Mountain tunnel accurate construction method and structure

The invention discloses a mountain tunnel accurate construction method and a structure. A tunnel face is divided into a smooth blasting area and a milling excavation layer through the method, the characteristic that a three-arm drill jumbo has an outer inserting angle during drilling is fully utilized, a space of 10 cm is reserved between peripheral holes of the tunnel face and a designed excavation contour line, the outer inserting angle of the peripheral holes is controlled, and the hole bottoms and the designed contour line are tightly attached. After the smooth blasting area is completed, a formed wedge-shaped reserved layer is constructed through a milling excavator. A spraying device of the milling excavator can effectively reduce dust in the milling excavation process. The method and the device have the advantages of less manpower, high construction speed, low construction cost, high construction efficiency, a low construction risk, a low requirement on the blasting effect of the smooth blasting area,