Front support of tunnel trapezoidal

The utility model discloses a trapezoidal tunnel cantilever support frame used for support in underground engineering, comprising a fixed beam, a rotating arm beam, a double-rocker mechanism for hanging beam clamps and rotating arms, etc. The double-rocker mechanism is fixed on an H-shaped steel top beam, and a screw rod mechanism is arranged in the fixed beam to make an inner beam and an outer beam capable of expanding and contracting relatively and walking forwards. The rise and the fall of the rotating arm is controlled by the double-rocker mechanism with a self-locking function, the length of the rotating arm is adjustable to be adapted to requirements of different shed distances. When the rotating arm droops, the top beam and top protecting net pieces are placed, and the gross area support can be provided when empty tops appear. All the operation and the control are completed by operating rods and chains. The utility model with the advantages of reasonable structure and safety can be used for blasting tunnels and broken stone tunnels which are supported by H-shaped steel.