the arch frame unit comprises a first support and a second support which are oppositely arranged, the first support and the second support are both U-shaped, and each of the first support and the second support is composed of an arc-shaped part and vertical parts located at two ends of the arc-shaped part. The two ends of the second support are in lap joint with the vertical parts of the first support and are fixed through clamping and fixing mechanisms, and the size of the arch frame unit can be changed by adjusting the length of the lap joint parts. The arch frame units are arranged in parallel, every two adjacent arch frame units are connected through a connecting rod, a supporting arch frame group is formed, and rapid supporting of the reserved filling air return duct is achieved. The variable-diameter arch frame has the advantages of being wide in application ra