Tunnel pre-supporting structure

The utility model relates to a tunnel pre-supporting structure, and provides a novel coupling forepoling bar pre-supporting structure so as to adapt to empty roof pre-supporting before permanent supporting of a tunnel blasting excavation working face. By adjusting the size of the hole opening of the center hoop, the design purpose of meeting the suspension fixing requirements of forepoling beams of different working conditions and different planning models is achieved. The tunnel pre-supporting structure comprises a forepoling bar and an anchor rod with the top end connected to a tunnel working face. The tail end of the anchor rod is connected to the coupling, and the forepoling bar is arranged in the axial center of the coupling in a penetrating mode. The coupling is provided with two semi-ring-shaped hoops which are in butt joint, and a screw and a nut are arranged on the two sides of each hoop in a penetrating mode respectively. An excavated tunnel working face top plate is connected with an anchor rod, an