Tunnel excavation supporting method under complex geological conditions of carbonaceous slate mixed with carbonaceous limestone and limestone

The invention provides a tunnel excavation and support method under complex geological conditions of carbonaceous slate mixed with carbonaceous limestone and limestone. The tunnel excavation and support method comprises the steps of tunnel excavation and tunnel support; the tunnel excavation comprises the steps of upper step area construction, lower step area construction and steel support installation. The upper step area construction comprises the steps that blasting operation is carried out firstly, an upper step area is blasted in a millisecond blasting mode, and temporary supporting is carried out; the construction of the lower step area comprises the following steps: blasting the lower step area in a millisecond blasting mode, and carrying out temporary support; the tunnel supporting comprises the step of steel support installation. By means of the method, large-area collapse and creep deformation of the soft rock tunnel in the later period caused by improper blasting in the excavation process can be ef